Dirt Bike Repair & Maintenance Forum

I have a 96 yz250 I bought last year. It needed crank bearings and seals, which I installed successfully, and the bike ran fine. In June this year I started noticing that the idle would be "weak" and my YZ125 would beat it (which didn't seem right) - if I adjusted the idle when is was warm (not hot) it would pick up as much as 2k rpm when it heated, up but when I adjusted it hot it wouldn't idle when restarting the bike until it ran 5 minutes and then it was a very high idle. It acts like a vacuum leak! I cleaned the carburetor and replaced the plug with no difference. I sprayed carb. cleaner around the intake & cylinder base with no change. It may be the crank seals, but I don't know how to check them. Any help would be appreciated

Thanks
Rick  

Check your reed valve for cracks.  
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Ruff!

personnally i don't run a idle. idles for people that don't twist the throttle.    i would check ur compression and start with a fresh plug. take sum plug readings at different throttle positions. is it jetted correctly? what fuel are u using?

if ur crank seals are still suspect, then look at them, if u see leakage, then there you go, but i doubt thats ur problem. start with the basics. compression, fuel, jetting with plug readings and so on.  

The plug reading is going to be lean. If the boot or reed has a crack then there you go on high idle. Unless he is running 50:1 the mix won't matter. And where does compression come in?
And i run a idle and all woods rideres i know because unless you opinion of woods is a few acres of back yard then when you get tight in there you can't just stay on the gas! And it comes in handy on deep down hill around trees ect..  
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Ruff!

never ran an idle never will. we ride woods for hours and hours tight, muckey, single track stuff with roots rocks water holes hillclimbs u name it.

Just prefrence i guess.  it literally takes 5-10 minutes to do a compression check on a 2 stroke. and with half the guys on this forum buying older bikes and then complaining about splooge and idle and throttle response problems and not realizing that there compression is 50-60 #'s off its like chasing ur tail. i always start with a test whenever i suspect a problem that i can't air screw out. its just my nature.

two stroke motors need compression to survive, its how they draw in fuel (not only through the carb, but then up through the ports as well,) combust it and then push it out.

yeah u can get any bike to run with weak compression after make countless jetting changes, but Y?

Whoa......were'd that come from?  

Well, the reed valve is fine. Compression may be an issue - I'll bring home a compression tester tomorow and take a reading.

WOW I didn't mean to start a debate about idle, or not to idle but I guess we all have opinions and different wrist twists.

by the way I don't think a 96 is old - I have a 72 a 73 and 2, 78's - I guess they are old but a 90's bike isn't old.

Thanks again
Rick
(an old timer)  

Thought it was a 06 not 96, My Bust. But the matter remains the same. Tell me how low compression makes for a high idle?
And no need to break down the operation and needs of a 2 stroke for me. The plug is going to be lean as the it's getting to much air. My next Question was going to be where the air/fuel screw is set and did this just start.
AND if you run no idle in REAL tight woods and just clutch and throttle when a idle fits better then compression breaking then i guess that IS prefrence. 2 strokes love to idle ALITTLE and run better when set for it in the woods.
Just my opinion.  
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Ruff!

yzwoods:
Thought it was a 06 not 96, My Bust. But the matter remains the same. Tell me how low compression makes for a high idle?
And no need to break down the operation and needs of a 2 stroke for me. The plug is going to be lean as the it's getting to much air. My next Question was going to be where the air/fuel screw is set and did this just start.
AND if you run no idle in REAL tight woods and just clutch and throttle when a idle fits better then compression breaking then i guess that IS prefrence. 2 strokes love to idle ALITTLE and run better when set for it in the woods.
Just my opinion.

My suggestion for compression test is this.  Why, when u know there is a problem ( he must he's asking for help) why, would u not start with a known compression number??

if the bike is designed to run with 180 #'s compression and he is at 150 (imaginatively) why would u look at the carb first?

in this case he is chasing a hunting idle...it goes up when the bike gets warmer, he says lean condition.....good call......now du u through more fuel at it,  or get the fuel he has to burn more effectively?  because just turning in air screws and increasing jet size is a band aid in my opinion.  

RMC1218:
Well, the reed valve is fine. Compression may be an issue - I'll bring home a compression tester tomorow and take a reading.

WOW I didn't mean to start a debate about idle, or not to idle but I guess we all have opinions and different wrist twists.

by the way I don't think a 96 is old - I have a 72 a 73 and 2, 78's - I guess they are old but a 90's bike isn't old.

Thanks again
Rick
(an old timer)

Ricker, got any pics of ur 70's machines? post em up. i'd like to see em. are they nice?  

and I'm right there with u I have a 97. great bike.




I hillclimb it at the races, ice race it, woods ride it W/E!!  

 

As i said, I thought it was a 06. But regardless, Do you suggest a compression test for a high rev? No. And throwing more fuel at it is not the sugjestion i'm working on. Why would i?
It's a air leak no? And 150 by the way will run fine. And not cause a hi rev. Bad fuel, Air, .  
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Ruff!

We don't mind RMC. Me and ML are cool and its just a part of how we do here. Banter is good when informative. NOW....Whats that PSI??? LOL.
Bet it's within limit.      
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Ruff!

I re-ring at 165.

Woods u wouldn't buy  a 96 without a compression check would u? U wouldn't ride a 250 that can get spanked by a 125 without a compression test would u? u wouldn't throw jets and reeds at a 96 that got spanked by a 125 without a compression test would u??

LOl jk just playing with ya.  

I'll send u my address. 92 should be answering these questions....not me.    

He OWNES the bike. And yes i would, As a top end is easy. Now what say you on the issue at hand? Hi REV!!!!!!! DOH.  
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Ruff!

masterlink:
I re-ring at 165.

Woods u wouldn't buy  a 96 without a compression check would u? U wouldn't ride a 250 that can get spanked by a 125 without a compression test would u? u wouldn't throw jets and reeds at a 96 that got spanked by a 125 without a compression test would u??

LOl jk just playing with ya.  

I'll send u my address. 92 should be answering these questions....not me.  

Okay, I'm here!
Oh darn, looks like you have answered all the questions.  
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