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Comet Valve Lifter

cometbaz

Website User
VOC Member
I have recently aquired a comet for restoration and I am wondering if it should have an exhaust valve lifter fitted. I did have a friend with a comet without one and it started ok but I was wondering about possible excess component wear if it should have one .
Cheers Baz
 

Hugo Myatt

Well Known and Active Website User
VOC Member
It should have a valve lifter and makes starting a lot easy with it. Unfortunately they are prone to leak oil, though less so on a Comet than a Twin. Some owners removed the mechanism and plugged the hole, a rather drastic remedy to stop a little oil seepage. If the mechanism is still in place (Left side of timing case, awkwardly tucked away on a Comet) You need handlebar lever, cable HB10AS, sleeve ET168, abutment ET172/2
 

Len Matthews

Well Known and Active Website User
VOC Member
Even more drastic,mostly on Twins, is to abandon the original lifter mechanism in favour of Enfield decompressors screwed in the cylinder heads. Why tap extra holes in the heads when, with a little patience, the standard set up can be entiely satifactory.
 

Tom Gaynor

Well Known and Active Website User
VOC Member
Valve lifter leaks

I'm reluctant to mention this when "Zeppelin" Myatt is around, but I bought and fitted the "patented Ron Kemp valve lifter leak suppression kit" AND improved the function of the breather. One or both of these actions worked.
 

nkt267

Well Known and Active Website User
VOC Member
I didn't know that the kit from kemps fitted a Comet,the one I ordered didn't.(someone told me it did).It will be passed on to someone in the section one day.
 

Hugo Myatt

Well Known and Active Website User
VOC Member
Zeppelin

Tom,
I am a little puzzled as to how I have gained the additional appellation 'Zeppelin' as I have no known Teutonic ancestory. Is it because of my burgeoning figure or my Steib S501 or some more sinister reason???
 

Tom Gaynor

Well Known and Active Website User
VOC Member
Zeppelins

Perhaps my memory has failed me again, but there is a priceless letter in FYO from, I'm sure, Hugo Myatt, describing experiments he conducted on engine breathing. He purchased "something for the weekend" - and fitted one of each (they come in packets of three) to the chaincase, the gearbox, and the engine breathers and took the bike out for a dander round the block. If the devices were inflated, then that pointed to the source of the breathing problem. I'm not in a position to check the reference right now, but Hugo Myatt or no, the rider got back to his house with one "device", now the size of a small Zeppelin under his arm, still attached to the engine. There was indeed pressure where there didn't ottabe.
Regardless of whether it was Hugo Myatt or AN Other, it's worth looking up the reference in FYO, both for the amusement it gives, and the insight into Vincent breathing problems. I followed the advice given (the Prof was involved) and it worked. I'd be happy to pass on what I learned and what I did.
 

Hugo Myatt

Well Known and Active Website User
VOC Member
Zeppelin

Tom,
You are quite right it was me. I quite failed to make the connection. I had long since forgotten. Since then I had the engine rebuilt by Bob Dunn. The problem was in fact as the Proff diagnosed. The mainshaft bearing seal (dive side) was acting as a oneway valve and pressurising the chaincase. As I had managed to make the chaincase completely oiltight and it seems airtight it pressurised the gearbox too. Since the rebuild no further trouble.
 

Tom Gaynor

Well Known and Active Website User
VOC Member
Zeppelins

It saved me a lot of grief because i had bought a mainshaft seal and realised two things before I attempted to fit it. Firstly, the seal would cure the symptom, not the disease (thank you, HM and Prof), and secondly (thank you, Trevor Southwell) the contact between ESA and main bearing inner is already pretty narrow, and a seal makes it narrower still. So the ESA wears, the chain become misaligned, the chain snaps bursting the chaincase, all just as a truck carrying an entire class of schoolchildren and laden with nuclear waste comes round the corner overtaking a petrol tanker.............. I made some of that up, but if you do use a seal it's a point to check.
However, the answer is to sort out the breathing when the self-filling chaincase / gearbox problem goes away.
 

clevtrev

Well Known and Active Website User
VOC Member
It saved me a lot of grief because i had bought a mainshaft seal and realised two things before I attempted to fit it. Firstly, the seal would cure the symptom, not the disease (thank you, HM and Prof), and secondly (thank you, Trevor Southwell) the contact between ESA and main bearing inner is already pretty narrow, and a seal makes it narrower still. So the ESA wears, the chain become misaligned, the chain snaps bursting the chaincase, all just as a truck carrying an entire class of schoolchildren and laden with nuclear waste comes round the corner overtaking a petrol tanker.............. I made some of that up, but if you do use a seal it's a point to check.
However, the answer is to sort out the breathing when the self-filling chaincase / gearbox problem goes away.
And remember not to sort the breathing out too well, otherwise you will find the crankcase filling at low speeds, due to no crankcase pressure to push the oil into the pump.
 

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