Originally Posted by lykos23 (Post 521410)

Is there any reason to avoid a larger idle jet? I'll order up a #35 from absolutelyscooters and see what happens since that's what they have in stock and they're the first ones I found that offer the extended length idle jet for easier starts. But I still don't understand the reasoning if my current setup seems fine, is there some chance I'm running too rich at 1/8 throttle?

The first few plug chops consisted of a five minute warm up in idle and a ten minute drive at WOT. The last plug chop was a longer drive because my mother asked me to go to the store for her - I got much better results with the longer drive, that's for sure. Sadly it just so happens that a lot of roads were flooded around town so I was confined to a small strip of road on 120 since my speeds are too high to do WOT around the neighborhood anymore.


Clean, or lean? It may just be your opinion, but I value your opinion Buford. :tup:



You think so? I've been running a restricted free flow filter for months now because I didn't have the proper jets. Millsc says I shouldn't have to go over 95 with jets and I'm trying to get the best performance possible - won't the restriction hinder that? I mean... the tip of my spark plug is white from my hotter coil, but the base is coffee colored - isn't that what I'm looking for?


In any case I'm ecstatic that I can almost hit 60mph now. I'll try a smaller idle jet for some reason, but otherwise I'm liking my setup so far.


Thanks for the input, Y'all!

Originally Posted by qwertydude (Post 521418)

There reason you don't want to run too big a pilot is it masks the symptoms of a lean top end. This is a dangerous situation because your plug may look well and good on a plug chop but you're in reality running lean on the top end. That's why a plug chop isn't the only tool to use when determining correct jetting. The top speed method works especially well for scooters especially well because on most bikes you won't be able to reach top speed in order to determine correct jetting.

It's a simple fact that the correct jetting gives you the most power so hence the jetting which gives you the highest top speed is the correct jetting. From there you work your way down, and experiment with needle height and then finally mixture screw. I don't know why it keeps getting posted over and over again if you're lean on the top end just turn the mixture screw. That's absolutely 100% bad advice as it doesn't solve your problem and only makes you foul spark plugs and again on a plug chop hides the true reading.

Originally Posted by qwertydude (Post 521418)

There reason you don't want to run too big a pilot is it masks the symptoms of a lean top end. This is a dangerous situation because your plug may look well and good on a plug chop but you're in reality running lean on the top end. That's why a plug chop isn't the only tool to use when determining correct jetting. The top speed method works especially well for scooters especially well because on most bikes you won't be able to reach top speed in order to determine correct jetting.

It's a simple fact that the correct jetting gives you the most power so hence the jetting which gives you the highest top speed is the correct jetting. From there you work your way down, and experiment with needle height and then finally mixture screw. I don't know why it keeps getting posted over and over again if you're lean on the top end just turn the mixture screw. That's absolutely 100% bad advice as it doesn't solve your problem and only makes you foul spark plugs and again on a plug chop hides the true reading.

Originally Posted by blueboy5000 (Post 521424)

On my three 139 bikes, all of them are properly upjetted, and NONE of them have had a thing done to the idle jets (which are all #34 stock jets). I agree that there should be no reason to switch to a bigger idle jet. Properly adjusting the needle and switching to a larger main jet should solve your mixture problems.

That said, I run a 95in a 83cc BBK, and I probably could get away with a 88 to 90 mainjet. My current 95 and tape-restricted air-filter proves that the 95 is too big.

I am going to suggest you adjust the needle to a richer position.