throat size 376 monobloc

[David Tinsley]

55 GF SA iron head
I have a 376 carb fitted at the moment which has a 1" throat size. The manual lists 1 1/6"
Will I get any issues with the !" carb?
Dave

[muskrat]

G'day Dave.
Best to have the port and carb match. The mismatch creates turbulence. Worse if it was the other way around (large carb/small port). A tufnol insulator can be tapered in the bore to take the step out. https://amalcarb.co.uk/phenolic-spacer-26mm.html
What is the condition of the slide and bore? What jet sizes are in it?
1" = 3.5 Cutaway Slide, 220 Main Jet, 106 Needle Jet, 25 Pilot Jet.
1,1/16" = 3.5 Cutaway slide, 250 Main Jet, 106 Needle Jet, 25 Pilot Jet. This is the standard set up off the shelf.
Cheers

[David Tinsley]

Hi Muskrat,

Thanks for reply.
There is a bit of slop between slide and bore, maybe 2mm. seems a bit excessive, but not sure?
all new jets and needle were fitted.
3.5 slide
25 pilot
106 needle
240 main - that seems to wrong size if 220 is the norm. Then again I have not really run it at full throttle which, if I understand correctly, is where the main jet comes in.
Given the slop between bore and slide and the wrong throat size I am thinking of a new carb. I just hate parting with money if I dont have to!
cheers,
Dave

[Rex]

If you've really got 2mm play the carb is totally spunked.
It needs sorting before attempting any sort of fine tuning, and even if you hate spending money (why fanny-around with old bikes then?) you're going to have to in this instance.

[David Tinsley]

If you've really got 2mm play the carb is totally spunked.
It needs sorting before attempting any sort of fine tuning, and even if you hate spending money (why fanny-around with old bikes then?) you're going to have to in this instance.

I love "fannying" around with old bikes and have done for years. I always try everything else before parting with dosh though - just my makeup
I suspected this carb is toast so just been looking at prices for a new one. And SWMBO never minds as she knows where I am and not down the pub!