How much does your GT750 vibrate?

[Toast]

Hello all, I've been working on refreshing a '75 GT750M. I've never been around another running buffalo so I don't know how much they shake. Mine seems to vibrate alot around 1500rpm. It clears up around 2000rpm. Obviously, its worse in neutral with no load on the engine. However, it can still be felt while riding the bike. Even outside the 1500 area, there seems to be a lot of buzz coming through the tank and footpegs. The handlebars are pretty buzz-free.

Things I've tried:
-timing (dial indicator & timing light)
-synching carbs (getting each individual cyl. to idle @ 1000)

I've also got Jemco pipes and I'm not sure if the carb is jetted for them (not sure that would cause rough running though). Any ideas or is this normal for the bike?

[GT750Battleship]

Hi,firstly mine has had a full engine rebuild 5 years ago,now has Wiseco pistons,rings,rods,she vibrates around 2,000-2,500rpm & again slightly around 3,500rpm,not enough to get worried about? Very smooth everywhere else in the rev range.These bikes can be very different from each other for what ever reason,if you've changed the pipes this could also induce a vibration through the frame if the rubber exhaust mounts are worn out etc,this can also be the case with the standard 3 into 4 system...Worn engine mounts can also be a source of unwanted vibrations...The GT750 is very smooth...have you ever ridden a Suzuki T/GT500 ? big twin vibes,if it gets really bad,I'd say the crankshaft may need attention...

Regards.
GT750Battleship.

[pearljam724]

All things Battleship stated is true. I would just like to add that all of these old bikes vibrate very much so. My 550 is in superb condition with every part imaginable being new or rebuilt. Vibrations on certain models are felt more compared to other models. Then add in wear and incorrect torque settings on those models. Some people are bothered by the slightest vibrations of modern bikes compared to other people not being affected by it. Vibrations do not bother me the slightest. Even so, I'll be honest in saying if I ride my 550 for a few hours non stop it starts to get to me. Type of exhaust and no baffles greatly affects vibration. Amongst several other things. Something as simple as type of handle grips greatly affects vibrations also. If you have original handle grips, they are extremely poor at absorbing those vibrations caused by other items. You would be amazed just how much that changes by simply changing those to a softer grip alone. A few things at the top of that list would have to be the crank being balanced, hardened rubber motor mounts and torque settings.

[oldjapanesebikes]

At low revs the GT750 may not be smooth for many reasons, but just curious - you have made sure that the rear exhaust hanger can 'float' ? A lot of folks don't bolt up the rear hanger correctly and cinch the pipe hanger tight to the frame - the rubber bush is in there for a reason make sure that you use some suitable washers to allow the tightened bolt to only bear on the centre ferrule of the bush so the rubber can do its thing. Just something to check.

[Toast]

You know, I think part of it might be the exhaust mounting like you guys suggested. I got the bike used and there were no rubber bushings for the exhaust bracket. I'll get on that and see how it goes. Thanks!

[Suzukidave]

If the Jemco's are mounted in the rear to the stock points there are rubber mounts in the frame , its just what Ian commented that you just have to make sure the pipes hangers are bolted to the center of these rubber mounts . You will have to use washers or spacers to get the pipes hangers off the frame when all is tightened down . This will also save your pipes as over time the constant flexing of the solid mounted pipe hangers will fracture them requireing them to need welding back up . I have even seen stock pipes with cracks running through them from being hard mounted .

[Suzukidave]

Did you resolve the problem ?

[GT750Battleship]

Did you resolve the problem ?

+1 on that,how are the vibes Man ?
Cheers,
GT750Battleship.

[Toast]

Hey guys, so I think I improved things a bit but there's still a little buzz going on. I got the exhaust bushings mounted correctly , re-checked the timing and the sync and found that one of my coils had a high resistance (cant remember if it was the primary or secondary). Installed a good coil. Anyway, all that seemed to help but there are still ranges in the rpm's where I feel like there is too much shaking going on. I probably should just find another buffalo rider and see what their's is like... maybe I'm just being picky!