Mk1 Concentric bad starting from warm

Bill Thomas

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Is the engine using any oil Bill? Could you be leaning it off to make the plugs hot enough to keep them clean of oil? ( I think you mentioned that possibility in a post above) What happens with the next grade hotter plug?
You might be right, It's not too bad Norm, Old type Race pistons, 10 thou gap. I tried 7 thou and locked it up on the M4 Playing with a HondaKwaki I am running Champion N5, Now gone over to N9yc, Don't really want to go any hotter, In case it holes a piston, Any colder, stops in 20 miles.
Cheers Bill.
 

Hugo Myatt

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When I swapped the standard but worn out original carbs on my Rapide for Mk 11s an established Vincent expert made me two beautiful inlet stubs that connected them directly to the heads. However I discovered that stopping for an interlude of one pint of fine ale was sufficient to make the machine a pig to re-start. Two pints and it was raring to go again but I would not be as the looming threat of the Road Traffic Act would be hanging over me. I reverted to less grandiose stubs with the Amal rubber connector and the problem disappeared. I reckon the rubber connector acted as an insulator against heat transfer and prevented the vapourising of the fuel in the float chamber. With the original standard carbs the float chamber was semi-remote and on a long arm so that heat transference was not such a a problem.
 

Bill Thomas

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Give me a clue Hugo, Am I going to get stuck at the Pub, Joke, I don't drink.
Surely with a Mk2 It will have to be rubber mounted ?.
I have just ordered a pair of Club Shop stubs, They look nice, 2 front heads type, Fairly short.
Cheers Bill.
 

Hugo Myatt

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Bill, as long as you only take circular rides you'll be all right.

On a practical note it pays to renew the rubber connections regularly as they eventually crack and then leak air. Also, as KTB recommends, use wider Jubilee clips than those supplied. I think mine are 12mm. Mk11s were intended to be additionally supported to some part of the bikes anatomy using the two threaded holes at the top of the carbs. This isn't really possible on the Vincent due to a lack of suitable fixing points, which means they waggle about more than on most conventional machines. I think it is this that leads to the degrading of the rubber connectors.
 

Bill Thomas

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I think the Mk2 s are much lighter than Mk1 s, Better metal etc.
Just got my Inlet Stubs from Club Shop, Very quick, Many thanks Jayne and Ian.
Now have to get all the bits that were missing, The Bloke said they came off a Shadow !,
If so, Shadows don't need Main jets, Float needles, Slide spring and special big washers to hold the needles in place, Choke lever, Some screws to hold the float bowl on etc, What Fun !!.
Don't watch this space !, It will be ages before I get it running on these. Cheers Bill.
 

Daytonanorton

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Just got back from first ride of the year, Gave a lot of thought to bad starting over the winter.
Just picked up a pair of Mk2, Bit of a joke, When I looked inside , Half the bits are missing, Don't buy unseen bits !!.
Anyway,Because of this rubbish Petrol, I have to run weak, Or the plugs will foul.
Back to Mk1,s, I have not been flooding enough !!. Partly because I don't like petrol all over my nice clean engine.
And a life time of a mechanic say's I should not !.
So on a hot day, Down on the coast, Quick chat, Then time to restart, I am being watched !, Gave it a real good flooding, Thought this is never going to work,
Starts first kick, Went round the bay a bit more, After a short stop, Same thing, First Kick, I can't tell you how much I have been kicking this bike these last few years,
Since I took my T.T. carb's off.
Learning All The Time !!. Cheers Bill. P.S. I have not touched the Carb's or Plugs etc over the Winter, Left old petrol in there.

Hi Bill, I've just joined this forum so I can give you some feed back. I have just finished building a Daytona spec norton dominator and have exactly the same problem with poor starting as you (and yes the excessive flooding technique works for me too), however looking in to this a bit deeper when I flood the float bowls no fuel actually gets out of the flat top spay tube so no fuel gets down the port into the engine. Having done some research on different spray tubes fitted to mk1 concentrics I found there were 4 types and one of them appearently was designed for the 850 commando which has a cut out on the engine side of the spray tube allowing the fuel into the port when the float is flooded. I read somewhere also that one of the reasons for this was that the larger capacity motor had a lower compression ratio and less suck to draw the fuel in to prime the cylinders - sounds very familiar doesn't it! So I have brought a couple to try and will let you know if it solves the problem. Also I believe that my shallow down draft angle is probably not helping as all the commands are steeper and most of the early commies have either single carb of 2x smaller ones so more suck - not 2x 30mm drain pipes like I have , Kind regards Sarah
 

Bill Thomas

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Good luck, All Bikes are Different, I tried the spray tube mod' for 4 strokes, Didn't work for me.
Now a Fan of Mk2, But as Stu told us, The Slides can stick bad, If the wrong type.
Funny, The Comet 500cc single, Seems to start and run well, What ever I put on it !!, And that Bike is the most worn out of them all !. Cheers Bill.
 

Chris Launders

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As regards Mk1s and float levels I had an instance last year of fuel starvation, I had the float level set with the float level .080 (2mm) below the face of the float bowl and a brass needle with Viton tip, so I couldn't understand what was happening as I had a good flow to the carb, I called Amal and was informed that with modern fuel the float should now be set level with the top of the float bowl and they have found that unless the float actually lifts the needle the brass one is too heavy to be lifted by the petrol pressure alone so now recommend an alloy needle with Viton tip. The latter was the problem I had, the float was hitting part of the float bowl before lifting the needle but was taking pressure off it so some fuel was getting through, enough for steady riding but anything over 60mph and it was being starved.
 
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