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Better late than never?

The seals are cheap, replace them, I would replace the water pump seal also, inspect water pump impeller, they are driven off the end of the crank, not gear driven. Plastic impeller is weak, they are still available from Suzuki for cheap. My 87 had massive air leaks on the stator side from case porosity. There are 3 indents in the case behind the stator, I performed a leak down test & was amazed to see air/gas/oil leaking right through the case! Only on a Suzuki! Apparently this was common on Suzuki cases, I epoxied the 3 spots on the...

Here is the manual pages regarding the trans & shift assy installation...note: the left case is loaded first, then right case goes on, with the orientation of the shift drum spring, you have to load left case first.

Not sure if these will help you,

I did it a bunch of times w/out the crank installed to make sure everything was installed correctly, bench test the trans gears etc. . I can take some photos of my service manual later in the week, if you need. , I am out of town at the moment.

It hooks on the left case, it makes assembly a little tricky , see the post just under the crank pocket at 7pm...I remember this because I was confused at first also. You have to load the left case half first...

I bought a 86 rm 125 a couple of years ago for $ 300.00. Took it home and pulled the head off it and was surprised with new piston on standard bore. Only problem was they put the piston in backwards and it seized. LOL

86- 87 RM125 would scorch a top end to the condition of the one in your pictures on the regular. That is detonation damage on the head. They would show good plug readings, jetted right, and the head would be ruined from detonation. About 6-8 races is a good life for one. Use the best gas you can buy.

This is a photo from a 1988 Suzuki RM125 service manual. Many changes from 87 to 88 RM125, I doubt the ignition was one of them, hope this helps. If you need any other info from the manual let me know. After you have assembled the engine, perform a leak down test, as I found out, the cases behind the stator are very porous, causing severe air leaks, easy fix, just clean really good & epoxy the case where it is leaking. Also pay close attention to the poorly designed water pump impeller, it is plastic & bolts to the...