Comet Gearbox Crunching

[Steve Burden]

Hi I'm a new member and new to Vincent's. Have a small problem with my 1952 Comet clutch. It crunch's quite bad when trying to put it into 1st or 2nd gear. So bad that I can't actually select a gear to pull off. I have played around with the cable adjuster right through the range and it does not help. I have ordered a workshop manual to aid me but want be here for a few days and I would like to if possible try to go for my first local ride this weekend. Before I attack it with spanners I thought I would do the sensible thing and ask any advice before hand. Would appreciate any help. Thank you in advance. Steve.

 

[vibrac]

It could be either the plates are not lifting squarely or the push rod adjustment is exhausted the push rod adjustment (really the operating lever) can be effected by rotating the 'dumbel' plate on the gearbox cover secured by two screws but its better since you need to take the primary cover off to check the plate is lifting correctly so at that point you can also adjust/check the push rod with the clutch centre screw (1/2 turn out from solid)

 

[timetraveller]

There are others on here who know far more than me about Comets but as a first test I would put it into gear, pull in the clutch and then try to gently kick the engine over. If you cant do that then almost certainly the clutch is not freeing off and if that is the case t hen there are adjustments to the cable and the lifting mechanism that might help. Others can give you more information than me on those adjustments. If it is possible to turn the engine over with the above test then it is not the clutch but possibly something in the gearbox or gear change mechanism. That might prove to be more expensive. Good luck and welcome to the Club.

 

[Gene Nehring]

Welcome Steve,

As the other Gus have mentioned clutch is a good place to start. Does your bike have the stock clutch or a Honda from conways?

The other thing to bear in mind is the you need a small amount of end float on the shafts. I made the mistake of shimming a little to snug and the beatbox was not happy.

Are you running semi fluid or straight oil. If just oil like I do, I use a bell-ray gear saver.

I assume you have "know thy beast" "Richardson" and other reading materials.


Best Eugene.

 

[Hugo Myatt]

The most likely cause is the clutch plates sticking together. The only cure is to take off the primary cover, dismantle the clutch plates and wash them in petrol. Unfortunately many Comet owners have used ATF ( Automatic Transmission Fluid) in the chaincase. This will work for a short time but does eventually stick the plates together. The best I have found so far is Motul Transoil 10W-30. Comets, like the twin, are apt to fill the chaincase with engine oil so it is essential to check that the level is no more than the level plug indicates. When the bikes were new and used every day this was not a problem as the plates never had time to stick together.

 

[Martyn Goodwin]

Hugo is right on the money. PM on its way to you.

 

[Steve Burden]

Thanks for all your advice I will digest it all this weekend and strip the clutch down and do a through cleaning. Don't know when the bike last run as the owner recently passed away. Have also ordered today 'Know Thy Beast' from the online shop so that will be here next week along with another I ordered beginning of the week. and see if I can strip it right back and set it back up.

 

[clevtrev]

Check to see if the outer plate is lifting square, if it`s not, you have to adjust the nuts, to achieve this, for that you will need a special plate driver with a slot to clear the screw post.

 

[Steve Burden]

Have this morning spent a little time on the new edition. Taken the primary case off after a trip to Halfords to buy some imperial hex keys. Does not matter how big my tool collection gets always need another. Stripped the clutch down for clean and inspection. Still not received my workshop manual yet so was just looking to see if anything jumped out at me. First of all the springs measure 30.35mm to 31.48mm. After printing some info from the technical pages on here I understand they should be 38.10mm min so this could be first problem found. Also after looking at the online drawing of the Burman clutch my steels don't seem to match this description. On taking off the clutch drum cover after removing the springs the first steel was a non splined steel. Next was a normal looking splined steel then 2 x clutch plates together with no steel in-between. I have done enough clutches in the past to know this is not correct is it? also i'm not sure what the first non-splined steel is doing is this acting as a shim?. The clutch plates don,t seen to have any meat on them measuring 2.99mm to 3.01mm. I would post a pic of the steels in the order I took them off. I took a picture just don't know how to upload. Any comments would be most welcomed. Not having the previous owner with us any more I cant ask the relevant questions as to why. Thanks Steve

 

[vibrac]

Dont bother with the pictures Steve you have found 2 obvious problems friction and steel should be interleaved as I am sure you are aware and the pressure spring plate bears onto a plain plate. If you ring Vincent spares new friction plates and springs will be with you by next week