5 replies to this topic

[pogie]

Damage to an MED Straight cut 22 tooth primary gear bush.

I had what I thought to be a leaking primary gear oil seal but on removing the primary gear I have found that the front bush has "picked up" and a lot of the bronze material is missing and is probably the cause the oil seal leak. On talking with MED, their opinion was that replacing the fixed bush with a fully floating item is the way to go, which is backed up by the Mini Spares brochure.

Before I go ahead and order one I would like to know of anyone who has had experience with these bushes and are the cure all that they are claimed to be? Also, what is the best way of removing the damaged bush from the primary gear?

Edited by pogie, 08 August 2011 - 05:10 PM.

[icklemini]

works well - never had a problem...

remove old one by carefully cutting it...(dremel) then knocking it out...

[Pigeonto]

Well I have fitted and am using the grand total of 2 of these so not sure if that is a very good guide but all I can say is that I have had no trouble.They seem a brilliant answer but of course to do it properly you have to address the other bush in the primary gear too and that will mean more work.Mine was set up in a 4 jaw chuck very accurately and bored out to give about 1 thou running tolerance.The biggest problem I could see would be if too tight then gear changes may be a problem due to the primary gear dragging on the crankshaft and preventing the clutch from releasing nicely. I removed the bushes carefully with a die grinder,making a lengthways slit along the bush so that it can close up and slide out....***EDIT do I know you Icklemini!!?? I must be copying you!!

Edited by PIGEONTO, 08 August 2011 - 06:17 PM.

[pogie]

Many thanks for the replies, I've got a Dremmel and a die grinder so I'll try both and see what works best for me.

The rear top hat bush looks to be OK and is bang on (as well as can be measured with a digi vernier calliper) the 1.503" measurement that MED gave me. MED said to make sure when using the floating bush that you to ensure that there is 5-thou radial clearance between the crank, the bush and the primary gear. This should be measured with a DTI on the seal face of the gear, is this the clearance that you guys are running?

PIGEONTO, do you think a new rear bush is essential? I had clearance issues when first building the engine and had to have 12-thou taken off the face of the rear bush to give enough primary gear end float so I shouldn't have any binding issues.

Edited by pogie, 08 August 2011 - 07:55 PM.

[Pigeonto]

Many thanks for the replies, I've got a Dremmel and a die grinder so I'll try both and see what works best for me.

The rear top hat bush looks to be OK and is bang on (as well as can be measured with a digi vernier calliper) the 1.503" measurement that MED gave me. MED said to make sure when using the floating bush that you to ensure that there is 5-thou radial clearance between the crank, the bush and the primary gear. This should be measured with a DTI on the seal face of the gear, is this the clearance that you guys are running?

PIGEONTO, do you think a new rear bush is essential? I had clearance issues when first building the engine and had to have 12-thou taken off the face of the rear bush to give enough primary gear end float so I shouldn't have any binding issues.

I only renewed it due to wear causing too much running clearance.If not worn I dont see any benefit in renewing it if the end float is correct....EDIT just noticed the other question.The fit of the floating bush arrangement is beyond your control really,its all done for you by Minispares! or whoever makes it

Edited by PIGEONTO, 08 August 2011 - 08:14 PM.

[pogie]

What did you set the rear clearance to ? You should of been aiming at 6 - 7 thou, if you used less this was probably the problem.

Do you meant the clearance between the primary and the backing ring/C washer? This was set at 12-thou.

MED mentioned to check that the oil feed holes to the front bush were clear but becasue of the damage they were full of bearing material. Have you heard of these holes being blocked as a common problem?

Quick edit, I've just double checked my notes and the end float was set at 6-thou.

Edited by pogie, 10 August 2011 - 09:08 AM.