Lightweight gearbox problem

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Ozmadman
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Joined: Wed Dec 14, 2011 1:02 am
Location: ESSEX UK

Re: Lightweight gearbox problem

Post by Ozmadman »

Steve S wrote:Thanks guys, I've eased the bush off with wet and dry but suspect that when I press it into the housing it will be tight again as it is a very close fit.

New problem is the sliding third gear which I bought (new) but doesn't slide on all the way and no amount of filing at the critical point is easing it; I guess it is hardened and therefore resistant to filing?

Steve S.
You're lucky as often they aren't that tight and spin in the casing hence that recess in the bush for a pin on the Norton version box. I seen to remember loctiting mine in just to be sure. I presume you have tried the gear round all the splines? only needs the minutest nick and it won't go on.
Paul
1960 Model 8
1974 Yamaha RD250B US Model 6 speed
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Ozmadman
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Joined: Wed Dec 14, 2011 1:02 am
Location: ESSEX UK

Re: Lightweight gearbox problem

Post by Ozmadman »

Just to add to Steve's comments about his 3rd gear and the differences between the old one and the new one. I got a spare from Andrews and there is a slight difference in height between the old and new as well as the difference between the peg and dog type. The new gear is slightly shorter, mainly due to the cog part not being not so deep. Just out of interest I took my spare box (M1738, so this should be the old type sleeve gear with the holes and the peg type 3rd gear) apart and was surprised to find as was Steve, that I have the later sleeve gear fitted but matched with the early 3rd gear but unlike Steve's box, there is no wear on either!! The box had been apart before as it had red Hermetite on the gaskets and the "Norton" type layshaft bush fitted. It was also very clean inside and all the gears are immaculate which makes me wonder why it has a 3rd gear whine?? The only thing amiss was the selector rod was loose in the casing so maybe that was causing the whine??? probably not though. Anyway, I fitted the 3rd gear despite the slight difference and put it back together and it changes down fine but on the up changes it does stick a bit on third but I put that down to the new gear being a bit "rough" no oil in the box and it just not being on the bike. Check out the photo's can anyone see a potential problem using the slightly shorter gear when up and running like jumping out of gear when it is used on the bike? This is just a spare box so I will not know unless I use it but Steve has this issue too and needs to use his box on the bike cheers Paul
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Paul
1960 Model 8
1974 Yamaha RD250B US Model 6 speed
Steve S
Posts: 123
Joined: Fri Sep 30, 2016 12:03 pm
Location: Hertfordshire United Kingdom

Re: Lightweight gearbox problem

Post by Steve S »

Thanks Paul for posting such a clear explanation of my current dilemma - to replace the worn third gear with the pegged one which doesn't sound right or to try the undercut dog version which Andrew Engineering found for me but which is 1.2mm shorter in overall length.

I would be grateful if someone has some knowledge on this or perhaps has a third gear on their bench with dogs so that I could compare measurements?

Thanks to you all as usual!

Steve S.
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Ozmadman
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Joined: Wed Dec 14, 2011 1:02 am
Location: ESSEX UK

Re: Lightweight gearbox problem

Post by Ozmadman »

Tried to ring Andrews yesterday(Friday) but they were closed
Paul
1960 Model 8
1974 Yamaha RD250B US Model 6 speed
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