I don't where this puts me in the great pantheon of Vincent ownership, I purchased my Rapide when I was 16 Y.O.A. About 16+3 months as I remember it ( just looked in the green log book to check, but sadly it is a continuation log book and the first date in that is 26/5/66) I had passed my test pretty soon after my 16th birthday on a BSA B31 combination, then very soon after swapped for Norton 77 solo, around the same time a mate of mine convinced his Dad to purchase him a Vincent outfit from Conways to learn on, you could do that in those days, anyway, totally inexperienced Ian set of on his outfit + L plates and on tearing through the sweeping bend in Harrow somewhere near the old Sopers department store the chair lifted and Ian stacked it, well his misfortune started what has so far been 47 years of Vincent ownership. I think Ian's Dad paid Conways £99.00 for the outfit, it was a truly dreadful machine, totally knackered, to give you an idea how bad, the rocker pins had worn themselves about halfway through the aluminum bearings and to compensate for the wear, all the tappet adjustment had been used up and the threaded part of the rocker arms had been ground down to get more adjustment, the whole engine was in an appalling state, but do you know what, it went, and it went bloody well, Ian eventually parted with his now, sort of repaired(not very well) Vincent for £65.00, I know that this is not a record as I have heard of cheaper purchases, but when I was 16 and earning £5.00 a week as an apprentice it was still plenty, but it remains to this day the best £65.00 that I have ever spent.
New (?) Comet Engine Noise
- Thread starter Martyn Goodwin
- Start date
So, with the crank out - and in the hands of Laurie Binns for expert repair, I am turning my attention to those myriad of minute details that would otherwise be ignored. THere is slight scoring of the bore and traces of the piston overheating. Evidence is a golden bake on the underside of the piston and minor levels of carbon build up inside the head and on the piston crown. I suspect that the motor may have been running a tad rich, washing the lubricating and cooling oil off the cylinder walls - so I am taking the operetunity to switch from a 210 main jet to a 200 - and I will also lower the needle one notch.
With the cases split I am also planning on having the oil filter chamber machined (it is in its raw cast state) so that the newer paper cartridge filters will work in it - at present it is ONLY suitable to use the older felt filters.
This misfortune had become a hot bed of opertunity. The expectation is that at the end of the rebuild I will have a bike with 100,000 mile mechanical reliability - wish I could say the same about the rider!
Martyn
With the cases split I am also planning on having the oil filter chamber machined (it is in its raw cast state) so that the newer paper cartridge filters will work in it - at present it is ONLY suitable to use the older felt filters.
This misfortune had become a hot bed of opertunity. The expectation is that at the end of the rebuild I will have a bike with 100,000 mile mechanical reliability - wish I could say the same about the rider!
Martyn
I wouldn't lower the needle past the middle notch, and a 210 main jet ain't that much over-rich. In any case not much riding is usually done on the main.
Martyn,
The singles are more prone to uneven heating than the twins. Many rebuilt Comets suffer from too little piston clearance. I also noticed bluing on my Carrillo rod at the small end and an extra .0005 clearance cured the bluing. I am with Chankly, I would not think that washdown is an isssue.
David
The singles are more prone to uneven heating than the twins. Many rebuilt Comets suffer from too little piston clearance. I also noticed bluing on my Carrillo rod at the small end and an extra .0005 clearance cured the bluing. I am with Chankly, I would not think that washdown is an isssue.
David
Comets always run wider throttle openings and so higher cylinder pressure than twins , thus their pistons show more discolored oil residue especially on the underside and carbon build up is to be expected . They need a richer mixture to live under the greater heat which explains the carbon build up . Rich is cool but loses a bit of power , lean creates greater power from the higher pressure thus speed , but is waiting for the excuse to cause problems , detonation , piston skirt damage , erosion of the crown , eventual melt down If ignored . At that point she will burn a hole through the crown blowing molten alloy down into the bottom end as she cries enough . Stay on the rich side , the plug porcelan coloring a chocolate brown , not a light tan and certainly not nearer white . These light colors are acceptable in a modern water cooled motor but are death to air cooled ones .
Matt's Shadow is still on the original carbs , running beautifully , with 220 mains . It is fitted with a Triumph original Burgess straight through Glas PAC muffler so needs that larger jet . Give a motor what it wants and needs , not what the book says or you think is correct . The motor IS BOSS . Sid .
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Matt's Shadow is still on the original carbs , running beautifully , with 220 mains . It is fitted with a Triumph original Burgess straight through Glas PAC muffler so needs that larger jet . Give a motor what it wants and needs , not what the book says or you think is correct . The motor IS BOSS . Sid .
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I can't stress that last point enough . An arrogant tuner is at odds with reality , you need to be the motors servant , reading it's signs and language which in fact convey its needs . Supply them and it's happy and long lived , ignore at its immenant demise , and you will push it home , silent , only your footfalls to be heard . Sid .
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What had me thinking it was generally too rich were some vertical score marks on both the piston skirt and the barrel - it suggested to me that the oil film was being washed off the surfaces by the over rich mixture. For now, once rebuilt I will stay with the 210 main and initially drop the needle just one notch then check the state of the plug after the first few miles.
I agree a probe up the rear orrofice is a better indication.
Martyn G
I agree a probe up the rear orrofice is a better indication.
Martyn G
Just heard back from Laurie. Bad news is it was the original big end and it is toast! Good news is that nothing else in the crankcase area needs attention - he measured less than 0.001 inch runout on the crank before he started in on it - no wonder it gave such a smooth ride. Mainshafts and the main bearings are just fine.
It seems that the cam lobes are worn, but not beyond saving with some judicial stonning - irrespective I will be fitting a new Mk1 cam and new cam followers. Given that I have the parts on hand I am also going with Lauries revcomendation to fit a new (oversize) liner to the muff and a new standard size piston.
While the cases are split I am also taking the opertunity to have the oil filter chamber machined so that it will accept the new paper element filters the Spares Co is now supplying.
I expect it to be a week ot two (at least) before I get the rebuilt crank back - so I guess it will be large does of patience (and red wine!) till then.
Martyn
It seems that the cam lobes are worn, but not beyond saving with some judicial stonning - irrespective I will be fitting a new Mk1 cam and new cam followers. Given that I have the parts on hand I am also going with Lauries revcomendation to fit a new (oversize) liner to the muff and a new standard size piston.
While the cases are split I am also taking the opertunity to have the oil filter chamber machined so that it will accept the new paper element filters the Spares Co is now supplying.
I expect it to be a week ot two (at least) before I get the rebuilt crank back - so I guess it will be large does of patience (and red wine!) till then.
Martyn