34 replies to this topic

[babsbrown]

*Update* to the post below:

Ran the car for 2x 20 min periods between 2200-2500 rpm.
Torquing head nuts in between.
It fluctuated on the ARF
Between 14.6 to 15 ish.
However, after about 20 mins it's started to go really lean.
To about 17 AFR.
It was also misfiring, so knocked it off. Timing is 8 deg BTDC. Plugs don't look
Like they've been really run that much with a slight brown tinge.
Before I start spraying everything and checking for air leaks

Is there anything obvious I've overlooked? Thanks

Hi guys,

I've installed my engine and I have it running..... to an extent.

I have to use the choke to start it. And once started, if I take the choke off she dies.

As I'm running it in and don't want bore wash. How do I get around using the choke as little as possible?

As the Haynes manual points out. Set the idle with the air cleaner off and after the engine has warmed.

I can't really warm the engine as I don't want to run It prolonged with the choke.
Bottom mixture adjuster nut is 10 flats from the top.

Fast idle screw is not touching until the choke is engaged.

Engine is 1130 with Hs4 AAA needle. 45d dizzy standard points. 7 deg BTDc

Please bare with me, as this is the first time doing this process.

I have a wideband gauge fitted although I haven't turned it on yet as I don't want to keep turning it on and off as the engine keeps stalling.

Any advice is much appreciated as always . Cheers

LUKE

Edited by babsbrown, 12 April 2025 - 03:03 PM.

[KTS]

when you say it dies when you take the choke off; is that just at idle or any engine speed ?

 

if it's just at idle, i'd adjust the idle speed to get to a point where it will continue to run without choke and work from there

[Cooperman]

Start it and run it with as little choke as necessary to keep it running. That won't hurt it at all. Then, when it's warmed through and the choke is pushed fully in, set the tick-over to around 1000 to 1100 rpm.

When it's fully warm with the choke in check the mixture. If it won't run with the choke in, even when fully warm, then it's either too weak or too far retarded timing-wise.

The normal mixture setting for initial start-up is 14 to 16 flats down from fully weak with 6 degrees of advance for the timing. That's a good start point and you tweak it from there until it runs nicely.

Edited by Cooperman, 31 March 2025 - 03:48 PM.

[babsbrown]

Excellent thanks gents. I'll have another go tomorrow. I'm so worried about bore washing. I think I'm probably been too overly cautious.

[Shooter63]

You might want to change the needle to a AAE, the AAA is quite rich.

Shooter

[Steve220]

If the engine has fresh piston rings and a hone, letting it idle will do greater damage than bore wash. You'd need to be close to 10:1 AFR to get bore washing, but the engine would run like garbage. If its running under choke, go drive it and put load on it as soon as possible!!

[alpder]

Excellent thanks gents. I'll have another go tomorrow. I'm so worried about bore washing. I think I'm probably been too overly cautious.

My engine was rebored by the best local engineer, rebuilt with immense care by me, fitted with a newly recon carb, run-in by-the-book for 500 miles, set up with a hand-made needle on a rolling road, and then driven another 3500 miles. Only at which point did I discover the "recon" carb had been built by a complete muppet so that the starter ("choke") was permanently full-on. Which gave me 30% excess fuel consumption for those 4000 miles.

 

It's not a great thing to happen. But the engine survived, sounds good, drives lovely, pulls like a train, and shows no sign of imminent demise. Your "little bit extra choke" is nothing in comparison. Just drive and enjoy.

[babsbrown]

You might want to change the needle to a AAE, the AAA is quite rich.

Shooter

Thanks shooter,

I don't have and AAE to hand, but I do however have an AAU, I'll try that in the meantime and see how it does.

[babsbrown]

If the engine has fresh piston rings and a hone, letting it idle will do greater damage than bore wash. You'd need to be close to 10:1 AFR to get bore washing, but the engine would run like garbage. If its running under choke, go drive it and put load on it as soon as possible!!

Ah that's reassuring, cheers.
To be honest, I'm just trying to get it adjusted to a sensible point, and then I'll get it on the road as soon as I can.

[babsbrown]

Excellent thanks gents. I'll have another go tomorrow. I'm so worried about bore washing. I think I'm probably been too overly cautious.

My engine was rebored by the best local engineer, rebuilt with immense care by me, fitted with a newly recon carb, run-in by-the-book for 500 miles, set up with a hand-made needle on a rolling road, and then driven another 3500 miles. Only at which point did I discover the "recon" carb had been built by a complete muppet so that the starter ("choke") was permanently full-on. Which gave me 30% excess fuel consumption for those 4000 miles.

It's not a great thing to happen. But the engine survived, sounds good, drives lovely, pulls like a train, and shows no sign of imminent demise. Your "little bit extra choke" is nothing in comparison. Just drive and enjoy.

Wow, how frustrating.
But just goes to show that its not the end of the world if not perfect straight away cheers

[timmy850]

Any needle will work for the initial 2000rpm, if you’re just starting and running it on the driveway. If it won’t run without choke it’s too lean, too cold, or a combination of the two

The 10 flats is just a guide, you’ll need to adjust to suit your engine. Preferably using an afr gauge!

One example of the break in:
https://youtu.be/IMi...IQ8JuzOa14PkGNt

Personally I got mine running for about a minute, then stopped the engine. Next I drove it around under load while checking the mixture with the afr gauge to make sure it wasn’t lean

AAA is the one AC Dodd warns about, as it’s normally much too rich for most engines

Edited by timmy850, 01 April 2025 - 01:02 AM.

[babsbrown]

Any needle will work for the initial 2000rpm, if you’re just starting and running it on the driveway. If it won’t run without choke it’s too lean, too cold, or a combination of the two

The 10 flats is just a guide, you’ll need to adjust to suit your engine. Preferably using an afr gauge!

One example of the break in:
https://youtu.be/IMi...IQ8JuzOa14PkGNt

Personally I got mine running for about a minute, then stopped the engine. Next I drove it around under load while checking the mixture with the afr gauge to make sure it wasn’t lean

AAA is the one AC Dodd warns about, as it’s normally much too rich for most engines

Thanks timmy, I've seen your mini on YouTube I believe. It sounds awesome, and looks really fast. I'll have another tinker this morning with the different needle. That might be a better idea. Just driving it rather than trying to get it sorted while stationary.
to be honest I should be delighted it started for my fist build just didn't anticipate it taking so long haha

[Lplus]

Two points - I was under the impression that the fast idle should begin to operate before the enrichening begins.

 

Secondly my AEM wideband A/F meter instructions state that running the engine without the sensor connected and powered may lead to failure.  I don't think it matters if it has to be turned on and off each time it starts.

Edited by Lplus, 01 April 2025 - 08:39 AM.

[Steve220]

Two points - I was under the impression that the fast idle should begin to operate before the enrichening begins.

 

Secondly my AEM wideband A/F meter instructions state that running the engine without the sensor connected and powered may lead to failure.  I don't think it matters if it has to be turned on and off each time it starts.

Kind of. The sensor usually goes through a heating cycle, but this should be after the engine starts as it lets the exhaust gas blow condensation off the bulb prior to the heating cycle starting. If it heats up then the engine starts, this can cause thermal shock to the bulb and break it.

 

On my haltech WB1 set up, the ecu won't read or warm the sensor up until the engine has started for a few seconds.

[Ethel]

What it does at idle can have little relation to how it runs under load. It it drives reasonably well under load then that'll be because the fuelling & ignition timing are reasonably correct.