1998 rm 250 running rich - Off-Road Forums & Discussion Groups
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post #1 of (permalink) Old 09-02-2007, 04:19 PM
white93pgtze
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1998 rm 250 running rich

ok guys heres one thats puzzles me i have a 98 rm 250 i just put a new piston and rings in it the bore is clean with gouges ,the reeds are barley hanging open like the top one like 1 mm at one corner no frays or cracks or chips off them..and my bike is running burn your eyes rich the carb breathers and overflows are not clogged and spark it fine the power is good all the way to the powerband then the power valve sticks once in a great while and the two bearings are new in those dont know why it sticks?i mix my gas 32 to 1 my air screw is 1.5 turns out the jets are stock if i let it idle for 1 min the spark plug done fouled to hell .wat could my problem be help!!!!!
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post #2 of (permalink) Old 09-03-2007, 12:40 AM
 
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Red face Time to change your plug

Try a sparkplug one range hotter. If it improves the issue without curing it ... then go another one up, (hotter) ... to a maximum of two steps upward.

Check out the post on "Choosing a Spark Plug - Fact vs. Fiction" in the post https://forums.off-road.com/dirtbike-...sprockets.html
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post #3 of (permalink) Old 09-03-2007, 12:42 PM
white93pgtze
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i have a br9es in it now and i took my powervalve apart and its all gummed up with two strok oil all burn to it imm clean it off but i think the new reeds fixed it the top of the piston shoud be dry right?
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post #4 of (permalink) Old 09-04-2007, 02:39 AM
 
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Cool

Those reeds should be closed???? ... In essence they are a one way valve to stop your lovely fuel mixture being pushed back out of the carb with aggressive inlet port timing / overlap, robbing you of your bottom end, whilst making the bike run leaner, (and oilier!).
As a test you could try and turn them around, however from the sounds of things they are poked and even that would be a temporary reprieve, as they won't last. Replace them!

Back to your plug tho';

You say you're currently using an NGK BR9ES, yet the recommended plug for your bike is a BPR8ES, (note the additional P in the part no.), which is a PROJECTED NOSE PLUG, and one range HOTTER than what you have in!!! ... try one, and as I previosly recommended, if this improves the problem, but doesn't cure it, the go to a BRP7ES, (even hotter plug)

Check the plugs porcelain colour after changing. If it's brown stay where you are as plugs go ... If it's white, and/or the motor shows any sign of pinging / detonation, then go colder. If it's black, and/or oily / fouled, then go hotter

As to your powervalve ... You should be servicing, (cleaning), your power valve, along with decoking your pipe on a fairly regular basis anyway!
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post #5 of (permalink) Old 09-05-2007, 10:47 AM
white93pgtze
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well im kinda new to this whole 2 stroke with a power valve thing all my bikes never had a powervalve how do i clean it on a regular basis and decoke my pipe ? and on the plug your saying that my plug is still to cool because i had a br8es and a br9es and they both turned black and oily and ended up fouling out so your saying i should start with a bpr8es? and then go to a bpr7es how long u thing i should ride it before i check them ? and the posilin color on the 8 and 9 is still white
post #6 of (permalink) Old 09-05-2007, 01:13 PM
white93pgtze
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well after examining my powervalve further it semm like the two side rotating ports jam up and the lager valve trys to move upward to open is there suposed to be play between the bore and the power valve ? it moves pretty good side to side?
post #7 of (permalink) Old 09-06-2007, 01:59 AM
 
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Talking BPR8ES not a BR8ES

BPR8ES not a BR8ES !!!! - Note the P ... It's supposed to be a projected nose plug .
As to reading your plug ... warm up your bike, take it for a ride and kill the motor immediatelly thereafter, (ie don't let it idle after your ride), then remove your plug and have a look .

With respect to your powervalve, clearly there should be a little "play" to facilitate it's movement, however it shouldn't be able to flop around, (which it seems your does? ), as then it will stick as it twists ... I have heard of people shimming them, but I would suggest replacement at this stage.

With respect to cleaning your engine / associated parts ...
I use pump fuel and a paint brush that I've cut the bristles shorter.
With respect to "two smoke" pipes ... remove the pipe / expansion box from the bike, and flush it out with a solvent, (kerosene or pump fuel).
Then mix up a solution of carbolic acid, (drain cleaner), block off one side of the pipe and pour it in ... leave it for a few minutes, drain and repeat.

WEAR RUBBER GLOVES, DO THIS OUTSIDE AND BE CAREFUL ... CARBOLIC ACID IS DANGEROUS!!!
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post #8 of (permalink) Old 09-06-2007, 06:36 PM
white93pgtze
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ok got all that the power valve has about 2 to 4 mm of play where or how can i shim the valve?
post #9 of (permalink) Old 09-07-2007, 06:27 AM
 
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Unhappy

I don't think you can shim something that is that @#$% - ed
... but then I can't see it? ...
You need to assess the damage and see what has worn ... the guides or the valve itself, (or both?), of which methinks your best bet would be to pop into an engineering shop and get their advice on the prob?
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post #10 of (permalink) Old 09-08-2007, 11:56 AM
white93pgtze
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ok the suzuki place said everything is still in spec.if i coat everything with wd40 it all moves smooth no grabs just smooth including the return my question is wat happens when i start it an the wd40 burns off?i got a bpr8es to run in it wat do u use to lubricate the powervalve ?will the engine alow some 2stroke oil threw the engine to the powervalve to lubricate it ? wat from the factory lubricates this system?
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