Serious vibrations at mid-high speeds

[Deleted member 27734]

2 days ago, I installed a high performance cylinder head on my Flying Horse. Everything is torqued properly, and I've had no sign of air leaks anywhere. I'm having a problem that is new, with very powerful uncomfortable vibration. I've tried tightening all mounting points and being sure nothing is loose, but I'm getting crazy vibration at maybe 40% throttle and up. This usually doesn't start happening until I've been riding for a few minutes. It's really smooth at first but then it gets crazy. Is there something I can do? Should I invest in rubber mounts? Could there be another problem I'm unsure of?

 

[bakaneko]

Dont use rubber mounts.

 

[Deleted member 27734]

Dont use rubber mounts.

Well, then what would you suggest to cut down on the vibrations?

 

[Frankenstein]

The Beach Boys?

 

[bakaneko]

Well, then what would you suggest to cut down on the vibrations?

I never used a high compression head so I have no idea, but no one uses rubber mounts. It will just make the problem worse. I do think you have some type of issue that needs to be addressed as those vibrations will eventually tear your bike apart. Also, are you using regular or premium gas? Just trying to bump your thread so maybe Jag or someone can comment.

 

[crassius]

if your frame isn't cracked, I'd guess your motor is loose

just because the mounts are tight doesn't mean the motor is - I've had customers come in saying there motor was tight, but I could see there was a gap between motor & frame from 6 feet away

it needs to be pushed down tight in frame before the mounts are ever tightened at all - all they do is hold it down there

 

[inspectorcritic]

2 days ago, I installed a high performance cylinder head on my Flying Horse. Everything is torqued properly, and I've had no sign of air leaks anywhere. I'm having a problem that is new, with very powerful uncomfortable vibration. I've tried tightening all mounting points and being sure nothing is loose, but I'm getting crazy vibration at maybe 40% throttle and up. This usually doesn't start happening until I've been riding for a few minutes. It's really smooth at first but then it gets crazy. Is there something I can do? Should I invest in rubber mounts? Could there be another problem I'm unsure of?

90% of the time vibration is sighn your motor mounts are loose it'll be in frame and handle bar seat vibration usually means 1 or more broken spokes.

 

[FurryOnTheInside]

2 days ago, I installed a high performance cylinder head on my Flying Horse. Everything is torqued properly......
... very powerful uncomfortable vibration. ......
... doesn't start happening until I've been riding for a few minutes. It's really smooth at first but then it gets crazy.

Taking these key points I would have to ask if you have done any test of piston/head clearance? Apparently the piston is not squashing the plug gap closed because it's still running, but perhaps around the periphery, the squish band?
I am a newbie to engines but this was mentioned on the forum that it can take the build up of heat to cause the problem of piston hitting the head and that takes a few minutes.

 

[butre]

rubber mounts make vibrations worse, mount the motor solid to the frame.

 

[crassius]

new builds always need tightening several times, usually on third time I loosen a bit first and using a steel rod, hammer motor mounts down solidly into any pockets the vibration may have formed, then retighten