RM 125 power valve / piston crash, HELP!

Joined
Apr 10, 2007
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#1
I was letting a friend of mine ride my 2000 RM 125, I was beside him, we were running hard. The RM bogged for a second then picked back up, I thought the plug was about to foul(a lot of new guys had been riding it), we rode a couple hundred feet and I heard a familiar piston beating the crap out of something so he stopped the bike.

I am not familiar with the newer 2 strokes with the power valve set up. I figured a peace of ring or pin broke and got on the top side of the piston. When I pulled the head off, the piston / head looked good but the piston had a weird looking relief on one side. I pulled the jug off and found that one of the power valves broke where it attaches to the rod(actuator) allowing the valve to be sucked into the cylinder enough for the piston to come up and nail the valve. When it hit the valve, it collapsed the ring grove and put a good impression on the edge of the piston. The cylinder appears to be unharmed.

Is it common for the valve to brake? Everything else appears to be good to go. Is there anything else I should check for?

I can get a piston kit off the net for $60-70 range. How much are the valves? Are they sold in sets? About how much do they cost? Will used valves function if I can find them? Are these high wear items?

The bike is used for recreation but I like to ride hard at times.

I want to fix the bike quickly and repair only what is necessary.

Thanks for any info...
 
Joined
Feb 9, 2005
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#2
Our 98 has done it twice. The valves were about $80 each (2-piece on the 98) We should have done BOTH valves at once, but I only did the one that broke, and the other one went about a year later. If you do a fairly good amount of riding, I'd do the powervalves about every-other year........based on our experience, life is about 100-150 hours.
 
Joined
Jul 9, 2007
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#3
The RM 125s are known for this happening more so then the other brands it seems. Ive had two buddys with RM 125s, a 97 and a 99, and they both have had this happen to them more then once. The 97 blew like 4-5 times because of this. Im not familiar with the design of the RM exhaust valve, but the 02 CR 125 RC valve we just dissasembled was considerably far away from the piston and I cannot see this design comming into contact with the rings and causing a break in anyway.
 
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#4
I just got a quote from my local dealer.

$101.99 each.

I haven't found any suppliers on the net that list the valves.

Do you guys know where I can buy these parts at a fair price?

Thanks for any info...