robe
Well-Known Member
The PZ 19 I got from Amazon on your suggestion looks great. It is about 19 mm through out. Haven't tried it yet but for less than $20 CDN can't complain.
79cc Predator carb question...............
- Thread starter michael whiteman
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Chainlube
Well-Known Member
Ovate venturi but 19mm exit.
robe
Well-Known Member
I had to look, yes it does narrow at the slide. I didn't realize that. Still has a larger area than the stock carb. That bike has been on the back burner for a while, looking forward to finishing it.
michael whiteman
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All carbruetors narrow down in the venturi to work properly. A guy named Bernoulli determined that this increased the air speed which created a low pressure area that sucked the fuel out of the jet. With out this you have fuel injection that requires a pump.
michael whiteman
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If you (like myself) are having trouble starting your Predator for the first time when it's cold I found the fix. Even though enlarging the pilot jet a little helps the off idle, the real fix is to eliminate the small hole in the choke butterfly. I put a piece of duct tape over mine and the engine started on the second pull, where before it took over ten. I'm going to remove the butterfly and either solder the hole closed or use JB Weld. File or grind the threads off that are sticking thru the shaft on the back side first or you will break the screw off in the shaft. Just put some thread lock on it during reassembly.
Chainlube
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The rebuild kit for my SU carbs came with new screws. Those are for the throttle plates though, SUs don't have a conventional choke plate.
meridianPeteJ
Well-Known Member
What's a SU carb?
Carburetors that were used on MG's, Triumph's and Jaguar's they usually worked on the principle of 1 carburetor for every two cyclinders on MG's and Triumph's and series one E type Jags in particular...Both of my four cylinder MG and Triumph Spitfire had twin SU carby's on them and my Jag had 3 of them for its six cylinder motor.
SU Carburetters | SU Carburetters
The SU Carburetters page for the SU Carburetters website.
Chainlube
Well-Known Member
My V8 Stag had 2, cross fire, goofy bowls.Carburetors that were used on MG's, Triumph's and Jaguar's they usually worked on the principle of 1 carburetor for every two cyclinders on MG's and Triumph's and series one E type Jags in particular...Both of my four cylinder MG and Triumph Spitfire had twin SU carby's on them and my Jag had 3 of them for its six cylinder motor.
SU Carburetters | SU Carburetters
The SU Carburetters page for the SU Carburetters website.sucarb.co.uk
michael whiteman
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Imagine a PZ carb Pete, with a butterfly added. Manifold vacuum sucked the piston up instead of a throttle cable. This prevented you from having WOT before the rpms were high enough to use the extra charge. It might be interesting to fit a throttle cable on a SU piston, just to see what happens.
I used to work on lots of Jags that had three. What a PITA to sync them all together. I got tired of doing it on my Sprite and put on a Judson supercharger which curred that problem.
Ya gotta love the Brits.................. SU carbs and Lucas elecrronics. "Lucas" the prince of darkness!
