Thanks Charlie - I figure then I should "lean off" the idle a tad - say move it from 1 1/2 turns to 1 3/4 turns??? Do you agree?
M
M
New Amal Premier 900 series Carb for Comets
- Thread starter craig
- Start date
Your experience is not unique. I would ask around and talk to some local racers. They require the same services you do, changing carb settings or checking pipes and timing settings. See who they use. Carleton once went to a dealer with a dyno and it was $100 for a run. He explained his need to do testing and it turned into $100 per hour with him doing the changes. So, it can be done. I have used Pete Talabach who has a dyno and is a Vincent owner. He caters mostly to racers and he understands what is needed. I have twice started at 10:00 AM and stopped at 4:00 PM because I was exhausted. Pete never charged me very much and I thank him.
David
Hi Martyn, A number 3 slide is probably going to be on the rich side a 3 and a half is better.....from what you have described all up so far with your Comet re the damage suffered by the piston etc, the biggest thing i would be looking at is detonation.....your ignition timing sounds all ok now...so keep playing with carb until you feel it is running fine. As you said change one thing at a time bit by bit. If you notice pulling up a hill, that the engine starts to rattle (ping) then change down and back off on the throttle, and make further changes. Detonation is usually caused by either a lean running condition or over advanced timing at that particular engine rpm verses load, and also the engines running temperature...that is that a very hot engine will detonate more readily than a cold one.......Cheers.....Greg.
Yeah, Martyn. Try a bit leaner on the pilot and then progress to the slide as Greg says. My heaps both run O.K. on a "3" slide and a "3 1/2" is a bit lean, but I run type 29's. You are doing the right thing by starting rich. You may even find you can fettle a "3 1/2" by carefully filing 1/16" off the bottom, which would be carrying your monomania to a sufficient extremity.
Another 70 mile run today. I lowered the needle one groove , from the bottom position to the middle position. Before doing this the entire spark plug (business end) was coated in black carbon - including the centre of the electrode and the "earth" bar (see my earlier post). Having made the needle change then the 70 mile run today there was still a lot of carbon on the plug but this time the tip of the centre electrode and the earth bar are free of carbon. I'm doing all this with a 250 main in place.
It was running very well with no trace of hesitation, mis-firing or detonation - and no sign of the exhaust "blueing" either. As I do not have an alternative slide available my next move is to go to a 240 main and then perform another 70 mile run then do a further plug check.
At least I am putting some miles into the running in process. In case you wondered I am installing a brand new plug before each test run - good thing I have a few on hand
Martyn
It was running very well with no trace of hesitation, mis-firing or detonation - and no sign of the exhaust "blueing" either. As I do not have an alternative slide available my next move is to go to a 240 main and then perform another 70 mile run then do a further plug check.
At least I am putting some miles into the running in process. In case you wondered I am installing a brand new plug before each test run - good thing I have a few on hand
Martyn
Today swapped out the 250 main for a 240 main and fitted a brand new plug and after around 50 miles checked the plug - it looks identical to the plug that I had removed when I had a 250 main in place - no surprise really, when , running in, I am using only very small throttle openings. The transition from idle jet to slide cutaway is very very smooth with no trace of hesitation or stumbling, and as I do not have a range of slides on hand my next step will be to move the needle from the middle to the top position, thus making things a bit leaner when its running on the needle. Again I will be using a brand new spark plug as an indicator and if it then seems too lean I will use a shim to get a needle position in-between the top and middle grooves.
One step at a time
Martyn
One step at a time
Martyn
Here is a photo of an unused spark plug
This plug was used for around 70 miles with a 250 main Jet, a 106 Needle jet and the needle in the bottom groove (richest) Seems WAY to rich to me
Next attempt was 250 main a 106 needle jet but the needle now in the middle groove. Still looks over rich to me.
Today I was able to get hold of a 105 needle jet - After 120 miles with the following settings, this is the plug. Amal MK1 Premier 930, #3 slide, 250 main jet, 105 needle jet, needle in centre position. I figure it now looks a wisker lean so I plan to put a shim under the needle to raise it by around a 1/2 groove height. Opinions welcome..
