G2 idle and running issues - with videos!

[clanger9]

What do you mean "sliding seal?? + there may be a bit of pressure build up if the engine breather is naff/blocked as there is no crank seal on that side of the engine

I mean the gearbox input shaft "sealing" plate on the rear of the primary case. It's not really a seal (more of a dust/muck trap) as it is a loose sliding fit. I would have thought any pressure here would just vent past the gearbox shaft...

[Janet]

I'm sure must have already looked at the information on the AMAL website, but just in case you haven't, this may be of help. http://amalcarb.co.uk/downloadfiles/ama ... d_Tips.pdf As Rob said, check you have all the correct parts. They are itemised in the parts list. Regarding the comment he made about the length of the fixing studs, here is a photo of mine showing how few threads there are at the end of the studs. You have to manufacture your own muck as this is not a stock item.

[Duncan]

It shouldn't have a fibre washer underneath the banjo fitting on the fuel intake.

This is where life starts to get interesting as the “new” Monobloc's do have a fibre washer here, the new carbs can usually be identified by a cast in fillet either side of the slide upstand, I am not sure if this is a fool proof method of identification though.

you are using the choke lever incorrectly... Pulling it toward you will take the choke off.. you are pushing it away from you which is putting the choke on!!

Looking at the video I think the bike has an advance/retard lever fitted in reverse giving the impression of incorrect use.

[BultacoBen]

Many thanks for all your quick responses! Just wrote a very long post addressing each of them individually but it seems to have disappeared into the ether when i tried previewing and submitting...

In summary though it seems the next steps for me today are:

- Check throttle slide for fit. This is the only possibility I hadn't considered before from amongst your suggestions. What is the rattle I should be listening for? When running or If I shake the carb? Is it obvious when the fit is too loose? Or is the measure of 'loose enough to slide but not too loose' one that comes from reference to one's own experience...? I've only got this carb to refer to...
- Check again jets and needle are as I believe they should be (carb 389/82, Pilot 20, Main 200, 0.11 Needle on the third notch from the top, number 3 slide cutaway)
- Check condition of gasket under jet block
- Check timing again, and see if moving on taper
- Source correct float (amal part number 376/083 whereas I appear to have RKC/391 which they offer as a direct alternative? Even that though isn't a brass one... Strikes me as of secondary importance if I've modified the float I've got to give correct fuel level.
- Check if although fuel level is correct when stationary could vibration be causing it to become higher or if it gets stuck somehow when running
- Check silencer isn't blocked

And as a counter so some suggestions:

-choke must be fitted differently on mine as moving lever towards me releases tension to lower the choke into the carb.
-gasket beneath banjo is not fitted, but even without it the fuel level was still too high until I added the shim to the float
-carb studs were correct according to diagram in manual and ordered from AMOC spares, but the spacer may be incorrect thickness. At least though it is 1 1/8" diameter as opposed to the 1 1/2" diameter spacer I found on there when I bought it!

[Rob Harknett]

What year is the G2. A worn throttle slide rattle will be heard on a fairly fast tick over. Touch the slide with your finger and it will stop rattling. A worn slid has never made much difference on any of my bikes. Even when they were almost new, back in the 50's. Wrong needle position wrong jets wrong slide will cause very noticeable difference. The only time fuel level has made any difference, is when a float has been punctured. It will keep flooding. Had a puncture on my 1936 bikes brass float at 2007 Jampot. After a couple of hours in my pocket, fuel in the float evaporated. A good helping of Araldite sealed it. Although I found another float at the rally jumble, 9 years later the repaired float is still in the bike. The stud threads showing on Janets carb are what I would expect to see, not about 1/4" as seen on your bike. I am not sure if there is a right or wrong way to screw these in the head. e.g there is a longer threaded part that goes in the head. Not fitted one of those for years.

As a point of interest Janet, your float cap AMAL is not reading horizontal, I could only manage to see one of my lightweights, its the same as yours. One screw fitting dead above AMAL. I had AMAL not reading horizontal on my G12 CSR, then I found an end cap where the holes were in different positions, the cap with holes in the different positions, when fitted, showed AMAL reading horizontal. So I wonder if we both have the wrong end covers. Perhaps I will look at my other lightweights , bikes, spares end covers etc. This may never happen, as I'm not that much bothered. If I do find one that reads horizontal, it will be the bent one that leaks. ( Should had dumped that one )

[Janet]

As a point of interest Janet, your float cap AMAL is not reading horizontal,

It does when I'm riding uphill.

On my bike, it being wonky is more in keeping than if it lined up properly.

[Ozmadman]

[quote
Looking at the video I think the bike has an advance/retard lever fitted in reverse giving the impression of incorrect use.

that is definitely the choke a G2 does not have an ADV/RTD lever as it has an automatic advance weigh system on the crank!!

[Ozmadman]

What do you mean "sliding seal?? + there may be a bit of pressure build up if the engine breather is naff/blocked as there is no crank seal on that side of the engine

I mean the gearbox input shaft "sealing" plate on the rear of the primary case. It's not really a seal (more of a dust/muck trap) as it is a loose sliding fit. I would have thought any pressure here would just vent past the gearbox shaft...

it should still have a felt seal in it

[Ozmadman]

Carb should be 376/99... jet 180 needle 106 central position 3.5 cutaway and pilot 25. If you remove the jet block then you must replace the gasket so just "checking it's condition" is just wasting your time and effort getting it apart

[Rob Harknett]

We cannot say what the carb should be not knowing the year.