SNATCHY RS 250

[xbally]

Is it me or does my CB250RS have overly snatchy ie excessive transmission slop?I know most singles suffer from this to a degree and i know it can be ameliorated by chain adjustment.I guess the chain and sprockets on mine could be worn?Mine just seems to suffer from this whenever i ride it.None of my other bikes are singles now so maybe it's me?Any ideas or suggestions please?

[SteveC#222]

Badly worn chain & sprockets?

Cush drive rubbers in the rear hub worn?

Unevenly worn chain - tight in some places loose in others - if you adjust it in a loose spot it'll run very tight in the tight spots which you can feel through the transmission.

My GN250 ate chains & sprockets - not good on a barely 16bhp bike (when it was new).

[themoudie]

Rev it, don't slog it! Pottering in too high a gear or lugging in 4th or 5th are the worst things you can do with these bikes. In my experience, if the engine is turning at less than 3,000rpm in 3rd, 4th or 5th gear on a constant throttle, you are liable to get "snatching" in the transmission. After all they rev out to 8,000 - 8,500rpm!  and providing the oil is changed every 1,000 miles and they are warmed through before thrashing, should go on delivering reliable service for years. I hope this solves the problem.
My regards, Bill

[steveD]

Rev it, don't slog it! Pottering in too high a gear or lugging in 4th or 5th are the worst things you can do with these bikes. In my experience, if the engine is turning at less than 3,000rpm in 3rd, 4th or 5th gear on a constant throttle, you are liable to get "snatching" in the transmission. After all they rev out to 8,000 - 8,500rpm!  and providing the oil is changed every 1,000 miles and they are warmed through before thrashing, should go on delivering reliable service for years. I hope this solves the problem.
My regards, Bill

Yeah I have to agree Bill. My little tiddler is happy when spinning at 4000rpm and is quite highly geared for top gear. I took it out for a bash the other night and it really thrives on revs. It can be off putting to get that 'rumble' when trundling along, I just drop a gear and all is fine.
It's just that my 660 single, now that I've messed with the fuelling, will pull from 2500rpm  in the lower gears and jumping from one to the other requires sympathetic adjustment. I have got some new cush drive rubbers ordered for the 250 and i will see if that improves things, along with a new chain!
cheers Steve.

[xbally]

Thanks guys....

As has been said the more you rev these little bikes the smoother they become but that's not easy when commuting in heavy traffic.

Unfortunately the parts for the basic RS cush drive  are NLA even from Dave Silver,or they were last time i checked.A set appeared on Ebay a few years ago and the price went through the roof!

The RS de luxe model has a better cush drive which you can still get the parts for or you could last time i checked.I was thinking at one time of replacing the whole rear wheel and cush drive assembly with the de luxe set up  but i'm reluctant as i'm now running on an original rear wheel but rebuilt with new spokes which was very kindly donated by Dick Scratcher (very many thanks Dave!.)

I'm sure a new(quality) chain and sprockets would help but if the cush drive assembly is flopping about it may only be of limited assistance.The bike is due for its MOT imminently and could,i imagine fail,if there's too much play so i may be forced to do something about it.

Has anyone else modded the cush drive of a basic RS 250 please?

[timbo]

I concur with the above. The Dommie hates being ridden below 4000 revs, it just doesn't feel happy, so could it just be a Thumper thing 

[johnr]

are the rs cush drive rubbers the ones that resemble a rubber bush from a shock absorber? ii think ive a new set in one of my sheds, should i book a holiday on the strength of that? perhaps not, i cant get through the doors at the moment!
 they dont like being laboured, some, like the dr big suzukis can actually damage the engine if they are laboured, you are reccomended to never run the engine at under 3000 revs in the top 3 gears because the hammering of that big piston can hammer flats in the big end and destroy it.

[Dick Scratcher]

Not only are there four 'Metalastic' bushes in the rear hub, which frankly I would not ever attempt to remove, there's bound to be a reaction between the steel outer sleeve and the alloy of the hub after 30-odd years, but there are is set of springs installed in the clutch hub which must also be past their best. I tend to 'rev' my RS and try to avoid 'lugging' the motor at low 'revs'.

[themoudie]

Aye xbally
Mailed you!
Regards, Bill

[xbally]

Reply sent-thanks Bill-Martin

[xbally]

I've done a bit more digging on the internet and it seems WE Moto do a one tooth larger and a one tooth smaller front sprocket.It has been suggested a + 1 ie 15 teeth front sprocket and a good quality chain and obviously a new rear sprocket may help?Also there's a supplier on Fleabay selling aftermarket cush dampers but they are £13 each-you need 4!

[CrazyFrog]

I think that most 'modern' singles suffer from transmission snatch at lower revs due to the lack of a heavy flywheel such as old British thumpers used to have. The heavy flywheel stores kinetic energy which goes a long way to smoothing out the power pulses. Doesn't do a lot for outright performance though....

[steveD]

I've done a bit more digging on the internet and it seems WE Moto do a one tooth larger and a one tooth smaller front sprocket.It has been suggested a + 1 ie 15 teeth front sprocket and a good quality chain and obviously a new rear sprocket may help?Also there's a supplier on Fleabay selling aftermarket cush dampers but they are £13 each-you need 4!

Hi xbally, I have had a look and cannot see the the info about cush rubbers for the RSA (non electric) on the ebay . Can you point me in the correct direction?
On another point, I remember 40 years ago when I was a Toolmaker we could get Urethane as a liquid, as a kit, to make 'strippers' for press tools. It was put into a mould around a piercing tool and when cured would 'strip' the tool out of the material that it had pierced.
I am looking to get some as I currently have a 660Tenere which has very soft rubbers, which don't last very long at all! I usually pack them out with inner tube.
My main problem is to find out the SHORE hardness of the original rubber so that I can get some and try to make some myself. In the Tenere hub it would be quite easy as the hub is a void and the drive hub has flanges. Mix the liquid and pour into the space between the drive portion once orientated and let cure. The spindle will be used to located the hub and driver to get optimum rubber in the drive space. I have been thinking about this for some time now and it appears that there is a supplier has a kit but it is 75 SHORE, which is comparable to a tough tyre tread.
Hmmmmmmmmmmmmmmm, any thoughts?

PS and yes the Tenere is an '09, just poor cush drive rubber material.........and yes the topic is widely discussed on XT660.com.

As an aside, again when I was toolmaking we would make a complicated punch and then cast a die around it to run small production runs to prove a component, so the technology is old, it's just getting the correct rubber compound to cast the bits that I need.

Cheers Steve

[xbally]

Steve,the Ebay item number is 391432898688 - sorry i'm not computer literate enough to post a link but search under Honda CB250 RSA 1980 Sprocket Cush Rubbers.
These aren't the conventional rubber wedges that most bikes have and yes i have packed these other types out with cut down inner tube to take up the play in the sprocket carrier /cush drive assy before.
Bill -the moudie has emailed me with a few possibilities as well-thanks Bill. Martin

[themoudie]

Aye Steve,

This link any use? Alchemie_rubber_resin

A wide range of SHORE hardness available and suspect a wee blether wouldn't go amiss. 

All the best, Bill