AJS & Matchless Owners Club

Hi, I have searched the forum and internet searches. I have a 1952 18s with a 389 monobloc fitted.
I'm getting spitting through the carb when throttling back and opening the throttle again. This obviously int the original carb. I have stripped the carb to check jet sizes etc.

I have the following,

No airfilter
Main jet 170
needle jet 106
primary 30
slide 3.5
needle 3rd notch

Main jet seems to small according to info found.

About to order some parts, if anyone as any recommendations on jet size, please let me know

Thanks
Steve

Take a look at the '56 handbook which uses a 389.

http://archives.jampot.dk/book/Owners_m ... ingles.pdf

Thanks for that, my main jet is too small according to this.
This also ties in with the Amal site

As well as the main being way too small the 3 1/2 slide will give the symptoms you are experiencing as it'll make the mixture too lean. You need a 3 slide and a 270 main jet.

389 what?? 389/1 perhaps, Main jet should be 260, others seem OK. But carb bore size may not be correct. 389/1 I believe is 1 3/32" but would that be the same as your 52 bike. ( Amal states 3 1/2 slide That is 1956 500 389/1 info )

Thanks for replies, the carb is marked as a 389/201, this measures as 1 1/8. Amal site states the 389/1 is 1 5/32.

Steve Harding wrote:Thanks for replies, the carb is marked as a 389/201, this measures as 1 1/8. Amal site states the 389/1 is 1 5/32.

1 5/32" probably correct, I looked quickly in bad light.
389/201 was used on 1963/65 650cc BSA Rocket A65, I can just see that's 1 1/82" bore, also checked my error, 1 5/32" not 1 3/32"
Don't go to Specsavers, they never made my glasses good enough to see very small print. I got fobbed off twice, first they said I needed to get used to them, then said, well you only had the cheap lens ???

Was the original pre monobloc 1 1/8 bore? Will this monobloc I've got be ok?

Thanks

Steve Harding wrote:Was the original pre monobloc 1 1/8 bore? Will this monobloc I've got be ok?

Thanks

1951/53 was 89B/1AK 1 3/32" bore, Look in tech tips, I made a file of all carbs on AMC.

In the Archives all info for 1940 /54 has been cropped off , so you only see the carb type used, not much else.

I'll rescan just AMC and tag the file as 1940 54 settings

Thanks for your help