Carb tune.

[rocketsteve]

My 2006 SB ZZ4 Hot Cam Mountain Hoss is fitted with a standard Holley with secondaries and I keep it well tuned & checked on a regular basis but have noticed something a bit strange…

All air/fuel mixture screws are about 1 to 1½ turns out from seated apart from the front left screw (sitting on the bike) which is about ¼ turn out.
All 8 spark plugs are a good light brown colour and she seems fairly happy at the moment, doing around 20 / 25 mpg which seems about right.

One other thing I’ve noticed, when conditions have been right and I’ve cracked the throttle wide open from stand-still, the back tyre doesn’t light up but she does take off up the road like a raped ape!

I’d be grateful if anyone has an idea about the ¼ turn mixture screw, could there be a blockage in the problem screw fuel passageways causing the rear wheel NOT to spin?

How about if I remove the mixture screw and try a few short blasts of compressed air in the screw hole or might this damage soft internal carb components?

[hogv8]

I've heard this from others that they can't light up their rear tire on their ZZ4 bikes . I have no problem at all with my 2000 ZZ4 with hot cam , 1.6 roller rockers and 750 Edelbrock with the Carburetor Mikes stage II mods . I can easily lite up my rear tire at 15 - 20 MPH .

[rocketsteve]

Okay, I'll try a 15 - 20 mph rolling start next time out and see what happens...

The mixture screw remains a puzzle

[wag]

Simple thing but I seen it where riders just don't go wide open quick enough with the wrist. Probably why in the past riders have experimented with quick turn throttles or relocated the throttle cable on the carb arm.

[hogv8]

Simple thing but I seen it where riders just don't go wide open quick enough with the wrist. Probably why in the past riders have experimented with quick turn throttles or relocated the throttle cable on the carb arm.

I forgot to mention I have a 1/4 turn quick turn throttle which makes it real fast to go wide open throttle .

[knockdolian]

Okay, I'll try a 15 - 20 mph rolling start next time out and see what happens...

The mixture screw remains a puzzle

Good question Steve. I’ve seen many a trike snaking up the road leaving big black number 11s. Can’t do it on mine. Just assumed it’s was down to slippage in the auto box. I’ve considered trying it in 1st but read somewhere once not to do that ? Good point about throttle operation. It’s a real struggle to get it on full in one go. Only just get the secondary’s to com in. Mines an Edelbrock 1901 by the way.
You’ll have to wait for next spring now Steve !!

[rocketsteve]

Looks like I have work to do, starting with a 1/4 turn throttle or reconfigure the throttle cam on the carb to work in a similar way.

I think we're only allowed to play in 1st Paul, don't risk stressing the Trans in 2nd gear... Bike is still on the road at the moment so I'll mess around until end of this month then SORN.