Advance And Retard

[Guest kleighton]

Good evening all,

 

I've found today that my car struggles to rev past 2500/3000 rpm, it stutters and back fires through the carb, but only when under load. It's fine when revving the engine standing still. I disconnected and blocked off the vacuum advance on the dizzy and the problem has now moved further up the rev range to about 4500 rpm.

 

Can anyone shed any light on what the problem might be please ? I'm a little confused.

 

Thanks

 

Keith

[speedtripledan]

what carb are you running ? and what is your dizzy set to?

[Guest kleighton]

Sorry mate, forgot to mention the important details, it's been a long day.

 

It's a 38 DGAS carb, and I'm not sure what the dizzy is set at, I took it to a garage to sort the carb and timing.

 

Cheers

 

Keith

[Guest The Modfather]

Have you tried sucking on the diaphragm to seek if it's leaking? Stick the vac pipe in ya gob, suck on it and stick ya tongue over the pipe end. Your tongu should stick to it. If it doesn't then its kapput!

If you have a timing light check what it is set at. I'm running at about 9* as I had a flat spot at about 3/4 pedal. If this don't work then I'll back off another degree or so and keep trying.

What condition is your cap, leads etc?

[speedtripledan]

that carb can be tricky to set up and are known to cause that problem i tried one before i did bike carbs tazzzman has one that works well after dyno tuning

 

As for timing it should be 8deg at tickover (standard) mine is now 14deg at tickover but thats due to all the tuning work

[Guest shaggy]

Keith, as you know mine went on RR a couple of weeks ago.

On a 32/36 twin carb and with a FR32 cam, the optimum timing was set to 15.7 degrees.

 

Si

[Grizzly]

I run 10 Degrees with a 32/36 Webber & Std Cam.

I did try backing it down to 8 Degrees a few weeks ago, but all that did was make it pop back through the exhaust.

[Guest kleighton]

Thanks for your replies gents,

 

Looks like I've got a little bit of playing around to do.

 

Also, I'm wondering if too much back pressure is messing things up a bit, any ideas ?

 

Thanks

 

Keith

[baj25]

From your post in IVA section, sounds like you could have constipation in your exhaust. I'd get the thing through IVA and then worry about this when you have cleared out the exhaust, might not be aproblem there after all. Brian