Drilling hole's into the

I wouldn't do it , it will be a weak point in the frame.

My very first motorized bike was built back in 2007...I think. Or early 2008. I drilled the down tube to mount the front of the engine on that bike because I basically didn't know better and that's what the kit said to do.

I finally retired that bike this spring, frame still intact. It was an aluminum frame too, built on an Electra Coaster 7.

That said, I always regretted the decision to drill the frame and wish I hadn't. I never drilled a frame again in the six or seven builds I've done since then. And part of the reason I retired the Electra was because I'd drilled the frame.

Now again, in this case it never showed any signs of cracking or weakness, but I still think it's a bad idea.

i have got about 1500 miles on a beach cruiser with the suplied mnount that requires drilling into the fram ...

its about a 1/4 inch hole lil bigger strait though the tube and bolt ythrough it . now my tube is more than2 in thick so i doubt its going to fail at all or be any weeker than a 1ich tube

a 1/4 to 5/16 hole in a 2.5 in tube is not going to weeken it noticably its still stronger than a 1 in tube !

would i drill through a 1 or 1.5 tube heck no !!!!! but 2.5 is huge and a 5/16 hole wont weaken it where it will fail in fact its still stronger than a 1 in tube with no hole ! just dont drill through anything under 2inch then your weakining it more than nesacary and asking for trouble

by the way the drill mount is solid as a rock !!! the rear mount snapped and i had to make a new clamp out of steel because the aluminum one suplied was soo chewap ! i trust a 5/16 bolt locked in place though a 2.5 in tube more than a cheap soft aluminum clamp. if you can get upgraded clamps do it and do not drill unless you have to andd your tube is large enough not to suffer.

Gotta keep up with torque and engine vibrations.

Otherwise....KA-BOOM.

2door said:

Although there are mounts available that require drilling a hole in the down tube most of us will advise against it. It has been done many times and I've actually never seen a report of a frame failure at the point of the drilled hole. Nevertheless there are many other options to mounting an engine that do not require compromising the integrity of the frame. A steel frame would be less likely to fail than an aluminum one. I'd never drill a hole in a main structural member of an aluminum framed bike to mount an engine.

Tom

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I've got a drilled front mount.......I didn't discover this forum until after I built the bike. No issues and I've ridden over some relatively rough stuff. With that being said, I always keep a close watch on the tightness of my fasteners. Maybe most that have had a cracked frame let the front bolt get a little loose. I've ridden this thing for about 6 months, I guess that time will tell.

I guess if it finally cracks, that'll be the sign to 'upgrade' my bike!!

I've drilled through the frame as the main engine supports for Briggs engines and a big Honda and I've never had anything bad come from it. I use a washer on either side of the hole and then tighten until the frame tube starts to compress a little bit.