350 GTO vibration issues

[grundlegrabber]

So, over the past year I have been working with my 69 GTO trying to get it running and back on the road again. I had finally had it running this past winter, but there were still some issues to be resolved. There was a local show that I wanted to put the bike in back in March (Modern Classics at Martin Motorsports). So I shifted my focus from the mechanical aspect to finishing the cosmetics and details. At the end of this month, they are hosting a ride-in event for the bikes that were in the show. So now I'm back in to the mechanicals of it. Long story short, I actually rode the bike for the first time today. Altough I had previously had it running, there were too many issues to actually ride it.
So, after getting the oil injection system to finally bleed out, I took it for a ride down the street. The damn thing vibrates terribly. I had a beautiful, probably NOS, bridgestone license plate backer on the bike. It was bolted down nice and snug. Rode down the street about a hallf mile, turned around and came back. My heart sank when I got home and realized the plate was missing! Ran back down the road and some ignorant f@!k had already run the thing over. Now it's all bent to hell and f*@ked up! Dammit dammit dammit! So my question here is, do these things inherently vibrate so bad that it feels like you're riding a jackhammer? The kickstarter won't stay in, gotta continuously hold it in with my leg. Rode it again, hands almost went numb this time. And of course the license plate thing-what rare, unobtainable part will be next to fly off in the road and get destroyed? I have looked at the engine mounts, and although I'm sure they are the ancient originals, I don't see anything obviously wrong with any of them.

[slawsonb]

Extreme vibration is NOT normal. I would suggest not running it again until you can determine the source. 350 BS's are pretty darn smooth when operation properly (nothing like you describe.) Good luck.
...bert

[reed]

Grundlegrabber,
Have had any work done on the crankshaft!!
Thanks.
Steve.

[disc_valve]

Another thought - Re the engine mounts all tightened properly, and are the rubber mounting bushes in good shape? If the bushes are shot, I believe Richard has some replacements.

Graham

[grundlegrabber]

Guess I'm going to go over the mounts again first. I did look at them and didn't see anything out of the ordinary. But guess I'll have to loosen up all the bolts and see what's up. I have no idea if the crank was ever removed or if anything was ever done with it. I've not done anything internal on the engine. The bike was restored by the previous owner (Larry Young), but no clue what if anything was done inside the engine. The bike does seem to run excellent, as far as the way it actually runs. Starts first kick, idles smooth and so on. Just seems to vibrate more than what I would consider normal when you rev it. I have a Yamaha RD400 and that bike is very smooth. I sure hope it's not a crank problem.

[OldSwartout]

The BS350 shouldn't vibrate much more than an RD. Larry might remember if he did anything to the engine internally, so you might call him. If the mounts check out to be OK, then check the points & timing. With a point ignition, things can get out of whack pretty quickly.

[BRT-GTR]

Grundlegrabber
  Sounds like there's something out of sync with the engine set up. Before you look for mechanical problems in the engine, there was a very good tune up sheet issued by Rockford which is available in the MANUALS/ARTICLES section of this site, see above. Select SERVICE MANUALS and then download the BRIDGESTONE DEALER SERVICE LETTERS and go to page39. Main items to check are the points, ignition timing and carb adjustment / synchronisation all of which is covered. Download the GTR/GTO Manual if you don't know how to do any of these operations or come back to the lads on this site. You should end up with an engine that runs like a turbine. Good luck
Brian the Brit.

[grundlegrabber]

Well it's been 2 months and I'm back at it again. Decided to order up a new set of engine mount dampers. Took the front mounts apart and the rubber in them was totally disintegrated. Pressed in a new set and they're good. Took the rear mounts off tonight. Looks like the inner part of the dampers that go against the engine are supposed to have a raised boss on them. Well guess what? Looks like someone ground them off for who knows what reason. They ground it away so that the whole surface is flat, and the outer shell of the damper is flush with the bracket. No doubt the bracket itself was pressing against the engine case, causing metal to metal contact between engine and frame. This should come as no surprise I guess. Every single thing that I've had to get in to on this bike was a complete butcher job. Wiring, lighting, cables, gauges, oiling system, most of the hardware, and now the engine mounts. I hope this resolves the issue. So, can anybody tell me, as far as the bottom mounts, can they be replaced without removing the engine from the frame? Like maybe trying to pull them out the bottom with a little slap hammer with a hook on it?