Jetting advice please

[alanscottj]

If when you rev it up and you wait for revs to come down it comes down instantly without any firing and then cuts out or really struggles to tick over and your tick over screw is more or less fully wound in and you have tried idle jets in th 48 to 55 range it is likely that your slide is too rich. Delly's normally come with a 40 slide. Check the number and if it is a 40 i would change to a 45. I have found most muggys like a 45 slide especially if running with a filter and not open mouthed. A slide will make a massive difference in the way the bike returns to tick over as a rich slide will create a higher vacuum (more fuel being pulled in) and lean slide will create less vacuum (less fuel being pulled in through jets).
In theory, when your throttle is shut off it should recieve mixture just from mixture screw circuit (first hole nearest the engine side of carb), if you have too much vacuum (slide too rich) you will get more fuel coming from pilot hole (second hole in venturi nearest engine side of carb) and main jet hole (last delivery hole) than engine can cope with.
Only when the throttle is 1/8 open the pilot hole should really start delivering and at about 1/4 or just before main jet hole starts delivering properly.

If it is taking longer than it should to return to tick over and gradually coming down on revs but "holding up" it is too weak and slide/pilot is lean.

Air screws normally run between 1 and 1/2 and 2 and 1/2 turns out.

Thanks Nelson pk,

My jetting so far:

53 pilot
118 main
40 slide
X4 2nd clip down
AV 266
No filter
Muggy 198 with JL4 pipe

Been checking my plug when it's been ticking over and it is really wet. Time to try a 40 slide?

[dave411]

No Alan,a 45

[alanscottj]

No Alan,a 45

Just had a look on the Cam Lam spreadsheet with all their recommendations and they reckon a 53, what u reckon?

[nelson pk]

If your idle screw is pretty much right in and it still struggles to tick over and needle clip changes dont really make a difference to tick over i would try a 45 slide for sure.
You could try an AV264 atomiser with a 40 slide but i would rather have a 45 slide with an AV266 myself every time.
I recently done a muggy 186 with 30mm delly and gori exhaust and ended up with 45 slide, 55 pilot, AV266, 115 main and x7 on 2nd clip down. It was close enough.

The 53 is probably an idle jet recommendation or misprint. For slide you want a 45 which is next weaker from the 40 that you have.

[alanscottj]

If your idle screw is pretty much right in and it still struggles to tick over and needle clip changes dont really make a difference to tick over i would try a 45 slide for sure.
You could try an AV264 atomiser with a 40 slide but i would rather have a 45 slide with an AV266 myself every time.
I recently done a muggy 186 with 30mm delly and gori exhaust and ended up with 45 slide, 55 pilot, AV266, 115 main and x7 on 2nd clip down. It was close enough.

The 53 is probably an idle jet recommendation or misprint. For slide you want a 45 which is next weaker from the 40 that you have.

It's ticking over ok on the stand now with the jetting above. It's just the engine response when I close the throttle when riding, shuts right down. I will see if I can get a 45 slide and see how that goes, it has also been suggested that I should change the 200 float valve to a 300 or 350

[nelson pk]

Change the 200 float valve to a 300. This will make sure the float bowl wont empty of fuel before it can fill up when riding at high speeds.....this is a must!
However it probably wont have any effect on what you are experiencing as normally if you shut off and the float bowl is draining quicker than filling ( which causes a weak mixture) the engine will experience high revving and running on for a bit.
If you shut off and you pull the clutch in and just coast to a stop.....is it ticking over or has the engine died totally? If the revs are dropping quickly and its going to tick over quickly that is not a problem at all unless the engine is completely cutting out......

[alanscottj]

Change the 200 float valve to a 300. This will make sure the float bowl wont empty of fuel before it can fill up when riding at high speeds.....this is a must!
However it probably wont have any effect on what you are experiencing as normally if you shut off and the float bowl is draining quicker than filling ( which causes a weak mixture) the engine will experience high revving and running on for a bit.
If you shut off and you pull the clutch in and just coast to a stop.....is it ticking over or has the engine died totally? If the revs are dropping quickly and its going to tick over quickly that is not a problem at all unless the engine is completely cutting out......

Ordered 300

If I pull the clutch in and coast to a stop the engine will die, unless I give it a blip on the throttle

[nelson pk]

Ok. When you go out for a test run what part of throttle are you riding at when you go to shut down?
Can i ask why you are using an X4 needle instead of an X7 or X13?

[alanscottj]

Ok. When you go out for a test run what part of throttle are you riding at when you go to shut down?
Can i ask why you are using an X4 needle instead of an X7 or X13?

I am now using (on Cam Lams recommendations via their spreadsheet)

118 main
Av 268
X7
53 pilot
40 slide - to be replaced today by a 45 if it arrives
200 float valve - to be replaced by a 300 if it arrives today
Air/fuel mixture - 1 1/2 out

As for which throttle position, it is when I am pulling up to a junction or traffic lights when I shut down, so only around town riding, half throttle I'd say, if that.

[alanscottj]

45 slide, 300 valve, 48 and 50 pilots have arrived. Will have a play this afternoon