engine/gearbox noise when hot.(6 miles)

[lam1962brettagg]

Hi all. (standard li 150 s3)
desperate help needed recent engine rebuild all new parts apart from Gears and cluster which seemed ok have had side casing off no unusual signs of rubbing damage etc nothing out of place that I can see but still get a really bad whirring noise after 6 miles slow down let it cool carry on disappears then comes back I'm at a loss can anybody shed any light please?

[HxPaul]

It sounds like your chain is to tight,did you check your chain and make sure you had 6mm up and down play just forward of the chain tensioner.

[lam1962brettagg]

hi Paul
thanks for info. i've got an iwis in it that was in the previous casing. seemed a little tight when i changed all the parts over to the 'newish' casing from the old one but didn't have this problem before. i have standard chain guides and am presumming i cant slacken the chain anyway can I?
cheers for any further input

[lam1962brettagg]

too tight a chain may account for the gearbox getting really hot though.
i'll take a look 2moz

[lam1962brettagg]

took the side casing off today. no visible signs of overheating parts. adjusted the chain. new oil. still overheated and started making a whiring noise after 5 miles running at average 25mph. pulled over noise stopped then carried on riding till home. idles and runs well with no noise even when clutch applied and gears selected when stationary.
any ideas anyone?
its got me.

[holty]

if the noise is only there when your moving it could either be hub bearing or needle bearing, is noise there in all gears ?

[MickYork]

What is overheating ?

[CHRIS in MARGATE]

When you took off the side casing did you check to see if there were any marks on the underside above the front drive sprocket. If this is not correctly fitted it will rub and get very hot.

[lam1962brettagg]

Hi Mick re 'overheating'
ie gearbox getting too hot to touch after only 10
mins running.

[lam1962brettagg]

Hi Chris
thanks for your reply.
all checked when side casing off no signs of marks above front sprocket or anywhere else.
been riding and working on varios scoots for 25yrs and never known anything like this???
thanks for your input Chris

[HxPaul]

hi Paul
thanks for info. i've got an iwis in it that was in the previous casing. seemed a little tight when i changed all the parts over to the 'newish' casing from the old one but didn't have this problem before. i have standard chain guides and am presumming i cant slacken the chain anyway can I?
cheers for any further input

How many links on the chain,how many teeth on the front and rear sprockets.

[lam1962brettagg]

Hi Paul thanks for your post from what I can remember I bought a brand new 81 link Iwis chain couple of years ago the rear sprocket and front sprocket are the same from when I bought the Li nearly 20 years ago and have had no problems up until now. (since all engine parts put into a newish casing of similar age) had new bearings/seals/piston rebore and new race layshaft from MB
hope that helps

[Warkton Tornado No.1]

There currently seems to be several issues that others are experiencing with transmission, though if the gearbox components are suspect, the only way of finding causes is to thoroughly check everything involved.

However, in your case, it could be due to a poor bearing overheating or breaking down, such as with the rear hub bearings that use a plastic cage, which I remove from any engines I encounter with them fitted.

Nonetheless, don't overlook that brake shoes only need to rub slightly, possibly due to an out of round hub, or even a tyre can be out of shape or expand & rub to cause such symptoms as you are experiencing.

I hope that helps.....

[HxPaul]

Hi Paul thanks for your post from what I can remember I bought a brand new 81 link Iwis chain couple of years ago the rear sprocket and front sprocket are the same from when I bought the Li nearly 20 years ago and have had no problems up until now. (since all engine parts put into a newish casing of similar age) had new bearings/seals/piston rebore and new race layshaft from MB
hope that helps

I really need to know how many teeth are on the front and rear sprockets.There have been cases were some people have swopped everything from one case to another and the chain is to tight.

[lam1962brettagg]

hi Paul
47 rear and 15 front with an iwis 80 chain.
this is what i had in previous casing and no probs.

[lam1962brettagg]

hi Warkton
thanks for the info. had rear wheel and hub off today and found no rubbing on tyre or hub?
will ask the guy who fitted rear wheel bearing if it had a plastic cage but i think hes pretty reliable and wouldt have fiited one of those.
cheers for info though

[HxPaul]

hi Paul
47 rear and 15 front with an iwis 80 chain.
this is what i had in previous casing and no probs.

47x15 uses a stretched 80 link chain,using an 80 link Iwis might not be stretched enough.

[HxPaul]

Hi lam1962brettagg,did you ever find a reason for the noise ?

[a.lo]

an iwis chain is no guarantee of correct fitting, I bought one a few years back from reputable dealer with holographic seals on packet and it will absolutely not fit on the correct sprocket combo i.e too tight

[lam1962brettagg]

Hi Paul and all
after trying an original 81 link chain. noise was still there finally realised it was on the verge of seizing .
striped the engine down can't find any problem part from scoring to the piston suspecting a dodgy crank and a possible slight fracture in the mag housing so changing those parts.
While I'm at it will fit new points to eliminate that possibility as well.
Cheers for asking if I've sorted it yet Paul
Truth is it's stripped down yet again in the garage and will stay there probably over winter.