Re: New motor troubles 1904 Weber progressive & Magnaspark d
Posted: Tue Oct 03, 2017 5:19 am
14 degrees before top dead center is little more than most set timing at idle. I use between 8 to 10 degrees at idle with total advance approx. 30-32 degrees total with a 009 or the early 010 distributors at 3,000RPMs.
Having a distributor where you can set the advance curve sound neat. Did it come with a basic advance program with it?
Good to hear you could get it to idle with larger jets.
The 110 cam is a good cam for all around performance.
Usually has good power from idle to around 5,000RPMs. Will run smoother with dual single throat carbs and even better with dual dual throat carbs like Weber 40mm IDF or the Empi HPMX.
Your compression numbers are not really that high. A guess would be somewhere around 8 to 1 compression ratio.
It sounds like the off idle stumble you are having is the accelerator pump circuit is not giving enough fuel when you open the throttle plate. On the Weber progressives I worked on (has been a few years) had different holes to locate the pivot pin for the accelerator pump to get more or less fuel out of the nozzle located inside the primary throat. Or it could be the nozzle has a blockage or needs to be enlarge to allow more fuel to flow.
Does John have any information at Aircooled.net about adjusting the accelerator pump or adjusting or opening up the nozzle?
Yes adjusting the air/fuel mixture idle screw is difficult. I have use the small pocket screwdrivers sideways and even bent them to get the angle I needed to move the screw. It takes time to adjust because of it being so close to fan housing.
Having a distributor where you can set the advance curve sound neat. Did it come with a basic advance program with it?
Good to hear you could get it to idle with larger jets.
The 110 cam is a good cam for all around performance.
Usually has good power from idle to around 5,000RPMs. Will run smoother with dual single throat carbs and even better with dual dual throat carbs like Weber 40mm IDF or the Empi HPMX.
Your compression numbers are not really that high. A guess would be somewhere around 8 to 1 compression ratio.
It sounds like the off idle stumble you are having is the accelerator pump circuit is not giving enough fuel when you open the throttle plate. On the Weber progressives I worked on (has been a few years) had different holes to locate the pivot pin for the accelerator pump to get more or less fuel out of the nozzle located inside the primary throat. Or it could be the nozzle has a blockage or needs to be enlarge to allow more fuel to flow.
Does John have any information at Aircooled.net about adjusting the accelerator pump or adjusting or opening up the nozzle?
Yes adjusting the air/fuel mixture idle screw is difficult. I have use the small pocket screwdrivers sideways and even bent them to get the angle I needed to move the screw. It takes time to adjust because of it being so close to fan housing.