My 1p39qmb Quest for... More... POWER!!!  By  lykos23 (Read 6,586 times)

The Things I've Learned:

Restrictions: There were no restrictions on my bike, but I hear about a lot of them being all over the place. First there's something in the carb that restricts fuel deliver, there are restrictions in the airbox that reduce the air you take in reducing speed, then there's a washer in the variator preventing the belt from riding high, then there can be restrictions in the exhaust such as a washer welded on to prevent you from reaching your top speed. Remember to try to stay within the confines of the law when thinking about your speed. Illinois requires a class L license for anything that goes over 30mph.

Valves: Valve Adjustment is crucial! When you get your scooter initially the valves are extremely tight more than likely and this causes plenty of problems, making your scooter hard to start and reducing performance while making it unable to maintain idle, and dying, etc.! Adjust your valves to .003 in, .004 out if you have a scooter like mine.

Oil: Oil is as important as it is in a car, you can't have too little, and too much is bad too. When you first get your bike you need to use that dinosaur based oil and after 2k miles or so it's allowable to use synthetic oil.

Gear Oil: Gear Oil is important too! Without it you risk seizing your engine or something I guess. High quality gear oil will also increase your performance a bit over the stock junk that comes inside your scooter from China.

Idle Adjustment: You want to have your idle high enough that your headlights don't dim and low enough that your back tire doesn't spin. It's a difficult balancing act for a newb, and your A/F adjustment will mess with your idle too if it's off by too much.

A/F Adjustment: Your air fuel ratio is apparently crucial to the engine. Too much fuel won't do much damage unless you're off by quite a bit, but too much air makes your engine run too hot risking all sorts of damage. If you have a freeflow filter you will not be able to adjust the A/F properly if you have a stock idle jet, you will need to restrict your air intake enough that you're not getting too much air. An idle jet of 38 should fix this.

Air Filter: Your air filter is an airbox when your scooter comes stock. This airbox is designed entirely to restrict air in a very specific way so as not to deliver too much air to the scooter. It is there to prevent damage, but it can also reduce performance in some cases, such as after installing a big bore kit. My airbox was damaged which caused me to have to replace it with a freeflow filter which was cheaper than replacing the stock box. The freeflow filter gave me nothing but trouble until my problems were identified at the cycle mechanic. My filter had to be taped in order to resemble the restrictions on the airbox so as not to deliver too much air during idle. Until I got my 38 jet I had to run my scooter with a ghetto-taped filter just in order to run.

The Battery: You want a decent sized battery. A flatout replacement for your stock is NOT good enough! You need something with more amperage, learn from my mistake. I can't even have a stereo plugged in without the battery draining on the way to the store. This also has to do with your stator being able to supply enough voltage and your idle being high enough not to discharge the battery.

Clutch Springs: Clutch springs come in three non-uniform varieties from each brand. there are 1k, 1.5k, and 2k, plus others. Each number represents the additional RPMs that your clutch should engage at. I installed 2k springs in my clutch so that my takeoff acceleration would be much better, the only thing it restricts is how slow you can go. Too tight of springs may mean you can only go 10mph or higher. If you want to keep your low end speeds and you're satisfied with your takeoff then there isn't really a need to change them. I just really like my better takeoff.

Variator Weights: I've learned a lot from messing around with my variator weights, and I would highly reccomend you buy yourself a kit of sorts to test out the different combinations until you find your perfect match. These really depend on your location, the roads you take, your weight, and other variables such as how fast you want your topend to be versus how fast you want your acceleration. There are Rollers and Sliders, stock scooters normally come with rollers, and they come in a variety of weights. Sliders, especially Dr. Pulley sliders, advertise higher topend and faster acceleration in general, however you need to add an additional 1g to equal the same weight of rollers. You will need a gram scale in order to weigh the ones that come with your scoot. The ones that came in mine were 6.5g. I myself found the perfect balance at 6.5g in the form of sliders, which is the equivalent of 5.5g rollers. Your variator weights are crucial in finding your optimal performance.

CDI: I don't know much about the CDI, but I do know that stock ones often come with a restriction which causes your scooter to be unable to reach its highest rpms. A high performance cdi removes this restriction and offers a better rpm range for better acceleration and top speed.

Re-Jetting: Rejetting is difficult and time consuming and requires you to take apart your carburetor multiple times. First you have to buy a fist full of sparkplugs, a range of sizes of jets, then you have to do what is called a plug chop every time you install a new jet. This indicates whether you go higher or lower in jet number. My main jet was due to the free flow filter, my idle jet is 38, again, due to the free flow filter. My stock should have been somewhere around 78 main and 32-35 idle. Rejetting to the perfect size is very much worth the trouble because you chance getting better performance, gas mileage, and longevity out of your scooter. Having the wrong jet size can severely impact performance and longevity.

PAIR system: There's an emissions system on a lot of scooters that brings fresh air into the exhaust to help with emissions. Get rid of it! If you want performance you're going to have to plug the extra nipple going off of your intake manifold and remove the whole thing that attaches to your valve head. Warning: You will need a replacement valve head which does not offer the PAIR system in order for this to work properly.

BBK: A Big Bore Kit often comes with an engine Cylinder and Piston (plus piston rings, gaskets, etc.) and the goal of the Big Bore Kit is to up the displacement of your engine. A 44mm BBK is 63cc, a 47mm BBK is 72cc, and a 50mm BBK is 81cc. These take a lot of work to install, and on my scooter I had to completely remove the engine from the frame just to access the parts necessary. With more CCs of fuel and air comes more power and performance. Depending on what you're after I'd say a BBK is totally worth the trouble. Once a BBK is identified (such as with the Secret 60) or installed, upjetting will be absolutely required. All BBKs with a free flow filter will require jets through just to be safe.

Gears: Gears effect the rpms in which your tire turns at what speed. In order to up gear you will have to first decide whether you want better acceleration or higher top speed and then you will have a variety of gear sets to choose from. The 16/50 gear set offered by scrappydogscooters offers a 6-10mph increase with only a tiny bit of reduced acceleration. The small shaft which comes in the gear set will have to have your original gear pressed on to it at a Machine Shop, DIY methods seldom work, if at all.

P! Sticker: Possibly more crucial than a gremlin bell, this sticker is from the Anime show FLCL and stands for "the pillows" an amazing Japanese rock band.

With my gears freshly installed my quest for more power is finally complete, (everything after this is just a bonus ;D). It took 5 months of frequent working on my scooter, but I've finally overcome that wall of 50mph (when my initial goal was 35mph!). I've come a long way and learned a lot and I owe it all to you, members of scootdawg.proboards/scootdawg.net/ItIsTheRide. Thank you all.


Take care and ride safely dear friends.
Yours, Garit.

Great write-up. It's all consolidated so someone else can find it.

Good stuff. I had to learn most of this the hard way and many hours looking everywhere for bits and pieces too.

Great and informative post right here! Just what I had been looking for. I just took delivery of a Bashan (Peace Powersports) 1p39qmb (63cc) that I swapped the stock airbox out for a free flow, replaced the non serviceable carb with an aftermarket unit and popped in a # main jet, but left the idle jet stock. I have been experiencing stalling at takeoffs and had been fiddling with a/f alot. Next step seems to be to replace the idle jet..
#38 ... Awesome post! Thanks
Sent from my SGH-M919 using proboards

Me too... I had a lot to just figure out on my own, like what the PAIR system was, and how and where to get replacement bolts, the importance of gaskets, and even brake bleeding. It was a long hard journey, but it was worth it!


Thanks, Rob. That means a lot to me. I feel like I've finally earned my place in the "Hardcore" group on scootdawg.net.

I've probably put just over $500 and LOTS of hours of work into my scooter. It averages out to probably a half hour per day since I got it, especially with that one week where I was changing my variator weights like twice a day. The most expensive things were probably... the BBK, the performance exhaust, and fixing the kickstarter. If I had to do it all again I'd be able to probably just make a big order and install all the parts in a matter of days rather than spread out over time like I've done; that would really cut the work down.

It would be pretty sweet to ride with someone, let alone a good friend from these awesome scooter forums.


Good luck! I know that I had severe problems with my stock idle jet and the A/F adjustment would do nothing about it. Alley would probably recommend a #35 unless your displacement is around 180cc or something but it really helped me. Because of the A/F screw all it really does is bump up the fuel consumption a bit, but in my case the extra fuel compensated for all the extra air I was getting.

You could probably get away with just a longer #35, but I like my #38, it kinda makes my bike unique, haha. In any case I'm glad you found some useful information here .


Thanks, Hank. That means a lot coming from you. I've learned a lot in these past few months, and you were there helping me all along the way.

Does this mean I finally get my metric lightsaber wrench set? ;D

Wow, I'm very impressed and a bit jealous of your knowledge... old grasshopper

Thanks for putting this in one thread for us. I might access this info someday when I begin wrenching on my scoot.