Page 2 of 2
Re: Twin Su idle high
Posted: Mon Nov 30, 2020 8:20 pm
by TrustNo1
you seem to be set on the idea that its the carbs causing fast idle, have you tried retarding the distributor slightly?
Re: Twin Su idle high
Posted: Mon Nov 30, 2020 9:48 pm
by GrahamFountain
TrustNo1 wrote: ↑Mon Nov 30, 2020 8:20 pm
you seem to be set on the idea that its the carbs causing fast idle, have you tried retarding the distributor slightly?
Even with an unsafe amount of advance, I'd still expect to be able to get the idle down to a reasonable value. So, even if there's a bit of error in the timing, there's still a problem, probably with the carbs, their set-up, or the linkage.
And the first post said set to 10 degrees before TDC with no vacuum.
If the only problem is the idle won't set low enough, you got to eliminate the easy to find and fix problems with the linkage first and try the WD40 test for air leaks. Then look to the more difficult to find problems like the butterflies misaligned in their spindles, and the poppet valves being worn.
Graham
Re: Twin Su idle high
Posted: Tue Dec 01, 2020 5:54 pm
by TrustNo1
sorry I was just trying to be helpful based on personal experience of a problem I recently had where although the timing appeared to be correct it was running at higher revs and this was cured by moving the distributor back slightly.
Re: Twin Su idle high
Posted: Tue Dec 01, 2020 9:50 pm
by GrahamFountain
Why be sorry? It was a valid point that idle speed depends on advance, and I had no intention of suggesting otherwise.
Just that I think that if everything is as it should be the butterflies will shut well enough the engine shouldn't idle wherever the ignition timing is set. So even if backing the ignition timing off a bit fixed the problem with the idle, there must still be an underlying problem that's not been fixed.
Graham
Re: Twin Su idle high
Posted: Wed Dec 02, 2020 9:55 pm
by TrustNo1
GrahamFountain wrote: ↑Tue Dec 01, 2020 9:50 pm
Why be sorry? It was a valid point that idle speed depends on advance, and I had no intention of suggesting otherwise.
Just that I think that if everything is as it should be the butterflies will shut well enough the engine shouldn't idle wherever the ignition timing is set. So even if backing the ignition timing off a bit fixed the problem with the idle, there must still be an underlying problem that's not been fixed.
Graham
The O/P said that he had set it at 10*BTDC,I assume by lining up the notch on the pulley to the TDC markings but has he checked that the spark was on plug one, so maybe everything isn't as it should be?
Its a very easy mistake to make