Engine coughing

[monomanx]

Hi all,

Here is my dilemma which I have written about before, have tried all suggestions...still having same problem:

1600 DP with PICT 34-3 and a SVDA with pertronix ignitor.

If I slowly give it throttle, I am ok. If I hit the throttle in first gear, I am fine...however the minute I got into second gear from a normal acceleration , the engine coughs and sputters...if I just jam the pedal down, the engine stumbles, then runs fine...each time...this is not an intermittent problem.

SVDA is from Kaddie Shack. Stock carb running vacuum advance.
All jets are clear.

Any ideas?

Chris

[BL3Manx]

I looked though all your posts and can't find the previous thread. It would be real helpful to see exactly what has been suggested and what you've tried.

[CrashedAgain]

It sounds like the accelerator pump is not working properly....probably the low speed circuit in the carb is running too lean as well.

Check the accel pump linkage. The link rod on mine was worn nearly half way through reducing the motion available. I made up a new link with pieces from an old carb. You can remove and check the little ball check valve from the accelerator pump discharge but it's usually not necessary. Make sure the linkage is set to the maximum...just enough free play at the beginning so that the accel pump linkage does not keep the throttle plate open.

If you have not yet done so, drill out the pilot jet. Start with 0.5 mm drill if you have one (.0197") then try #76 or #75 drill (.020" & .021"). Mine is now #75 drill. This jet is undersize originally to lean out the mixture as an early attempt at smog control.

You could also try this modification...http://www.aircooledtech.com/34pict3_modification/

I have done this on mine but I'm not sure if it was the answer becuase I stll had the flat spot after modification....better but still there. I only just recently got it to the point where I do not have a flat spot after a proper thorough carb clean out in carb cleaner & open out the pilot jet to #75 drill. At the same time I found & repaired the worn accel pump linkage and also found that the point setting was off as was the timing. I'm using an SVDA distrubuter off a 36HP. Timing is set approx 8 deg BTDC.

Right now I can bang the throttle wide open from 1500 rpm & have the engine pull smoothly all the way once it is warmed up.

[LeeVW]

Yeah, a link to any previous thread(s) would help a lot.

First things to check are timing (time it at 30 degrees BTDC, 3500 RPM, vacuum line removed and plugged), accelerator pump adjustment, verify that accelerator pump nozzle is in place and is properly aimed, verify vacuum advance is working (vacuum can sometimes gets rotted out because vacuum line going to it does not have the proper 'upside-down J' pipe installed, so gas runs into it), verify mechanical advance is working by removing vacuum line from dizzy, plugging line, and watching for the advance with a stroboscopic timing light. Stuff like that.

[monomanx]

The post was a long time ago (around arch or April). I will try to find it.
To answer some questions:
Timing is dead on using strobe. With vac line off. With the vac line on, it is advancing upwwards of 40.

I changed the accelerator diaphragm thinking that might be a problem but did NOT think to check the actuating arm on the accelerator pump...come to think of it, the rod was a little bit worn....that might be the ticket.

I will check that out tonight.

I will also try to find the original post.

[BL3Manx]

[LeeVW]

[Mike_CNYBuggy]

I had this same exact issue and we thought it was accelerator pump but it turned out to be the gap was too close on the points.

Mike
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[Mike_CNYBuggy]

Read slower this time. Not likely your points since you don't have any.
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