Suspect carburetter

Information relating to the Matchless G5 or AJS Model 8 350cc Lightweight
cbranni
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Re: Suspect carburetter

Post by cbranni »

An 018 is set up as below

389/018 AJS 347cc 1957-59; 16MCS Scrambler 1 1/8" 30 3 280 0.11 3

042............

389/042 AJS 350cc 1960-61; Lightweight 1 1/8" 25 3.5 220 0.11 3

So pilot jet, cutaway and main jet needs changing, I would be wary of buying off ebay unseen, you have been struggling with this problem for few months now so how about cutting your loses and buying a new carb, I know its a lot of money but it will be worth it if you are going to keep the bike, if you going to sell it on well that's different story.

Do club spares sell carbs jetted for lightweights?
only dead fish go with the flow
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clanger9
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Re: Suspect carburetter

Post by clanger9 »

As long as the bore is correct, the second number doesn't matter. You can re-jet it to suit, and all will be fine.
1989 Moto Morini Dart 350
1993 Ducati 750SS
vigo
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Re: Suspect carburetter

Post by vigo »

Gents,
After 4 months absence completed carb rebuild replacing wrong original carb from a 500cc. Starts and settles to an idle. Took off up nearby steep hill pulled well, missed once then started fading at the top, cut out. This symptom is consistant since purchase. Since buying I have replaced, carb,coil,condensor and plug. Checked and lubed advance ret weights, springs are good and they return. Timing several times.
I am pretty sure oil is enterring the cylinder and fouling the plug. Plug looks "washed" with oil around rim. No evidence of combustion even after running. Wipe the piston with a stick, oil. Exhaust port has oil in it. And some blue smoke. If I clean plug and leave overnight will start again, as soon as the oil gets round, about 5 mins will cut out.
About a year ago I took the head off after fitting new gasket and oil was where it shouldn't be but hadn't seemed to migrate into cylinder, there are pics going back a bit. I'm now thinking head off again valves, guides maybe seats machining.
Any tips on how oil could enter cylinder? The compression is very good but could oil come up from the bottom?
Mick D
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Re: Suspect carburetter

Post by Mick D »

Hi

Is the fuel cap vent clear? Does it start after the cap has been removed and refitted?

Regards Mick
SPRIDDLER
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Re: Suspect carburetter

Post by SPRIDDLER »

I've briefly scanned the whole thread but can't see if you've checked the inlet valve oil regulator.
Page 12 of the Owners Manual here:
http://archives.jampot.dk/book/Owners_m ... n_Book.pdf
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Which taken at the flood............'
vigo
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Re: Suspect carburetter

Post by vigo »

Thanks fellas,
Yes I'm 2 years down the road with this problem, there were loads of things done wrong by ppo. Run with fuel cap off and checkd fuel in float chamber, and level. Inlet v. Lube screw also adjusted, many times.
SPRIDDLER
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Re: Suspect carburetter

Post by SPRIDDLER »

vigo wrote: Fri Apr 23, 2021 3:41 pm Any tips on how oil could enter cylinder? The compression is very good but could oil come up from the bottom?
It's either coming down from the valve guides or up from the c/case.

Accepting the likelihood that all scenarios have already been covered I think you'll need to recheck them to make any progress although it often doesn't help to check your own work as the same 'mistakes' can easily be repeated. However, since the OP has done a couple of unexpected things he may have fitted the piston' oil control ring badly or with a too great end gap...........or it may be broken which would enable oil to bypass the piston and enter the cylinder. Stuff the c/case mouth with rag before lifting off the barrel. (I guess you knew that anyway).
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Which taken at the flood............'
SPRIDDLER
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Re: Suspect carburetter

Post by SPRIDDLER »

vigo wrote: Fri Apr 23, 2021 6:29 pm Yes I'm 2 years down the road with this problem, there were loads of things done wrong by ppo. ......Inlet v. Lube screw also adjusted, many times.
It's a long shot/idle thought but as you've been trying to sort it for two years I wonder whether in view of the PO's 'ineptitude' he could possibly have just used an ordinary bolt instead of the correct tapered/pointed screw. It should look like this:
inlet valve oil dims 009 (740x555).jpg
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Groily
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Re: Suspect carburetter

Post by Groily »

vigo wrote: Fri Apr 23, 2021 3:41 pm The compression is very good but could oil come up from the bottom?
I'm rather 'with' Spriddler's of 2.41pm re ring grooves if all valve & head checks come to nothing.
You'd maybe still have good compression, depending on how tested etc, but if the rings can move in their slots, or the gaps are huge and not spaced properly, they'll act like a pump and can push surprising amounts of oil up top.
Got more than one T shirt for this fault, on other engines.
vigo
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Re: Suspect carburetter

Post by vigo »

Inlet valve lube screw looks like the one pictured anyway definately tapered. Check this out, head off and large pool of oil on top of piston. Also covering gasket on contact area between cylinder and head.
What's got me perplexed is if oil originates from inside the cylinder via piston rings or valve guides, how does it cross the copper head gasket to "outside."
Before I search the manual, how can I release the cylinder can't find any hidden bolts. Thought it might slide up the studs, perhaps a mallet!
20210424_131226.jpg
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