bpilgrim Posted March 16, 2011 Report Share Posted March 16, 2011 Hi, I failed to finish a trial on Sunday as my bike had some running issues, it eventually cut out, I pushed it back up the quarry, sort of fixed it and then I ran out of time! It started the day running perfectly, started easily, tickover was good and it revved cleanly. After 2 laps, idle started being a little funny, it was wanting to cut out, and seemed to be surging slightly, like it was running out of fuel. I then noticed that it was dumping fuel out of the overflow pipes when I revved it and then backed off, I have heard this is the float sticking, so I had a go at tapping the body of the carb, which didn't really fix it. I managed another lap, struggling to keep it running, until it finally packed up. After about 40 mins, fiddling, tapping the carb, I managed to get it going again, it struggled to start and was very smokey, but after about a minute, it ran perfectly well again, and I carried on until I ran out of time. I stripped the carb today, as I have heard ethanol affects the plastic float (although I'm running it on shell 95, which I believe doesn't contain ethanol), and it was fine, I was expecting a sludge, but it was clean, I checked the filter in the bottom of the carb, and the inline fuel filter and they are both clean. After stripping the carb today, I ran it for a while, and I let it idle on the spot for a while until it was very hot, to see if it was just doing it when it was hot, but it was fine. I'm now slightly puzzled as to why (I think) the float is sticking and why it seems to happen at random... Any help would be much appreciated, Ben Quote Link to comment Share on other sites More sharing options...
belldane Posted March 16, 2011 Report Share Posted March 16, 2011 It sounds like the needle is sticking for some reason. Put a new one in and see how that goes. Also check the seat that the needle goes into as there could be a bit of rubbish in there causing it to stick. Quote Link to comment Share on other sites More sharing options...
bpilgrim Posted March 16, 2011 Author Report Share Posted March 16, 2011 It sounds like the needle is sticking for some reason. Put a new one in and see how that goes. Also check the seat that the needle goes into as there could be a bit of rubbish in there causing it to stick. Hi, I really don't know much about carbs, so is this the big needle in the centre? Is that the main needle? I was looking at this today, I noticed on the top, there was a little washer type clip, and there were I think 5 slots on the top of the needle, is this for main adjustment? Quote Link to comment Share on other sites More sharing options...
breeze Posted March 16, 2011 Report Share Posted March 16, 2011 Hi, I really don't know much about carbs, so is this the big needle in the centre? Is that the main needle? I was looking at this today, I noticed on the top, there was a little washer type clip, and there were I think 5 slots on the top of the needle, is this for main adjustment? Yes that is the main needle & the clip position raises/lowers the needle within the needle jet, richens/leans the mixture from approx 1/4 to 3/4 slide position. This is not what you need to be replacing, it is the needle & seat that the floats are controlling. A long time since a looked at an amal - but I assume there is a pin holding the floats, withdraw the pin & remove the floats, the inner part of the needle/seat will probably be attatched, it has a tappered seat, some are viton tipped (sort of rubber), the seat can then be unscrewed & checked. On most carbs the seat is marked with its size 200, 250,300 which relates to the fuel flow - replace with like for like (assuming it had the correct size before) I have found these needle valves can be a problem even on new carbs that have been storred upside down - thus with the weight of the floats pushing the valve against its seat & marking it, causing it to flood when used, simple answer - if in doubt fit a new valve & seat (always as a pair) Quote Link to comment Share on other sites More sharing options...
keychange Posted March 16, 2011 Report Share Posted March 16, 2011 (edited) I'm not sure you are both talking about the same thing. The float needle is NOT the long thin needle in the centre. The float needle is under the float ie: remove the float by sliding the holding bar out and you will find a short (1/2 inch) and thickish (1/8th inch) brass needle with what looks like a teflon point and that is the needle that controls the flow of fuel into the carbie bowl. A very tiny bit of muck is all it takes to stop the float needle from closing off the fuel flow and as a result you get fuel overflowing. Have a close look at the following http://www.oldbritts.com/amal_tun.html Edited March 16, 2011 by keychange Quote Link to comment Share on other sites More sharing options...
lee harris Posted March 17, 2011 Report Share Posted March 17, 2011 Maybe put a dellorto on it....carburetors are just over engineered watering cans and if that be true an amal is a plated tin one with dents and rust! Quote Link to comment Share on other sites More sharing options...
bpilgrim Posted March 21, 2011 Author Report Share Posted March 21, 2011 (edited) I'm not sure you are both talking about the same thing. The float needle is NOT the long thin needle in the centre. The float needle is under the float ie: remove the float by sliding the holding bar out and you will find a short (1/2 inch) and thickish (1/8th inch) brass needle with what looks like a teflon point and that is the needle that controls the flow of fuel into the carbie bowl. A very tiny bit of muck is all it takes to stop the float needle from closing off the fuel flow and as a result you get fuel overflowing. Have a close look at the following http://www.oldbritts.com/amal_tun.html Right, I've opened up the the carb again to check the 'float needle' (I'm learning!). It looks quite a technical little needle, my one is of a triangular sort, with 3 points that make contact with the jet, and it has a funny little tip. I've cleaned the needle, the jet and also made sure the float moves freely on the brass spindle, and the bike's running well. I'll see how it goes, and if the problem appears again I'll change the float needle as you suggest. Is this type of carb, standard 348 Amal (L2627/402), is it a 600 series Amal? As the parts are split into categories for the 600, 900, Mk2 and Monobloc. I think this is the right sort: http://www.trialsbits.co.uk/product_info.php?cPath=34_35&products_id=85 Do float needles only ever come in one size? Thanks, Ben Edited March 21, 2011 by BPilgrim Quote Link to comment Share on other sites More sharing options...
keychange Posted March 21, 2011 Report Share Posted March 21, 2011 It's usually called the 'needle and seat' where the float needle (or needle valve) is one part and the brass bore that it goes into is the seat (it is not really a jet. The needle can wear and so can the seat - also the seat can move - it is simply held in place by the tight fit but can be adjusted. If what you have done has improved the overflow then there is no reason to suspect that any of the parts are worn - dirt from you tank is the most common cause and so you should have a small in-line fuel filter and replace it often. Cleaning your carby is a standard part of ownership - so get used to it - after 12 months ownership I can remove, strip and replace mine it in around 15 minutes - I think I could do it blindfolded You should keep a spare needle anyway as it will eventually get scored or worn from all the rubbish coming through and they are cheap enough. If your Amal is a 627 ( as is my 247) simply make sure that you quote that when you buy the new parts and they will be the correct ones. The needle and seat are one of the few parts in a carbie that don't come in a range of sizes. You can also get repair kits from the manufacturer http://www.amalcarb.co.uk/ if you are ordering these make sure you check all the current jet sizes in your existing setup to ensure you keep the same settings ( jets have a small number written on the side near the top) - take a look at the technical tips http://www.amalcarb.co.uk/Technical.aspx Quote Link to comment Share on other sites More sharing options...
nh014 Posted March 21, 2011 Report Share Posted March 21, 2011 (edited) The Amal L2627/402 carb is a MK2 2600 series. As previously noted, see the Amal website for parts and technical information Edited March 21, 2011 by nh014 Quote Link to comment Share on other sites More sharing options...
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