250 Motor Repair

[TomG]

Here's one I haven't heard before.  I have a 250 Penton MC5 I bought new in 1976 that's been sitting in the garage since about 1981. Around '85 my son, around 4 at the time, managed to fuel the bike with Clorox bleach which then sat in the tank until it leaked through the petcocks into the carb and motor (he did live by the way). Did a pretty good number on all the metal parts it came in contact with, got a little on the outside of the cases but not to bad there.  Now I'm trying to restore it and have managed to get the head and cylinder off but crank is frozen solid.  Service manual I have talks about all sort of special tools I don't have that are needed to split cases. I had a CZ before the Penton so never needed to go this deep into a motor. Anyone have any advice on how to go about getting this running again.  Everthing else on the bike is in very good condition, just needs the motor to go with it.

Thanks in advance

[john durrill]

Tom,
 we had to make the tool the pushes the crank through the wet side engine case. Used a 1/4 in piece of plate steel. used the clutch cover for the hole pattern. Use 3 or 4 long case screws to pullit down where it touchs the crank . mark where the crank touches the plate. then drill a large hole ( we used an 1 and 1/4 inch hole saw ) . get a piece of pipe that is the diameter of the hole and 3 or so inches long and weld to the plate. weld a nut center of the pipe hole and use a long bolt to push the crank through the wet side case.
The cases themselves should come apart with out a special tool. the Main bearings are 3 piece and the inner race stay's on the crank. the outer race in the cases.
if not the the bleach has corroded the magniezium and you might have to do something like the above tool that pushes on the countershaft and the crank at the same time.
Good luck
John & Peter

 

[mikey]

for what its worth I use an old steel sprocket (big sucker) and can usually line up two or three holes in the cover with holes in the steel sprocket or I burn or drill new ones(looks like swiss cheese by now!) and bolt a standard steering wheel puller to the center of the sprocket and use that to push the crank..works more times than not..if you had a CZ and kept the old points type puller it will bolt to two holes on the ignition side and push the ign side out!

quote:
Here's one I haven't heard before.  I have a 250 Penton MC5 I bought new in 1976 that's been sitting in the garage since about 1981. Around '85 my son, around 4 at the time, managed to fuel the bike with Clorox bleach which then sat in the tank until it leaked through the petcocks into the carb and motor (he did live by the way). Did a pretty good number on all the metal parts it came in contact with, got a little on the outside of the cases but not to bad there.  Now I'm trying to restore it and have managed to get the head and cylinder off but crank is frozen solid.  Service manual I have talks about all sort of special tools I don't have that are needed to split cases. I had a CZ before the Penton so never needed to go this deep into a motor. Anyone have any advice on how to go about getting this running again.  Everthing else on the bike is in very good condition, just needs the motor to go with it.

Thanks in advance

 

[TomG]

Thanks for the info. I do still have the old CZ so I'll try that out first.