• Welcome to the forum website of the Vincent H.R.D. Owners Club.

    Should you have any questions relating to the Vincent H.R.D. Owners Club, or Vincent H.R.D. motorcycles in general, please contact Graham Smith, Online Forum Webmaster by calling 07977 001 025 or please CLICK HERE.

    You are unrecognised, and therefore, only have VERY restricted access to the many features of this forum website.

    If you have previously registered to use this forum website, you should log in now. CLICK HERE.

    If you have never registered to use this forum website before, please CLICK HERE.

Is it the valve guides, the cylinder sleeve or the piston?

Ducvelo

Well Known and Active Forum Website User
VOC Member
I had the heads and barrels off my Series C twin last year, and since I've put them back oil consumption has been enormous - c.2 pints in 100 miles. Based on the plugs, this seems to be confined to the rear cylinder. When I stripped the top end, valve guide clearance was large but not very excessive, 0.004" inlet, 0.008" exhaust. Rocker tunnels/bearings had had the usual treatment (dremel work on the valve well, and good grooves in the bearings) to improve oil drainage. Piston clearance about 0.004" at bottom of skirt (pistons/rings are from the mid-70s). Sleeves 'rang' well when knocked on the top - no sign of movement, but I don't have a press to really check. Little wear on the sleeves - I think the engine has only done 20,000 miles since the 70s rebuild. Was on a 0.030" oversize. Breathers are working well, and hardly passing any oil, and no leaks. The rebuild was to sort out the timing side - I swapped out badly worn Mk 2 cams and fitted the Gary Robinson 105s. I checked carefully clearance on the valve guide with the increased lift. Also fitted the restrictor disks for the cylinder oil feeds. I did remove the joggle wires, but now put one back on the No 1 inlet feed - hasn't made any difference.

Before I strip down again, any one got any tips on how to work out which is causing the problem?
 

Kansas Bad Man

Well Known and Active Forum Website User
Non-VOC Member
First, plug the joggle wire hole , 4and 8 is a lot on the valve to guide, could be the scrapper ring was put in up side down on the bad pot.

Cheers
 

greg brillus

Well Known and Active Forum Website User
VOC Member
Have a look down the bottom of the bores and see if the marks left by the rings are ABOVE the oil feed holes at the rear of each cylinder. Most all engines I have pulled apart, the oil holes are feeding oil between the rings......not real good for oil consumption. As Max said before, if your guides are showing up to 8 thou clearance, your oil consumption will be higher than petrol..!!! Should be more like 0.0015 to 0.002 on the inlets and half a thou more for the exhausts. If the oil holes in the liners are above the lowermost ring, you can plug them up and drill them lower. Get your heads /guides done by someone who is Vincent savvy, as most engine rebuild shops don't know how to align the upper/ lower guides correctly....I found this out years ago, got the heads back from the shop, only to find the valves way too tight in the guides, not from incorrect clearance but from poor alignment. Perhaps Trevor can explain how this is done, but experience counts big time on this issue.....Cheers.....Greg.
 

Kansas Bad Man

Well Known and Active Forum Website User
Non-VOC Member
Just to fortify what Greg said, the miss alignment of the guides is usually caused by the registry of the top guide seat not being correct , the seat registry must be a 360 degree 90 degree to the bottom guide. Tighten the guides up, put some Kemp seals in, get some chrome rings,
depends on the pistons you have but if the ring groove is correct, Honda rings are good , ask DAN SMITH about that, he will set you straight.

Cheers
 

chankly bore

Well Known and Active Forum Website User
Non-VOC Member
Unless you have had some energetic Rwandan primate hefting at the cylinder head bolts, then the alignment of the top guide-lower guide register and valve seat should still be O.K. That being the case, bore out an upper guide to 3/8" and use a piloted reamer to ream your new lower guides. Kemp sealed guides are a great fix. Make sure you use a low ash oil so you don't get the stuff burning on to the exhaust valve. Check that the rocker tunnel hasn't broken through to the exhaust port-don't ask me how I know this problem!I have had success with .002" clearance exhaust and Brasso clearance inlet. Heed the above advice re piston oil feed.
 

Ducvelo

Well Known and Active Forum Website User
VOC Member
Just to say, I lifted heads etc and examined. An over-enthusiastic porting of the inlet port on the No 1 head by a would-be racer in the past had broken through into the rocker tunnel. This had been filled (looks like an alloy weld) but this had now cracked and oil was seeping into the port. I guess under vacuum quite a draw of oil. Any views on best way to repair this crack - it's only quite small, but of course the alloy heats up a bit?
Guides also have quite a lot of clearance so I'll do these as well, and the liners - feels expensive. Any views on whether to fit the oil seals?
 

timetraveller

Well Known and Active Forum Website User
VOC Member
A very good welder could repair the break through and then there was a picture a few days ago of what can be done to a rocker bush to make it fit around a weld. Alternatively, and if you have access to a good machinist, think about boring out the inlet tract and then fitting a piece of ali tube to be a good interference fit in the inlet tract. It will depend upon just where the break through is as to what you can get away with. If all else fails then there are new heads available and someone who has fitted a Terry Prince top end might well be happy to recover some of the cost be selling their old head. Good luck.
 

Martyn Goodwin

Well Known and Active Forum Website User
VOC Member
Why not ask someone like Conway Motors for a quote to repair the welding and fit new valve guides and valve stem seals. May be way less cost that you might think.
 
Warning! This thread is more than 9yrs ago old.
It's likely that no further discussion is required, in which case we recommend starting a new thread. If however you feel your response is required you can still do so.

Photos from the 2022 North American Rally

Photos from the 2022 Annual Rally

Photos from the 2022 French Rally


Top