Club 80-90 Forums

OK. So.

Power valve nearly fully open.

Bias 12 flats

Bypass. Half turn.

Engine will start and idle. The idle is slightly erratic and gradually slows until the engine. Dies.

I can increase the bias to 15 flats and the idle gets faster but still slowly gets erratic and then dies.

Should I try 0 bypass and increase the bias some?

I guess it's the bias that increases and decreases the idle speed?

I want blos.
Is it diy-able Andy

Everything is DIYable if you know how

Just when I thought I was tuned for all driving conditions I discovered today that full chat over 70mph is lean, up until that speed it's rich.
Looks like some more bias or power valve needed, will have a play

I don't see how anybody would know this without an Air fuel gauge and thats a danger zone because your engine it hot and working hard, you deffo don't want it lean.

More power valve on 2nd Venturi screw (assuming yours is a double).
BLOS is diy fit if you have (access to) a gas analyser, preferably 4 gas!
Must have ignition system in tiptop order though, as dirty dizzy caps, bad leads etc can cause backfires, and with a BLOS that could blow your pancake apart. Fit anti-backfire toilet seat too.

So to report back. The van is starting easily on Lpg now, and drives fantastic. No flat spots or spluttering right through to 70. It's however idling way to fast. I tried reducing the bypass a tad but then I couldn't start on Lpg hot or cold so raised it.

I assume it's running rich on Lpg so I need to reduce the power valve, correct?

Does it idle high on petrol too?

No idles and runs perfectly on petrol.

Do you have two or one powervalve?

Single. Y piece.

If it's driving, running and starting so well on LPG, leave it. The problem is on the carb. You need to find out why it needs the idle screw turned in so far to get the correct idle speed on petrol. (You may have gone as far as you can without a gas analyser (I sound like a broken record)). It's probably lean on petrol, either mixture screw or air leak, so someone has screwed the idle speed screw in to compensate. Then when you've got the gas mixture correct it revs too high. You never then lean it off to reduce idle speed, and certainly not with the power valve, as that only restricts the delivery at high revs/demand. It has virtually no effect at idle.

ajsimmo wrote:If it's driving, running and starting so well on LPG, leave it. The problem is on the carb. You need to find out why it needs the idle screw turned in so far to get the correct idle speed on petrol. (You may have gone as far as you can without a gas analyser (I sound like a broken record)). It's probably lean on petrol, either mixture screw or air leak, so someone has screwed the idle speed screw in to compensate. Then when you've got the gas mixture correct it revs too high. You never then lean it off to reduce idle speed, and certainly not with the power valve, as that only restricts the delivery at high revs/demand. It has virtually no effect at idle.

But it's performing so well on petrol. Idles great and drives better than ever. I'll have to do some more investigation somewhere.

Just try richening it up on petrol to see if the idle speed increases. If so, you've cracked it.