97 RM 250 Rebuild

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Feb 2, 2001
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#1
When I bought this bike in 2000, it was rebuilt once before. It is now due for another rebuild since I was getting 100-110 on the compression gauge and I'm going through spark plugs after each ride now. The bike still runs pretty good, just goes through plugs.

I yanked the jug and everything looked good and I started disassembling the powervalve so I can have the cylinder honed. I'm sure it isn't good to hone it with bearings and power valve stuff still installed.

Anyway, the powervalve stuff is oily and cruddy. Should I try to clean all of this off or leave some of it on. I'm afraid that the oily crud might actually help some of this stuff seal and I might make more trouble for myself to clean it (Naturally, i would like to clean it all up though).

Also, if anyone has tips on the Suzuki powervalve for reinstallation - and on break in I would appreciate it.

Micah
 
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#3
If your fouling plugs repeatedly I doubt its because of a worn top end,
though it never hurts to freshen it up.

I have owned a 97 rm250 since it was new. Maybe you can learn from my suffering :)

I had a stator go bad after 3 years. It would actually foul plugs while riding because of this. I would measure the resistance of your stator to see if its within specs if it fouls out like this.

Other fouling problem I had was a worn needle/main jet. It would foul a plug every time it was shut off long enough to cool down a little.

Last fouling problem I had was a leaky float needle and seat.
(dripping from the vent hoses)
Unfortunately the seat is part of the carb body itself. The needle is rubber tipped and replaceable. My seat was worn out of round so bad I had to replace the entire carb. A new needle did not help stop the leak.

http://www.eric-gorr.com/techarticles/mxbooktun97.html

You may want to consider modifying the power as described in the above link. I noticed a nice boost in top end and overrev after doing this.

Good Luck
 
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#4
Thanks for the replies guys.

As for the fouling....it never fouled since I owned the bike. Maybe 3 plugs over a couple years. But then one weekend it was going through plugs very quickly. After checking the compression, it was in fact low at just over 100. So I'm pretty sure it was just rings.

BUT.................I've got bigger problems now. I would appreciate some more advice:

http://www.dirtrider.net/forums3/showthread.php?threadid=84981
 
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#5
I wasn't trying to cause panic......... All those things didn't happen to me all at once.

I was just listing what for you may want to check out.
You never did get specific about under what conditions your plugs were fouling.

Do the topend and see if that helps first.
 

Mr. Clean

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#6
Worn out top ends on two strokes do not make plugs foul quicker because there is no oil in the crankcase to squeeze past worn rings. I would listen to berno11 if I were you. By the way, these problems happen to all high performance two strokes in time. My yz 250 had similar problems and it happened to be a bad coil wire. I snipped off about half an inch at the cap and the problem went away and had more power. Good luck.
 
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#7
I do appreciate the advice guys. To better describe the fouling....I changed the plug, bike fired right up and I went riding. I went through a tank of gas, came back to the camp site and put the bike up.

A few hours later I would fire the bike up, head out to the trails.....and within minutes it would bog and go dead.

A fresh plug would get me good for another long stint of riding, but would do the same thing if I tried to go out again.

I even ran a HS race for 2.5 hours on a plug and the bike ran good, but afterward it would be dead.

Since I haven't rebuilt the bike since I've had it (3 years) and riden it fairly hard, I decided to check compression. It came up low at just over 100, so if that has anything to do with the plug or not, we do all agree that it is pretty low on compression right? And I'm not surprised. You can't ride a 2 stroke bike for 3 years with no work into it and expect it to keep running forever.

BUT, if it continues to do this after the rebuild, at least I'll have some good ideas on what to check out next. Thanks for the help.

Micah
 
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#8
If your float isn't leaking gas out the vent hoses it most likely needs a new needle & main jet.
 
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#9
I think you should check the reeds the main jet the nedle, the float jet(where gas first comes in) and the needle that closes the float jet and the float level. Generaly it has to be on of these,
 
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#10
also clean the power valve, either hot tank it or oven cleaner.
debur it if there are any and get it as smooth as possible.
might want to replate the cylinder while you have it apart.
power valves depending on riding conditions and the bike need to be cleaned periodically. some cases every 6 months.


Red
 
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#11
check the powervalve for sticking first.
Remove the right side cylinder cover (about 6 screws, and yep, pipe has to come off), and gently lift the powervalve lever upward. there will be a small wire rod that lifts the valve lever at the top of the cylinder. It should have easy travel, and not be stick at any position. When your are looking in, the powervalve lever shold be at 7 o'clock position, and it should move freely up to about the 9 o'clock position. If it has good spring tension, and does not hang up, leave it alone, and look elsewhere.
I just had a stuck piston ring on my 97RM250, and it started fouling plugs like crazy. If your compression is low, I suspect a stuck ring. Let us know what you find.