Thumper Club Forum
Technical => Bike Problems/Questions => Topic started by: xbally on April 26, 2020, 08:06:30 AM
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I have a new chain and sprocket set to fit to my bike as a job to do during the lockdown.There's some play in the rear sprocket-I don't think it's excessive but would like to try and tackle it.The RSA (as opposed to the D model) has a cush drive which consists of 4 bearings in the sprocket carrier as opposed to the usual rubber vanes. I've manage to get the bearings but the Haynes manual tells me to go to my friendly local Honda dealer to get these out as a special puller is apparently needed.I have a mate who can do the job for me as he's a bike mechanic but I can't get the bike to him until the restrictions are removed.Has anyone ever tackled this job please?
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Hi Martin, yes those four 'Metalastic' bushes in the CB250RS rear hub are utter bar-stewards to swap so much so that I never even tried. As they've now been in situ for 40 years there has to be some steel to alloy reaction. I found that as long as the items are still in a recognisable state with the rubber parts intact, a lot of 'slop' between the sprocket and the hub can be successfully reduced by the fitting of a thicker washer under that large circlip. Some years ago my 250 was an MOT failure (by a worthy on the Stourport to Worcester Road who later was told by Ben at Alec Dorrell's "All they're all like that don't worry about it", but it was too late then as he'd already failed it. I scrounged a piece of 2mm (I think) steel plate off a friend and using the original washer as a template I made one, took the bike back later in the day and it passed. All the best.....Dave.
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Thanks Dave.I think I'll leave well alone -as you say and from my on line enquiries this doesn't look like a job I'd be confident in tackling.One of my previous RS's had a lot more play there and like your's the MOT tester queried it.I'll have a further look when I get the rear sprocket off and see if I can do anything to take up the play under the circlip. My mate will be able to sort it I'm sure.I've probably got a spare washer but whether there's room for 2 under there I'm not sure.
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If you can get four new pins and pack the bushes with grease it takes out some of the forward and backward movement and that coupled with a thicker washer does help quite a bit.
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If you can get four new pins and pack the bushes with grease it takes out some of the forward and backward movement and that coupled with a thicker washer does help quite a bit.
That's a plan...Got quite a few used ones I could try as well.Dave Silver lists these at £7.25 each + VAT + P&P but there's a seller on Ebay selling them with the bushes and nuts as a set of 4 for £18.95 BUT they are for the CG125. I wonder if they will fit the RS?
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Just checked and the CG part numbers aren't the same unfortunately but CSM also have parts in stock.
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As a short term fix I've even wrapped the pins in shim steel to take up the slack. Unfortunately the bushes wear into an oval shape so there's always a bit of movement.
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Just had a report from my mate who has now been able to start working on my bike and he tells me the bushes have no wear but the play in the sprocket was caused by an undersize washer being fitted under the circlip.
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Just had a report from my mate who has now been able to start working on my bike and he tells me the bushes have no wear but the play in the sprocket was caused by an undersize washer being fitted under the circlip.
Wow, excellent result! ;D
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Yes and luckily I had the correct sized washer in my cashe of spares.He's also been able to select the best mounting pins from my spares and these steps have totally eliminated any excess play
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It's a proper Aladdin's cave, round at Martin's - the king of spares and very generous with sorting out members in need 👍😁😎
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A friend of mine also had a CB250RS came up with a solution that I 'borrowed' off him and that was to buy from a bearing supplier four Neoprene 'o' rings that were a snug fit over the four drive 'pegs' with thin stainless washers against the Metalistic bushes and then replacing the sprocket carrier back on the hub. It can be a bit of a struggle compressing the carrier adequately to get the large securing circlip into it's groove. I got around it with two strips of metal plus a short length of 8mm threaded rod as a 'puller' to squeeze the 'o' rings just enough.
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Thanks.......Well it's also having its balance chain adjusted-apparently this way way overdue,engine cases and fork legs painted and some other jobs I'm not able/not competent or just too lazy to do.Oh and trying to get rid of the ever present rocker cover oil leak.
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Hi Martin, yes those four 'Metalastic' bushes in the CB250RS rear hub are utter bar-stewards to swap so much so that I never even tried. As they've now been in situ for 40 years there has to be some steel to alloy reaction. I found that as long as the items are still in a recognisable state with the rubber parts intact, a lot of 'slop' between the sprocket and the hub can be successfully reduced by the fitting of a thicker washer under that large circlip. Some years ago my 250 was an MOT failure (by a worthy on the Stourport to Worcester Road who later was told by Ben at Alec Dorrell's "All they're all like that don't worry about it", but it was too late then as he'd already failed it. I scrounged a piece of 2mm (I think) steel plate off a friend and using the original washer as a template I made one, took the bike back later in the day and it passed. All the best.....Dave.
That's jogged a vague memory of waggly sprockets on zsuperdreams in the 90s, and I think thicker washers were the trick there. I was told that the sprocket eventually wore the wheel out, as it was harder (never found out, my 250N died after 3-4 years of urban commute, outside parking, vandalism, and trips to Shetland, Norway, and Cornwall from Embra).
Never an issue on the 250RSs I had, but only had one RSA (Deluxe). I'm sad to say i blew that one up and to my shame it was my fault. Lnly time I've ever done that.
Xbally, delighted you got a cheap easy fix! Looks like God not on his Harkey...this week.
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Superdream just not the same as the RS-had a couple-Ok but too heavy for a 250-I believe they were designed as 400 originally .
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Yes, it was sleeved down to 250 for UK L market at the time, so bizarrely, the 400 was LIGHTER than the 250!
I had one just as a commuter, but since my T140 was squashed and getting slowly sirted at the time, it was for a bit my only bike. Nowhere near as fast or as nice as the rs, I agree. BUT, laden down with huge aMounts of luggage it was no wirse !
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I also used both mine as commuters/ 2nd bikes and they did give good service to be fair.Put a Rickman (Hondastyle)fairing on one of them and panniers.Used to carry my work files and they would get marked by the inner material from the panniers.I think I bought my first for £75 after the 125 learner law killed the 250 market-my wife managed to negotiate the price down from £90. Petrol tanks and front and rear mudguards used to rot out like most other old bikes but spares were cheap and plentiful.They sold 1000s of the 250 in UK from 79-until the 125 law came in. I always liked the Euro (CB900) styling-which I much preferred to the earlier 3 valve model.
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Oh... the fun I used to have going out to hunt down wet.... eerr sorry, super, dream owners on my trusty RS250. Then have a decent dice with them, before blowing them into the weeds. Oh to be young and stupid again 😉😉👍.
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Well I picked up the RS yesterday and there's now absolutely no transmission snatch. My mate's also made a good workable gear linkage from the one on the bike and the spares I had,painted the engine,fork lowers,kick start,brake caliper and parts of the frame. He welded up the broken frame (see previous posts),welded the helmet holder bracket and a new lock,and sorted out another load of issues including adjusting the loose balance shaft chain, fixing the cam cover oil leak which most of my RSs have had and checking out the advance/retard is working correctly so I am well pleased.
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Thinks that’s called a ‘result “ Martin 👍👍
Happy daze, you just need to get out for a few rides now then.
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Yes Michael-all sorted now-just got to put some miles on it :P