80 carbs

[donebysunday]

were all the main nozzles the same in the later carbs ?
Or were the middle 2 & 3 different ?
Thanks, Don

[dbeardslee]

Some of 'em had the jetting a bit fatter in the middle cylinders so they'd run a bit cooler. There were also bastardized carbs on some 80's that are kind of a cross between the earlier and later carbs. They can be identified by a connecting tunnel between the pilot and main jet towers, and a rubber plug in the pilot tower.

[donebysunday]

80 carbs

with no plugs, no crossover ?
Seems the PO took the threads out of this nozzle in the # 4 carb.

Some of 'em had the jetting a bit fatter in the middle cylinders so they'd run a bit cooler. There were also bastardized carbs on some 80's that are kind of a cross between the earlier and later carbs. They can be identified by a connecting tunnel between the pilot and main jet towers, and a rubber plug in the pilot tower.

[dbeardslee]

with no plugs, no crossover ?
Seems the PO took the threads out of this nozzle in the # 4 carb.

No plugs and no tunnel between towers would be the "conventional" late model carbs. With a stock setup I think conventional wisdom is 110's across the board, but you might need to go a little fatter with the aftermarket exhaust. A colortune plug comes in real handy when you're trying to dial in jetting. JAT

[donebysunday]

Colortune

went bye bye with my 75 RD350.
I'll start looking for another colortune.
Thanks, Don

No plugs and no tunnel between towers would be the "conventional" late model carbs. With a stock setup I think conventional wisdom is 110's across the board, but you might need to go a little fatter with the aftermarket exhaust. A colortune plug comes in real handy when you're trying to dial in jetting. JAT

[dbeardslee]

went bye bye with my 75 RD350.
I'll start looking for another colortune.
Thanks, Don

Gunson or Amazon will have the colortune plug. The way I use one for jetting is this - I check to make sure I can adjust all the way from yellow to bunsen blue to blue white using the mixture screw. If I can't get a good rich yellow with the screw dialed out 3 or 4 turns I go a little fatter. If I can't get the blue white when the screw is almost all the way in... a little leaner. When I think I've got it right, I run it a while and then check the condition of the plugs.

[skids]

Don, The colortune is nice for dialing in near idle conditions. It really is not too good for high throttle positions when the mains are being used. At least that is my opinion!

[motoman]

Don, The colortune is nice for dialing in near idle conditions. It really is not too good for high throttle positions when the mains are being used. At least that is my opinion!

At idle, initial, correct mixture setting IS realative throughout rest of rpm range.

[skids]

At idle, initial, correct mixture setting IS realative throughout rest of rpm range.

Sorry Brant, but I couldn't disagree with you more. The pilot screws and throttle plate tweeking becomes less significant as the throttle is opened beyond the idle circuit. Watch your synch vacuum NOT change at higher throttle positions while you try and adjust your synch.

Perhaps I am not understanding fully what you are saying...

[donebysunday]

Idle

mix screws, used to get very fussy and spent lots of time, riding tuning over and over. Took my hand tooled screwdriver along and tuned on the ride. Got lazy in my old age, set the screws at 3 turns out with after market exhaust, good enough.

I think I feel fussy coming on ? };-)
Thanks guys ! Don