G19 gearbox mainshaft spacer

[highbury731]

I think we are getting a few mistakes here, Highbury started by saying he had G19 at .012 " thick at the shaft, I think Gregs 0.120 thou sounds better !, Have you had that end of the box apart ?, Any History of the bike running ? I was thinking , If there was a fault at the final drive sprocket end, It might upset the reading at the clutch end, Just my thoughts, Cheers Bill.

I measured the G19 with a micrometer. It's 12 thou thick, or .012". It's not more than a tenth of an inch.

The history of the bike is a bit thin. I have a 1960 tax disc, and a May 1962 newspaper was found under the mostly dismantled engine. The box was still in situ at that point. Why do you think that there must be a fault at the final drive end? I can add that the bearings have been checked.

 

[litnman]

Can G45 bearing lock ring be used as an adjustment where even without E76 there is no gap between G4 and G6? The mating surfaces of my crankcases appear to have been lapped heavily.

 

[clevtrev]

Can G45 bearing lock ring be used as an adjustment where even without E76 there is no gap between G4 and G6? The mating surfaces of my crankcases appear to have been lapped heavily.

Only if you are prepared to put a shim between the bearing and G2.

 

[litnman]

Trev, my G2 has been welded on quite a bit. You said you have an extra one. I've emailed you a couple of times for your address.

 

[Bill Thomas]

Sorry Highbury, Just thinking out loud !, I don't have a G19 in my hand, But remember them as being a bit thick, And you said it was thinner away from the shaft, Litnman has come up with something I did not think of, If somebody has refaced the case joint, I thought 31 thou was the norm for E 76, But old hand built bikes, I guess anything goes. Cheers Bill.

 

[greg brillus]

Can G45 bearing lock ring be used as an adjustment where even without E76 there is no gap between G4 and G6? The mating surfaces of my crankcases appear to have been lapped heavily.

You are probably better off taking a small amount off the end of the G4. You may also need to carefully check many other parts in the gearbox, as you have lost clearance on the whole lot not just one shaft. On my racebike project I had to do quite a bit in this area, as we had lost around 0.012 thou through the center due to the cases being machined. Be particularly careful that the G5 shaft still has some slight movement, or else it will hold the G2 cover plate from bolting home fully. Getting back to the other......I am not aware of the G19 being available in a thicker size, apart from perhaps reshimming the endfloat on the G3 shaft, I would reassemble the gearbox as is and all will be well. There does not appear to me to be anything majorly wrong with what you have.

 

[highbury731]

Getting back to the other......I am not aware of the G19 being available in a thicker size, apart from perhaps reshimming the endfloat on the G3 shaft, I would reassemble the gearbox as is and all will be well. There does not appear to me to be anything majorly wrong with what you have.

Do you mean mine?

 

[bmetcalf]

Jeff Barkes had a long article in MPH maybe in the '80's about reclaiming a set of cases, including cuts on the joint faces. He must have had to deal with these issues.

 

[greg brillus]

Hi there Highbury........Yes the last part was meant for you. Perhaps all of this is confusing you a little, but from what you have described, there seems not much to worry about to me, even the 0.021 thou at your G 3 shaft I wouldn't worry about. It is not going to cause it to jump out of gear, but if you want to fit a 0.015 thou shim between G6 and the bearing, it's easy enough to do. These gearboxes are like a truck, and very strong. You are better to have a bit more clearance than too little. Cheers.........Greg.

 

[Albervin]

I measured the G19 with a micrometer. It's 12 thou thick, or .012". It's not more than a tenth of an inch.

The history of the bike is a bit thin. I have a 1960 tax disc, and a May 1962 newspaper was found under the mostly dismantled engine. The box was still in situ at that point. Why do you think that there must be a fault at the final drive end? I can add that the bearings have been checked.

A tenth of an inch = 100 thou; 1/10= 0.1 = 100/1000. If it is a "bit more than 1/10" then probably 120 thou. If it was 12 thou you would be able to bend it easily between finger and thumb. It is
more like a thick washer with a polished annulus around the internal diameter, yes? Have you a copy of the latest instruction sheets? They are very clear on how to carry out assembly and measurement. I am no expert but have recently rebuilt my gear box twice, the last time due to failed G16 and G17. The instruction sheets were absolutely essential for me to get it right e.g. not inserting the G5 back to front! It mentions a 0.005 clearance between G12 and G20 (I think). Always best to walk away for a while when tired and confused; sometimes you need to approach a job with a clear mind and fresh outlook.