engine problem

P

peppers

New Member
OK, I let somebody else ride one of my bikes I was not all the way through the break in period and I had a 40 tooth sprocket on there he went a good distance apparently running full throttle the hole way so apparently wile going up a large hill the engine broke down.

Now it wont start and sounds pretty rough, its pretty much fudged right?

It so happens that I happen to have a new crank case if that would help although I lack the knowledge to properly connect the the top and bottom end
 
You "might" be able to just get a new piston and rings and new head and base gaskets. Depends. If you think the motor is toast then take the head and cylinder off and have a look. if the piston looks burned or like the aluminum looks smeared over the rings then the piston is burnt up. Examine the cylinder walls, if their scratched up then a new cylinder is needed.

With a new crank case you might think on getting a new same sized motor and installing it then get into a real good rebuild with the best parts you can get.

http://motorbicycling.com/f13/66cc-engine-tear-down-setting-high-27007.html

This thread is excellent for what to do and what parts are needed. Many times, though, the aftermarket parts from the stock dealers are actually much better that stock. Like the boygofast on eBay exhaust gaskets are the highest quality exhaust gaskets I've seen. Metal cored with real exhaust gasket material. I used up a Dremel sanding drum grinding it to fit the port and that's a good thing. The stock gasket crumbles to bits if you remove the pipe after it has run a while.

With a motor on the bike and one to rebuild you have a safety margin. At least I felt better when I was raceing to have a motor in the car and another wrapped in plastic waiting to be swapped in when needed, sooo easy to do with a China motor as inexpensive as they aredance1
 
yeah, its too bad its biking season, it looks like they are going for 95 shipped on ebay at the moment. not a huge sum but I wish I dint have to piss it away. We should buy spares during the off seasons so we can get better prices
 
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I have a related question, I usually use a larger sprocket but I deiced on 40 for this bike. I would like to know if what the likely cause on the fairly new engine breaking. If it likely due the somebody Redlining the **** out of it during the break in period or due to the extra stress put on the bike by me using and smaller sprocket?

Should a swap out the sprocket with a larger one before I run the new engine? the ability to climb moderate hills is needed for me if the 40 tooth was a mistake I'm gonna need to know before I gotta blot another 95 bucks on a new new engine.
 
If you plan on rebuilding it...I would contact Frank Bowman and get a custom Frank Bowman ring made for it. I convert weedwacker engines into RC aircraft engines and have used Franks rings in other smaller RC 2 strokes as well as my wacker conversions. His rings are the best and he can make rings for almost anything and he is really reasonable on price. Definately worth checking into if you plan to rebuild. Here is Franks email
[email protected]
 
What kind of engine are we talking about? What carb?

Just having a 40T shouldn't hurt anything. Actually that should have helped, because it lowers your revs.
 
on flat ground yes but having the smaller sprocket up hill makes it have to pull harder though right?
 
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peppers said:
on flat ground yes but having the smaller sprocket up hill makes it have to pull harder though right?
Click to expand...

That is correct.
_______________

If your friend was riding at full WOT for a good distance while the engine was still breaking in, that is what caused the failure.
Riding at WOT while an engine is breaking in is actually a very good thing when done in short 5 to 10 second bursts, then running it much slower for a few minutes to let things cool back down. It allows the piston rings to break in properly.
The cool down part is extremely important though because if you don't allow that, you end up with what you have now.
 
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that is what I thought, I just wanted to check since I did something new on this bike, thank you.

BTW I believe I will be attempting a rebuild after a wile, I have enough engine parts so I should be able to cobble together something working out of what I got.
 
wile I am waiting on the new engine I tried putting my the top end from my broken engine onto my new crank case and its doing what the broken engine was doing. both the piston and cylinder looks ok but its would seem I am not good at identifying a good piston. I want to try getting a new piston and put it on there and see how it goes so I guess I will.
 
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