Hitchcocks Forum

Just carried out the following mods and I'm having real problems with excessive vibration.

PAV removed, Straight through header and turn out muffler fitted.
Air box and filter removed and sports filter fitted.
Carb re-jetted and slide upgraded.
Electric starter removed. (my timing was too advanced and it kicked back and shredded the sprag clutch)
Kick start only inner primary fitted.
18 tooth sprocket fitted.

Timing is now spot on 0.8mm before TDC. Starts first kick!!
Carbs are running a little too rich now.

The engine idles nicely. BUT....

In neutral with the bike on the centre stand the bike walks backwards if you open the throttle! the vibration at anything above low revs is unbearable, like a hammer drill.
Even through the sprung seat. After a five minute test ride, my arms ache and it's given me a headache. it's a lot more sluggish than I was expecting after the upgrades and doesn't seem to have much oomph.

Tearing my hair out and hoping someone out there knows what I've screwed up


Anybody got any ideas?

You've done quite a lot there; are you 100% sure there's nothing simple like you've slackened off an engine steady bolt? Dead easy to check on that before delving deeper. Good luck, Chris

You've done quite a lot there; are you 100% sure there's nothing simple like you've slackened off an engine steady bolt? Dead easy to check on that before delving deeper. Good luck, Chris

oops I didn't mean to send it twice. Good luck anyway -C

I think Chris is right, check security of all engine mounting bolts and head steady. Also, check you didn't do something daft when rebuilding the primary. Yes, they vibrate, but not that much.

Vibration is much higher than before the mods. This is like a road drill. will slacken all engine mounts in the morning and run on idle, hopefully that will bed them all in. Then I'll tighten everything back up and report back. Pretty sure everything on the primary build is OK, It was pretty straightforward. As it happens in Neutral, I can pretty much discount the clutch. I checked the gap between the rotor and stator on the alternator all around, so I'm sure that it's not clipping as it spins. That only leaves the new Engine sprocket. That was a simple push fit and replace the woodruff key. Can't think what's happening but it's pretty unrideable.

Why discount the clutch? It's revolving in neutral just the same as when in gear. Probably not the problem anyway.

Pull the primary off and do it again, only place that sort of vibration can come from. Got the clutch steels in correctly?, clutch working ok? can't go wrong with the engine sprocket. Woodruff ke didn't get sucked out by the magnet and get caught behind the rotor, I have had that happen before because you can't actually see behind the rotor as you push it on

yes Pete yer right. Discounted it because I lifted it out and refitted it in one piece (bar the thrust plate, bolts and springs and didn't disturb the plates. never heard of a clutch causing this kinda vibration so was hoping it was ok

Pull the primary case off and give it a run, to cause that much vibration you will be able to see what is running out of round