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A couple problems with my 03 CR 250 engine rebuild

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I'm currently running in to two problems as I'm rebuilding the engine. The first, and more critical, is that this engine holds no pressure. When I hook up my air compressor at a regulated 8 psi through the spark plug hole, the air just comes pouring out in the valley between the reed intake and the cylinder. As this is my first rebuild, I'm looking for insight as to what can cause this. I've attempted to seal it up with some black gasket maker, but I'm not sure if this is sufficient.

 

Secondly, I'm having trouble installing all the shifter components. The pin that fits in the drum seems too long. When I try to install that little star piece, which mates to the pin via a little cutout, it always bolts in cock-eyed since the pin is so long. I've measured it up with a caliper, and there is no way I'm not installing the pin far enough; it's in the drum as far as it will go. Unless that little star piece is supposed to follow an eccentric path, I'm not sure how you could ever install it flush into the drum.

 

Thanks for the help in advance!

 

 

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Have you read the post on how to pressure test your two stroke? It explains it pretty clear by plugging the exhaust port and adding pressure in the intake with the plug in to test. Check it out if not, there is some good info and instruction there. Good luck. Sorry I can't help out with your shifter components.

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I have read that article. I think that applying pressure through the spark plug bore should achieve the same thing as doing it through the intake. I mistakenly assumed that new reeds would hold the pressure without plugging the intake boot, but this is certainly not the case. As I only have one adjustable freeze plug, I have to wait until tomorrow to pick up an additional one to see if that old leak persists. I'm mostly interested in if you guys would trust permatex black to seal up the case leak.

 

The shifter stuff is driving me crazy. I can't see what I'm doing wrong. The drum pin physically cannot be driven into the drum further. I'm really confused by this, as I'm not even sure where the stopper arm wheel rests on the drum center (the star piece which won't line up). I really need some help on this one.

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I've attached some photos. The hole in the center gasket is pretty clear, and if possible I'd like to not split the cases again! I'm not sure how this could have happened to be honest.

 

With the pin fully inserted into the shift drum, it sticks out past the bearing race about 1.6 mm. When the pin isn't in there, the star shifter fits great and runs smooth in that bearing, but there is no way it can seat with the pin sticking out beyond the race. The only thing I can think of is that I accidently grabbed a different pin, but that seems extremely unlikely.

gasket leak.JPG

star.JPG

crooked star.JPG

pin.JPG

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Hmmm, how would you be able to grab the wrong star piece? Do you have more than 1 shifter setup?

 

I put mine together today and it fit nicely. But you HAVE to make sure it sits in the slot of the star device, otherwise it will be bent over to one side.

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I think I have the pin issue figured out. Somehow, I was left with only one pin and I mistakenly assumed it belonged to the shift drum. As it turns out, that one is for the RC valve, which I had totally forgotten about. So that's the good news, and I have a new pin on the way.

 

What are your thoughts on the case? Can everyone see where the green gasket just seems to disappear in the above picture? I can either try and seal it up, or split it and install a new center gasket. I like doing things the right way, and I do have a new gasket coming, but I'll have to wait at least a week for the crankshaft installer (tusk) to arrive in the mail. Am I OK to reuse the base gasket? It's the metal 05-07 style, and has been torqued down twice, but obviously the engine has never been started.

 

Thanks!

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I think I have the pin issue figured out. Somehow, I was left with only one pin and I mistakenly assumed it belonged to the shift drum. As it turns out, that one is for the RC valve, which I had totally forgotten about. So that's the good news, and I have a new pin on the way.

 

What are your thoughts on the case? Can everyone see where the green gasket just seems to disappear in the above picture? I can either try and seal it up, or split it and install a new center gasket. I like doing things the right way, and I do have a new gasket coming, but I'll have to wait at least a week for the crankshaft installer (tusk) to arrive in the mail. Am I OK to reuse the base gasket? It's the metal 05-07 style, and has been torqued down twice, but obviously the engine has never been started.

 

Thanks!

 

use hondabond or yamabond on the seams of the case and it should seal your gasket surface. 

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