pilot jet?

[BryanMcc]

couple questions on pilot jets and general jetting....
got my head back from RB so i re jetted slightly richer to start with...
here is what i ended up with... 42 pilot 172 main and JD red in clip pos 3... Altitude is 3500 ft and 45 degrees temp. after i ride it it seems to idle slightly high for a few seconds when i come off the throttle. I went up from a 40 pilot jet to the 42 after the head mod and it didnt do this before. Bike make zero spooge, and upon cold start and warmup it takes a little time to clear out..like riding it it seems reluctant to rev out for a few mins, even after it has idled to warm up for several min. Lots of smoke while warming up... Some symtoms point lean to me while others seem rich? should i move to a 44 PJ? the odd thing is the AS1 in my husky 300 is jetted about the same, actually leaner on the PJ and it is a spooge factory. I thought the AS2 in my gas gas liked leaner settings? Could the head mod have anything to do with this?

 

[Jakobi]

The head mod has changed everything up some. Is it a 36mm carb? If so the 172 sounds alright, if not (or if its been oval bored) you should be looking more towards a 178 main. You could also move the clip pos back to #4 to evaluate. The high idle sounds like its resulting from a lack of fuel on the needle. Also, you've probably got quite a bit more compression now, which will enjoy having a bit more fuel.

 

[BryanMcc]

38mm as2 carb

ok... i can change some jets out...Jake you think even at this altitude 3500 feet and up go that rich? My riding area is at 5k but i havent ridden it there yet, only been buzzing it around the house... i had it down to a 168 last summer before the head mod, but that was for like 6500 feet and 60 degrees plus.. what about the pilot? or leave the pilot and change the needle clip pos?
bike is a 300 also...not a 250, the other bike were working on getting the jetting sorted is a 250 with a 36mm, but thats not the one in question right now...

 

[n_green]

My 300 with the red needle in it always idled high. Everything pointed to the pilot being correct but as you've said it idled high especially after being worked hard up a climb which made me think it was lean. In the end it just turned out to be the slide just needed to be lowered some using idle screw and it was fine again. This was with the std 36mm and again with the oval bored 36mm AS2.

What's weird is if I put any other needle in it I have to lift the slide again otherwise it won't idle. Seems to be a red needle specific thing? Dunno maybe Jake can offer a theory.

 

[n_green]

And a 42 should be fine at your elevations. I was using a 42 pilot at 1100m / 18 deg C with air screw 2 turns out. I went up to a 45 and 1.5 turns on the air screw as it was racing and idling high but as I just said it turned out to be the slide height so I could have left the 42 in it.

 

[BryanMcc]

the weird thing tho is once the idle comes down it has a very low idle...like i think if i lowered it any more it probably would die... Did you try moving your clip pos ever like Jake sugested me to do?

 

[zeuszuki]

I experience a similar thing.
I know that my needle (N3CJ) is a clip on the rich side but I like it running a little "fat" in that area. I use big throttle openings down low and either get into the initial part of the power band or right into it often. This keeps the motor running pretty clean and doesn't "load up". It always idles fine.

However, when friends of mine ride it the power band scares them a fair bit (pussies) so they tend to lug the motor with small throttle openings and thus load up the motor. This eventually causes a low idle situation or it is so loaded up it just stalls. If it was their bike I would lean up the needle to keep the motor running cleaner and maybe bring the AS out a 1/4 to 1/2 turn and adjust idle screw accordingly.

Does any of that make sense or help ?

 

[n_green]

the weird thing tho is once the idle comes down it has a very low idle...like i think if i lowered it any more it probably would die... Did you try moving your clip pos ever like Jake sugested me to do?

I started at clip 3 and moved to clip 2. But I have an oval bored 36mm so unless you also do don't pay too much attention to what I did. I set the slide using Jakobis method - ie carb out of bike set slide to just barely open. With the needles I usually run (JD Blue, N3xH) I needed to raise the slide a turn or two on the idle screw to get a nice idle. (I like it to idle so it won't stall down steep snotty hills).
With the red needle both in the 36mm and then oval bored 36mm I have to lower the slide a turn or two to get the same idle.

Also while it did idle high a lot of the time occasionally it would settle into a decent idle. It would always race and idle high after being worked hard though. Dunno worked for me, try it and see.

What's your air screw set at? You may be too rich on the pilot already and that's why it dies when it does settle into an idle?

 

[Jakobi]

Well based on the info here you'll have to tinker to find out what works and what doesn't. The real trick is only making one adjustment at a time. Nathan makes a super strong point regarding the slide height too. If its raised too high it will definitely result in some inconsistant idling including racing at idle and unexpected stalling. The best way to check for you now is probably to pull the air filter off and take a photo down the carb boot. I did the same with the lectron in the other day. See my thread. Slide just open.

My logic was that its super easy to to change the clip position and will net you instant results which is why I suggested it. It'll immediately be clear if the bike runs better or worse. I've personally found that having the slide high the bike will do the racy idle from the moment its warmed up, not just after riding under load. If its only under load (say it idles and runs fine, but will race after lugging up a long steep hill gear high) then its more an indication of being lean on the particular throttle position you were using. Probably well on the needle if lugging throttle open and revs low. JD recommends a 180 for sea level. You might be right with the 172 yet for alt, but its also cold. Much colder than I'd ever see here. Change on circuit at a time and evaluate the change it made. When you see a positive result you've done good. If its not put it back where it was and try something else.

 

[BryanMcc]

Slide height??

Is this anywhere close?

 

[Jakobi]

You're lucky I have my PWK sitting on the work bench as it was set. I'll take a pic and post back for you. It doesn't look too bad to me though.

 

[BryanMcc]

ok, changed the red needle out...clip 4 was to rich clip three seemed lean, so i tried an n3eh because it adds extra fuel at quarter throttle over the red needle but then leans up a little over half throttle. seemed to do the trick... also ended up going to a 40 pilot jet, i think the 42 was to rich and that caused the erratic ide. So day as i went higher in elevation i really noticed the WOT performance degrading leading me to believe im rich off the main jet, it was also raining pretty good. I really am hesitant to lean it up anymore then i have...I know its not a reliable sign, but there is absolutly zero spooge...Thoughts??

 

[Jakobi]

I don't get any spooge either unless if I fanny around like a granny for a full days ride and that just doesn't happen. Don't use smoke or spooge as an indication of your jetting. More variables in action there including ratios, brands, riding styles, etc etc etc. The only time my bike ever had a real drool to it was with the stock needle (but I was also new to 2T's and pretty new to bikes in general).

Like I said previously. Make one change at a time and evaluate. If you're hesitant to go leaner, try richer first and if its worse than go back the other way. If its an improvement continue, and vice versa. Its all a methodical approach.

For me it includes setting the float level as per sticky by Andoman. Then setting the slide height as per images below. From there I start with a needle diameter and pilot thats in the expected range. Work the air screw to determine which idles and shuffle pilots appropriately. Once the idle is setup feel the 1/4 - 1/2 throttle response. If lean (crisp but lacking balls) lower the clip position. If rich (breaks up burbling and smoking excessively) lift the clip position. Then finally start stepping the main jet down to get the best response. I monitor the change in max rpm as well but mostly go by feel. When I think I'm close I'll pull some plug chops on used plugs. That way if you can turn a black plug white and ashy you have zero doubt that its too lean. This can sometimes be hard to judge on a new plug (takes a while to colour up). Then when its 75% right top to bottom I go back and revisit the circuits. If the bike idles well, but breaks up at 1/8th throttle a bit too much and then pulls clean I'll swap to a leaner needle diameter and a larger pilot. If the bike is flat off the bottom, and going richer on the pilot degrades the idle I go leaner on the pilot and richer on the diameter. Work around in that order, from top to bottom, identifying areas for improvement and acting on them and you'll end up with great jetting. Its just a methodical process that takes a bit of time and patience, but if done will net you fantastic results.