what in the sam hell!

[yeppimcody]

:mad: so i just rebuilt my 250r r and have been babying it to break in my piston and rings. well i was going down the road half throttel and the b*^#& cesed once agin. i pushed it home now theres no compresion! last time it leand out but this time the plugs black and wet as all hell? any in put

[yeppimcody]

there is a tube that comes out like a breather tube between the carb and the intake manifold. what is this for there is a cap on it should this be there?

[Yamaha_Rules69]

Is the tube coming from the intake manifold? If so, it sounds to me like a spot for a boost bottle. What year is your 250R would be very helpful in trying to help you out.

[Twilight]

what oil, what mix ration?

[yeppimcody]

its a 84 air cooled ans i was running honda premix oil at 32:1

[Yamaha_Rules69]

I would have run it richer at like 20:1 for break in, but somehow I dont think that was the problem. How/where did the top end get rebuilt? Did you do any measurements to be sure the piston/rings and bore were all within specs? Sounds to me like it could be a tolerance issue. Also, have you taken the top end back off since this happened? It could also be a bottom end bearring/seal failure that caused this. Take the top end off and tell what you find out.

[yeppimcody]

i had the top end taken to competition cycle and bored out and they orded and fitted piston for me i put back to gether. i also flused the hole bottem end. i haven takin it of yet it was still hot when i posted this

[DeePa]

if there was a boost bottle port on the intake....did you put a boost bootle on that port? thatd be a nice huge air leak for you...

[AutoXer]

Looking at your old piston I would have took the lower-end apart

[Twilight]

did u do an air leak before u ran it?

[yeppimcody]

i had my buddy do one and he said as far as he could tell ther was no air leak

[yeppimcody]

and no i dint put a boost bottel on this port due to the fact that when i bought it there was no bottle on it justr the cap. thats what i figured but by looking at the plug it dint lean out witch makes me wonder if ther was a air leak there

[hoser]

WOW that sux!

Any pictures?

Any updates their is plenty of things that could have happen but first it would be nice to know exactly what happen to your engine currently, what do you mean when you say you fused the whole bottom end?

Their should be no open holes between the carb and the engine.

I have a 83 ATC250R have had it since new if you need some help with yours just let me know.

Currently I am running a 300 kit on mine
http://www.pilotodyssey.com/phpBB2/viewtopic.php?t=5403

Be sure to check out Twilight's Buyer Seller Feedback !

[yeppimcody]

okay well i belive that my rings dint seat because well thats what my dad says. and theres more compreson then last time i mean a lot more. but i cant get the top off bc i sealed the s*$& out of it with Great Stuff seler. and tips to get this apart?? then i can get some pics posted of every thing. i also ment to say flushed*** to get all the ols piston shavings out.

[hoser]

okay well i belive that my rings dint seat because well thats what my dad says. and theres more compreson then last time i mean a lot more. but i cant get the top off bc i sealed the s*$& out of it with Great Stuff seler. and tips to get this apart?? then i can get some pics posted of every thing. i also ment to say flushed*** to get all the ols piston shavings out.

What was your compression after the rebuild before you started it for the first time?
What is the current compression?

What is great stuff sealer?

Why did you use sealer, does it say in the manual to use sealer if it does I must have missed it.

No doubt something will soften the sealer you used, brake cleaner or carb cleaner?

What was your plans to get it apart when you applied the sealer?

[Yamaha_Rules69]

^ Hoser, really interesting info on your post at that website! Thanks for sharing! Cody, you never want to use great stuff sealer on a top end of ANY engine! I have experience with that stuff, and I wouldnt really recommend it for anything other than a torn clutch cover gasket, and a small amount at that.Also, anytime a piston breaks and falls into the crankcase, it is time for a tear down (split cases) You learn from your mistakes, and become better afterward. If you need some advice, post here, and we will try to help you out. Good luck!

[yeppimcody]

yeaa thanks yamaha i talked to my small engin teacher at school and he said thats what i should use it on the had bc the instrustions that came with it said use a good amount on the head gasket

[hoser]

yeaa thanks yamaha i talked to my small engin teacher at school and he said thats what i should use it on the had bc the instrustions that came with it said use a good amount on the head gasket

Any updates?

[atcrider1]

could be a carb problem, i recently rebuilt an 87 vmax 540 with new 30 over wiseco pistons and melted a hole it one the first time i took it out due to a plugged power jet, in the 3 days it took me to put the motor together, tune it in and blow it up, wiseco discontinued all oversized pistons for vmax's

[hoser]

could be a carb problem, i recently rebuilt an 87 vmax 540 with new 30 over wiseco pistons and melted a hole it one the first time i took it out due to a plugged power jet, in the 3 days it took me to put the motor together, tune it in and blow it up, wiseco discontinued all oversized pistons for vmax's

Is their any other brand pistons still available for that engine? I use to have a 540 but used the Yamahaha pistons.