HELP, Left Crank just rubbing frame mounted motor, right crank fine

[Jammer]

I am certain others have had this same issue, I searched all posts.
I have a mid 80's heavy duty steel frame mountain bike. I have frame mounted an "80" CC motor at the the bottom of the "V". The right side crank(sprocket side) clears fine. The left side is just rubbing. the Cranks are shimano. Do I add an extender to the crank axel to give me another 1/4" for clearance? Is this normal ? I tried various ways of mounting the motor in the same place to get this extra 1/4" but it isnt working. I tried to move the engine above the range of cranks (above the bottom of the V) but it isnt feasible to secure the motor down well. I am sure other veterans have seen this, wanted to see how they have dealt with it. Thank you for your input, I am eager to get this thing going !!

 

[srdavo]

your local bike shop (or crazy local bike guy) should have cranks that are more offset. I had to change some really straight cranks to an offset pair once, for the same reason.
good luck.

 

[cooltoy]

I've heard of rubbing against the muffler but never the motor.
Sounds like srdavo has the solution.

 

[relaxxx]

Don't do what I did, which was to take an angle grinder to the crank and remove 1/3rd of the inside thickness. Got too weak around the pedal thread and eventually failed.

 

[Jammer]

Thanks for the reply Relaxx... I took SRDAVOs advice and went looking for an offset crank. I have 3 piece cranks (crank arms are dead straight) . I told by bike shop guy what the deal was, he fixed me up with an offset crank (only for the left side) , it works perfectly. It gives me a 1/2" clearance on the motor... ALSO, I found out later , that you also need a little more to get by the exhaust when that it is installed and I got that too. Hopefully, this information will help anyone who has the same issue...

 

[srdavo]

Jammer....glad it worked out for you.