72 ST engine bogging down

[gturner008]

I’ve noticed my 2.5 twin spark, Rothsport built engine is suffering from intermittent bogging down on throttle.

I’m changing from first to second, say, and put my foot down to accelerate, but get a delay and hesitation. Sometimes the revs drop and feels like it’s short of petrol. Then it picks up and accelerates fine. Lots of power.

Any suggestions on where to look? My instinct is carbs. Lack of fuel. It has new 46 Weber with only 5k miles. Maybe not getting that squirt of gas? I’ve never had Weber’s apart. Easy to dismantle and take a look? Anything to watch out for or check?

Alternatively, what else might be the cause? Has electronic ignition.

[964RS]

Does it do it on gentle throttle or just hard throttle?

[yoda]

I had something similar on one of my cars where fuel delivery seemed to be interrupted intermittently. Went through the fuel system - cleaned the tank, replaced filters, cleaned and checked the carbs etc. Turned out to be an electrical problem with the power supply to the fuel pump that caused the issue. It wasn't consistent though, happened every now and again but once it happened, it would repeat.

[gturner008]

I checked out the carbs. All fine. What I did see was my JB Racing twin plug distributor the culprit. Cracked rotor base and generally worn out contact areas. That’ll cause the issue I’ve been experiencing.

JB Racing will take back the distributor and refurb for me. Good service.

[gturner008]

Update. JB Racing did a good job of restoring the twin plug. It didn’t fix the hesitation.

I then replaced the twin coils. That improved it 90%. This pretty much fixed my issue.

[gturner008]

Finally solved the issue. Turns out the accelerator pumps were giving too much fuel. Blowing the spark out. Knocked them back about three full turns each. No issues at all now.

[yoda]

Good you've fixed it as those sort of problems are very irritating. Always the electrics!