Swing arm fractures

[rob w]

Looking over a new project for the first time today.
'74 1/2, '75, '76 style frame and swing arm.
Found these cracks half way around, on both sides of the swing arm. Front end of the top gusset, 2" behind pivot.
I've seen a lot of them, but never saw this before. Has anyone else found this before ?
Thanks,
Bob

[Larry Perkins]

Bob,

I have seen those bend but that is the first time I have seen one fracture and I used to jump them unmercifully.  Wonder if it wacked hard multiple times with blown shocks.  A puzzle.

Larry P

[firstturn]

I have seen it from seized or blown shocks.  Was the swing arm bent?

Ron Carbaugh

[gooddirt]

I have a Spring Sale on Swinger's this weekend.

[jeff greenberg]

Would not be a good idea to land a 70 foot triple with that swing arm !!  :-)

[Daniel P. McEntee]

It might be stronger than you think. The previous owner/rider obviously rode the bike like that? Hercules swing arms were notorious for cracking if you ran the shocks in the wrong position on the swing arm, but I never heard of one breaking clean. I was leaning against my '77 250 Herc waiting for my grass track race at the '08 ISDTRR in Tulsa, and the bike was on it's side stand. Suddenly, me and the bike fell over! The swing side stand had broken off at the toe of the weld all the way around! i just about did a #2 in my pants as my race was next. Rick Grant, a former Hercules factory rider, said not to worry. He rode a 250 with the hole in the swing arm one year for several races, and it never got any worse. I'm not a big "air getter" so I wasn't too concerned. I concentrated on getting a good start and managed to get the hole shot and was at least among the first three riders going into the first turn, a wide left hand 180. I pulled up high into the turn and just let everyone by and putt putted the rest of the race. I rec rode the bike a couple of times after that before I was able to take the TIG torch to it and weld it back in place and it didn't get any worse. Definitely not something to take a risk on, though. Clean off the old paint, grind a small notch in it, TIG weld it up, Grind it smooth, and if you are still concerned, form a 16ga. oval shaped steel patch to tightly lay against the tubing, then TIG weld that in place. I know you know what to do, Rob. But I haven't ever seen a crack of any kind in any of the Pentons or KTMs I have  worked on. I'll be looking forward to seeing the finished product, knowing what a good job you always do.
   Type at you later,
    Dan McEntee

[ALB]

Wow! That looks scary.
I have never seen one like that.

Is that off of one of Larry's old bikes? [)]

Alan Buehner

[Larry Perkins]

You be funny Al!  LOL! I guess they didn't call me "The Flying Monkey" for nothing.

Larry P

[ALB]

Wow! That looks scary.
I have never seen one like that.

Is that off of one of Larry's old bikes? [)]

Alan Buehner

[Larry Perkins]

You be funny Al!  LOL! I guess they didn't call me "The Flying Monkey" for nothing.

Larry P