carb query

Information relating to the Matchless G3 or AJS Model 16 350cc Heavyweight
Steve
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carb query

Post by Steve »

Hi all I have recently joined having purchased an 1953 AJS 16 MS.
upon checking over a few things after downloading a maintenance manual which said the carb should be a 76AE/1AK 1 inch with a 150 main jet and a 6/4 throttle valve. mine is fitted with a 376 Monoblock 1 inch with a 210 main jet with a 376/3 throttle valve.
now where I'm getting even more confused is I phoned a compony (cant remember the name) that deals with these carbs and the guy I spoke to suggested that it should have a 180 main jet and a 376/4 throttle valve. all good then I thought but I then phoned the company that supplied the carb Hitchcock's because on the invoice there is a note (please use settings main jet 210, pilot position 30, throttle valve 376/3 needle jet 106)

so as you can see lots of different information from what I can glean I think around the 200 - 220 is possibly for a 376 1"/16th monobloc carb which I believe was fitted as standard a few years after mine. not sure why a previous owner went for the 1 inch but hay ho.

sorry for the long explanation, so can anyone help with what size jet etc I should be using in a 376 1 inch monobloc please. I took the plug out and it was sooty if that helps. ill try and put a picture of the bike up at some point (if I can work out how) as it may be known possibly by a former owner.
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dave16mct
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Re: carb query

Post by dave16mct »

Those jets are the settings for the '55 350 with 1 1/16" monobbloc. I would leave those in and ride the bike to see how it goes. The needle should be in the central notch and start with the pilot air screw 1 1/2 turns out. The sootiness may just be from the pilot setting on tick-over. Try a new Champion N5C plug. Enjoy your new bike, it looks very nice.
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clive
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Re: carb query

Post by clive »

Nice looking bike. Changing carbs can be a bag of worms, however a few things are straightforward. One of these is that the bore of the carb ought to match the bore of the spacer and the bore of the inlet tract into the head so the one inch 376 was probably a good choice. If the supplier specified the settings you have, they pretty much mirror the settings for the later 3 1/16 376 which is what I would have expected.
You don't say how the bike had been used when the plug was sooty, full bore or slow riding. My first thought would be to check the needle position, it ought to be slot 3 (the middle slot). The next point would be to check the idle setting, turning the adjuster out allows more air though and so weakens the idle mixture. If you whipped the plug out immediately after stopping following a greater than 3/4 throttle run and it was sooty only then would I be thinking about dropping the main jet by 10 despite the suppliers recommendation.
clive
if it ain't broke don't fix
SPRIDDLER
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Re: carb query

Post by SPRIDDLER »

I've had a 1" Monobloc 376 on my '54 G3LS for 16 years, until fairly recently covering between 4,500 and 5,000 miles a year - Pyrenees, Alps etc. and it has been fine. So faultless that I can't remember how it's jetted. I have it noted somewhere so will have look later but yours should be fine so best to ride it and tune it. There's a good tuning guide on the Hitchcock website.
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Steve
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Re: carb query

Post by Steve »

thanks for the reply's dave16mct, clive and SPRIDDLER most appreciated.
Steve
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Re: carb query

Post by Steve »

SPRIDDLER wrote: Thu Aug 26, 2021 9:10 am I've had a 1" Monobloc 376 on my '54 G3LS for 16 years, until fairly recently covering between 4,500 and 5,000 miles a year - Pyrenees, Alps etc. and it has been fine. So faultless that I can't remember how it's jetted. I have it noted somewhere so will have look later but yours should be fine so best to ride it and tune it. There's a good tuning guide on the Hitchcock website.
hi SPRIDDLER if you can find your jetting sizes and which throttle valve you have been using please
it would be great to know I'm starting from a known and trusted position.
I'm not running an air filter.

cheers Steve
SPRIDDLER
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Re: carb query

Post by SPRIDDLER »

I have (or had) the settings written on a piece of the box that the carb came in and although I've been all through my bike folders I can't find it. :x
I can't get at the carb until the weekend when a son will give me a hand. In short, it's behind two other bikes in the shed which I can't wheel around one-handed but I realise it would be handy to have tried and tested settings so I'll post details soonest.

BTW - Nice mod for the kickstart rubber. Maybe once you get the carb sorted you won't have to kick it over so many times ;)
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Which taken at the flood............'
Steve
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Re: carb query

Post by Steve »

SPRIDDLER wrote: Thu Aug 26, 2021 3:54 pm I have (or had) the settings written on a piece of the box that the carb came in and although I've been all through my bike folders I can't find it. :x
I can't get at the carb until the weekend when a son will give me a hand. In short, it's behind two other bikes in the shed which I can't wheel around one-handed but I realise it would be handy to have tried and tested settings so I'll post details soonest.

BTW - Nice mod for the kickstart rubber. Maybe once you get the carb sorted you won't have to kick it over so many times ;)
thanks SPRIDDLER that will be a big help after the weekend will be fine as I'm off to Silverstone for the moto gp Saturday and Sunday.
never been before but wanted to see Rossi live just once even if he will probably be towards the rear of the field.

re-kickstart yeah would be nice if it started a little easier. I'm changing the handle bars as well for scramble bars will be a little bit higher and wider
so more comfortable I've got cable stuff to make longer cables just waiting on a few more parts to finish making them hopefully get them next week.

then next year will probably pull the engine out as its a bit incontinent. but that can wait as I have a tray catching it at the moment.
Steve
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Re: carb query

Post by Steve »

just thought I'd add a little bit of back story
I purchased the bike from from a guy in Bristol just a few weeks ago and although I rode it home it was a bit iffy at times hence my thinking the carburettor was a little of. although I did get a reading of 65mph on the M4 all be it down hill with the wind behind.
it was on this run that I found the handlebars were not quite right for me hence my decision to change them.
as a matter of interest what would the normal top speed generally be.
SPRIDDLER
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Re: carb query

Post by SPRIDDLER »

My son has dropped in during his dog walk and extricated the G3 so I'll whip the carb off at the weekend and note all the details. You've given me the nudge that I needed to clean the carb as it has been stood unused since the start of the lockdowns.

I can't confirm the top speed with any accuracy as these chronometric speedos tend to over-read but I did have an indicated 75 'ish on a couple of trial runs when carb tuning. I think that's about the max but I'm never in a hurry and the brakes aren't up to 'high speeds' either.
Incidentally, I don't get much vibration at all but curiously (probably due to the factory crank balance factor) at 60 'ish and above the engine smooths out and runs like a turbine. En route to the Italian Jampot loaded with camping gear I happened to meet up at a camp site with a section member in his modern motorhome and followed him next day for about 50 miles until he wanted to join the autostrada (I don't do motorways). I had told him not to exceed 60 - 65 on dual carriageways which he said he complied with according to his Satnav but I found that my speedo registered 65 - 70 much of the time.
Enjoy Silverstone. I used to ride my Greeves Hawkstone in scrambles in the 60's but I'm no fan of watching, especially today's grip-defying racing which gives me the willies.

I've widened my 'bars by 2" each end as I need room for my adaptation which puts the clutch and front brake levers on the l/h side.
The feeble front brake cable at the top that's squashing at the ferrule was purely whilst experimenting and was replaced with a meaty one (like the clutch cable below it) from Venhill Cables.
K-Lever%20on%20Marigold.jpg
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