E: Engine Comet Problems

[vibrac]

The long held preferences of plugs to use on a Vincent are moving under the effects of modern so called petrol and the prevalence of rogue NGK on the market .
I have started to make the unheard of choice afer 40 odd years of trying Champion plugs again (using the Green spark plug company) but who knows?
your choice is 'in the ball park'

 

[Black Flash]

I suggest you recheck your cam timing. Easiest is equal lift at 4°btdc.
If have seen Vincents running being one tooth of the cam wheel out, but really gutless.

 

[Bill Thomas]

I had Big Flames out the injectors in 1970 on My Blue Twin in the IOM,
I had home made Wal Philips Fuel injectors and blamed them,
Put Concentric Carb's on and it was the same !,
Turned out it was the Magneto.

 

[Steve Morris]

OK, Ive replaced the plug first, fitted the Denso W20 TT. Gap is 0.0018".

Started very easily, second kick, gently warmed it up and it sounded OK, revs cleaner, or appears to, I think the plug has definitely made a difference, but i still have back-firing when the revs come down to idle, which i never had before..

Stripped the carb again, clean as a whistle, needle in the middle position, but noticed something odd? The needle from memory was 'pointed' at the end, like a needle, now it looks stubby, almost like a piece has come off, looked in the bottom of the main jet, nothing, no idea how it could have happened, if indeed it is that, (clutching at straws here), so, can anybody please tell me how long the needle should be? (std Amal 229F/1DV)

Another thing, and again perhaps i am barking up the wrong tree here as well, the exhaust appears much much noisier than it did before? Almost as if the baffles are missing?

Its so frustrating, ive been over what ive done time and time again, but here's the 'pattern'

Bike was running OK, but the idle was 'hanging up' when the bike was warm. A 'blip' on the throttle got it down. I replaced the carb with a known good one, still the same.

Replaced ATD springs, appeared slightly better but still had the idle hang up. After a few conversations on here i decided to replace the ATD. Got one from Tony Cooper in Halesowen.

Removed the timing cover to fit the ATD, and decided to check the cam gears/end float/breather timing etc. Noticed the cam spindle was loose, and the exhaust follower spindle. Ordered and fitted new o/size spindles, re-built cam gears to correct tolerances, end floats etc. Triple checked timing!

Set the ignition timing static at 'points just beginning to open at TDC (BOTH VALVES CLOSED).


Put it all back together and started. It started well, better than its ever done in fact, but was backfiring through the exhaust and stuttering. The bike seemed to perform very well, in fact i dont remember it ever being that fast! and the idle hang up was cured.

On a 30 mile test, the fuel consumption was awful! In fact as i arrived home it ran out.

And the rest as they say is history,

I am starting to wonder if the ATD could cause this problem??

 

[Peter Holmes]

I don't think the needle jet was ever supplied with a sharp point, I doubt very much that you have lost the tip, I can't see how that could possibly happen, and I am sure they were originally supplied with a blunt end. You might have diagnosed your problem with the noisy exhaust, I would remove the silencer and give it a rattle, if the baffles are floating around and intermittently blocking the silencer that would for sure upset clean running.
I don't use any modern plugs, preferring to search out KLG FE70, they have served me very well through the years.

 

[Bill Thomas]

Put the old carb' back on , Quick and easy test ?.

 

[Steve Morris]

I’d love to but I ‘loaned’ the other one Bill! I’m going to give it a ride later if it stops raining....

 

[Bill Thomas]

Sorry Steve , I found an old 229 but no needle is in it,
The Amal book does not talk about the 229 !,
I must have it but I have so many needles from so many other carb's,
I could not tell .

Did you have the exhaust pipe off when you did the work,
I mean an air leak on the exhaust would make it bang in the exhaust ?.

 

[Steve Morris]

I didn't remove the exhaust Bill, Ive checked it today though and its pretty air tight. Ive had another play this afternoon, removed the points, cleaned and checked the gap, points were a bit dirty but not burnt or worn, gap was 0.0012" so alls good there. If the weather holds i am going to take it out tomorrow morning for a run and see how it feels on the road.

I checked the ignition timing again, just to be sure, and on TDC the points are just about to open so I'm sure alls well there.

I'll report tomorrow!

 

[Bill Thomas]

You could play with the float height,
As had been said by twisting the carb' on the stub, Just a little ! ?.

Is it worth checking the earth screw and brush on the flange end of the mag' ?.