Prop choice

[_Ed_]

Looks like progress is being made. I have not looked at those ignition systems, but that is SO SO basic. I had expected something more exciting to justify a 'thunderbolt' name, but really its just a primitive design going back 30+ years! At least it makes it easy to figure out any problems, if you still have any.

[shibbs]

Well that didn't work out as I'd hoped.
Re-connected the ignition module and still the same, didn't want to idle without a bit of throttle. Checked all sparks but all ok now which confused me somewhat.
I think I can now discount the ignition module though as when I played about with that while the engine was running, as soon as I disconnected it the engine stopped.
I'm wondering now if Italy be something to do with timing, but why all of a sudden will it not idle..?
Thought I'd give some of the electrical connections another check and managed to snap one off of the coil..

I suppose now I'll have to replace that and at least I will then be able to discount the coil!
Not really too sure where to go now.

[mark101]

Oh the joys of boating Stu . Still bit unfair to blame Italy

[shibbs]

Oh the joys of boating Stu . Still bit unfair to blame Italy

Very good,
Might be, I meant, I have nothing to blame Italy for.

[Ianfs]

I suppose now I'll have to replace that and at least I will then be able to discount the coil!

Don't get despondent, you are on the right track. First of all, you have all sparks (inc. no 5 ) and they are good yes? Did it idle well previously and what is the difference now? If the engine is cold, is the choke working? When you said it won't idle unless revved, do you mean it idles roughly or dies? When revved does it sound ok and full of life, in other words better than before?

Pop another coil on, they are not expensive.

Now that you have all 8 cylinders running you may find that the engine needs retuning, that's is "if" the choke is working. If it is, then it might be either the idle mixture or timing!

Ed will know best but I would start with replacing the coil then check the choke is closed when cold. Then check the mixture screws you'll have two, each will adjust the mixture for its own bank/side. Standard practice is when the engine is cold and off, wind both the screws in until they stop, not too tight but until you find a stop. Then wind out 1.5 turns, start her up to temp then adjust by turning in until hunting and then out until hunting then find the happy medium between the two.

Once you have done this you could check the timing if you have a light, if not Colin has a good supply!!

I think you should connect the light to no1 cylinder then at idle it should be 8 degrees btdc.

Once you know all is on track you can then look at other things, but I hope this is all it is.

[shibbs]

Hi Ian, Yes have all sparks now, and all seem to be fairly good. with the running, it needs throttle or it will die. I had a fiddle with the idle screw on the carb and it will sit in neutral running but only at about 1000rpm, which is obviously too high. Previously it would start easily and sit at idle nicely. a while back i thought it was running a little slow on idle and sometimes stalled when coming out of gear so i raised the tick over rpm slightly thinking that was the problem, then the recent problems occurred (not directly after that) and were now where we are.
When revved in neutral it sounds and revs as it should. I did run out again this afternoon but it ran the same, lumpy and as if there was a mis-fire.
New coil then i will check the choke, i hadn't considered that..
followed by the timing.
Thanks again Ian.

[shibbs]

This is the position of the choke when warm at about 800rpm, is this correct?

[Ianfs]

Yes Stu, when warm the choke should be open like that, but when cold should be closed.

You need to check both warm and cold!

What I am looking for is, if the engine is cold and the choke is in that position then there is a problem!! If when the engine is cold and the choke is fully closed then the choke is ok!

[Ianfs]

Stu
Any joy?

The more I think about it the more my simple non expert mind thinks you could be suffering from a weak mixture. Assuming its now firing on all cylinders when running. Previously with one cylinder out it had enough fuel at idle to idle at the right speed.
1/ Engine won't idle but runs at 1000 rpm and above
2/ when running full speed cannot be found and a misfire.
Apologies if this is nonsense!

[shibbs]

Hi Ian,
I've annoyingly been away all week so no further progress.
I also now believe this may well be an issue with the carb. My next plan is to give the jets a clean out, and go through the process as you pointed out of checking the mixture.
As you say, I now have all sparks so it does point towards a fuel problem somewhere.
The investigation will continue...