Main bearings?

[Karl_h]

Since getting the bike back up to full power I've noticed a fairly severe vibration when the motor is under load.
I can feel the vibration mainly in the pegs (fairly equally in both so not chain, plus that's brand new) and coming up through the tank. When its under load it feels a bit like a cement mixer but when cruising it feels (comparatively) good.
Seen a few other people with similar symptoms which suggest its the main bearings, what can I do to confirm this?
If it is that what is it going to cost me?
Not been a great start to the biking year really!
Cheers guys

Karl

[AMCQ46]

I spoke to Revolution Roger and even though he is not sure if my high frequency vibes are the main brgs, we discussed te cost

when you have it stripped down he reconed you would cover £250 in parts as you would do all shells and brgs, the valave guides and then head gaskets.

If he did the job he was talking about £800 parts & labour.

maybe Tony.mon would give a quote beter than that? but that was Rogers view

[Karl_h]

Did he mention any test to confirm the problems? At £250 quid I'd be getting a new motor and swapping that.
Bugger!

[AMCQ46]

he said checking oil pressure was not going to help, but his comment to me was "you will know if the mains are gone, the vibration on acceleration will be like a tractor"

I only have a high frq buzz, so not obviously mains

[Karl_h]

Oh joy!

[tony.mon]

I spoke to Revolution Roger and even though he is not sure if my high frequency vibes are the main brgs, we discussed te cost

when you have it stripped down he reconed you would cover £250 in parts as you would do all shells and brgs, the valave guides and then head gaskets.

If he did the job he was talking about £800 parts & labour.

maybe Tony.mon would give a quote beter than that? but that was Rogers view

Price the parts up yourself, David Silvers or Wemoto lists.
That price would include oil, coolant and filters.

Doesn't sound a bad labour rate, it would be a good two long days to get it done, but that's assuming no problems with seized engine mounting bolts.
And they are more often seized than not, so add in frame adjusters at a tenner or so each, maybe frame bolts at similar cost.
But it adds lots of time; they don't come out easily.....
I did one a while ago for one of the guys on here, quoted less for the job but regretted taking it on at the price, as yes, seized frame bolts added a full day to the job.

So a replacement engine might be a good option, better yet, an engine that has already been rebuilt to a professional standard with new mains and big end bearings.

But while you're there you might as well fit high comp pistons (£250 or so) and new rings; it might need a rebore to get good tolerances.......... then you have a reliable 115 bhp and an engine that'll last another 50,000 miles.

I could be persuaded to quote for the engine supply and rebuild, as I have a spare engine to hand. Won't be much less than rebuilding your own one, though, even with yours as a p/ex.

HOWEVER! hold your horses, it would be better to get someone who knows these engines to ride your bike and see if they felt it was that causing the problem. there are a few other potential causes for this vibration.

[Karl_h]

Thanks Tony. I think one of things you mentioned when you listened to the sound recording I made previously was the main bearings so I'm not hopeful! Don't know what to do now, might go down the spares or repairs route with it as I only paid a grand for it in total and to get it to the standard I'd like ideally is going to cost me quite a bit

[tony.mon]

Another option might be to look for a smashed/bashed/stolen recovered one, and make a good one out of the two.

[benny hedges]

he said checking oil pressure was not going to help, but his comment to me was "you will know if the mains are gone, the vibration on acceleration will be like a tractor"

I only have a high frq buzz, so not obviously mains

as roger says, mains are a growling under load and rumbling / knocking felt through the footpegs.
if you have run it low on oil it could well be the camshaft journals worn as the top end would get starved first.
easy to strip down & have a look i spose

also... doesnt yours have a grabby clutch?
the clutch spins faster too.... and there is that big bearing...

[AMCQ46]

as roger says, mains are a growling under load and rumbling / knocking felt through the footpegs.
if you have run it low on oil it could well be the camshaft journals worn as the top end would get starved first.
easy to strip down & have a look i spose

Roger pointed out that if you let the bike idle on the side stand and the oil is low, the clutch side main brg is at the end of the oil feed and can get starved & pick up. he didnt mention the cam journals

[Karl_h]

Well I haven't run it low on oil but its a 97 bike and only had it a year so I that doesn't mean anything! The Clutch is fine as far as I'm aware. It is significantly more powerful than before when I had fuelling issues so I'm guessing the increase in power stroke has made the problem noticeable.

The description of being on a tractor is very apt!

[Karl_h]

Further to this I haven't had time to look at the bike for a couple of weeks due to uni, but been speaking to a few bike savvy mates today about the problem and they all said along with the vibrating I should also be able to hear the bearings, which I can't! Also the distance I've covered the bearing would have lunched itself in spectacular fashion by now.

Any thoughts on this?

Cheers Karl

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[tony.mon]

Could have a look at rear wheel bearings, cush drive and front sprocket, to make sure they're all ok?

[Karl_h]

Cheers Tony, just to clarify, would you agree with what I have written above, I've done the old screw driver to the ear job and nothing sounds amiss with both cylinders sounding very similar.

Cheers

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[tony.mon]

Can't tell without listening to it.
But if it's not engine, and happening under load, it's likely to be transmission or rear wheel.
Or gearbox.......