Running rich 1956 16ms

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Running rich 1956 16ms

Postby Taid » Sun Jan 03, 2021 12:36 pm

oops, sorry, should be in help, not general topics .. mods, can you shift it please?

A while back I concluded that for some reason the bike was running rich ..

tried adjusting the carb to no effect, so I rebuilt it with new jets, needle etc ..

all to no avail.

Checked the fuel level in the float chamber as best I could .. had a lot of trouble clearing bubbles from the plastic pipe .. seemed ok, though I did note that maybe some PO had probably had same problem in that there is a big blob of solder raising the needle surface on the float, presumably to close the needle earlier.

Here is a pic of a couple of plugs ..the one on the left is new .. only done a couple of miles and about 3 minutes tick-over before the run .. the other has done about 40 miles, the last run about 10 miles. in neither case did the bike sit ticking over afterwards .

I have debated trying replacing the brass float with a new plastic version, but don't really see that it would make any difference ..

Any thoughts, please?


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Currently ..1956 AJS 16MS Bitsa .. HSU 414 .. rebuilt/re-registered 1987

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Re: Running rich 1956 16ms

Postby Mick D » Sun Jan 03, 2021 1:01 pm

Hi

I'd see what effect dropping the needle one notch has.

Regards Mick

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Re: Running rich 1956 16ms

Postby dave16mct » Sun Jan 03, 2021 1:03 pm

I presume you've tried lowering the needle, checked jet sizes and slide ctaway are correct. If all looks OK it's probably a worn carb bore and slide. Push/pull the slide when slightly raised, you can feel for wear.
Dave.

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Re: Running rich 1956 16ms

Postby Taid » Sun Jan 03, 2021 1:23 pm

Mick D wrote:
I'd see what effect dropping the needle one notch has.



I'll do that, M, thanks ..

dave16mct wrote:I presume you've tried lowering the needle, checked jet sizes and slide ctaway are correct. If all looks OK it's probably a worn carb bore and slide. Push/pull the slide when slightly raised, you can feel for wear.
Dave.


Thanks D, I haven't lowered the needle, but all jets are new from Burlen .. I'll check for worn bore, and probably strip the carb down again and recheck that everything is the right size..

....


Generally, it starts and runs OK, but on occasion it doesn't want to know from cold .. I then take out the plug and it's soaking wet .. dry it off, or put a dry one in and it goes fine ..,

These things are sent to try us .......
______________________________________________________________________________________________________________________________

Nostalgia taking over ..

Currently ..1956 AJS 16MS Bitsa .. HSU 414 .. rebuilt/re-registered 1987

Member
Posts: 299
Joined: Mon Oct 07, 2019 2:35 pm
Location: Shropshire UK

Re: Running rich 1956 16ms

Postby Taid » Mon Jan 04, 2021 12:30 pm

Started this AM on priming kick, choke closed, not tickled carb .. not been run for some days ..

Checked slide .. half-open throttle, can detect some play, but very little ..

surely loose slider would tend to weaken mixture? allowing more air through without causing greater vacuum above main jet?
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Nostalgia taking over ..

Currently ..1956 AJS 16MS Bitsa .. HSU 414 .. rebuilt/re-registered 1987

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Posts: 2500
Joined: Mon Mar 24, 2014 5:44 pm
Location: Aberdeenshire

Re: Running rich 1956 16ms

Postby Mick D » Mon Jan 04, 2021 1:17 pm

Hi

Your symptoms of starting from cold with no tickle and soaked plug when it won't start would lead me to check the float valve was sealing correctly - with the bike on the cenrtre stand open the fuel tap and observe the carb (for up to five minutes), does fuel dribble out of the venturi or holes below it? if so the valve is leaking.

I would agree, a worn slide is more likely to weaken the mixture and affect even slow running.

Regards Mick

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Re: Running rich 1956 16ms

Postby Taid » Fri Jan 08, 2021 11:22 am

Mick D wrote:Hi

Your symptoms of starting from cold with no tickle and soaked plug when it won't start would lead me to check the float valve was sealing correctly - with the bike on the cenrtre stand open the fuel tap and observe the carb (for up to five minutes), does fuel dribble out of the venturi or holes below it? if so the valve is leaking.

I would agree, a worn slide is more likely to weaken the mixture and affect even slow running.

Regards Mick



Thanks M.

I can confirm there are no leaks when left standing with the fuel turned on, but before I start taking things apart (again) I'd just like to check my base line ..

Fuel level in the chamber ,,

When I bought the AJ the float chamber end cap was plain, non-original, so on my previous foray, I bought a new one from Burlen, along with jets etc. This end cap carries the Amal logo and a small pip just below it on the vertical centre line, which I understood to be the fuel level setting point.

Looking on the net on the subject I found one entry, where the OP of the forum thread had a plain end cap, asking for set up details. The answer was that the pip should be at the 'geometric centre' of the cap, which, since the cap is a circle, I take to mean the centre of both the horizontal and vertical diameters.

The pip on my end cap is central on the horizontal but is about 1/8" above the centre of the vertical diameter.

I did check the level was at the pip (bubbles in the pipe gave me some trouble) when I was checking earlier, but if the level should be central, that would make mine high, and account for the rich running .

Sorry for the diatribe, but can someone confirm where the level should be, please?
______________________________________________________________________________________________________________________________

Nostalgia taking over ..

Currently ..1956 AJS 16MS Bitsa .. HSU 414 .. rebuilt/re-registered 1987

Member
Posts: 2500
Joined: Mon Mar 24, 2014 5:44 pm
Location: Aberdeenshire

Re: Running rich 1956 16ms

Postby Mick D » Fri Jan 08, 2021 11:47 am

Hi

As you have observed, the pip is not at the centre of the cover, however I believe it indicates the designed fuel level in the float chamber.

Regards Mick

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Re: Running rich 1956 16ms

Postby Taid » Fri Jan 08, 2021 2:36 pm

Close enough to on the button, maybe a little low, but that would weaken the mixture? .. have to check the needle next .. position 3 (the centre) if memory serves .. after that strip the carb and check jets, I suppose

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______________________________________________________________________________________________________________________________

Nostalgia taking over ..

Currently ..1956 AJS 16MS Bitsa .. HSU 414 .. rebuilt/re-registered 1987

Member
Posts: 2500
Joined: Mon Mar 24, 2014 5:44 pm
Location: Aberdeenshire

Re: Running rich 1956 16ms

Postby Mick D » Fri Jan 08, 2021 2:55 pm

Hi

It looks like you don't have the fibre washer under the float needle seat. Later carbs are designed to have one and this will raise the level in the float chamber a little. If your carb has been replaced it may be worth installing this washer.

Regards Mick

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