AJS & Matchless Owners Club

I am looking to replace my old carb.
According to Roy Bacons book the carb I require is a 389/52. 1 5/32

The closest Jampot has is this

389/18.5 389/3732.AMAL 389 1 5/32




389 Amal 1 5/32" Monobloc Carburettor.(NOTE;carbs can not be returned for exchange/credit once fitted)

Price : £130.00 each Other currencies

Price incl. tax : £156.00 Other currencies

Stock : Available

389 and 1 5/32 is correct but the other numbers are different not sure what the 18.5 and the 3732 stands for and if it will cause a problem.

Can't help but there were threads on this topic before and I bought a newie monobloc from AMOC and all good.

Johnny B

Do these links help?
http://amalcarb.co.uk/carbspec/carburet ... s/id/5285/
http://amalcarb.co.uk/standard-1-5-32in ... ettor.html

Main jet seems to be different, maybe the slide. Can the carb be ordered to your spec.

Would you expect to have to allow some tuning for modern fuel?

Hi

3732 is another way of expressing the bore - read it as thirty seven thirtyseconds of an inch, ie. 37/32" or 1 5/32"

18.5 is possibly the bore expressed as sixteenths of an inch

Regards Mick

Just let the parts service know you require a 1 5/32 carb and what jettings you require and they'll set it up accordingly for no extra charge.

Thanks very much, I will contact spares, best price anywhere.

hope this info is of use Mickey. For my '54 G80s I got a brand new Amal monobloc (389/3732) off spares with standard jetting (260MJ, 106NJ, 30PJ) - I found she ran very week/pinking etc (yes timing is spot) no air filter fitted, even with needle on the lowest notch (richest) (I believe this is because of methanol in modern fuel). So, I have been playing with jets and 270MJ seems to be about right, 280 is a little lumpy when she is opened up fully. Still to suss out the best needle position but suspect it will be one up from richest setting. So you might want to order 270 MJ at the same time as your new carb PS - there are folk on here with far more experience of carbs than me so I am not claiming any expertise - just sharing my recent findings.

My Monobloc from the Club was standard and experience differs from Stephen's. I will be re-checking the timing next week but currently the plug is darker than I'd wish and the threaded part is sooty and Matchless flattens out at a little over 70mph whereas with the knackered Concentric it would pull a higher indicated speed.

Pulls fine at lower speeds so I guess it's the jetting / needle position but always a chance I've set it a bit too retarded.

I'll post up my results when I get home next week.

Johnny B

Very interesting information.
My new carb should MJ 300 PJ 25 NJ.106
As only a couple of squid, I will order a 280 and 320 always useful as spares for other bikes, and have a tinker.
Thanks again.