Vibration at 4K and above on my GS1000

[Anonymous]

I just recently did a complete transmission and engine rebuild of my '81 GS1000GL. Everything went back together just fine. I thought since new pistons were in order, I ordered Wiseco's 1085cc kit, had the cylinders bored, and put everything together. Engine runs great! Once the carbs were rebuilt and sync'd, it was like new again! Except for one thing...when the tach gets around 4000 rpm's, the vibration is to the point that my throttle hand starts to go numb, and the mirrors are vibrating so much that the're useless. This annoying behavior sort of limits my cruising speed a bit.
Should I have weighed the pistons before assembly? Since the engine was completely apart, should I have sent the crank to Falicon to be balanced? What options do I have now, short of tearing the engine down again?
Thanks for any advice.

 

[SqDancerLynn1]

Short of rechecking your carbs?? Wait a few days for Keith to get home he has experience with the wiseco 1085 kit

 

[Guest]

I had the same problem with my stock katana 1100. I had to cruise at 55 or 65 so I bypassed the problem by cruising at 80. ahhaahaha

 

[Anonymous]

Carbs were checked and resynced two months ago...but still the same problem. The vibration doesn't "resonate", so I can't go through it, no matter how fast I go (my speedo only goes to 85) the vibration is there, and simply increases in magnitude.
Pretty shaky feeling. I Keith could shed a bit of light when he gets back I would really appreciate it.

 

[robinjo]

How many miles have you put on it since the rebuild? I have noticed increased vibration when running in a new engine every time, a bit of a tight feeling till everything was a bit worn into each other. And personally I would have tried to match the pistons to the old ones.

 

[Anonymous]

I have about 1,100 miles on the new engine so far. Mostly mild cruising through rural roads and some commuting, and the vibration has remained despite all my efforts. I should have thought about matching the pistons, but didn't. At this point, is it worth breaking the engine down again? and should I take it to the point of removing the crank to have balanced?

 

[RacingJake]

Are all 4 pistons new or used. If new then they should all weigh the same.
It doesn't matter how heavy a piston is just as long as all four weigh the same.

If one piston is heavy'er than the rest it could cause a vibration.

A twisted crank could do it.

Loose motor mount's

Ignition problem, check timing and firing order at the plugs, does all four exhaust pipes heat up about the same.

Cam timing ??

Are all 4 carbs working right, no trash in the bowls, good fuel flow to carbs.

With the bike in neutral rev it up pass 4K does it still vibrate.

Check the shaft drive, loose bolts ??

How did the bike run before the upgrade

 

[ToddB3]

Definetely check your motor mounts, its happened to me. I did a complete rebuild on another bike and triple checked everything while putting the engine back together but I evidently got anxious to go for a ride and left a motor mount bolt out which left me looking for suspension problems only to find the missing bolt on my work bench.

 

[Anonymous]

I thank everyone for the input...certainly addressed areas I hadn't considered. Prior to the rebuild vibration was normal - for an inline four - Carbs have all been rebuilt - new diaphragms even - plugs, wires and electronics are all in order too. I did find one of the motor mount bolts that looks like I may have overtorqued, because when I checked this morning, the head of the bolt was gone! Looks like I need to drill and easy-out the bolt and install a new one. Hopefully that will help.

Thanks, and anyone with any more ideas are welcome. I'll update this thread soon as I get a new bolt installed.