Ben Johnson

Member
Nov 5, 2001
4
0
:ride: About a month ago my 03 ktm 450 exc was having bike problems. It wouldn't start unless roll started and would barely run when started. someone told me to check the valves. The valves were too tight but the bike still didn't run. I did a compression test and found the bike didn't have enough compression so I took the head off and found a broken compression ring. I called aroun and everyone said they had never seen such a thing it must have been a fluke so I replaced it and thounght nothing of it.

Yesterday my bike did it again. A broke compression ring in less than four rides! Does anyone know what causes a ring to break in a bike? What I can do to prevent this in the future? I am takin the cylinder in today to be tested I have no clue what to do.

thanx
 

Ben Johnson

Member
Nov 5, 2001
4
0
ktm motor problem

:ride: About a month ago my 03 ktm 450 exc was having bike problems. It wouldn't start unless roll started and would barely run when started. someone told me to check the valves. The valves were too tight but the bike still didn't run. I did a compression test and found the bike didn't have enough compression so I took the head off and found a broken compression ring. I called around and everyone said they had never seen such a thing it must have been a fluke so I replaced it and thounght nothing of it.

Yesterday my bike did it again. A broken compression ring in less than four rides! Does anyone know what causes a ring to break in a bike? What I can do to prevent this in the future? I am takin the cylinder in today to be tested I have no clue what to do.

thanx
 
B

biglou

I think there is an ongoing issue with the valve springs. I'm going on memory though. Anyone? Wasn't there a long thread about this a while back? I can't remember if it was in here or the thumper forum...
 

Slomack

Member
Oct 27, 2003
11
0
I haven't heard of any issues with valve springs on 03 450 exc's, not that I'm the last word. I have heard of cam bearings in 02 rfs motors, and rocker arm bolts breaking on 04's, but certainly not chronic compression ring problems. The most common problems I've heard of for 03's are the fork seals, once again, I'm not the last word. Try the guys at www.ktmtalk.com in the Four Stroke Forum, some of the guru's there might be able to help. Send pics if you can.
Good luck
Mark
 

gnarlykaw

Sponsoring Member
May 20, 2001
986
0
a broken compression ring? I assume it's the top one? what kind of piston clearance to cylinder did you have. if excessive, this ring will fracture first. was the ring landing in the piston ok? I hate to say it, but, was it installed corrrectly? all the ring stampings should be pointing up. "top" on the oil ring, others have an "o" stamped on them.
 

endowiper

Member
May 25, 2004
20
0
Since this same thing has occured twice, first time with original (?) factory installed rings, maybe the ring groove in the piston is out of spec...I'd replace the piston next time this happens.
 

FAST JACK

Member
Apr 6, 2004
23
0
Shortly (about 3 weeks) after purchasing my new '04 450 exc, the same thing happened, top ring land mangled and compression ring broken, cracks in crankshaft around big end rod bearing. had to replace cylinder, piston, rings, and crank assy. My first assumption was possibly detonation, later dealer that preformed repairs under warranty said trash was culprit. Carb did have some dirt in it and after very first ride, I found the air filter was not seald to air box correctly. I still am not exactly sure of cause but have had no reoccurring problems.
 
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