Can't keep tight

[Jorygirot]

Ive got the bbshd motor on my bike and I cant keep the bolt tight on the pedal arm going into the drive I've tried blue and red locktight. It will come loose within 2 miles of riding. Any ideas

[max_volt]

If you let it get too loose it will deform the tapered hole and never work right anymore. If you tighten and then remove the bolt the arm should need a puller to come off.

[Jorygirot]

Is there anyway to fix it ?

[max_volt]

Replace the arms.

[max_volt]

And snug down the bolts before you take it out for a ride.

[Jorygirot]

Great thank you

[artdrectr]

The Luna wrench or similar is not the greatest tool for tightening this nut down. It really needs a big torque wrench. I’ve yet to hear of anyone stripping the threads but I suppose it’s possible.
Add a very tight bungee cord around motor and downtube for reassurance.

[MoneyPit]

I think he is talking about the crankarms, not the motor mount.

Jorygirot is that it? You are talking about the arm that attaches directly to the pedal? If so them to expand on max_volt's advice:

Use a torque wrench and tighten the crankarm bolt down to 35 ft lbs. Keep checking it over time as the bolts do loosen. I ride every day and I re-tighten my bolts about once a month. They have always loosened some.

If you have already let it get too loose then the crankarm's interior can round off and then you can tighten it all you want and it will never be the same again. You have to replace the arms at that point. If you have been pedaling with loose crankarms then its very likely you have caused this kind of damage and the arms have to be replaced. But still, try tightening them properly and see if that fixes it.

If its getting loose as fast as you say it is, then you are nowhere close to using enough force to tighten the thing. Get that torque wrench and let it tell you when to stop.