Hey guys i just put my 98' RM 250 back togather, everything went fine this time thankgod. Sometimes it idles fine, then all of a sudden it like revs wide open. The slide isn't stuck, the cables are working fine, and i cleaned the carb out + the floats are working properly. What the heck could be going on here? :bang:
rebuilt top end, bike revs like crazy!
- Thread starter 1998RM250
- Start date
- Jul 16, 2004
- 1,207
- 0
Does it start easily? I would think a crack in the boot as well. I think the idle on that year is 6 turns out from all the way in but just mess with it and see if you can get it to calm down. Did you mess with the idle during the rebuild?
- Thread starter
- #8
I did pull the reeds out to make sure they were okay... Maybe I should take the carb off again and remove them to clean the gasket a little better? Like it revs 3/4 throttle and stays there, doesn't sound like its running right either? Hmmm i wish i could take a video...
- Thread starter
- #9
I just cleaned the reeds, and around the seal then put it all back togather... Ran fine for a minute, then the rev's came up slowly and almost WOT everytime. It also seems to be splooging some oil, and its dripping down on to the front of the pipe. I'd hate to have to tear it all down again, but I don't see what could have gone wrong?
- Thread starter
- #10
I'm thinking maybe the base gasket didnt seal good enough? It kind of looks a little "wet" on the outside around the gasket... The head bolts are a little stripped so I'm thinking tomorrow I will take them off, slide the jug up a bit and silicone the gasket with a tiny bead. I can just use some new fasteners from the hardware store no problem right? Should I apply the silicon on both sides of the gasket as well? Thanks guys, I'm guessing thats where my problem lies...
- Jul 16, 2004
- 1,207
- 0
if your head gasket was shot, you would most likely be spitting coolant everywhere. Is the piston in the correct way? How easy is it to kick over, does it fire right up or do you have to kick it a crap load of times. It sounds like an air leak somewhere though with how the RPM's build then stay there.
Check your air screw as well and see how many turns out it is, make sure your throttle isn't hanging up somewhere, adjust the throttle so there is slack in the cable and see if it still rev's to the moon, if not your cable could be pinched somewhere and holding it open just a little. DO the RPM's build if your turn your bars?
Check your air screw as well and see how many turns out it is, make sure your throttle isn't hanging up somewhere, adjust the throttle so there is slack in the cable and see if it still rev's to the moon, if not your cable could be pinched somewhere and holding it open just a little. DO the RPM's build if your turn your bars?
- Thread starter
- #12
No sign of spitting coolant anywhere, and the piston is in correctly. It has a TON of compression, I can barely kick it over now and starts right up! It idle's a little lower (and almost perfect) until it slightly warms up, then the idle goes to like 3/4 throttle and stays. The cable is free, and turning the bars does nothing! I was thinking it was an air leak in the head gasket, the crank seals and everything was fine before i changed the top end!
eagles22793
Member
- May 25, 2008
- 146
- 0
replace all of the gaskets and make sure everything it tight
- Thread starter
- #14
i took it apart and applied some silicone gasket maker and tightened everything down properly... just waitin on the silicone to dry and see if it helped.The head gasket was new when i put it together yesterday, as well as the o rings. I did notice a little water in the tranny oil so hopefully its just the head gasket leaking.
- Thread starter
- #15
Just fired it up, and same problem still! I just don't get it... The bike seems to be splooging some oil out from the exhaust where it goes into the head, but no thick white smoke or smell of tranny oil burning. What should I do at this point!?!
1998RM250 said:
... and you know this how? Divine intervention, psychic powers, or maybe you had a vison? :coocoo:
Unless you TEST for air leaks you don't know for sure, and what you are describing is a text book air leak problem.
- Thread starter
- #18
What is the best way to test for leaks? I heard spray brake cleaner around the gaskets or something? As soon as it starts revving up I kill it though, I dont want to seize it running lean. Another member suggested using baby power, how does this work?
You're doing too much gasket reusing. Liquid gasket is usually not necessary on a dirt bike engine. Just a fresh gasket on a perfectly clean surface and proper torque is all you need. Did you make sure the base and head nuts were properly torqued? All the old gasket material off? Alot of the time a gasket (like the one on the reed cage) will tear if you seperate it from it's mating suface. You may not see it visually but it draws air in. Even if it is still intact it will have been conformed to the irregularities in the metal it was sealing.
- Thread starter
- #23
Yeah i only tried the silicone as a temp fix, if thats the problem I planned on replacing the gasket along with the reed gasket as well. Today when i pulled the reeds off I noticed some of the new piston has scoring on the intake side, and took a nice pic for you guys. If i run my finger across it, you can feel it on the surface. When i first started the bike, i let it idle on the stand for a couple minutes and the reving started. Do you think the bike could have overheated the piston and caused damage? I was trying to figure out if that would cause the bike to lean out and rev like crazy!
- Thread starter
- #24
ok so i just changed the reed gasket and changed the oil... Same problem, let the bike run for a minute then shut it down when it started to rev up slighty... You can almost feel it leaning out as it warms up by the way it idles. Checked the fresh oil, and it already appears to be milky, what is going on here!?!
2strokerfun
Member
- May 19, 2006
- 1,500
- 1
I've had this happen with a crank seal. Worked find until I rebuilt the top end. After the added pressure from a fresh top end, the seal leaked and the engine revved to the moon. Kill switch wouldn't kill it. Had to kick it in gear and pop the clutch. Piston could now be scarred from lean condition, it's a viscious circle. I popped for new bearings, seals, gaskets and another new piston and just completely redid engine (except for lower rod bearing). Problem solved.
Bottom line: You have an air leak. Either on base gasket, intake, head gasket or crank seal. You also seem to have water mixing in your oil. Have you checked the mating surfaces of the head and cylinder? Something could be warped.
Bottom line: You have an air leak. Either on base gasket, intake, head gasket or crank seal. You also seem to have water mixing in your oil. Have you checked the mating surfaces of the head and cylinder? Something could be warped.
