Cafe Racer Forum banner

1 - 11 of 11 Posts

·
Registered
Joined
·
3,086 Posts
Discussion Starter #1
I had taken the seat off my 350 to make some other work easier a little bit ago. Last night I found some cracks in the frame I had not seen before. The upper frame rails are cracked on both sides halfway between the shock mounts and frame rail loops. Each crack is about 1" long. There is also a couple of smaller cracks on the inside of the frame rails at the shock mount itself.
I'd like to think it was the byproduct of scary fast lap times but can only chalk it up to stress from being on the track. I've got to check for this stuff more often. It sure would have stunk to find out after something broke
BFD
 

·
Registered
Joined
·
13,809 Posts
wow. ive never seen anything like that. i just pulled my frame apart in the past few weeks and everything looked good. but i am working on a new one with alot less sshit on it. thats my biggest worry. over lightening.

id like to see your frame.

jc
 

·
Premium Member
Joined
·
11,267 Posts
Yeah...I wanna see your crack too!

I agree with Joe...very unusual. Those frames are tanks. Sure the bike was never in an accident....or maybe a lot of rust inside the tubes? Maybe used as a dirt bike at some point. Usually one crack begets more cracks as things start to flex more.

By the way....Rock climbers like to jam it in the crack.
JohnnyB
 

·
Registered
Joined
·
3,086 Posts
Discussion Starter #7
I've got no idea about the bikes past life but I bought the thing from Gary in VT and it was a inspected street bike at that point. It's almost like what you'd expect to see if it had an overloaded milk crate rack on it for a long time. That accessory wasn't on it when I got it though. It rides straight. This model does have the HRC bracing with the shock mounts braced with a tube running between them. Maybe it's too stiff there now and transferred the stess.
If I can get some photos to show the cracks well I'll send them to somebody who can post it here.
BFD
 

·
Registered
Joined
·
5,379 Posts
mine had a cracked down tube behind the plate that the passenger pegs/ swing arm pivot are thru. cracked in half. really cool

mt
 

·
Registered
Joined
·
13,809 Posts
i cracked mine hauling it into the shop when i built it. i acci-dent-ly dropped it and one of the lower frame tubes cracked. mike o brazed it up , i filed and painted it, and never looked at it again. (actually, i was totally paranoid about it for months. i finally just kind started to forget about it.

jc
 

·
Registered
Joined
·
3,086 Posts
Discussion Starter #10
after spending some time cleaning up the areas it looks like the extra stiffening is probably the cause. Tyeing the shocks together moved the flexing stress upstream.
Pretty wild thinking about how much movement is going on there normally if putting a tube between the shock mounts can create that much extra stress. I took a couple of photos but it's tough to see. I'll email them to anybody if they want to take a look.

After the first season I was pulling this thing up the basement stairs and the small scrape over the edge of the bulkhead caused the water filled lower frame rail to start dripping. a poke with punch caused all the water to gush out. Talk about a sick feeling in the pit of your stomach. Welded up the rust hole and haven't seen any more problems there.
BFD
 

·
Registered
Joined
·
8,388 Posts
quote:
After the first season I was pulling this thing up the basement stairs and the small scrape over the edge of the bulkhead caused the water filled lower frame rail to start dripping. a poke with punch caused all the water to gush out. Talk about a sick feeling in the pit of your stomach. Welded up the rust hole and haven't seen any more problems there.
lol... cheap japanses crap!

I think I broke Doug Donelan's RD350 frame when i borrowed his bike up at Mosport 3-4 years ago. Second to last corner, got one helluva headshake. Gave him his bike back, told him it handled like shit. Might've been because I broke it... Broke on the downtube near the motor mount.

You can break the RD350 frames if you use the top rear motor mount. They do handle well, but it would be neat to measure the amount of stress that the tubes are put through.
 
1 - 11 of 11 Posts
Top