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Discussion Starter · #1 ·
Doing a mock-up with the motor and frame I have 2 questions. All the hardware lined up nice in the appropriate holes. I'm thinking the bottom 7 7/8" stud should be tightened first? Second, I noticed with the engine plates snug on each side everything looks plumb and square, but I have a space behind the plate where the shouldered nut tightens to the swing arm casting stud. The left side has a .060" gap and the right has .030". I plan to put a shim in there so the nut can be torqued properly. This area doesn't look or would have a need to modify, so I'm writing this off to 50+ year old production line saw-cut tolerances. Any thoughts? Gary
 

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Hi Prodigal, The '69 Bonnie had a pretty good gap at the frame to motor. My '73 Tiger had huge gaps.

Both pulled together fine. Chain line to rear wheel was fine with bolts tight. Before that we never gave a look, just tightened & shipped it.

If you're going to shim, which may be best & needed, keep chain line in mind.

On the '73, I'm talking near a 1/4" at least .200". Did it concern me. Yes! But it covered 36K miles without issues, & chain line was close enough so I shipped it. Have proven fine again for nearly 100 miles so far.
Don
 

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I have an opinion like Paul, never tighten to close gaps, shim and make sure the gearbox sprocket and rear wheel sprocket are parallel and inline..And the front and rear wheel centers are in line…
 

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The '69 Bonnie had a pretty good gap at the frame to motor. My '73 Tiger had huge gaps.

Both pulled together fine. Chain line to rear wheel was fine with bolts tight. Before that we never gave a look, just tightened & shipped it.

If you're going to shim, which may be best & needed, keep chain line in mind.

...it covered 36K miles without issues, & chain line was close enough so I shipped it.
(see bold highlights above)
 

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Discussion Starter · #6 ·
Thanks to all that responded. I looked today again and measured the back of the motor where the motor mounts are is 9 7/8"
the frame where the flanged nuts go is 9 7/8". the rear most bolt holes on the rear frame section is 10". So, it looks like the angled tubes the bolt to the bottom of the front frame are bowed outward a bit. I'll think on it overnight and maybe a .030" and .060" shim is the way to go. I'm not looking to re-invent the wheel here. It's possible a few plus sized people hit some good bumps the last 50 years. Thanks again for the info. Gary
 

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Hi All, I agree flexing frame is not desirable. It seems especially on the OIF this wide fit is very common. Remove swing arm on many OIF bikes it goes even wider.
Don’t know what to make of why Triumuph does this. We’re they like this from new? My bike has never been crashed or even fallen over. No big boys have ridden it. Wife & I ride 2 up but we’re not large people. I’d wager it was like this on assembly line.

I gave a lot of thought about making new spacers. I decided to just do what I surmise factory did.
Don
 

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My thinking on this (in line with some others) is these bikes did not have any shims to the engine mounts fitted at Meriden - so i always just fit the engine / plates etc and bolt up - never had a problem
 

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Discussion Starter · #9 ·
spoke with a structural engineer acquaintance who is not into motorcycles. I sent him a couple pictures. He said it's possible with the motor being a casting, and the way it's mounted, would be a fixed dimension. The swing arm mount would be fixed. However, the rear frame section might have been designed to be under tension for stability to limit flexing. Made sense to me. He suggested tightening the hardware and if the motor plates don't bow to much, forget about it. Gary
 
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