Author Topic: Going at last!  (Read 435 times)

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Offline tck

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Going at last!
« on: 19 Jun 2021 at 14:55 »
Well its been over a year  and a long road helped a lot by this forum but today the rebuilt MK4/90+ ran on the rollers for 5 minutes
it took full choke to start it and it would not run even when hot without full choke
It is fitted with the same carbs it had when I bought it 30 years ago they are 1" pre monoblocks  Think the Amal designation was 275? ( I think 276 was 1"+)
It did run on them before and apart from cleaning them thoroughly I left the jets  and slides the same
The inlet pipe is pretty substantial and I cant see any leaks so its need for a very rich mixture is a bit of a puzzle
I would like to retain them as they look the part and are in good condition however if I draw a blank it will have to be a couple of Mikuni :-0

Offline DJS

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Re: Going at last!
« Reply #1 on: 19 Jun 2021 at 17:46 »
Congratulations Tim!!

Offline tck

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Re: Going at last!
« Reply #2 on: 20 Jun 2021 at 09:32 »
Thanks
I suppose its a matter of checking and revising settings one thing I did ponder on is that one carb wont 'tickel' I took the top off the float chamber and it does fill with fuel but the level ceases at a point below the reach of the tickler which is I think by comparison the correct length. Nowadays I know there are often two grooves in the float needle dependent on float material but this is an ancient copper float (no leaks) and I think the float needles were all the same I will compare it with the other side but perhaps someone has found this problem before.  (1" bore)

Offline EW-Ron

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Re: Going at last!
« Reply #3 on: 20 Jun 2021 at 09:53 »
Congrats. !

The idle passages can take a LOT of cleaning out before they are truly clean.
Ask me how I know this.
The rule here is to clean and clean and clean until they work. ?

I'd try swapping those floats over, and seeing where that takes you.
The float needles can be ground to their seats using a fine metal polish.
You may need to watch that both floats float at the same depth ?

And you may also want a fine fuel filter in the piping to filter out any rust or grunge in the petrol,
this can play havoc with idling jetting etc.  Watch that some filters can limit petrol flow, choose carefully.
Have fun !