GT750 Exhaust issues

[Mr Bonehead]

Hi,astrax,just had a quick measure on my GT 750 A 1976 and I get 37 cm centre of the exhaust hanger nut either side on a 4.00/18/64 H tyre.
Good luck and cheers from France Mr B

Thank you Mr B

Out of interest can you remember what the dimension for lower shock mount was as well?

Thanks
Ian

Hi just measured the lower shock ,from the center of the nut to the ground is 39.5 cm same both sides,hope this helps ,
Cheers Mr B

[astrax]

This may help describe some of the differences that I have been seeing
I have drawn a straight line between the front footrest bolt and the rear exhaust mount, they both cross the exhaust can at a similar place, but the position of the rear lower shock mount is completely different, so they will not notice if the can faces in a few degrees as nothing there to come in contact with

This fitment is the same on both my GT750's

There will be slight differences due to the angle the photo is taken, but what I am seeing is much more than a slight difference in the camera angle
Both bikes have 300mm rear shocks.

My bike

Their test jig

[astrax]

Hi,astrax,just had a quick measure on my GT 750 A 1976 and I get 37 cm centre of the exhaust hanger nut either side on a 4.00/18/64 H tyre.
Good luck and cheers from France Mr B

Thank you Mr B

Out of interest can you remember what the dimension for lower shock mount was as well?

Thanks
Ian

Hi just measured the lower shock ,from the center of the nut to the ground is 39.5 cm same both sides,hope this helps ,
Cheers Mr B

Thanks Mr B

[teazer]

Ian,
If I understand it, their bike/s has/have the mount at different heights on each side, but all the bikes we have measured are symmetrical.

If I got that right then there is something wrong with the frame(s) they are using. The shocks on both on my stock framed bikes are 320mm and the straight line in my case falls about 20mm above the lower shock mount as you would expect. Your frame is the same side to side, and apparently so are everyone else's.

How can the vendor have two frames that are non symmetrical when all our bikes are the same side to side? I would like to see their frames on a frame jig to see what's wrong with them.

edit: I just went back and looked at the photos again. The line in the photo of the right side of your bike is hard to see perfectly because of the slight angle, but it looks as if a line through the exhaust mount (and not the rear footpeg mount) might not be through the lower shock mount. That is probably a parallax effect.
If the straight line passes through all 3 points on both sides of your bike and both sides of everyone's frames, then there is something wrong with their set up.

I was going to suggest a bent swingarm on theirs with different length shocks side to side, but the motor and frame should still be correct, regardless. Could their motor be mounted high on the right side? I don't see how, but this is a mystery that needs to be solved.

[astrax]

Ian,
If I understand it, their bike/s has/have the mount at different heights on each side, but all the bikes we have measured are symmetrical.

If I got that right then there is something wrong with the frame(s) they are using. The shocks on both on my stock framed bikes are 320mm and the straight line in my case falls about 20mm above the lower shock mount as you would expect. Your frame is the same side to side, and apparently so are everyone else's.

How can the vendor have two frames that are non symmetrical when all our bikes are the same side to side? I would like to see their frames on a frame jig to see what's wrong with them.

edit: I just went back and looked at the photos again. The line in the photo of the right side of your bike is hard to see perfectly because of the slight angle, but it looks as if a line through the exhaust mount (and not the rear footpeg mount) might not be through the lower shock mount. That is probably a parallax effect.
If the straight line passes through all 3 points on both sides of your bike and both sides of everyone's frames, then there is something wrong with their set up.

I was going to suggest a bent swingarm on theirs with different length shocks side to side, but the motor and frame should still be correct, regardless. Could their motor be mounted high on the right side? I don't see how, but this is a mystery that needs to be solved.

Hi Richard

Their lower rear shock mounts are the same height both side on their bikes, and within mm's of the dimensions for mine, but their exhaust hangers appear to be at least 15mm lower to the ground than mine, so the exhaust sits at a different angle, miles away from the lower shock mount.

Where as my bike the rear can is close to the shock mount, and error in the positioning before welding puts it too close to the mount, but they do not see it on their setup as the shock mounts appear to be a couple of cm's above the pipes.

Yes my line passes very close to the shock mount, line drawn from, front footrest bolt through the rear hanger bolt hole on both photos.

[teazer]

If their frame is also symmetrical side to side, then the reason that their exhaust mounts is higher is because their shocks are shorter than yours. The relationship between frame, pipes and motor would be the same on yours and theirs, but on theirs, the pipes clear the lower shock mount because it's higher - relative to the pipes. Or put another way, with the rear wheel on the ground, their frame and pipes are lower than yours.

They may have thought that their shocks are 300mm, but I am pretty sure they are wrong or are measuring a different way - you center to center, them outside of the eye to outside of eye. Stock shocks are only 285mm IIRC. I don't think I have any here, but I can look if you want.