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Thu Aug 21, 2008 12:34 am

Hi all

Will heat raisers eliminate my problem of a flat spot if I quickly pull away?

Solex Pict 34 carb and vacuum advance dizzy.

Thu Aug 21, 2008 1:48 am

No. Check your accelerator pump.

Thu Aug 21, 2008 8:27 am

They could be a factor.

Also check the accelerator pump like Dan said.

Also make sure the vacuum portion of the dizzy is working properly.

Make sure the engine is timed correctly.

Check valve clearance just for the heck of it.

How are the points? Or do you have Compufire / Pertronix?

Spark plugs in good shape?

Engines are dynamic things. A fault in one area can manifest itself into a symptom somewhere else. Best plan is to establich a baseline of known values, then work your way inwards.

But yes, heat risers are an important part and must be functioning properly for center mount carb setups. Dual carbs don't care.

Lee

Thu Aug 21, 2008 5:15 pm

The heat risers are to combat a problem known as carburetor icing. It will cause your engine to stall. With duals the carbs are much closer to the heads so the heat generated stops the icing.

Hesitation on accel is 99% accel pump. To test the pump try accel slowly to 60mph. If it is fine but hesitates {flat spot} on hard accel, replace the pump.

Sun Aug 24, 2008 11:27 pm

in the butterfly is a hole, use a pop rivit to close hole this will help with that prob alot of times.some guys use jb weld ive only used the pop rivit method.

Mon Aug 25, 2008 7:12 am

bowtie56jw wrote: in the butterfly is a hole, use a pop rivit to close hole this will help with that prob alot of times.some guys use jb weld ive only used the pop rivit method.
Plugging this hole is just a bandaid for another problem {vac leak or running too lean}.

Mon Aug 25, 2008 6:53 pm

How do you check the accelerator pump? I have HORRIBLE hesitation off idle, to the point that it will actually stall sometimes.

Fri Aug 29, 2008 3:02 pm

Bump!

Fri Aug 29, 2008 10:11 pm

What carb(s) are you running? The adjustment is done at the adjustment on the linkage, but each carb is different.

Lee

Thu Sep 04, 2008 1:34 pm

73SpeedBuggy wrote: How do you check the accelerator pump? I have HORRIBLE hesitation off idle, to the point that it will actually stall sometimes.
Take off the air cleaner assy. open the choke. look into the carb for a small brass tube. Slowly open the throttle and look for a steady stream of fuel coming out of the tube and going into the carb. Make sure the stream does not hit the throttle butterfly or the throttle shaft.

Sat Sep 06, 2008 9:32 am

Accelerator pump/ Injector Nozzle.
In a buggy it's likely you'll be better off just removing the carb.
1 wire, two nuts, the fuel line and the throttle cable- you literally CAN remove the carb faster than you can explain to someone how to remove it.
Once its off, open the choke plate and look inside the carb as you operate the throttle lever.
As stated, look for a very small brass nozzle to squirt, or possibly just drip fuel as the throttle is moved.
There's a decent chance that nozzle may be missing all together, they can fall out and go into the head (they're brass, so don't worry).
If its missing get another and install.
At this point you might as well take the carb apart and clean it up too.
The nozzle, if its present but not working, can plug pretty easily- it just pulls/twists out. Use air to blow it AND the carb passages clear and reinstall.

Sun Sep 07, 2008 9:16 am

Believe it or not, there's a spec for the volume of fuel that should come out of the accelerator pump nozzle. The procedure is to attach a hose to the nozzle and put the other end into a graduated container. Work the throttle something like 5-6 times, measure the amount of gas that comes out, then divide by the number of times you worked the throttle.

I just adjust the linkage to one extreme, drive it, adjust to the other extreme, drive it, adjust with the linkage in the center, drive it, then make the final adjustment based on the results from the drive tests. The end result is very smooth acceleration with no flat spots or hesitation, and you don't burn excessive amounts of gas in the process.

Lee