Avanti supersport 65 cc kit problems


My friend just got a 65 cc kit for his avanti, and I installed it for him, It goes slower than before, and it uses the same carb, There is also a base gasket leak, and it stalls all the time. WHY doesnt it go any faster???

And when I go up a hill, it makes a clunk noise, and stops.

Re: Avanti supersport 65 cc kit problems

the clunk noise may be a pre lockup noise before the engine seizes, you shouldnt know whether it is slower than before because it means your not breaking the motor in( which is why it may be slower) you should be running half throttle until its broken in and adding extra oil to the mix, mileage for break-in varies from person to person but I'd say a minimum of 50 miles before you go full throttle some recomend up to 600 miles. Rog

Re: Avanti supersport 65 cc kit problems

Well, on my 79 maxi, when I installed a 70cc kit, it immediately had SO MUCH POWER! I broke it in for the 1st 300 mi at under 1/2 thotltle. It doesnt even accelerate with better power. And the machining quallity looks like garbage, the milling of the bottom of the cyl looks uneven causing a vaccum leak at the base.

Re: Avanti supersport 65 cc kit problems

Ok I know you two are busy brainstorming but did you ever stop to think that maybe you installed it wrong and maybe the kit is defective, that could be it to. Why don't you try re-installing or just take the kit off and seal all leaks and tune up the bike before hand. Eliminate the complexity first. just an idea!

Re: Avanti supersport 65 cc kit problems

Well, the bike only has 200 miles, and u cant really screw up an install, it only goes one way

Re: Avanti supersport 65 cc kit problems

Where did you get the 65cc kit? I had the 65cc kit put on by Steve's Mopeds in DuMont NJ. I have had problems with the clutch lockup like others but the engine is running fine. The cylinder I got I was told came direct from Avanti. Also I had an AMAL carburetor put on mine. I can say that TOP SPEED has not increased on the flat ground but has significantly increased going down hill...I blame the lack of increase in Top Speed due to the fact that although the cylinder is bigger and I have a better carburetor that the Stock Pipe is the limiting factor on Top Speed. If you take the stock pipe apart you will see it is very convuluted. It looks like a performance pipe from the outside but is anything but that when you investigate the inside...I'm hoping a pipe will be out for it by next spring...Also regarding speed...Although my top speed has not increased take off and pickup to top speed has improved dramatically and the engine is very torquey now (Another reason I think the top speed limit is due to the pipe)...Only downside is that the 65cc cylinder has made the bike extremely BUZZY (Lots of vibration)...

Re: Avanti supersport 65 cc kit problems

Thanks for the info Dave!. I got the kit from andy's cycle (half hour from steves), but it uses the same carb. I found out the problem, the base gasket was leaking. As far as you trans goes, i think the added power messes it up, because mine makes that clunk, but I can get it to run again.

Re: Avanti supersport 65 cc kit problems


I just got the Avanti 65cc kit from Andy's also, and am using the old stock carb..... their repairman put the kit in for me... I got my bike home and rode it for 100 miles and saw no increase in power...and, everytime I went uphill the motor would overheat and konk out.... but now I have found out the problem..I know he meant well, but he put a hotter sparkplug in my motor and it was causing it to overheat.... I went to an autoparts store and found a colder NGK B7HS plug.... I am still mixing in extra oil and trying not to run it at full throttle.... so far on my long morning work commutes I am getting about a 5 mile an hour increase on the flats to about 40mph and downhill she can go up to 50mph... I've also got nearly 5 ounces of oil to gallon just during this break-in period..I am still keeping the throttle down and hope that after the break-in I can make the mix leaner and the motor performance gets even better.... At first, I was very unhappy with the kit, thinking that my motor might meltdown....but now with the colder plug it seems that the bike is getting quicker....perhaps a bigger carb is next ??? :)

I dont believe it is 65 cc's

Yeah, i measured the piston, and it is NOT a 42 mm. I think that andy;s is selling this kit, but it really isnt a 65cc kit. In fact, the old and new cylander look alike, except for the fact that the new one has a bigger intake port. I think there should be SOME improvement with a motor 15 cc's bigger, and you should notice this power immediately.

On my puch, when I installed the 70 cc kit, I barely touched the thottle and had SO much more power. ON the avanti, there should be some notice of power, but it feels slower than before.

Re: I dont believe it is 65 cc's

Ron Brown /


Do the pistons interchange?


Re: I dont believe it is 65 cc's

Havent tried yet, but they are within close tolerences of each other, about 1mm. I think only the new one is ported, but that is a lie, it isnt 65 cc then.

Re: I dont believe it is 65 cc's

This is just ball-park Anthony,but I think I figured my 60cckit would be about 1 and7/8ths bore compared to my 50cc which is approx. 1 and 3/8ths bore.So the difference in piston size from a 50cc to a 65cc should be very noticeable,I would think.

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