ET: Engine (Twin) Fogging for Mosquitos; Valve Guide Issues and Solutions
- Thread starter ClassicBiker
- Start date
I am going to add my story here. After investigating an oil leak on the way home from the Annual Rally, turns out the Comet has exactly the same problem.
Seeing as Chris just did this on the Rapide, we thought it would be relatively straight forward, ha ! wrong.
This Comet head has had a hard life. How was this bike even running? One of the locking rings was glued in, the other disintegrated, the valves are toast.
The work needs an engineer, new guides, valves, re-cut the seats etc.
Trouble is, there is nobody that can do the job and get the head back in time for me to ride it before Summer's over. Unbelievable.
{ Wouldn't it be great if a rich person/company sponsored a Vincent apprentice scheme to get young or established engineers learning the speciality, knowing they had customers lined up waiting ? Perhaps it would create an interest in the Marque amongst young people? }
Anyway, Chris is going to do it himself. The oversize guide is 566", and I can order everything he needs.
Buying a valve cutter, learning how to use it and getting that angle right should be fun.
Photos of the metal flying around in the head, the damage and the valve which looks like it's been used for golf.
Seeing as Chris just did this on the Rapide, we thought it would be relatively straight forward, ha ! wrong.
This Comet head has had a hard life. How was this bike even running? One of the locking rings was glued in, the other disintegrated, the valves are toast.
The work needs an engineer, new guides, valves, re-cut the seats etc.
Trouble is, there is nobody that can do the job and get the head back in time for me to ride it before Summer's over. Unbelievable.
{ Wouldn't it be great if a rich person/company sponsored a Vincent apprentice scheme to get young or established engineers learning the speciality, knowing they had customers lined up waiting ? Perhaps it would create an interest in the Marque amongst young people? }
Anyway, Chris is going to do it himself. The oversize guide is 566", and I can order everything he needs.
Buying a valve cutter, learning how to use it and getting that angle right should be fun.
Photos of the metal flying around in the head, the damage and the valve which looks like it's been used for golf.
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I agree, things are getting very difficult on the Vincent front, there are plenty of cosmetic restorers around, we are probably spoilt for choice, but skilled Vincent engineers are quite a different story, very thin on the ground, and as for hoping to get a cylinder head rebuild done before the end of the summer, well my first question would be what summer were you thinking of.
Tracey, did your bike come from a known source or an auction house or dealer, you see so many bikes that purportedly have been rebuilt by a respected Vincent engineer that no one has actually heard of, it is all a bit risky when Comets are changing hands for £20k+
Tracey, did your bike come from a known source or an auction house or dealer, you see so many bikes that purportedly have been rebuilt by a respected Vincent engineer that no one has actually heard of, it is all a bit risky when Comets are changing hands for £20k+
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Hi Tracy, sorry to read of your troubles. The thing is you will keep riding it! Before you get a valve seat cutter find out what type of valve seats you have. If the originals have been replaced with lead free seats at some stage then these are much harder than the originals and some of the seat cutters will not touch them. I use a purpose designed grind stone, 45 on one side and 30 on the other. One of the Sussex section chaps tells me that the correct, expensive cutter will work on the hard seats but check it out before you spend your money.
Thanks, Norman. I will relay your advice to my " engineer".
It seems that some of you have long delays on your engine rebuilds. If anyone needs mechanical assistance on his engine, my well equipped workshop and I could get you on the road again quickly. Just contact me.
cheers, Hartmut
cheers, Hartmut
I found the attached in a 1983 magazine at the back of my bookcase. It may have some information of interest. It describes how (back then) Maughan's did the job.
I read Martyn's attachment and it got me thinking. So I started to make my own steady bush that will locate on the upper valve guide seat area. As I am going to ream the hole for front exhaust lower guide in the head to clean up that hole, I was thinking of making my guide bush with interchangeable bushes at the very top to accommodate the different size shanks of the reamers I will be using rather than make two steady bushes.
Which then lead me to thinking about cutting the valves seats prior to lapping them in. Which leads to the question which cutter sizes? I believe from searching through threads here the angle I need is 30 degrees as they are the original seats. I was thinking on purchasing one or two of these cutters https://www.cylinderheadsupply.com/cu616.html but wasn't sure of the size. I was worried that the inserts might contact the lip of the cylinder head. Has anyone used this type of cutter or similar?
Slowly and cautiously moving forward.
Steven
Which then lead me to thinking about cutting the valves seats prior to lapping them in. Which leads to the question which cutter sizes? I believe from searching through threads here the angle I need is 30 degrees as they are the original seats. I was thinking on purchasing one or two of these cutters https://www.cylinderheadsupply.com/cu616.html but wasn't sure of the size. I was worried that the inserts might contact the lip of the cylinder head. Has anyone used this type of cutter or similar?
Slowly and cautiously moving forward.
Steven
I have used them and sometimes you can get some chatter. Personally I prefer stones, but there are folks out there that think I’m nuts and they prefer Neway. Whatever you are used to I suppose. Only thing with stones, small drivers seem to be extremely uncommon, at least around here, so end up using automotive equipment. Not a problem, just a little unwieldy for smaller delicate heads.