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OK, bizarre question, between idle and quarter throttle, the engine runs like a popcorn machine and runs like it's missing a bit, open the throttle it wheelies like no other bike I have "ever" had, quite incredible really.

35 pilot, 2.25 turns out
stock needle - c clip on top
#138 Main
Stock 33mm carb
Pro Circuit Platinum I Pipe and Silencer

It's been awhile since I have had a 2 stroke, been riding 4 strokes for the last 20 years, so I don't know if this is normal.

I am speculating that a needle change is in order, to lean things out, so I don't have the clip at the top to eliminate the popcorning, any ideas ???

Thx !!! Michael

Sounds like you main jet is to rich. My 220 was 42/145 and I change the jets to 38/138, now she runs crisp and very responsive. I live in the caribbean at sea level with hight humidity and hot weather (85F).

My apologies, I failed to mention where my issue is, which in the idle to 1/8th to 1/4 of a throttle, i.e. just above idle.

When I crack the throttle 1/2 to full, she is a wheelie machine.

When I had the 38 pj in there it was somewhat lethargic, the 35 crispened things up nicely.

The 33mm is fine for me, I don't need any more top end.

My gut tells me that a needle change would reduce it, if not eliminate the pop corning.

Just looking for guidance on some possibilities for needles, or other potential solutions.

Many Thanks in Advance !!!

Michael

My YZ did this after a pipe change. All I did was turn the airbleed in a bit and bingo. She was just a bit lean. Worth a try. Good luck!

Went riding yesterday and experienced the same thing, just at 3500 ft, vs. sea level. It is closer to idle to 1/8th of a throttle, then it gets 4 stroke torquey from 1/8th, to 3/8th's, then it becomes your typical 2 stroke rush of rpms and horsepower. My gut tells me it is either the cutaway slide, or the needle, leaning more towards the cutaway slide, as I think I am dealing with a rich mixture, vs. a lean mixture.

Michael

The stock mains are notoriously rich. What you're describing sounds like '4-cycling' which is the result of a rich condition. Needles/slide cut can be used for very fine tuning(needles can also tune power delivery profile), and you're not there jet. Need to jet the main using a plug chop method. Search on here.

fuzzy wrote:The stock mains are notoriously rich. What you're describing sounds like '4-cycling' which is the result of a rich condition. Needles/slide cut can be used for very fine tuning(needles can also tune power delivery profile), and you're not there jet. Need to jet the main using a plug chop method. Search on here.

+1, make sure you don't have a defective jet block o-ring on the carb.

Right now I am discounting the jet block gasket, as in my opinion it runs to well except for a small portion of the power band, unfortunately given my last 20 years of riding 4 strokes, it is the most important to me. You gotta remember, I have the PC Platinum Pipe and stinger and am guessing I have either the Boyesen RAD Valve, or the reeds, as that is the only thing that makes sense wanting leaner jetting. I wasn't going to just take the reed block out to confirm this, just an educated guess.

I tried touching base with Ron Black to ask if he could machine the idle circuit and machine the cutaway to #6 vs. the stock #5, but I got a generic answer to have the carb bored and the whole nine yards. I personally don't want any more top end, which his carb would provide, the 33mm has ample for me. The PC pipe provides plenty of flow throughout the power band.

At this point I am researching several needles, which btw, is confusing to say the least. Right now I have the stock R1173L C clip in top position with a #35 pilot, which runs quite well, just trying to get the popcorning part of the throttle cleaned up.

Hey, I will take any suggestions on the needle, the research is driving me nuts, they really could have come up with an easier reference system.

Michael

Does anyone know what the R1173L conversion is for the stock needle, I.e., BPL etc...

Many Thanks in Advance !!!

Michael

BFQ maybe? I don't think there is a true conversion since it is a Kawi specific needle.

Pulled reed cage out and have stockers, so ordered up 607's.

Hoping this will help, however the stockers looked quite good.

Checked compression 152 psi, very little carbon on top of piston through spark plug hole.

OK, so I got the 607's installed and I had a major idling issue with it idling way to high. Had to back off the throttle adjustment at the throttle to back off the rpm's. Still after adjusting the throttle it only fixed 25% of the popcorning, however this is driving around the neighborhood, not actual riding. Once I get a ride in, will report, however, my gut tells me that a head mod is in order.

Michael

Have (2) rides on 'er now and popcorning, still exists. #35 pilot, stock needle in the top position and #138 main.

607 reeds, fully advanced ignition, spooge is almost non existent now.

Any suggestions on a needle w/ the stock 33mm carburetor ???

Many Thanks in Advance !!!

Michael

OK, so tried a #130 main and it did squat, just made the delivery run like crap and it still 4 stroked in the 1st 1/8th of the throttle, I put the #138 back in and it ran a whole lot better. i retarded the timing and it helped transition better througout the power delivery. I read the following article on Wikipedia and http://en.wikipedia.org/wiki/Four-stroking and tried it and it made a difference on the transition, the 4 stroking still exists, but is a bit better. The transition from idle to the mid range is noticably smoother. This is at sea level, so we'll see how well it runs in elevation.

Michael

Ok, broke down and called Forward Motion, actually got to speak with Eric himself, as his Technician did not feel comfortable enough to answer my question. I had pretty much eliminated everything except the head mod (increase in compression) and the throttle slide. At this point, I was willing to pony up and get the head mod and asked Eric straight up, should I get a head mod, or a new throttle slide. He said right away throttle slide. He recommended removing ~ 1mm of material from the slide with a dremel and polish it up afterwards. Now I am no expert on removing material, especially a concave design, so looks like I will have to pony up for a new #6 slide.

Michael

RB will just cut your slide too as a service. http://www.rb-designs.com/slide-mod.htm

Solid point, I was thinking about doing it myself, but best left to someone who has experience.

Michael

Well I was all prepared to send my slide to RB Designs, however there was a slight nick in the chrome from normal wear and tear and decided that is probably something Ron would not want to work on due to the liability. I ended up going through Sudco for a #6 slide to the tune of $80 delivered. So I finally installed the #6 slide and it would not start, so I kicked and kicked and gave it some throttle and it fired up a bit. Finally got it lit up and had to adjust the air screw in ~ 1.25 turns for it to idle correctly. Mind you it was raining pretty heavy yesterday and I took it up and down the street just to see if the 4 stroking was eliminated and no, it is not.

So the throttle slide definitely effects the pilot circuit. I found that I went from 2.5 turns out in the air screw to 1.25 turns out to be about right. The only positive I can pull out of this is at least when I go up in elevation, I will be able to lean the idle circuit out more than I could before. When the front moves through, I will test it again, but I don't think there will be much if any difference.

Michael