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Low rpm operation is controlled by the intermediate jet (#11). If sneezing or popping is experienced below approximately 3000 rpms the intermediate jet must be replaced with a larger sized (richer) jet. If the engine does not run smoothly at low speeds, fouls plugs, blows black smoke or gets bad gas mileage a smaller (leaner) intermediate jet needs to be installed. Always readjust the idle mixture (#2) and idle speed (#1) screws after making a jet change.
The main jet has nothing to do with fouling plugs.
To test the main jet, do a roll-on from 50-mph to 70-mph in 3rd gear. If the engine backfires or breaks up in the carb, increase the main jet size .004". If the engine is flat or will not accelerate, decrease the main jet by .004".
As for altitudes it does make some difference but you would have to get up a little higher than 600. The valley I lived in upstate NY at the railroad croosing stated 1154' ASL and never made a difference between there and Albany which isn't far above sea level. A few feet.
I remember once in an episode of that British show "Top Gear" they decided to go over the Andes instead of around and the air got so thin that their 4wd trucks couldn't go faster that 15 miles an hour because of the extremely rich condition. Eventually thy barely even run, so they decided to turn around. It was pretty cool...
As for altitudes it does make some difference but you would have to get up a little higher than 600. The valley I lived in upstate NY at the railroad croosing stated 1154' ASL and never made a difference between there and Albany which isn't far above sea level. A few feet.
I remember once in an episode of that British show "Top Gear" they decided to go over the Andes instead of around and the air got so thin that their 4wd trucks couldn't go faster that 15 miles an hour because of the extremely rich condition. Eventually thy barely even run, so they decided to turn around. It was pretty cool...
Something I find interesting is that after I built my motor up a little I have coughing below 3k rpms and bad gas mileage.
According to the instructions that means I have to raise and lower my intermediate jet so I just leave it where it is.
I love British Top Gear!!!!!!!!!!!
I was very sad to find out that it is canceled.
Believe it or not, as I increased the compression on my motor my builder told me that the higher compression would actually need a smaller intermediate jet. I didn't believe him at first but seeing is believing. At 10.8: static and 9.6 dynamic I'm only using a 295 intermediate and a 72 main. Awesome plug color....
Believe it or not, as I increased the compression on my motor my builder told me that the higher compression would actually need a smaller intermediate jet. I didn't believe him at first but seeing is believing. At 10.8: static and 9.6 dynamic I'm only using a 295 intermediate and a 72 main. Awesome plug color....
I'm running the same jets with less compression.
A dyno run says I need to be using a 74 for cooling at WOT but I already get shitty enough gas mileage so I stick with the 72.
I'm gonna try out the 295 Intermediate and 68 main and see how it plays out. So far, with the very little bit of riding that I have been able to do it seems to run pretty well. Still hesitating off of idle a little. I have a new VOEs switch on order and will replace that this weekend. Supposed to be here today (check's in the mail). That may change nothing but, I think a 26 year old switch ought to be changed for reliability anyway.
Only change one jet at a time. Then tune your idle mixture, then tune your accelerator pump. A little hesitation off idle is either idle mixture or more likely accelerator pump.
I have gone up and down on the main jet size and basically have the same issue. I'm going to replace they coil since I have a new spare and install new wires and see if it changes anything. I'm beginning to believe that the 70 main was good all along.
I have gone up and down on the main jet size and basically have the same issue. I'm going to replace they coil since I have a new spare and install new wires and see if it changes anything. I'm beginning to believe that the 70 main was good all along.
When was the last time you cleaned your carb?
What does that rubber according looking thing (part of the accelerator pump) look like.
On mine it was running bad and I found that that rubber piece was very worn out. It had holes in it.
Once I replaced it everything was fine again.
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