Monobloc on a '51 Comet

[Desmond]

If your talking about Greg's Mods with the Carbs, I don't think that was Monoblocs ?.
I played with a monobloc On my Flash spec' Comet and hated it , I rubber mounted it,
Because I have a rear Cyl' Head, And it was Very heavy, I would not do it again !.
Your problem with the Concentric I think was distortion after the flange was overtightened ?,
At some time in it's life.
I can only give you spec' for the Black Prince, !. 1 1/8" Monobloc ,Because the Amal book won't show the Victor, Only 2 made !!, 280 main, But comets like it a bit richer, I would say 300 ?,
30 pilot, Needle 106, Needle position 3, I think that's from the top ?,
The Amal book say the slide 604, I think that means 4 slide ?.

Just looked in Know Thy Beast, It says some people have trouble with the 30 pilot,
And it's fixed by fitting a 25.

I have been told that monoblocs can have sticking float trouble ?, Something to check ?.
I think you have flooding problems, Easy way is switch the petrol OFF ,
As the float level goes down , If it smooths out you know it was too rich ?.

Did you try Conways for the BIG piston ?, I am interested because am thinking one for myself ,
Only dreaming at this point !., But they say they have big barrels !!.
Good Luck, Bill.

Bill:---Ah! now that is great guidance. I did just get a note from Mike at Surrey Cycles and he aimed me at a sticking slide due to a possible flange problem and close inspection of the Concentric has now shown up a hairline crack. It had to be the slide but I could not identify that or why. I'll work with your recommendations on the guts of the Monobloc. I do not have Know thy Beast but I do have Forty Years On as well as Richardson and others. The only info I could get on Monoblocs was for Rapide and Shadows and we are likely to be a bit different---as you say.
I have a bored out Nikasil barrel for the 90 mm that you might get from Venolia like Vibrac did. Someone else now has the modified head but we might be able to get it back as well if you were interested. Bear in mind that you need to modify the crankcase for this barrel. That is why I sent the bike off to a Vincent machinist friend for rebuilding so that he could machine a modification of the crankcase back to take the standard barrel.--------Desmond

 

[Bill Thomas]

I found once that the last flat of doing up the flange bolts, Would distort the body,
And make the slide stick,
I think I just ground the flange flat, On a bit of glass and wetanddry paper,
Or something like, A simple fix !.

Thanks for the offer, I have a lot banging around in my head at the moment,
I am trying to Stroke a Comet !,
Just lost Confidence, Getting Old and Daft !,
I have been thinking of buying C/Cases already bored,
But didn't like the Nikasil type, Conways say they can do normal barrels ?.

 

[Bill Thomas]

Desmond, If you had it going as a Big engine,
What happened to the old piston, Did it nip up ?.
Cheers Bill.

 

[vibrac]

Vibrac---Thank you for that input. I think we have the timing right as she always started beautifully on the Concentric after being brought back to standard. She used to kick back a lot under Bob Dunn's modification but I learned to live with that and she ran very well. What guts are you using in your Monobloc?

Without taking it apart I cant say what I have in the Monoblock whatever it is is a good starter as its been on at least 3 of my bikes without alteration

 

[oexing]

Seems Desmond got two problems, a distorted Concentric, and in the Monobloc a blocked pilot jet. A dry spark plug will tell, no fuel at kicking speed, the pilot jet is critical for kicking, no other components responsible here. Also check for air leaks on the carb flange or stub . The slide cutout comes only next for picking up from idle speed.

Vic

 

[Bill Thomas]

I had to put weaker slides in my Bikes when we went ethanol,
Or I wetted plugs after a 5 to 10 miles.
Then my Plug Threads went loose and had to helicoil on my Special, Not Happy !.
But after having the Bike for 55 years,
And 10 years racing that engine, Maybe not Too Bad !!.

 

[Bill Thomas]

In case you want a photo.