I'm having trouble getting my 1938 ES2 to idle due to to lean a mixture. Before I go any further I will tell you that it has a 76/012 carb fitted which was originally put on the 350's. Es2 500's had a 76/022 originally.
I have the pilot screw screwed in all the way for richest mixture possible. If I tickle the carb I can get it to run although slightly rich, and then as the fuel level drops it will run nicely but fuel level drops to the point where it starts to run lean then stop. Another tickle to bring fuel level up and it will start again. So, I raised the float level to allow more fuel to be stored in the bowl and could get it to idle perfectly. However, the point at which the float has been raised to, to allow this nice running is so high that I can't screw the lid on without pushing float back down and flooding carby. Also at this level when I do stop the bike fuel comes out of the small pin hole underneath pilot screw.
I have checked for any air leaks and renewed fibre washers etc.
Any thoughts ? I'm wondering if maybe the pilot fuel passage (no pilot jet remember) in these 350 carbs is to small to allow a 500 to idle properly.
The first thing I'd check…
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Is it running OK out on th…
Is it running OK out on the road under load? Could be fuel starvation as dave suggests.
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Thanks for you reply's gu…
Thanks for you reply's guys. I have it all fixed now. All it was was either the pilot outlet or pilot bypass outlet blocked, but I don't know which one. I pulled the carby apart and then poked around with a bit of thin wire. Those holes are tiny. Then blew out with compressed air. I guess which ever one it was it could have been partially blocked also. I figure raising the float level as high as I did must have allowed fuel to come straight up through the main needle jet and dribble into carby throat providing enough to keep it running at idle. Not an ideal scenario. I must say that having looked and looked at diagrams of these carbys along with descriptions it wasn't until I actually pulled it completely apart that I really understood how it worked, well I think I do anyway. I recommend others give it a go if they haven't before.
The difference between the 76/012 carby that I have and the 76/022 that is supposed to be on my ES2 is the throat diameter. On the 012 it is 1" and on the ES2 it is 1 1/16". I wouldn't reckon that would make bugger all difference unless you were running with carb wide open and then I don't reckon it would be noticeable but I could be wrong. 16H and Big 4 models only had 1" as well. I might try a slightly bigger main jet, 170, and see what happens. At the moment only running 160.
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Thanks for you reply's gu…
Thanks for you reply's guys. I have it all fixed now. All it was was either the pilot outlet or pilot bypass outlet blocked, but I don't know which one. I pulled the carby apart and then poked around with a bit of thin wire. Those holes are tiny. Then blew out with compressed air. I guess which ever one it was it could have been partially blocked also. I figure raising the float level as high as I did must have allowed fuel to come straight up through the main needle jet and dribble into carby throat providing enough to keep it running at idle. Not an ideal scenario. I must say that having looked and looked at diagrams of these carbys along with descriptions it wasn't until I actually pulled it completely apart that I really understood how it worked, well I think I do anyway. I recommend others give it a go if they haven't before.
The difference between the 76/012 carby that I have and the 76/022 that is supposed to be on my ES2 is the throat diameter. On the 012 it is 1" and on the ES2 it is 1 1/16". I wouldn't reckon that would make bugger all difference unless you were running with carb wide open and then I don't reckon it would be noticeable but I could be wrong. 16H and Big 4 models only had 1" as well. I might try a slightly bigger main jet, 170, and see what happens. At the moment only running 160.
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The carb with the 1-1/16"…
The carb with the 1-1/16" opening will give you about 13% greater air handling capability over the 1" unit. Mind you, this would only be while the carb is fully open. Seeing as how the ES2 has a 30% greater displacement it might well make a difference.
The 16H and Big 4 units were flat head models. The overhead valve ES2 unit should be breathing easier.
Mike
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The carb with the 1-1/16"…
The carb with the 1-1/16" opening will give you about 13% greater air handling capability over the 1" unit. Mind you, this would only be while the carb is fully open. Seeing as how the ES2 has a 30% greater displacement it might well make a difference.
The 16H and Big 4 units were flat head models. The overhead valve ES2 unit should be breathing easier.
Mike
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Hmmm food for thought Mich…
Hmmm food for thought Michael. I never thought of it the way you have. I may look at getting a brand new Amal 276 for it. I know another member of our club here in Tasmania ordered one to suit his pre-war Big 4 direct from Amal. They set them up for what ever model you have. He said he just bolted it on and his bike has never run better. The other option would be to wait for a second hand 76/022 to become available but sometimes second hand carbys are more trouble than their worth.
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The first thing I'd check is that the petrol is flowing freely from the tap. I have known of someone changing carbs, magnetos etc and couldn't get there bike runningproperly. When I looked at the bike and started from basics, there was very little flow from the brand new taps. A drill bit pushed up to clear the excess rubbersealdid the job.
I don't know the differences between the 2 carbs, but I'm guessing the 350 carb is smaller. So you're trying to sort out a problem that you've created by using the wrong part. I would have thought the bike would still tick over, but starting with the right size carb is the best thing to do.