Twincam expert help

[chrisbeck]

I think it's time to seek expert help, I've got a low throttle misfire and have run out of ideas. Replaced everything on the ignition side and have eliminated a high speed RFI issue, now think it must be carburation.
Can anyone recommend someone who knows their way around a Twincam with Dellorto's local to me in South Bucks, UK, who can do a diagnosis?
Thanks.

[cliveyboy]

I have Heard good things about these people. Based near Winchester
https://www.aireytuning.com/

[chrisbeck]

Thanks, I spoke briefly to a guy at Kop Hillclimb on Sunday and he recommended a garage in Maidenhead (I think) who'd worked wonders on his Elan. He said he visits this forum frequently so maybe he'll spot this and remind me of their name!

[lotusfan]

he recommended a garage in Maidenhead (I think) who'd worked wonders on his Elan.

Maybe Steve Williams Sportscars?

http://swlotus.com

[JohnP]

Max Hurst. Max 500 in Guildford.

[cliveyboy]

Chris
That might have been me.
I used a local classic car specialist in Oxfordshire.
https://classic-car-services-oxford.co.uk/
Toni sorted out my Sprint running badly when I was struggling. (Newish Lumenition faulty which caused some other electrical issues).
He does not have a rolling road but worth a call.
Clive

[nmauduit]

I think it's time to seek expert help, I've got a low throttle misfire and have run out of ideas. Replaced everything on the ignition side and have eliminated a high speed RFI issue, now think it must be carburation.
Can anyone recommend someone who knows their way around a Twincam with Dellorto's local to me in South Bucks, UK, who can do a diagnosis?
Thanks.

if you are unsure about the carburetion somehow (I understand you've cleared out possible ignition issues, and would have made sure carbs are clean and nominally jetted - but also and more importantly if everything else is stock the fuel level in the bowls), a measure of richness may be a quick way to assess that more accurately than by the look of spark color via the use of a wideband lambda sensor. The best is to have a bung welded to the exhaust, but one can also get a measure at the exhaust, though less accurate (esp. a low revs)

[69S4]

Chris
That might have been me.
I used a local classic car specialist in Oxfordshire.
https://classic-car-services-oxford.co.uk/
Toni sorted out my Sprint running badly when I was struggling. (Newish Lumenition faulty which caused some other electrical issues).
He does not have a rolling road but worth a call.
Clive

Hi Clive

Great to chat to you at Kop Hill on Sunday. I went there expecting to spend most of my time amongst the two wheelers but the Lotus owners were much more interesting!

Despite being just up the road from me I hadn't come across Classic Car Services before. That's another one to add to my list of small local specialists to turn to when things go pear shaped.

Stuart

[LaikaTheDog]

Novatech in Slough
Novatech.info
he worked on my Weber's and removed a Low rev stumble, I have seen him tuning a 2 seater Elan also.

Knows what he is doing.

[chrisbeck]

I think it's time to seek expert help, I've got a low throttle misfire and have run out of ideas. Replaced everything on the ignition side and have eliminated a high speed RFI issue, now think it must be carburation.
Can anyone recommend someone who knows their way around a Twincam with Dellorto's local to me in South Bucks, UK, who can do a diagnosis?
Thanks.

if you are unsure about the carburetion somehow (I understand you've cleared out possible ignition issues, and would have made sure carbs are clean and nominally jetted - but also and more importantly if everything else is stock the fuel level in the bowls), a measure of richness may be a quick way to assess that more accurately than by the look of spark color via the use of a wideband lambda sensor. The best is to have a bung welded to the exhaust, but one can also get a measure at the exhaust, though less accurate (esp. a low revs)

I wonder if I've disturbed some debris when I removed the carbs, either that or should have fitted new O-Rings on the manifold plates and I'm sucking in air? How difficult is it to check the jets are clear? Can I do it with the carbs in situ?

[ericbushby]

Hi Chris,
An easy test for air leaks inwards at the carburettor plates is to spray a little carb cleaner or similar volatile fuel there. Propane will probably work equally well.
If there is a leak then the engine will respond to it.
Eric in Burnley
1967 S3SE DHC

[chrisbeck]

Good idea, thanks!
I'm reminded of listening to a colleague's +2 and being able to hear the carb sucking air because he'd trapped an O-Ring, it was too high a frequency for him to hear. Next time I saw him he had hearing aids!