1954 Comet C - broken cam follower

[charlottevictoria]

Dear all,

I have found a piece of metal which may come from the exhaust cam follower. So I want to remove the steady plate and the cam sprocket to see where is the problem. Now I have some questions:
1) Should I use new nuts for the steady plate or may I use the old ones at the end?
2) Are there any problems removing the cam pinion?
3) how does the cam fit togeather with the cam pinion?
4) does anybody have a photo, which shows how it looks behind the cam idler?
5) do I have to remove the large idler too?
6) is it possible (and helpful) to fit a black lightning camshaft?
I drive the bike with a blacknell bullet sidecar an 60 teeth on the rear sprocket. It runs 65mph. A few horspowers more shold help climbing hills.

Thanks a lot for your help. Please answer to my e-mail-address kohl.lalo@web.de

Yours
Peter Kohl

 

[timetraveller]

Hi Peter, here are some answers.
1) If the nuts are in good condition you can use them again. Check that the tab washers are in good condition or replace them.
2) The cam and the pinion can be regarded as one item and will slide off once you have removed the push rods and lifted the followers up off the cams. If you find that either the cam spindle or the bushes inside the camshaft are worn now is a good time to replace them.
3) The pinion is a press fit onto the camshaft with 0.015" interference fit.
4) You need to buy a book by Paul Richardson from the VOC Spares Company which has the diagram in it that you need.
5) Yes, you do need to remove the large idler.
6) A lot of us have used a Black Lightening cam shaft on the road for years but it only gives more power above 4,000 rpm and it makes the engine harsher at low revs. You should be able to go faster than 65 mph and you should consider what compression ratio you are using, the size of the carburettor, whether the cam and followers are worn etc. Generally there are lot of small things all wrong and you need to put those right otherwise a hotter cam will not work anyway.
Good luck

 

[ET43]

For a Comet with a Blacknell Bullet, 65mph is pretty good, and achieved because Peter has the correct gearing on the bike. People who know me realise I bang on about about this matter, but when you have only 28bhp, the only way to get speed is to get the gearing right, as this gentleman has done. Anything less than this gearing will make the engine work too hard. Free revs are better than slogged revs!! Peter Gerrish on the IOM in 1967 on a Comet outfit and passenger managed 85 mph on the flat and this with wicked c/r and a one and half inch carb, and that says it all. Peter, if you fit a Mk11 cam, say, a 9 to 1 c/r, a long inlet stub with at least a 32mm carb, you might, and I say might get another 5mph. Sadly, with a Comet it just ain't worth the expense, but keep riding the combo, they are great fun.
Cheers, The Charioteer, aka ET43

 

[timetraveller]

According to the Rider's Handbook a Comet with 60 tooth rear sprocket does 763 rpm for every 10 mph. Therefore at 60 mph the revs should be about 4578 rpm, at 70 mph about 5341 rpm and at 80 mph about 6104 rpm. These figures are all well within the capabilities of a Vincent. So it is lack of power which is the problem,not an inability to rev higher. Try the outfit down a steep hill and if it will not exceed 65 mph then something is stopping it breathing properly or something in the transmission is not free. I was lent a Comet to ride solo a few years ago and it really was gutless. It did about 70 mph with me looking like a young tearaway down on the tank. The owner thinks that it is fine but I rode a Comet as a 'go to work bike' over 40 years ago and it was much better than that. Even the lack of 5 star fuel should not be causing that much of a deterioration.

 

[Bill Thomas]

Hello Peter, Don't forget if you use a race cam, you have to take the cyl' head off to shorten the the bottom valve guide. I also think 65mph is good for a Comet, I don't think the engine will last long at much higher revs for a long run. My solo is full race engine and likes 65 on a 48 sprocket !!. Norman do you mean 15 thou or 1 1/2 thou ? 15 seems a lot or have I read it wrong? Good Luck. Bill.

 

[ET43]

Hi Norman,
I agree with the figures in the rider's handbook, but, they do not allow for a ferkin great sidecar being bolted on to the side of the machine. The Blacknell Bullet is perhaps the largest single seater around, and probably the heaviest too, so the combined weight is likely to be around 640lbs, add to that an extra 4 square feet of frontal area and you are not going to go anywhere quickly. I have ridden around ten Comet outfits and none of them came close to 65mph, except Dick Sherwin's which had 8-1cr, Mk11 cam, a 56t rws I think, and that did 60mph. Even riding the plot down a steep hill will not advance the speed overly much due to the frontal area. So, if Peter gets 65mph from his machine, then to my mind it is in good order. Going on a bit further, Steib recommend not having a screen and a tonnaeu cover on together if no passenger is carried. Why, because of the drag of the screen! Why have one up if there is no passenger in the sidecar, that is unless you are a high street poser. Wind, and I do not mean the Baked Bean variety, is a killer! Cheers ET43

 

[charlottevictoria]

Dear all,

thanks very much. I use a 32mm caburater of the Ducati 900 SS which is fully open. The "pipe" between carb and Head also is 32mm. I also use a 7,3 Piston with a 0,25mm compression plate under the cylinder, because my cylinder is a little bit shorter as usual. The piston is original.

Do I need to have special tools to remove the parts or will the dismanteling work with usual tools?

I guess the reason of the damage was that the cable of the carburater was blocked an the engine turned into high rpm after having it started. So I tried to calm it down with the decompression part. That must have been too much!

What ist the usual way to stop the engine? Decompression or what else?

Best regards
Peter

 

[Comet Rider]

Hi Peter,
It is a bad idea to use the decompressor lever when the engine is racing, as this will lead to the little roller coming out of the valve lifter arm and going through the gears in the timing chest.
When engine is racing either strangle it by putting a glove or similar into the carburator or pull off the ht lead.

With regard to gearing, my fathers Comet outfit (Swallow Jet80) is 600cc (Terry Prince conversion) and will happilly pull 70 MPH with 19/54 gearing, but at a steady 55-60 MPH the RPM is slighty lower.

Best of luck
Neil

 

[timetraveller]

OOOOPPPPPSSSS!!!!! Sorry Bill and well spotted. Yes I did mean one and a half thou, not fifteen, not enough decimal points. Just a thought for Peter; we do not know what he has found which he thinks might be part of the cam follower. I wonder if it could just be the roller out of the valve lifter? And Peter you do not need any special tools.

 

[charlottevictoria]

I wonted to upload two fotos of the broken Part and got that message:
Error creating thumbnail! Error code: 1

Command:

"/usr/bin/mogrify" +profile "*" -size 0x100 -quality 70 -geometry 0x100 '/var/www/html/photos/data/500/thumbs/IMG_10581.jpg'

Do you have any idea how to add a Photo to that forum?