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View Full Version : I blow up top ends like its my job


200xkwit
10-24-2005, 07:57 PM
well here I am sicker then ((Don't Bypass the Word Filter!)) hanging around and I thought id take a look at my blow head gasket on my 200x motor I pull earlier in the month. I break it down and find the blow head gasket I knew was there and then I see rust all on the piston and the piston was slightly seized in there. I mean theres not even 10 hours on this thing. I blew the gasket in the middle of a race because my clutch went (it was horrible to begin with) and I was in 3rd gear pinned and the motor got reved sky high. I dont understand it though besides the clutch the bike was running mint. I think its got to be the carb with a lean setting. my main jett is a 105 I think, everyone tells me that its too small for the motor. I have uni intake/exhaust/max bore high compression piston and I run race gas. One thing I did notice tho was theres small amounts if no carbon deposits on the piston top. I dont know what to make of all these lost top ends. this is got to be my 5th :wondering
Yamahauler
10-24-2005, 08:04 PM
What did your plug look like? You should have done some plug chops to see how it was running.
bigredhead
10-24-2005, 08:21 PM
Not even 10 hours ?

and this is your 5th ???

I think you need to have a proffesional help you out.. or find another shop if you are having the work done. like.. whoa..

Are you breaking in the new motor properly ? how many hours do you need to run a new piston in ? Were the valves ticking ? etc...
Tri-ZNate
10-24-2005, 08:25 PM
how high of a compression piston is it? Maybe its too much if your blowing you head gasket out
xman23
10-25-2005, 10:00 AM
you only have a 105 jet, dont they come stock with a 108 well thats what my 84 200x had on it, but now i put a pipe and **** on it and have a 115
200xkwit
10-26-2005, 12:05 PM
the carbs got to be set really lean or somthin. the thing is tho when i do plug chops and check the plug and everything its always good nice tan color no white spots or nothin
Motoboy
10-26-2005, 12:19 PM
I had a CR125 that went through top-ends like that, it turned out to be an slightly "egg-shaped" cylinder (It was new from the factory that way).

It would run perfect then POOF......went through half a dozen top-ends before finding the problem.
Rm250RF900R
10-26-2005, 12:21 PM
Do you break it in correctly? Or do you go like a bat out of hell the first day you ride it?
OldSchoolin86
10-26-2005, 03:01 PM
Do you break it in correctly? Or do you go like a bat out of hell the first day you ride it?
Even so he should get more then 10hrs
YAMAHA_Jim
10-26-2005, 05:14 PM
Sry to hear about your bad luck. I guess some people have better luck than others.I havent blown a top end since I was 14 yrs old(29 now). That was on a 1984 rm 80. It blew up while I was in the air.WHen it locked up the bike flipped frontwards instantly and I had a spectacular crash.lol Since then I've raced a KDX200,KX250,owned a few sleds,Tri-Z's and Blasters and have ridden them for yrs without any motor problems.Just recently I replaced the base gasket on my trailriding blaster.I blew the base gasket over the summer and rode it as is for a few months in mud and fairly deep water and she kept right on running.I only fixed it b/c of the slight power loss from the gasket leaking.When I had the top end off I didnt notice any damage either. Been about a month since I installed the new base and head gasket and the blaster still runs like new.
Solid Snake
10-26-2005, 05:21 PM
I had a CR125 that went through top-ends like that, it turned out to be an slightly "egg-shaped" cylinder (It was new from the factory that way).

It would run perfect then POOF......went through half a dozen top-ends before finding the problem.



You may want to see if your problem is similar to this. The gasket surface may have become slightly warped over time and that would definately cause blown gaskets. Next time you have the top end off take it to a shop and have them check for any warpage on the gasket surface of the jug and the head (the two surfaces that squeeze the gasket) and if there is any they can hone it into spec for you.
TeamGeek6
10-26-2005, 09:08 PM
Super high revs make the cylinder pressure go very high, might have been too much for the stock design, but ill bet theres some warpage too, especially since its gone out before. Detonation can do it too.

Not hard to fix with sandpaper and plate glass if its not too severe.