Forum

[Matt]

Hi everyone. Some of you might have seen that I've been posting about a gearbox problem. I think I'm now getting somewhere.

The problem was that 2nd gear would spit it'self out.


My Dad and I stripped it down today, I learned a lot.

I've identified that the dogs that slot into the cog for second gear appear to be worn at an angle, see this picture:





Do you think that's what's causing it? 

A new layshaft part number 111073 is £43.50 which is a shame.

Do you think it can be repaired or I can find a second hand one from a dead Bullet somewhere?



Incedently, if and when I do get a new layshaft how will I remove the end cog that seems so stuck on there? Will I need a press? How is it fastened?

Thanks again for all your help, I never would have done all this myself without the forum.


 

[Matt]

Direct link to photo:


 http://img.photobucket.com/albums/v292/ ... 2.jpg 

[Dennis C]

Hi Matt


Yes that is worn out, also check the corresponding dogs inside the gear if they are worn replace that as well.


to remove the gear, heat the whole thing to around 200c, rest the gear on a solid support with the shaft hanging then knock it out preferably with a brass hammer/drift, though that is not too important as the shaft is scrap anyway

[Matt]

Thanks dennis. I thought it was the culprit.


OK, I understand removal now, but how about fitting the gear on the new one? Heat the new gear but not the shaft and then "persuade" it onto the new shaft? (Obviously I wouldn't want to heat it to much and mess up the hardening.)


I'll check the dogs inside the gear tomorrow.



How has this happened do you think? A poorly adjusted detent starting a problem that's just got worse and worse? The bike's done 25,000km's


If anyone knows of a way of doing this on the cheap that'd be appreiated, I thought about grinding back the dogs but apparently that's not an option.


Thanks again. 

[PeteF]

Matt,


You might find the gear just slides on. RE tolerances are not what they might be. If not, put the cog in the oven at about 200f and the shaft in the freezer. The oven will get the cog nice and evenly hot and is better than a blow torch.


My missus found a cylinder head in "her" oven once and was not at all happy. I was only fitting new valve guides and, dammit, it was her bike!!!!

[Matt]

I've managed to remove the gears from the shaft no problem.


The second gear cog seems fine inside.

Here's a photo:


http://img.photobucket.com/albums/v292/ ... 050002.jpg


So, once I have a new layshaft I'll need to put it all back together and rebuild the box and then it should all work fine.

I'm going to order a worshop manual for the rebuild so that I can follow any proper procedures for adjusting the detent becasue I believe that to be the origin of the problem..? 

Any hints or tips out there?


Thanks again. 

[Mark M]

Matt, I don't think a poorly adjusted detent plunger is the root cause, itlooks like poor metallurgy to me, probably inadequate hardening. If your gearbox selected gears ok before, but they jumped out, then the selectors are probably ok and the jumping out is as a result of the worn dogs. By the way, don't overtighten the plunger when you fit it, one or two turns should be enough in my experience.


REgards, Mark 

[Matt]

OK, thanks again.


I already have a tin of 00 grease for the gearbox there's 950grams will this be enough to refill? If not I could top it up with oil I guess?


Seeing as the gear box is open I'll be able to pack the grease in before I close it up and then top up with oil to the desired level.


What lubricant goes in the gearbox end cover? More grease? (It seems that way from what I've dismantled.) 

[PeteF]

The outer cover isn't packed with grease. Just grease anything that moves. Spray grease is good as it gets in everywhere. Don't forget the clutch cable arm where the cable nipple fits and where it goes through case. This is a favourite place for cable breakage.

[John R]

"Cry Havoc and let slip! The dogs've wore".


- Shakespeare.