You probably need to talk to an engineer. Some owners have had the worn part on the balancer shaft sleeved which then allows for a different (more available) bearing to be used.

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I'm not sure. When I had my original Mk1 in 1989 it did run a little hot under pretty extreme conditions.

I put one on a Mk1. Mount a 10cm CPU cooling fan against a radiator.

Epoxy the bolts through the gaps in the vanes. Wire it into the electrics. I used the indicator switch to power the fan as I had no indicators mounted.

The AR has a standard piston size of 66.40mm that is sometimes quite difficult to get hold of because it doesn't match any of the steel lined piston sizes. The sizes for the steel liner are much easier to get hold of and perhaps cheaper for that reason. So a few owners with damaged liners and have i...

Wossner are better than original.

If that damage was pre seizure then it seems very likely that the issue was caused by overheating or a 'cold seizure' - sudden cooling of the cylinder when the piston is still hot. I had this once on a KTM125 driving through a ford. Unlikely though???? I would be very wary of using that piston again...

If that is your piston with the hell beaten out of the top then something has gotten in that shouldn't be there!

The bore looks fine but you need to find out what happened.

How does the cylinder head look like inside? Did the plug loose some insulator?

If you have an AR then it is a Nikasil bore if not then you have a steel liner. Is the bore bad? You may need a rebore or re-Nikasil. Very difficult to tell without photos! Upload your photos on to a hosting site and then copy a link to the photo on to a post on here. Reasons for seizing other than ...

crm and nsr 125s are possible.

One DEP pipe will fit the Mk1, 2 and 3 or a different pipe for the AR. The difference is the mounting of the neck of the pipe to the barrel. Basically the exhaust studs are in different places. Sometimes owners modify the pipes so they fit.

Good to be using a CRM in competition. CRE will be a completely different animal!!

1) There can be an amount of sideways 'waggle' at the small end but NOT in the line of the connecting rod. 2) The sizes of the 'dog bones' and linkages are different but you probably could use the linkage to attach the XR250 shock to but I don't know. The reason for changing the swing arm and linkag...

Answers - 1. From what I can tell of your big end it seems fine. AR specs are transferable. 2. The shock is rebuildable but it was pretty poor to begin with. I rebuilt 2 mk1s (see Motards /Specials /Rebuilds) and replaced the rear shocks with XR250 shocks. They are so much better BUT you need to rep...

The Mk1 and Mk2 have different sensor positions mounted on the crank case. From memory (and I can't guarantee this) you would be better off putting a Mk3 system on.

There are definite differences between the Mk1 & 2 but I cannot guarantee there are none between the Mk2 & 3.

Nothing will work without severe modifications. The flywheels have different timing. So even if you use the Mk1 flywheel and loom with a Mk1 ECU and PV controller it won't work as the pickup positions on the crankcase are different.