Ok, so after finally getting the Gemini ready for MOT I was lucky enough to be able to run it up a private road to see how it was running after a six year hiatus.

No good is the answer sadly....

Ok firstly the facts:

1600 crossflow, with ( as hey Unchecked) stage three head , fast road cam and twin dellorto 40s
Ignition is dizzy and luminition

So it idles very well, maybe hunting a little but seems generally very good. Initially when setting off it runs fine, the after a few seconds feels like it's misfiring or running on three. Idles badly, lots of back fires and difficult to get it moving.

After sitting for a few moments it'll fire up ok, and the same set of syptoms present themselves after setting off.

So my question is where to start. Working on the principle that when it was laced up it was in a reasonable state of tune, what are the first things to check? Fuel line is flowing fine, so issues there. Checked spark on all four, no problems there.

Coil? I don't know a lot about luminition, anything to go wrong there? Timing possibly?

I have a sneaky suspicion it's something fairly majorly out, but only with the car under load. Blocked jet?

Car is due for MOT tomorrow, then I wanted to book an RR session, but would like to sort this issue first to keep the bill down.

On the plus side, I drove the car for the first time and it felt tight as a drum :-)

If you know what cam it has start by checking the valve clearances , often overlooked tight tappets will cause problems

Sounds very much like a fuel supply issue, a blocked fuel line ? fuel tank not vented? fuel pump problem?



Hunting sugests either weak mixture at idle or too much ignition advance at idle speed neither of which would cause your main problem.

Had a very similar sounding problem a few months ago on my crossflow for which I had bought everything ignition wise brand new. It turned out the HT leads I bought (Accuspark) were not up to the job once under load, tick over was fine. Swapped them for some OE ones for less than £10 and bingo!

Thanks guys.

Valve clearance - hadn't thought of that, will check and report back.

Fuel - seems to be coming through well, certainly with fuel line off and pumping into a can. Pressure wrong maybe? Blocked carb? How would imcheck the jets for a blockage?

Leads - possible, I'll buy some replacements and try that too.

Keep suggestions coming!

6 years of sitting idle, the fuel will have evaporated away and left hard deposits, I would pull the jets, emulation tubes etc and give a bloody good clean.

Looking on the bright side, MOT is at idle so it should not even matter for tomorrow

quote:

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Originally posted by mark chandler
6 years of sitting idle, the fuel will have evaporated away and left hard deposits, I would pull the jets, emulation tubes etc and give a bloody good clean.

Looking on the bright side, MOT is at idle so it should not even matter for tomorrow

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My bets on carbs need a good clean.

First thing to check is compressions. If any of them are low, check valve clearances.
If all ok, I'd check out ignition timing. Then the fuel system, filters and lines, get rid of stale
fuel, clean out carbs, check carb mounting and seals.

If they are anything like the twin 40's I used to play with you just undo the wing nut on the top, this will reveal the jest et al, get a can of carb cleaner then pull everything in site out, so main jets at the bottom of the fuel bowl, air corrector jets at the top and carefully pull the emulsion tube out ( they are long tubes held in by the air correction jets so hook out) then give a good clean and restore.

Place everything on a clean cloth so you can replace in order, make a note of the markings as they should all be the same relative to position in the carbs then blow some air through to move any crude on.

Do not twiddle the screws, they do not usually go out of tune despite people always playing with these things.

If you remove from the car make sure you do not over tighten on the manifold, they should be free to move slightly, in the old days they used thackery washers, a kind of double washer in a spiral which you tightened until the two halves meet on the washer, over tighten and the fuel will froth in the carbs upsetting the fuel level and mixtures.

If you do twiddle the balance then a small tube to listen is actually quite accurate if you do not have a carb balancer.

Regards Mark

Thanks gents,

All super helpful. I'll report back when I know more.

:-)

do you not know anyone nearby with a twin choke carb they can lend you? Get through MOT then play
with the 40s after...

Quick update - managed to pop, bang and fart my way to the test centre.

Still idling ok, so fingers crossed for a pass!

good luck

A fail, but only on a binding rear drum, so should be an easy fix. not bad after 6 years.

pics to follow as i've no idea what axle it is.......