2003 RM125 make a lot of engine noise, safe to ride still?

[funkyflynz]

Hey all,

Fairly new to motorcross and esp 2 strokes, i got a 2003 rm125 that i love, i brought it last month, its making a lot of engine noise though and blowing blue smoke even when its hot. It also has some blue smoke coming out of a hose at the front of the engine.

Im to excited riding to pull the motor apart right now and im hoping im not doing any serious damage to the internals, it certainly goes well still.

Just wondering if its ok to still ride it or if i could acutally be damaging the motor?

Thanks

Lee

 

[robwbright]

Could you describe the engine noise?

Which hose is the blue smoke coming out of?

Do you have any experience jetting?

 

[rmrider125]

i have a 03 rm 125 also and it does the same thing. except for then engine noise.

 

[funkyflynz]

Engine noise

Could you describe the engine noise?

Which hose is the blue smoke coming out of?

Do you have any experience jetting?

Sounds like a chainsaw, rattley. I had heard that RM's have noisy motors but you can hear the motor noise from the other side of the track.

The blue smoke is coming out of a hose attached to the front left of the motor, its attached quite high up on the barrell.

Yes i have jetted my old CR, you think its running rich rather than a stuffed motor?

 

[Ford357]

I think it could be a clutchside crankseal. The hose is probly your powervalve vent.

 

[robwbright]

My RM was just built by Eric Gorr and has a top end rattle (just like it did before), although I doubt I could hear it from the other side of the track . . .

Does it still run strong? How long since a top end rebuild?

You describe the hose as being front left - that does sound like the power valve vent. If you want to verify what it is, go to:

http://www.bikebandit.com/partsbandit/OEM-Parts.asp

Enter your info and then look at the schematic.

The power valves can get plugged up with spooge. When I did my last top end, there was a bit of that black gook coming out of that hose. My cylinder was slightly out of spec, and I think the AV gas I was running tends to create a bit more spooge than some other fuels.

If you don't have one, get a manual. Borrow a compression tester from someone and test the motor's compression. Pull the top end and measure everything to see if it's in spec. . .

Other than that, I don't know what to tell you. Without hearing it, I can't tell if the rattle is louder than mine or not.

 

[funkyflynz]

Thanks

Thanks for that info, the hose looks to be connected to the exhaust valve filter (comes from the side of the big square box hangin off the front of the cylinder, when the bike tipped over the other day some oily black stuff did come out. Time to replace the filter in there?

Is the exhaust valve the same as the "power valve" you mention?

Any idea what compression should be? To test do you hold throttle wide open and just kick really fast?

 

[robwbright]

Yes, exhaust valve = power valve.

Compression, if I'm recalling, should be a MINIMUM of 120 psi - probably more in the range of 150-180, but do a search on here to get more info. Even good compression does not really tell you that much though - the top end could still be worn out - it just gives you an idea.

It sounds like your RM might be running rich or your premix makes a lot of spooge or your gas isn't burning completely (i.e. pump fuel) or a combination of all of the above.

I don't think changing that filter will do anything to help the problem. When I had mine apart the filter was easily cleaned up with straight gas. The problem is that the bike is rich or . . .

And the other guy is probably right - if your jetting is ok, then the crankcase seal is a likely culprit.

As to checking compression, you get a thread in compression tester, remove the spark plug, kick it over and . . . from there you'll have to do some more research cuz I've never actually done it . . . ;)

 

[oldguy]

when kicking it over be sure to keep the shutdown button pushed in so you are not kicking a charge

 

[funkyflynz]

Changed the bottom end bearings and put in new piston

when kicking it over be sure to keep the shutdown button pushed in so you are not kicking a charge

Well i have changed the bearings, they were rooted! engine noise is no more.

I also replaced the piston, i didnt hone the bore or anything though, i simply put the new piston in.

The instructions that came with the piston mentioned honing the cylinder etc if its cast iron, but i think these 2003 rm125's have some special coating so i didnt.

Hope it will be ok.

 

[robwbright]

You need to hone if there is no cross hatch visible on the cylinder wall. . .

The coating is so hard you can't really hurt it with the proper hone.

 

[yz125223]

if u dont hone the cylinder, the piston wont have proper lubrication, the whole reason u hone it is so the oil sits in the cross hatches and doesnt just sink to the bottom of the case

 

[funkyflynz]

Bummer

if u dont hone the cylinder, the piston wont have proper lubrication, the whole reason u hone it is so the oil sits in the cross hatches and doesnt just sink to the bottom of the case

Thanks for that, i figured it would just be fine.

I guess i have to pull it apart again - bummer.

 

[robwbright]

It may be fine . . . a lot of times the cross hatch is not worn off . . . You just won't know unless you check.

 

[MX Junkie]

[Could of just looked up the exaust port.