New Main Jet Lifan LF200GY-5

[Andi]

I purchased a few different sizes of main jets from Bruce at EJ Cycles, because I just couldn't find the right setting for my carburetor.

I changed the needle up and down and played around with the adjustment screw, but nothing worked. It either ran good at low rpm or at high rpm no happy medium.

My LF200GY-5 came with the Keihin - Sheng Way 30mm carb and a 98 Main Jet Size. I now switched to a 105 Main Jet and have taken it for a good few rides. It runs alot better now almost perfect, I checked the sparkplug and for the first time it had the proper appearance, light brown inside, but maybe a little too much black sud around the outer edge by the threading.

I'm still getting a slight pinging, but only when the engine is well hot. It seems to happen around 4000 rpm or less, when I'm opening up the throttle to get the bike to accelerate, used to be really bad with the smaller jet.

So based on that analysis I figured I might just want to try the 110 Main Jet (or try a higher octane?). I also find it get's really hot, more than it should although not quiet as bad as before (maybe I'm just paranoid though). I was wondering if I should maybe do the exhaust mod I read about on the forum, might allow it to run a little cooler also.

Anybody have any other suggestions?



The vibration has gotten alot worse too, can really notice it after a long ride. I think part of it is the rear fender and license plate combo as it is an add on extending from the end of the frame. I'm probably going to run two braces from the license plate bolts to a bolting point in front of the rear end of the frame, to act like a gusset. I figured I will use some 3/8" or 1/2" OD Stainless Tubing, flatten the ends in a vise and the drill a hole into the flattened ends, kind of like a truck mirror bracket.

The other source I think is from the skid plate, might look at changing the rubber bumbers and maybe even add some by the front underside of the engine. There is nothing to prevent vibration between the mounting point in front and the rubber bumpers and mounting point in the rear. I figured if I get some small rubber bumpers with threaded hole on one end, I'll match up the height to the space between the engine and skid plate to then bolt the rubbers onto the skid plate.

What do you all think??

Andi

[czowner]

Andi,
How many miles (of km's) has your bike done? I had similar slight pinging (pinking for those in the UK) when it was brand new, now at 2500km it's virtually dissapeared. It's also a sign of a weak mixture, with a 30mm carb I'd try the 110 jet. My 250 has a 27mm carb, a 107 main jet and the needle's on it's highest setting.

Jonathan

[ob1]

Have you done any adjustments to the fuel/air screw since rejetting? Might need to look there first.

After that, I think I would try higher octane fuel first, its an easy fix and a good tool to learn from.

If HO fuel eliminates the ping, you might go up slightly on the jet and return to regular fuel.

If HO fuel doesnt eliminate the ping, maybe a bigger jump in jet size is needed.

[Andi]

Thanks for the feedback guys, I was wondering what other sized carburetors these bikes come with. I think 30mm is large for a 200cc and the 98 jet is small for the carb, you find that size more on the 250cc bikes and then with a 120 or slighty larger jet. I figured 28mm would have been a more standard size carb for a 200cc.

I've got 1100 km on the bike now and I'm running with the DR8EA NGK Sparkplug as I'm mostly commuting (not off roading) with the bike, I figured it's running hot enough.

I've set the needle at the factory setting in the center and the adjustment screw also at the factory 1 3/4 turns out. Figured I would first try the jets with the factory setting and then finetune from there with the best performing jet.

The local bike shops don't recommend using the premium (high octane) fuel as it has additives which are not really desirable for these small bike engines. I'm going to check if I can find out a little more about that, before using it.

In the meantime I'm going to put on the 110 main jet tommrow to see what difference the makes.

Anybody have a suggestion about modifying the stock muffler, I read about drilling the back plate above the outlet pipe what is the best size to start with?

Andi

[Savage]

I did 3/4" and it's awesome!