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Spark Plugs

Jim Richardson

Well Known and Active Website User
VOC Member
I have a 1949 series C Rapide, with standard carbs and a Sintilla Mag.
I will except that the 276 carbs are worn but it is difficult to start, if I clean the plugs ( which are sooty, not oily ) it will start easily, after that much leaping up and down is needed.
It is currently fitted with B7Es plugs are these the correct ones for the bike and/or could I go to a hotter plug and eliminate the sooting.

Jim
 

Tom Gaynor

Well Known and Active Website User
VOC Member
Poor starting

I would say they were too cold. I currently use NGK6, but have used 5 with no problems. I have a copy of an NGK applications chart (presumably made up by comparison) which covers Brough Superiors, Rudges, and Vincents. The Vincent recommendation is NGK B6ES. NGK 7 is verging on a racing plug, AJS 7R's use NGK 8.
If that doesn't work (and my opinion is that your plugs are at least one and possibly two grades too hard), then I would be suspicious that it was time to send the mag to rehab. They don't last forever, or to be more accurate, the condensers on which they depend, don't. Dr Lindsley runs a good clinic......
 

Jim Richardson

Well Known and Active Website User
VOC Member
I had mag problems on my Comet, so I binned it and fitted a D type distributor, end of problem ! but as the sintilla is a bit of a curiosity I would prefer to stick with it for now, that and refurbed mags don't appear to last to long.
The bike is running a bit rich and rather than splash out on refurbed or new carbs, I hope to get by with a plug change for a little while as it starts and runs fine when hot.
 

Tom Gaynor

Well Known and Active Website User
VOC Member
Magneto problems

I'm not an expert on this. The 2MTT mag on my Manx Norton has failed three times, each time when very hot - either a hot day, or on long circuits like Chimay or the Ulster GP. Two times out of three it has restarted once it cooled off a little. The exception was at Chimay where the ambient temperature was about 34 and I was within an inch of heatstroke. One piece black leathers.......
I've been told by (the many) people who know more about it than I do that the problem is in the condensor, that with modern varnish the windings last forever, and that the go-to magneto guys do NOT use radio condensors from Radio Shack or Maplins, but condensors designed for the application. These are of a different construction from the usual Lucas ones. I wouldn't know if this was true or not, but believe it is. There was something on this on jtan a while back.
I've always had good results on road mags from Dave Lindsley, so that's where I'd send my Scintilla. I take your point that if it ain't broke, don't fix it, however if it does stop when hot, then restarts once it cools, it's telling you something. Either start on a headstone for it, or send it to be overhauled.
(This discussion is parallel to one on the Sunbeam S7/8 "jtan" where Lucas condensors are occasionally dead when they come off the shelf, having broken down in storage.)
 

BlackLightning998

Well Known and Active Website User
VOC Member
Jim - have a look at the thread on my 276 carbs running rich

Hi Jim,

If you search under technical advice on this Forum you will find a long thread where I recently had a front cylinder running rich after a changed throttle cable - plugs and carbs were discussed at length and you may find some of the advice helpful from my own experience.

I finally (after a lot of plug changing) traced the fault to worn parts in the 276 - I replaced with a new needle, new needle jet (106) and new main jet (170) and this cured the problem. Burlen Fuel Systems were great - bought over the net and delivered next day - recommended.

I am (on advice) running Denso platinum electrode plugs though I have electronic ignition - I think whatever type you use you should have projected electrode plugs which will stand a better chance of clearing.

If you need any more information on how I sorted the problem beyond what you find on the thread - let me know.

Regards

Stuart

I'm not an expert on this. The 2MTT mag on my Manx Norton has failed three times, each time when very hot - either a hot day, or on long circuits like Chimay or the Ulster GP. Two times out of three it has restarted once it cooled off a little. The exception was at Chimay where the ambient temperature was about 34 and I was within an inch of heatstroke. One piece black leathers.......
I've been told by (the many) people who know more about it than I do that the problem is in the condensor, that with modern varnish the windings last forever, and that the go-to magneto guys do NOT use radio condensors from Radio Shack or Maplins, but condensors designed for the application. These are of a different construction from the usual Lucas ones. I wouldn't know if this was true or not, but believe it is. There was something on this on jtan a while back.
I've always had good results on road mags from Dave Lindsley, so that's where I'd send my Scintilla. I take your point that if it ain't broke, don't fix it, however if it does stop when hot, then restarts once it cools, it's telling you something. Either start on a headstone for it, or send it to be overhauled.
(This discussion is parallel to one on the Sunbeam S7/8 "jtan" where Lucas condensors are occasionally dead when they come off the shelf, having broken down in storage.)
 

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