Take a gander at the following picture. There is burring to the shift drum as the fork pin locates for 3rd. I'm pretty sure that this is what the problem is. What are your thoughts?
HellFire would you have a spare shift drum or Chris Gamlin??????
Rescued attachment Picture.jpg

Which engine? Have you split the engine casings? Although there is clearly a chunk missing from the drum, I think you should investigate further to see if you can find the cause of it. Have you checked the face of the selector fork to see if its worn any?

It looks as though there may be something else which is causing the fork to try and jump out of the drum channel.

Phil

[Edited on 4-2-06 by Hellfire]

There is some rounding of the dogs and the slots in the corresponding gears on 2nd and 3rd but this was probably caused by the dogs no engaging properly. Difficult to say at what extent the rounding is excessive. The forks appear to be ok, again there is some wearing but the 2nd & 3rd gear fork looks generally the same as the other two.
I have not split the casing yet as I dont want to unless I have to.
The engine is a 1992 893cc and has probably done in the region of 30000 miles. It uses a bit of oil too . Now if there is a lot to replace then it may be more cost effectine to replace it. I am tempted to put another drum back and run it into the ground then replace the whole lot.

If, however, I do split the casing, the book says that the altenator has to be removed. Is that true?? Or just the casing?


The clutch is obviously off. The oil pump can have the chain removed. what else?

Sorry there is a lot of question in the above , but this is new to me and I dont want to f*** it up.

As much as it pains you to split the crankcase halves, I'd definitely do it so I could properly check all the gear faces and dogs on the transmission main and countershafts and see how they feel. You only get a partial view of the shafts with the sump pan removed and it's really not that big a job to seperate the crankcase. Just follow the Haynes manual and you can't go far wrong.

I'm pretty sure its only the alternator cover that needs removing.

Do it once and do it right........ as they say.

I'm sure we have a selector drum for an 893 it's just a question of where. I'll have a scrounge round and see if I can find it.

Phil

Thought you would say that.

Looking at the forks . The one to select 2nd & 3rd has more wear. With a micrometer 0.02mm less that the opposite ine also there is wear on the body and not just on the fingers. see photo. Be best to replace that too.

If the gears need replacing would you have some??
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If there's wear on the body of the selector fork, you need to split the crankcase halves and fix the problem. It really depends which gears might need replacing but unfortunately Tony (AKA MK Blade) had a few of our gears for his engine, although I'm not sure which ones he used, might be worth dropping him a U2U.

Once you've determined what you require to fix it, let me know and I'll see what I can find.

What I need is the shift drum, the associated fork, third gear ,third gear bush and if possible sixth gear and second gear (all on the countershaft)
If you wouldn't mind can you see what you have. I will do some phoning around on Monday to see if I can source elsewhere. Don't want to buy all new as it just wont be cast effective.

Hellfire...Solved the gear problem. I bought another engine £205
The added bonus is that it is better that the old one. NOw I have loads of spare parts too.
I found some oil emmulsion in the water from the old engine so I think I'll take the head off and have a butchers. I'll also keep an eye out for gearbox parts. I could have a spare running engine then.