underpowered Mk3 update

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Your MkIII wouldn't happen to be fitted with Black caps and a set of un-balanced pipes by any chance, would it?
 
In reply to your question LAB no blackcaps bike is fitted with straight through peashooters
 
My 850 is a MK2A that came from the factory with black caps and stock 230 main jets, I bought it with peashooters and 230 mains but it ran out of puff at the higher rev range, had to go to 260's to get it to pull full revs under load.
 
brf1957 said:
In reply to your question LAB no blackcaps bike is fitted with straight through peashooters
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OK, as I'd read that an unbalanced exhaust with Black caps restricted performance to about 80 MPH.
 
LAB,

Do you mean that Norton sold some restricted bikes? Honda had some Goldwings that had a restriction put in the exhaust nad 85 MPH speedos I think. I have read of folks removing the restriction on those bikes. I can't recall which years the US was trying to do restricted speed.
 
Cookie said:
LAB,

Do you mean that Norton sold some restricted bikes?
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No, not that I know of? But Black caps need the balanced exhaust pipe system in order to work properly, apparently?
 
Got me on that one. Every Norton I ever rode would give you at least an indicated 110 but I've never been on the late bikes.
 
The 850 models would normally have had the balanced pipe system in any case, and those models that had Black caps (MkIA, IIA & MkIII) certainly should have had balanced pipes.
 
kommando said:
My 850 is a MK2A that came from the factory with black caps and stock 230 main jets, I bought it with peashooters and 230 mains but it ran out of puff at the higher rev range, had to go to 260's to get it to pull full revs under load.
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Same with my pure stock Mark III.
Peashooters, K & N, and 260 mains opened it up.
He is running a single Amal MkI?
I believe it is in the carb. Your running out of air, fuel or both.
Double check you slide and choke opening. Check the float level.
Has it ever run correctly?
I thought I read somewhere that a single Amal MkI does not hold enough fuel in the float bowl for a 'Big Bore' Commando?
 
In retrospect, I recall the post with the worn camshaft picture. I did in fact make it to over 100 mph with that cam last season. Couldn't dial the idle in for a damm, but the engine ran suprisingly well considering. Don't wanna scare the poor fella into selling the C-do.

Fuel flow is also my guess. I know that my 850 will hit the "rev limit" in 4th gear if I don't have both fuel taps open. Once I had inline fuel filters (those cheesy plastic clear things they put on lawn mowers) and couldn't get to over 75 mph.
 
Fuel flow sounds like , its often the simple things that confound the wise! restricted fuel taps would prevent high revs/speeds but idleing and slow running would't be affected. and its pretty easy to check clean out the tank see if the gauze filter on the taps is blocked. Or the filters in the carb bowls inlet.
 
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