Tech Talk with Mo!
Submit your tech questions to MO! at mailto:tech@scrappydogscooters.com

Proper installation of our roller sliders ( similar to the Dr. Pulley units )
shown in a GY6-150 variator. If these are not installed correctly, the variator will not function, and speed will be limited.
Installation video here: http://www.youtube.com/watch?v=8KRBJHbvG1A


Hey MO! How do I know what engine I have? I have heard all this talk about 1PE40QMB and 157QMJ blah blah. It seems so darn confusing to get parts for these Chinese bikes! What can you do to help? -Lost in Las Vegas.

Chinese bikes and ATV's can really be confusing, that is why scrappy dogs was started. There are two identifications to remember by using this site for help, not only to know what you have, but to get what you need. The first is the engine type. While this site uses a simplified directory at the left, you really need to know the engine number to get your parts right. This engine number is typically in two parts on the same stamp location. Most of the time the numbers are stamped on the left side of the engine, under the belt cover, near the front close to the engine mount to the frame. The bottom number is the reg. number, the top number is the one to pay attention to, this is the engine identification number. It tells you what you have. Below is a picture of a number plate for a 50cc 4stroke, also known as a 139QMB.

The engine number is very significant, and reveals alot. Take for example a popular engine, like the Honda Monkey (chinese copy) The number stamped on it is a 1P39FMB. The first number is the number of cylinders, the second, a P, is code for a horizontal engine. The next 2 numbers, 39, is the bore diameter in mm, 39mm bore. The next letter, F, indicates that it is natural (not forced) air-cooled style. The next letter designates that it is a motorcycle engine "M". The next letter reveals the full engine displacement. B is code for a 50. C for a 60, D for a 70, F for a 90, G for a 100, H for a 110, I for a 125, J for a 150, and so forth. Notice that the size graduation increase is indicated by an increment in the alphabetical letter? It's no coincidence. It's amazing to me the cooperation in standards of China. There is also prefix letters on many, designating the manufacturer, like Quinjiang (we have them all on file), which stamps there acronym, QJ, as the first two letters in there code. It's also very revealing, as the QJ139qmb is quite different then the other 139qmb's. It uses the 1E40qmb (2T) transmission components, and the engine case is a little different. There are also suffix numbers at the end, which designate iteration levels, like -3 in the photo below, which denotes that it is the third design, or improvment.  Call or email us if you have any questions. We love to help. Here is the Chinese engine code chart with the example of the JOG 2stroke engine number 1PE40QMB-4 

Some engines have the number plate on the upper rear side of the belt cover. GY6 engines are on the fron, bottom, left had side near the centerstand pivot. 2stroke JOG's are near the rear wheel like Honda Spree elite and DIO. They are often on a sticker on the belt case. Sometime the airbox needs to be removed and alot of grime washed off on the 2strokes. By federal law they are stamped on the engine case and are there, even if you don't see it at first inspection. Either way it will help you significantly to know this.  As far as the chassis body parts go, you can reference your body appearance to the listing shown in the Chassis directory given at the left, or simply click here- http://www.scrappydogscooters.com/CHASSIS_PARTS.html
This list is growing weekly, so if you don't see your bike here, check later, or better yet use the Parts Finder form on the home page. Scrappy dogs are committed to making the Chinese vehicle market easy and fun for everyone, and affordable too!
Thanks for the question, hope your not so lost anymore.







AC vs DC fired or pulsed CDI IGNITION SYSTEMS

Hey MO! What's all this I hear about AC and DC fired or pulsed CDI'S? - Harried in Henderson

Ok first the short answer.
Here is the readers digest of how a CDI works
In all cases there is a magnet that passes a magnetic coil and induces a pulse in that coil which then is wired to the CDI and causes the small induced pulse to fire an  electronic device (there are more than 1 type but this all happens inside the CDI)  Which discharges the larger pulse stored in a capacitor.  This larger output pulse is wired to the coil where the large pulse is able to make the coil function as a voltage increasing transformer thereby producing the very high voltage necessary to create a spark across the gap of the spark plug.
Now for the 2 main type of CDI used in the 49 cc scooter market,  AC and DC  Both function  essentially the same.  With the AC unit, alternating plus and minus varying voltages are used to charge the capacitor described in the paragraph above.  The DC unit takes 12 volts more or less DC from the battery and that voltage is used to charge the capacitor described in the paragraph above.
Pros and Cons:
AC unit allows the engine to run without the need for a battery or charging system of any kind.
DC unit was created to allow higher RPM ranges due to the instantaneous availability of the Charging current.  Where the AC one has lots of complex and difficult to explain things like coil flux density and residual decay etc.
The wiring is different also usually but not always, the ac ones have a rectifier or diode ahead of the CDI and the DC ones just connect directly to the battery.
the way to tell for sure is to turn on the key and see if 12v is present at the CDI assuming all else is correct. Some units that are DC include:
Kymco Agility 50, Diamo Velocity, Vento Triton, Schwinn, Tomos, and other high end Chinese, Korean, and Taiwanese scooters.
One easy way to tell is the size of your CDI unit. The AC fired CDI will be much smaller than the DC fired CDI, as shown in this picture. Also, you have two plugs on the CDI, one with four, the other two. If the two wire plug actually has only one wire in it, it's a DC. If it has two wires in it, it is an AC fired. The number of wires is only a loose guide. The size of the box, along with this guide is a better determination. An AC box will be smaller (see pic) and will measure about 1 1/2 by 2 1/2 approximately, the DC box will be much larger as it has a DC-DC converter in it. Such words as AC or DC pulsed or AC or DC triggered are the same thing as the AC or DC fired units.  One quick warning on performance units, with the advanced angle of our CDI's your engine may actually run worse if it's not running right or is carbureted too lean. I'd recommend installing a larger main jet to take full advantage of these units.

Here is  somewhat simplified checklist to determine type:
Headlights turn on with key, DC.  Headlights turn on with engine,AC
Engine does not run without batter, DC. Engine runs without battery, AC
CDI box is pretty large, DC. CDI box is smaller, AC (note: our new digital DC units are smaller)
There is one wire on the two part plug, DC. There is two wires on the two part plug, DC.

Hope this helps. MO!

Here is a standard ignition circuit for a chinese scooter. Note that the red wire from the stator to the CDI will not be on a DC fired system. The kill switch wire will instead be the positive power source from the igntion key switch.

and variator size difference

Hey MO! How the heck do I know if my Minarelli based engine has a 12mm or 10mm wrist pin, without taking it all apart first? - Confused in Chicago

Our knowledge database is growing, but we know a few things. Adly's and Hammerheads are 10, so are the Italian Minarelli engines like Malaguti, Italjet, Beta, and Aprillia. The 12mm pin is found on later CDI's, chinese JOG-2T, Vento Triton. These engines are poplular in 2-stroke full size scooters and ATVs such as Malaguti, Yamati, United Motors X-Speed, Aprilla, CPI, Benelli, Vento, Eton, Adly and many more. Italian made units tend to use 10mm pins (Chinese JOG 2T clones tend to use 12mm) please measure and check before ordering. Certain brands such as CPI / United Motors / Muz older models used 10mm newer post 2004 use 12mm. All Italian made models use the 10mm such as Aprilia / Malaguti / Italjet that are Yamaha Minarelli based.
Probably the most accurate, without complete disassembly, is to measure the inside diameter of your variator pulley. If it is 21mm, your wrist pin is 12mm. If it is 18mm, your wrist pin is 10mm. You can also count the number of splines on the outer variator face where it mates with the crank. The smaller 18/10mm crank has 17 splines, the larger 21/12mm crank has 15. The larger crank was originally designed for the JOG90 engine, but comes in 50cc too. Also, don't confuse your Minarelli 2stroke with the Franco Morini type two stroke found in TGB R5 Laser, Key West, 101S, the Suzuki Address, and some Italjets. These kits are also available from Scrappydogs, as they are authorized dealers for TGB products.
Hope this helps. MO!
Here are our Minarelli based parts link.  Minarelli

Variator roller weight choice

Hey MO! I want to get some more speed out of my scoot, but I don't want to spend much money. I've heard that by changing the variator roller weights you can do this the most economically. Is this right? and if so, what weight should I go with?        -cheapskate in Baltimore

Yes, rollers are an economical way of increasing performance, however, it comes with a compromise as any performance upgrades do. The over simplified explaination that is very common is that heavier weights give you more top speed, and lighter weights more take off. This is true to a point, but not really. The variator weights control what is called the "constant engine speed". I'm sure you've noticed when you give your scoot full throttle it holds a certain engine speed while the vehicle accelerates. The variator controls this engine speed. If your engine is above it's maximum torque because of too light of of weight, it will not accelerate like it could. If your engine is below it's maximium torque because of too heavy of weight, it also will not accelerate well as it will bog. So, this being said, you can actually gain top speed AND acceleration by lightening the rollers. This is true for a number of reasons. Your engine has a certain engine speed, RPM, that is it's most powerful and most efficient, this is called the torque peak. You cannot get maximum performance without being at this RPM. Second, remember that the variator get to it's maximum contraction almost immediately upon acceleration, and holds there, it's the rear pulley that slowly contracts as rear wheel speed increase, therby increasing the ratio between engine and wheel, making for more road speed.
To conclude and simplify: lighter rollers increase the "constant engine speed", and heavier rollers decrease it.


Hey MO! I've seen all these clutch and torque spring, blue, red, yellow, and I'm confused as to what they do and which one to pick?       -Wanting more power in Philly

Ok, first the torque spring, or what some call the big spring. This controls the rear driven pulley sheave. Lighter springs let the sheave spread soon, stiffer later. A heavier spring is equivalent to a larger sprocket on the rear of a motorcycle, and vice versa. If your having trouble climbing hills or you hear the engine bogging a little just after take-off, you likely need a stiffer spring. To the extent that you have the above symptoms, the stiffer you need to go. Also, the heavier you and you passenger is, the stiffer you should go.
The clutch springs determine the engine speed that the clutch engages. The stiffer springs allow the engine to spin up higher, giving you a harder launch. The drawback is that you will not engage in lower engine speeds, making it kinda racy everytime you take off.

Not running very well (oil change /  carburetor diaphragm)

Hey MO! My scoot runs like crap! I can't get the darn thing run much past 20mph! I've put all kinds of high
performance parts on it, brought it to the mechanic, etc. What can I do! I keep it well maintained and have rebuild the carburetor and changed the oil. I'm stuck.

Well, you've indicated a couple of things that may be of help. Many people that ride scooter do so because the have to, often because they lost their license, or are just plain broke. I bring this up because they most likely are working on their own scooters, or are paying the local "mechanic" who works out of his own house, not that that is bad, there are many excellent backyard mechanics, I was one myself, but most of them just don't know what they are doing when it comes to sccoters. 20+ years for motorcycle or car mechanic experience does not qualify you as a scooter mechanic, they are unique. So what happens is the many mistakes are made. One is that when the carb is "rebuilt" the slide diaphragm is torn or pinched when re-installed. You can see this if you have the airbox boot off and try revving the engine up and the carb slide does not rise up very far. Get it replaced and install it correctly.
Next, oil changes. It never ceases to amaze me how often I see the oil sumps of scooters overfilled. I pull the dipstick out and it is filled all the way to the top! This causes a partial hydro-lock and saps power considerably. It will also damage the rings by bending them. Even if you adjust the oil properly by using the dipstick the top end is ruined. Don't do it!


Dear Sir I have a VMOTO 125cc Monaco engine QJ153, I would like to know, what upgrade 150cc piston and head kit would fit my bike and what would be the total cost? an answer would be most appreciated.
I have already purchased parts from You.       -Upgrader in Houston
Nice to see you again, and thanks for your tech question. Your engine designator QJ153 is decoded as such. The QJ stands for the manufacturer, which is Quanjiang, a quality factory in Zhejiang province of China. The first number is the number of cylinders, 1. The last two, 53, is the diameter of the bore, 53mm. Often there is a suffix of three letter, in your case, a QMI or a QMJ, this denotes the engine style. The Q would suggest a GY6 type configuration.
I would suggest our 150cc standard bore kit for just 59.95 delivered priority mail. You can upgrade the head to a 150, however it is not necessary. Heads are 49.95 additional. I have found that often the smaller combustion chamber of the 125 makes for a nice high compression engine. The 150 is a 57mm standard. We also have 59mm, which is the largest upgrade without machining of the cases.
Thanks for your interest. You can order by phone, email, or by secure server via Paypal payments on this link.


How do I know if my 150cc GY6 is a long or short case? I want to change my belt and it has no indication on it?

With a few exceptions, the 125/150 GY6 has two belt sizes: 743 for the short case, and 842 for the long. If you have a 10 inch rim on the rear with a tire that is 3.50 wide or less, it's a short case. The belt cover will also measure 16 inches from end to end. If you have a 10" rim with a 4.00 wide, or a 12 or 13" rim, you have a long case. The belt cover will measure 17 1/8" long. Another easy way to tell is simply to count the number of retaining bolts for the belt cover, the short case has 8, the long one has 10. When in doubt, ask the experts at tech@scrappydogscooters.com We know this stuff like no other.

 got from scooterdogs an 80 cc.cylinder kit for my 50 cc. Rocketa
scooter.It's aQMB139 moter.All went well runs .Had 2 rides only notticed it needed to break in.Now I cant get it beyond 3/4 throtle without it wantting to die,unless I lower the throtle quickly. The timming   is allright,spark continues, carberettor is fine .I gave it a spray shot of gas when it was dieing but no saving it.Ignition and carb. don't seem at fault. Do you think a valve spring is broke? even though it seems fine up to 3/4 throtle,or about 3000 RPM.
Me again. I adjusted the valves and it still didn't work past 3/4 throtle. I tried the spray gas in the carb. idea and this time it made a diferance' for the better. so I guess it is carburetion after all. Funny it rode well the first 2 times' but maybe since it wasent broke in yet and now is more so the piston is pulling in more gas now. Carb. is a CVK with # 78 h maine fule jet and # 34 h low speed jet. low speed seems o.k.
What do I do now scrappin dog?
                                                    Hope you can help!                                                      Thanks
Without being able to see what has been changed or modified, it's difficult to tell. I'm inferring by your statement that your spraying gas in that you've removed the stock airbox? This might explain some things. These airboxes are very restrictive to pass DOT noise regulations. When this restriction is removed in the pursuit of suppossedly more power, the vaccuum is grealy reduced at the venturi nozzle point, which leads to a lean-below stoic condition. This is very common for scooters to just not want to run when airboxes are removed. It's even more common to hear all the subjective analysis that everthing was working fine "until" this or that was done, or it worked like that before eg. "it's not the carb because I spuirted gas into the carb with no change". The piston seal will improve with proper break-in, but not to that degree to make that kind of difference. I'd recommend replacing the stock airbox for baseline test. I normally install a #85 main whenever I remove the airbox, and even then, because of resonance differences, a substantial loss in bottom end power results.
Last of all, when all else fails, seek a professional that can tactilly repair your vehicle. (hard to find I know) If it was possible I'd invite you to Arlen Ness motorcycles where I consult part-time for a challenge fix. Was this CVK a stock carb or a later addition? MO!

Me again.You really know your stuff, I'm glad your there man.I put the air filter box back on like original.And it runs great now! I had taken it off in place of a new 3"round x 2"tall chrome air filter.Looked great,but I guess it's running right is better than looks. I'll bet you get in opperation vs.looks with Arlen Ness sometimes.ha.ha. Your not scrap to me man. Have a good day.and thanks


Carburetor jetting
you seem to know your stuff. I have that baja sc50, with that odd ball motor Qj139qmb, motor. what's the trick to getting  to getting the most topend out that motor. I have tried 4.5 to 6.5 gram weight, I stalled a 72cc big bore kit, its got a lot better tork, a new mod Exhaust system. new cdi w/ no rev. No noticeable change in rpm.

holy smokes dude, a #125 on a 50?! No wonder your not running right, your drowning the poor little thing. Too much fuel is very detrimental. It must be properly mixed at the stoic ratio of 14.7:1 by weight. If more fuel was better all the time, we'd just eliminate the carb and hook the fuel line up directly to the engine. Engines are air pumps, the more air the better, not the more fuel the better. I'd recommend installing at most a #85 main jet ONLY if you have a high performance air filter. If not, I'd go with the standard #75. You must set the jettin correctly by experiment. Put the main jet in, and run it full throttle long enough to get the plug colored. The best reading on a 4sroke is a light tan, with perhaps some darkness around the edges. Some factory setting are so lean that they are bright white. Your plug is probably black with soot.  

Big bore kit installation
Hey MO! How do I install that cool new big bore kit that I bought from you guys? I'm somewhat mechanically inclined, but I'd like some instructions.

No problem, just follow this link which should help you out some. Our kits install just the standard top end, with no modifications needed. Link:http://www.livefromhawaii.com/geelyscooters/80ccinstall.htm


QJ139QMB-3 and QJ1P39QMB-3 anomaly engine tech facts

Hey MO! I've got this QJ engine in my Baja Sun City SC50, it's also found in the Vento Triton, and MotoMojo Roadster 50.  I'm just confused about what parts fit what?

Yes, that is a pretty unique engine. We call it the QJ anomaly. This engine is fundamentally the same, with these differences:
1) The aperture in the crankcase for the cylinder is slightly smaller, making big bore kits difficult without some modification
2) The belt size is unique, using the 836-17-30, which we have here.  
To confuse things a little, it seems the Vento and MotoMojo uses an 891-17-30 belt.
3) The QJ anomoly uses 21mm 2stroke JOG engine variators, rollers and rear clutch pulleys, which are available here.
4) The belt cover is unique also
5) These are often fitted with disc brakes in the rear, making some of these components difficult to acquire.
6) The carburetors that are fitted on these use a different type than standard 139qmb. We would recommend changing the carb to the more common type.

Other than these differences, it is essentially a standard 139QMB engine.

GY6-150 engine type differences in parts

MO, I've noticed that there are a few different heads types and other parts on GY6-125/150 engines. I thought they were all the same? All these engines had the 157QMJ in the engine code. What gives!

Yes, there are a few different types, but are easily distinguished, and thankfully most are interchangable. The standard GY6 engine parts your will find on our site fit and work perfectly. There are two variations that I will identify now.
GY6 Scooter Version B - This engine is found in alot of higher priced quality scooters like Zhen, Lance, Fly, etc. The engine number will be BN157QMJ, and will have a 16" rear wheel ( although some Lance Duke Tourings have the smaller wheel BN engines, which are standard parts, with some other exceptions). This engine is made by BenNeng of the Zhongneng Industry Group. This engine has alot of non-interchangable parts, like the variator, head, stator, etc. The head on these is taller than a standard GY6 head, and has longer valve stems. The stators are 12pole DC types. The belts are longer than standard, and are often 906. The cylinders however will fit from standard parts. Our big bore kits will fit -B models. The performance 4 valve head will fit these without use of the longer chain and retention studs, as this engine already has them.
GY6 ATV Version B - This engine is found almost exclusively in ATV, Buggy, and Go-Cart's. Externally they look identical to a standard GY6, with one prominent, yet subtle difference. They have two bolts holding the cam cover down, while the standard GY6 has 4. The other differences are internal, and on the top end only. The cylinder retaining studs are slightly wider spaced than a standard engine, not allowing the use of standard heads and cylinders. The apperature in the crankcase is larger than normal, which allows a larger big  bore kit without machining of the case, but the kits that fit are nearly impossible to find. One last thing on Kazuma ATV engines, model KZM157QMJ. Nothing fits these except Kazuma specific parts. The QJ157QMJ and QJ156QMJ by Quinjiang is also a unique oddity.

Trying to figure out the whole -B case thing

hey MO! I have a Bintelli Havoc 150cc and still can't figure out which -B case gy6 engine I have, or if I even have a -B case engine in my scooter! Help! dmartin95

Yes, you are correct dmartin95. The BN157qmj has 54mm stud spacing, however, it loosely is considered a B case engine by some, but not by ScrappyDog. We call it the BN
The BN157 with extra long case (16" wheel) has a standard A case cylinder, but has a taller head, and also has a slightly longer crankshaft. The variator and rollers are different also. This BN engine that is deviant typically has a -3 at the end of it. To confuse matter more, there is a BN157QMB (no -3) that was used in some scooters, like the Lance Duke, that uses 12" wheels and is NOT a deviant -B. Parts for this variant are at the below link, and we are adding some more BN parts including complete engines which will arrive next week:
The engine we call a -B has 57mm stud spacing, which we sell as the gy6-200. The cylinder and head are different of course, but the crank and variator are overall the same enough to interchange. We sell stock, and even now performance parts for the larger case -B and these can be built out to 232cc's. The gy6-200 is generally built to a beefier and high quality standard and also includes oil cooling:
Now we confuse things even more with the -B engines as there are some other deviant gy6's out there, especially with ATV based engines, like Kazuma. Let's not forget that QJ (Quingiang) has another variant engine which has a different cylinder and head, but not much different. We sell the QJ parts at the below link:

Belts breaking all the time!
Here is a reverse MO! question answer. This time it was MO! calling out to all those scootdawgs out there who might know why so many belts are broken on certain scooters. This was a reply from someone who kept breaking belt after belt, and seemed to try everything, then after he changed the rear clutch/pulley assembly, he wrote back this reply below. It seems that the inner bearing would pit and run rough, causing excessive heat, and transfering heat to the belt through the rear sheaves of the pulley. Heat and rubber don't do well together for long!
MO! It (rear clutch/pulley) was causing  all the heat (a bad needle bearing in the clutch), and I have about 500 miles on my scooter since replacing the clutch with the one I purchased on your site, and it's running great, so you my want to advise people to pull the clutch as part of their normal maintenance routine (every 1,500 – 2,000 miles should suffice), and feel if the bearing has any rough spots in it; this can easily be done by inserting your index finger into the bearing and spinning the clutch on your finger, and if the bearing does not roll freely, or you can feel any rough spots in it, it’s probably getting close to time to change the bearing (if you can find one), or the clutch, because you can warn them if they don’t, they’ll probably be pushing their scooter home from wherever they are when the heat from the bad bearing, melts the belt.  -helpful scootdawg no longer changing belts all the time!

Possible carb issues.
Hey MO! My engine didn't run right even after I cleaned the carb thoroughly, so I bought a new one from ScrappyDog, and it still doesn't run right! I know it's the carb, it has to be. I'm an experienced mechanic of 20 years, and have build race engines before, so I know what I"m talking about. I'm not a happy camper. I think you sold me a defective carb.

While defective parts do happen, especially in the super high production volumes that Chinese product are made, perhaps something else is at fault. In a scooter, there is a vacuum operated fuel valve called a petcock. It has been found that when the diaphragm in the valves is defective, it allows fuel to run through it, directly into the vacuum line, which is attached to the intake manifold. This causes a seriously high rich fuel mixture ratio, making for very poor running, if at all. Usually the symptoms are bike will only run at very full throttle, and then only poorly. Also may run only at idle, and quit as soon as throttle is opened. While we are in the business of selling parts, it may be that you could save some money and get a new petcock. I'd recommend checking to see if there is fuel in the vacuum line. If there is any at all, that's what it is!

Mo, I have a 2 stroke 50cc scooter that I just put one of your big bore kits on. I can’t find any information on how to bleed the oil pump.Tom.

Tom,Bleeding the oil pump is fairly straight forward and something some people tend to overlook. You want to make sure you get all the air out of the system so you don’t damage the motor. First, you want to make sure that the oil tank and the oil supply hose is full of oil. To check the hose, simply disconnect the hose from the pump and make sure oil flows out the hose and then reconnect it. Next, loosen the bleed screw on the pump and wait until oil flows out of the hole without air bubbles, and then retighten it. Double check the oil supply tank at this time to make sure it is still full. Now you want to disconnect the pump outlet hose from the carburetor. Make sure the key is off and use the kick starter to crank the motor while watching the hose until oil flows without air bubbles, and then reconnect the hose. You could also use an external fuel tank with premixed gas and run the motor and follow the above procedure. Caution: Do not crank the motor on the starter or run a 2 stroke motor without an oil supply. Also do not crank a 2 stroke with the ignition on and the spark plug disconnected; you could damage the ignition system.

Mo,I have a 139QMB motor that will not charge. I have changed the rectifier with one from my other scooter and it still will not charge. How do I test the stator? Steve

Steve,To test the stator you will need a multimeter with an ohms (resistance) function and an AC Volts function. First locate the stator wiring coming out of the motor on the right hand side. Disconnect the 3 wire plug. Now with your multimeter in Ohms X 1, on the stator side of the wiring, take one lead and probe the green wire and the other lead and probe the white wire, you should read around 1 ohm. Now probe the yellow wire with one lead and the green wire with the other, again you should read around 1 ohm. If either reading is zero or no reading (infinite ohms) the stator is bad. Another way to check a stator is with a voltage reading with the scooter running. Be careful not to get your leads around any moving parts, such as an open stator fan or the rear wheel. It may help to have someone help you with this test. Place the multimeter to AC Volts and place your leads across the green wire and the white wire just like in the resistance test. Start the scooter and momentarily rev the motor above 4000 rpm, you should read above 30VAC, do the same with the yellow and green wires.

Mo,I have a 50cc scooter and just rebuilt the carburetor. Now, I have a slight bog when I pull away from a dead stop. Otherwise, the scooter runs great. Help, it is annoying! Cindy

Cindy,The problem may very well be that when you removed and reinstalled the fuel bowl that you may have bent the tab that actuates the accelerator pump. If it is not adjusted right, it will actuate the pump after the throttle is partially open and give a shot of fuel causing a brief moment of extra gas and bog.  Remove your carburetor again, on the right side of the carburetor (throttle cable side) you will see a tab that sits right above the accelerator pump rod. With a pair of needle nose pliers, bend the tab down to where it touches the accelerator pump rod. Reinstall the carburetor and ride the scooter and see if the bog is gone. If it is better, but not quite gone, repeat the procedure and bend the tab down just a little more. This should fix your problem.







Chinese clone copies

Hey MO! How on earth do these darn Chinese get off copying everyone else's product? Doesn't seem legal to me, and I'm really sick of seeing all this Chinese clone parts. They are real junk!

Yes, Chinese parts do seem to be "copies" and "clones", but in reality, most really aren't. You see many Japanese and American companies have been using Chinese factories for years to produce their products at a more affordable rate. Honda used CFmoto, Kymco, and TGB for example. Yamaha used Linhai and others. These Chinese factories were setup to make such bikes as the ubiquitous GY6. When Honda decided to discontinue this model, the factories that had tooling and training invested in such a venture rightly decided to continue making this product, and to great success. While under Japanese management, some product was understandably a better quality. The Chinese are masters at producing a good product at an unbelievably low price. While many like to complain of Chinese quality, they certainly don't complain of Chinese price. The price to quality ratio is unbeatable. In the earlier years, quality was unbearable and aweful. It's getting better and better. The factories still offer different grad parts for different prices, so don't think that all Chinese parts are the same. Many vendors will show low prices, with junky parts. ScrappyDog is able to offer good quality parts at unbelievable low prices as we are a direct importer, and buy in big volume. This buying power allows us to sell direct to the public at otherwise dealer prices, getting you back on the road for much less.
Timing Marks 50/150cc Motors
Hey MO! I just installed the big bore kit and performance camshaft, but I don't know how to time the cam to the crank!   -desparate in Detroit
I have been getting a few inquiries on timing marks and cam timing. The first picture shows the flywheel in the Top Dead Center position. Do not confuse the 2 marks. The F mark is the mark for when the magnetic pick-up fires the CDI. The T mark is for when the piston is at the top of it’s travel. The T mark must be aligned with the alignment mark in the case. The next picture shows the correct position of the cam for Top Dead Center.
When installing the chain on the cam make sure that the chain slack is on top of the chain and the bottom of the chain is tight. After you install the chain, tensioner and tighten all your bolts, rotate the motor over a few times by hand and then check to make sure the alignments are correct. Sometimes you may be a tooth off and have to redo the alignment.

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