Rm250 top end Rebuild Questions.

[UlyssesGuz24]

Ok so I have a 2000 Rm250 that I got a couple weeks ago and I pulled the pipe to see what the piston looked like. The bike smokes and I think it sucks tranny oil but I want to rebuild it. Here are the pics.

[argclh6670]

Yes, do a compression test. Itll give u some indication of shape topend is in.

IMHO, id put a new topend in....clean PV and inspect other components while yourw at it just for piece of mind.

The piston doesnt look too bad....some obvious wear of course. Id measure the piston once you get it apart....thatll tell you the size to reorder.

Your cyl is NIKASIL plated..which does wear. It is very durable and lasts along time. (Mine lasted 20 yrs) if its thin you may wanna thibk about replating.

As far as honing.. Ive always been told to use scotchbrite pads on plated cyl along with WD and alot of elbow grease. Alls youre after is to deglaze it. No new cyl requied to do a top end unless current one is damaged beyond repair.

If youre sucking tranny oil....that would mean you have a bad crank seal (oil side obviously).

Edited September 14, 2015 by argclh6670

[ManBearPig.]

Just based on those pictures, the piston looks alright. The cylinder looks worn enough to require measuring. The exhaust pipe O-ring needs replaced. 

 

Since this is a used bike, verify that the cylinder has not been overbored before buying a top end kit (previous owner can tell you). Other than that, it doesn't really matter when you buy the top end kit. Most people will wait until they have the new parts in their hands before disassembling anything, but that is just a personal preference.  

 

The cylinder comes with a nikasil plating from the factory and when that wears away, it can be replated for under $200. Never use a hone on a nikasil cylinder. Here is a good video on cylinder care: 

https://www.youtube.com/watch?v=vaFp8aYkHNA.

 As long as the cylinder bore is within the limits and there is no damage then it is still serviceable. Don't worry about not being able to see the cross hatches.    

 

Doing a compression test will not provide any useful information since there is no specification for compression tests.

 

To save money on shipping, disassemble everything first in case there are other small parts that need replaced. 

 

Good luck with the rebuild!

Edited September 14, 2015 by ManBearPig.

[UlyssesGuz24]

Yes, do a compression test. Itll give u some indication of shape topend is in.

IMHO, id put a new topend in....clean PV and inspect other components while yourw at it just for piece of mind.

The piston doesnt look too bad....some obvious wear of course. Id measure the piston once you get it apart....thatll tell you the size to reorder.

Your cyl is NIKASIL plated..which does wear. It is very durable and lasts along time. (Mine lasted 20 yrs) if its thin you may wanna thibk about replating.

As far as honing.. Ive always been told to use scotchbrite pads on plated cyl along with WD and alot of elbow grease. Alls youre after is to deglaze it. No new cyl requied to do a top end unless current one is damaged beyond repair.

If youre sucking tranny oil....that would mean you have a bad crank seal (oil side obviously).

Ok so I did a compression test with the throttle wide open. I got almost 180 psi.

Is that any good?

I tried it twice and almost got 180 psi I think it's like 177-179 psi.

Another thing I did was look in the spark plug hole and I saw like some brown sludge on the piston.

It looked like melted chocolate.

I got a cotton swab and cleaned it and some sludge came of.

Is this a good or bad sign?

The bike smokes white when idling and seems sluggish on higher speeds. And I get a quite a lot of spooge from the silencer.

I appreciate the help. Thanks

[mjvoket8]

compression looks good. your jetting is rich. resulting in all that melted chocolate, spooge, and causing your experienced sluggish performance. check out the jetting thread and RM set-up "database"

[argclh6670]

Compression IMO is starting towards the low side but should still be fine. I agree that jetting is rich or float level is set incorrectly. Agree on going through the jetting guide.

Edited September 15, 2015 by argclh6670

[UlyssesGuz24]

Well the jetting on the bike is still Stock. The jets it has are the stock ones. should I still go and change it?

How would I know if the problem is just my crank seal leaking?

Or could it just be the wrong jetting that's causing the spooge and sluggish performance on the top End?

These are the stock settings.

Thanks for the help.