'95 RM250 help!

RM250_sutton · Jul 19, 2009

okay i have a 1995 RM250. it was running great when i bought it. changed the spark, cleaned the carb, new radiator fluid. the usual when buying a new bike. but it started over heating really rapidly. boiling over and shooting out of the overflow. so i changed the fluid again and kept riding. (50-50 mix with distilled) but recently whent for a really quick spin and when i would open her up, it would start dying out on power.. so with both of that happening, i would think it is a bad water pump? bad head gasket?

i would love to hear your opinions.

Also if you could explain how to check if its a bad water pump.

and how easy is it to change a head gasket?

thanks a lot everyone :ride:

upstateny · Jul 19, 2009

Hello,

I happen to have the same bike, only a 93. I just got done rebuilding the top end. They are stupid simple (aren't most 2 strokes?) and through Moose (Parts Unlimited) you can put a top end in for around $200 (gaskets, piston assembly, etc.). If its loosing power and compression (hard to start, have to kick more than 8 times to start) definitely put a top end in it.

In my opinion these bikes are worth rebuilding.

RM250_sutton · Jul 19, 2009

yeah they are worth it =]

ummm what would you say about the over heating?

1998RM250 · Jul 19, 2009

pull the cover off your waterpump on the right side of the case where the hose attaches and inspect the fins inside for damage. Does the oil look milky or any oil in the coolant?

RM250_sutton · Jul 19, 2009

no not milky or oil in coolant.

is the fins inside the only way the water pump can malfunction?

upstateny · Jul 19, 2009

Are the Radiators clean? I would pull them off (its not hard, pull the rad guards off, and theres 2 bolts on each side that hold them on, with 2 radiator cross lines), and make sure they are clean, and flush them out really well. Also make sure there is nothing inhibitting flow of the coolant, on my 93 one of the bottom spouts on the right hand radiator was caved in. Not only will it inhibit flow, it also will allow air into the coolant system if the hose does not seal well.

RM250_sutton · Jul 19, 2009

anyone else got a say?

upstateny · Jul 19, 2009

RM250_sutton said:
no not milky or oil in coolant.

is the fins inside the only way the water pump can malfunction?

Only other thing that could go wrong is the bearing that the shaft for the water pump spins in, and that could create other issues in the engine. IF the bearing is bad, and slowly deteriorating (the cage around the balls), could send metal throughout the engine.

I suppose that if the bearing set up, it could ruin the impeller shaft, and impede cooling.

RM250_sutton · Jul 19, 2009

so if there is metal throughout the engine im looking at a complete rebuild on the entire engine?!?!?!?!

whenfoxforks-ruled · Jul 19, 2009

Is the plug really black? Could be a head gasket or lean condition causing it to overheat. With the bike cool, open the radiator and start it up. Bubbles upon acceleration means a leak. Some can even have the head gasket installed upside down and block a water passage. Do not let it get hot, aluminum does odd things to cost you more money!

RM250_sutton · Jul 19, 2009

RM250_sutton · Jul 19, 2009

there is my spark plug right out of the bike today.

upstateny · Jul 19, 2009

Plug looks, Okay from what I can see in the pics.

These bikes dont have a "head gasket" they have O-rings in place of a fiber gasket in between the cylinder and the head. They do have a fiber gasket between the case and the cylinder.

RM250_sutton · Jul 19, 2009

so can the o rings be bad? could it be the fiber gasket between the case and cylinder?

BTW this site is amazing! you guys are helping me sooooo much haha

upstateny · Jul 19, 2009

When mine lost compression (rings were SHOT), I tore it down, and the o rings squish out to compensate for the "void" they have to fill, so depending on how long its been since it was rebuilt, yes in deed they could be bad.

Chances are if its hard to start, that it needs piston rings (I personally would throw the $90 bucks or so into a Vertex/ProX piston assembly and install that w/it.). You probably know this, but when the rings wear, they create "blow by" allowing the compessed air to escape back down into the case, and it will run poorly and start VERY hard.

To do the top end, you will need a piston assembly (should come w/piston, rings, wrist pin, wrist pin bearing, and circlips), gasket set (moose makes really good gaskets that are cheaper than the rest), coolant (you will loose most of it, and its good practice to change when you rebuild an engine), and you should (or at least I do, change the oil in the tranny) the tranny takes 750ml of oil, I run 20w50 synthetic Spectro in mine.

This is all very fresh in my mind because I only rebuilt mine at the beginning of the week.

Also if you run across a set of rear number plates for that bike (stock white preferably, let me know, I really could use a set).

whenfoxforks-ruled · Jul 19, 2009

From the iffy pics, your spark plug was not sealed, or is pretty old. It does not look like its burning much coolant. That is whats on the threads, pretty sure. The engine slowed down by itself, that is called a seizure, the top end needs to come off for inspection.

upstateny · Jul 19, 2009

It could be the wrong plug.......and old/worn out. The pic showing the gap is pretty fuzzy, but it looks like the gap might be a bit much.

RM250_sutton · Jul 19, 2009

well i set the gap my self. i think it was 26? dont quote me on that. and i do have low compression so i was already thinking of replacing the top end. the man i bought it off of said he had an hour and a half on the new top end. that was the beginning of this spring.

so i need to check my water pump. if thats bad replace it.
check the radiator for obstructions and clear them.
also a new top end. (piston rings bearings etc).
new o-ring instead of the head gasket
new plug.

did i miss anything?

if someone could hook me up with pictures or a video on how to check a water pump that would be awesome!

also i know a guy who is ripping apart a '95 RM250 (where im getting some parts from) i'll see if he has the plastics.

upstateny · Jul 19, 2009

Heres the parts list I have for the top end.

Piston assembly $150 or so (this includes wrist pin and bearing, rings, circlips)

Gasket set $20-25 (this will include both the O-rings for the top of the cylinder, the fiber gasket for inbetween the case and the cylinder, the gasket for the both the exhaust valve openings, the gasket for the Intake on the case, a New O-ring/Gasket for the pipe, and an o-ring for the powervalve (that is the 2 bolts on the left hand side of the cylinder that have an 8mm head on them), oh..and it will come w/an extra one for the reed area or the exhaust valve, different years took different ones.)

If you've never had the exhaust valve off on this era RM, there is a spring in there that is wound up, IT WILL HIT YOU IN THE FACE if your arent careful taking it apart. This provides the rebound for the exhaust valves. It is only wound 1/2 a turn or so (at least mine was/is), but had enough there to surprise you.

*edit*

As for checking the waterpump, like someone else said, pull the cover, check the fins, and try to wiggle it around, if there is excessive movement, chances are the bearing is worn/wearing out.

*/edit*

Here are the diagrams of the Case Cover for the water pump
http://www.mrcycles.com/fiche_image...cycles&dc=792&name=CRANKCASE+COVER+(MODEL+R/S)

and for the exhaust valve. Number 15 is the one that will surprise you.
http://www.mrcycles.com/fiche_image...ategory=Motorcycles&dc=792&name=EXHAUST+VALVE

And thanks ahead for checking on those plastics.

RM250_sutton · Jul 19, 2009

awesome! thanks for the diagrams. what website did you buy all that off of?

and also whats the easiest way to drain the coolant out of the radiators?

no problem! i'll give the guy a call tomorrow.

upstateny · Jul 20, 2009

I work for a small town parts store so I buy stuff there. But go to any Dealer that buys through parts unlimited, and you can get the stuff.

Draining the Radiators. When I pulled the lower hoses off of mine, they drained themselves.if you open the cap on the right one and disconnect the upper cross line on the left one, they should drain.

If he has a carb boot and Air Box I may be interested in those too, mine have been fubar'd and ziptied back together....before I got the bike.

RM250_sutton · Jul 20, 2009

okay well i took off the radiators and all hoses are clean. here is a picture of my water pump.

<a href="http://s89.photobucket.com/albums/k207/sutton_13/?action=view&current=0720091251.jpg" target="_blank"><img src="http://i89.photobucket.com/albums/k207/sutton_13/0720091251.jpg" border="0" alt="water pump '95 RM250"></a>

<a href="http://s89.photobucket.com/albums/k207/sutton_13/?action=view&current=0720091252.jpg" target="_blank"><img src="http://i89.photobucket.com/albums/k207/sutton_13/0720091252.jpg" border="0" alt="water pump '95 RM250"></a>

do i need to just do the two screws on the top were the hose connects or take off the four bolts to disconnect the entire cover?

RM250_sutton · Jul 20, 2009

also the camera makes the engine look worse than it already is! its just not clean ATM!!!

RM250_sutton · Jul 20, 2009

RM250_sutton · Jul 20, 2009

do i need to just do the two screws on the top were the hose connects or take off the four bolts to disconnect the entire cover?

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