2003 RM65 Crank/rod help

mdb413
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mdb413
Edited Date/Time 6/2/2016 8:28am
Well my son's 03 RM65 seized yesterday while at the track. I figured it was a piston/cylinder issue. Got it home, pulled the cylinder off to discover that the rod was frozen to the crank. I just replaced the clutch basket and plates but he did ride it once all day before this with no problems. Is there something that I did to cause this? Also, I have never split cases and/or replaced a rod. I have only done top ends. Where in the heck do I even start? This sucks!!! I feel like setting it on fire and walking away.

Thanks for any advice. You guys so far this month helped me fix my sons PW50 and helped me to get the backfire squelched on my 06 450 (that's what I was busy doing while my son was wrecking is bike. lol).
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pete24
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pete24 5/29/2016 6:52am
5/29/2016 6:52am
watch a couple utube vids and do the bottom end its pretty easy, id rather the crank went than have the cylinder be wrecked, buy a wrench rabbit kit and you will be good to go
Paw Paw 271
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Paw Paw 271 5/29/2016 7:42am
5/29/2016 7:42am
A good service manual will walk you through it step by step.
You can replace the rod on the crank or just replace the complete assemble for just a few dollars more.
If you just do the rod, you will need a good machine shop to actually install it on the crank. If you do the complete assemble, you can install it with very few special tools.

Paw PAw
809
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809 5/29/2016 7:52am
5/29/2016 7:52am
The most common cause I see at my shop for a seized rod is dirt, if it is caused by the owner. I have seen air filters not seated correctly or even with holes in them. It may not be something you did wrong though
Matt Fisher
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Matt Fisher 5/29/2016 8:14am
5/29/2016 8:14am
Unless you decide to have the crank rebuilt by someone like cookseycrank you'll likely end up buying a new one and dropping it in there.


Suggestions:
Avoid Wiseco cranks.
Hot Rods have a decent rep
OEM is generally regarded as the best, but make sure you compare the cost of KX65 and RM65 parts, as they are identical and there can be a significant difference in cost.

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project racer 5/29/2016 9:11am
5/29/2016 9:11am
Dirt ingestion can kill them. But also, keep some oil to them. Ultra lean oil ratio can kill a lower rod bearing in short order. Smaller, higher revving engines need a bit more oil in the mix. 40:1 is as far as I go on small bore two strokes.
mdb413
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mdb413 5/29/2016 5:07pm
5/29/2016 5:07pm
Thanks all for the replies and advice. I got as far as the flywheel. Now I guess I get to buy a puller. 3 years as an auto tech and none of my pullers will fit. Go figure. Any suggestions? I saw two on rockymatv that should work(motion pro and tusk 12$). Does anyone sell a one for all? What else will I need while I'm at it as far as tools go? I'll have to save up for the crank assembly. Hard to sneak that cost by the wife.
kevkx125
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kevkx125 5/30/2016 7:21pm
5/30/2016 7:21pm
Crank case splitter and clutch holder.
mdb413
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mdb413 5/31/2016 5:08pm
5/31/2016 5:08pm
Can anyone tell me why there is a "B" on top of the piston of the RM65? I think my 96 yz250 has a "B" cylinder and takes an OEM compliant piston to go with it. That is what I have always bought since another after market piston wrecked my 94 yz250. That is what the shop told me anyhow. So I assume that is the case with the RM65. That said I am looking at rockymountainatv and there is no different options for pistons. Any ideas? And I haven't got the cases split yet. Waiting on flywheel puller and a couple other tools. I will let y'all know how I am doing. Definitely leaning towards buying the entire assembly. I am not sure piece meal with parts will be any cheaper plus trying to find a shop that could put it together.

Matt
Matt Fisher
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Matt Fisher 6/2/2016 8:28am
6/2/2016 8:28am
RMATV is a great place to get the flywheel puller and case splitter from. Their Tusk stuff works great.

Traditionally there were A, B and C cylinders and pistons. As time goes on most people just use the B or C pistons in whichever cylinder they have, since they're larger than A pistons (I think Honda is the opposite though) and the idea is to compensate for cylinder wear.

As mentioned earlier, make sure to check the KX65 prices, as the RM65's are the same as 02+ KX65's. My son rode a RM65 for several years and I got lots of practice with them.

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