Tranny issues I think

[loiterin]

I was riding my yz in the trails today and it was working great shifting perfect no noise etc. I broke the chain guide off on a large rock so i had to remove it trailside as it was rubbing my chain . Once i got to a fairly quick section i accelerated hard and shifted from 1st thru 3rd. As soon as i kicked into third my chain flew off and wedged itself between the swingarm and the front sprocket, it was wedged in so tight that after i pused home i had to remove my swing arm to get the chain out. So i get home and put on a new chain and front and rear sprockets a chaing guide and a new swingarm/chain guard as it destroyed this aswell as putting some pretty nasty gouges in my swing arm.

So i start my bike up with no issues at all it runs great as usual, I click down to first gear and start hearing fairly loud clunks etc i drove for a couple feet to feel what was going on and the back tire locked up. I started the bike up and now i could hear theese noises in neutral and it distinctly clunked when i hit the kill and the bike was revving down.

Is it possible the chain coming off added so much stress to the primary shaft that it destroyed it ? has anyone ever had this happen ?

[cwtoyota]

I broke the main shaft on a KX250 about 12 years ago in some whoops. just shattered from the torsional shock load.

You probably have some bent shift forks or something... These YZ trannies occasionally have issues, but it's usually a broken 4th gear.

[loiterin]

Has anyone ever bought the wr gearset through there dealer ? id like to do all 1-5 with new everything in the tranny, i wonder how much im looking at.

I should probably replace the crank n bearings aswell, anyone have a recmendation on crank and rod assy ?

[dirtdan]

Has anyone ever bought the wr gearset through there dealer ? id like to do all 1-5 with new everything in the tranny, i wonder how much im looking at.

Gears and shaft, without bearings or seals.

[bikedude127]

You very likely broke 3rd gear set when your chain broke.. Lots of momentum coming to an instant halt means that things break.. So far as changing to the WR set, I think you also need one of the shafts to do the complete mod.. You can do 3-5 without the shaft I hope its not too bad in there.. I also had a tranny failure and Im deep inside my YZ at the moment...? Sucks, but it happens

[dkwkid]

What about shot peening the gearset to relieve stresses on the parts? I picked up an old Motorcycle Repair Manual from the early 70,s and it has a chapter on various metal treating processes to strengthen parts.They claimed back then that a Triumph rod would last 3 races stock but after stot peening it would go 18 or more. any thoughts?

[loiterin]

What about shot peening the gearset to relieve stresses on the parts? I picked up an old Motorcycle Repair Manual from the early 70,s and it has a chapter on various metal treating processes to strengthen parts.They claimed back then that a Triumph rod would last 3 races stock but after stot peening it would go 18 or more. any thoughts?

I was very much considering something like this. Im an auto mechanic and shotpeening and cryotreating are widley used to strengthen parts in the automotive industry. I would think it would apply well to a motorcycle especially were the yz trannies are a little weak.