50cc big bore kit question

[Josh_SLR]

I have a yamaha champ and I was putting a big bore kit on it today and I ran into a problem.

The motor is the same as pw50.

When I installed the kit and started it up and there was a squeaking sound. I tore it back down and the cylinder is not scored and the ring is still in tact. I cleaned it and put it back together and the same thing is still happening.

Does anyone have any thoughts on what this can be.

 

[byke]

That sounds odd. I assume it changes with engine RPM regardless of wheel speed? Have you done a compression test? Did you do any other work at all? Are you pre-mixing, or using the injector?

 

[slydrite]

Did you forget the feed the hamster inside the engine?

 

[Josh_SLR]

Hahaha. The hamster has food and water.

The bike is an oil injection system and all I changed was the cylinder, piston and wrist pin and ring. Oh and with higher rpm the squeak goes away.

 

[07chuck]

Did you use assembly lube on the wrist pin? Did you bleed the oil system?

 

[Stormdragon]

Did you turn the motor over without the piston? Did it move freely?

Was the reason for the big bore kit something involving a top end problem? One that might have left fragged aluminum/bearing bits in the bottom end bearings?

 

[Diezel]

Josh, what big bore kit did you get, and what did it include? I'm assume Piston, Cylinder, and Cylinder Head correct? If so, did it include anything else? Reed's, Reed Cage....

If so there are only a few things a "squeak" could be from.

If I had to guess I would say to check the cylinder and look for ANY scratches.

After that, Inspect the piston rings. I have seen some piston/ring sets that the rings must be installed a certain direction!, and installing them incorrectly leads to noises and the piston not sealing.

 

[Josh_SLR]

How do I bleed the oil injection system?

The kit was the malossi big bore kit and it came with the cylinder, piston, wrist pin and ring for the piston. no reeds or anything else.

 

[jafo]

co worker did the big bore in his applria, the kit ditched the stock oil injection. He was forced go pre mix. You sure you're supposed to stick with the stock oil injection?

from another smoker forum-

When a Big-Bore kit is installed, suddenly the pre-set oil pump supply becomes overmatched by the increased displacement and fuel consumption. Remember the pump is set to be "just enough" for 49cc's worth of fuel per cycle. When that volume increases to 66, 72 or more, there's no longer enough oil to keep things lubricated

 

[Josh_SLR]

co worker did the big bore in his applria, the kit ditched the stock oil injection. He was forced go pre mix. You sure you're supposed to stick with the stock oil injection?

from another smoker forum-

When a Big-Bore kit is installed, suddenly the pre-set oil pump supply becomes overmatched by the increased displacement and fuel consumption. Remember the pump is set to be "just enough" for 49cc's worth of fuel per cycle. When that volume increases to 66, 72 or more, there's no longer enough oil to keep things lubricated

I will try and pre mix the gas and see how it sounds, thanks for the info.

 

[Diezel]

The kit should have had some sort of instructions that say if pre-mix in the gas is needed on top of the oil injection system. OR if you should go to just pre-mix and NO injection system.

And on the wrist pin. Is it a press in, free float, or free float with retainers ?

 

[Josh_SLR]

The wrist pin i pressed in by hand and it has retainer clips.

I will bypass the injection system and do premix and see how that goes.

 

[Ironbutt]

That's called 'squeeked'.. It's probably sacked by now, it'll still work but not as well. Try breaking in the new piston with a 32:1 mix and lean the oil mix out from there..

 

[Phaedrus]

What does it sound like if you kick it over with the kit installed and the spark plug out? How does it feel? Any undue drag?

Are you certain it's not a huge air leak causing a squeak or a whistle?