KE175 wheelie!

[CRXSi90]

So last night I went to the grocery store at like 9:30pm because I fit in better with the late night crowd than the 10am soccer moms. Anyway, it took me a 1/2 hour or so to do my shopping. I tossed the 5# bag of grapefruit in the bag on my rear rack (remainder in my backpack) and then swung my leg over the bike. Not sure if I would need the choke or not, I gave it a few kicks w/o the choke. No cigar. Put the choke on and it came to life on the first or second kick. I usually have to keep the choke on for a few hundred feet unless I let it idle for a long time to warm up. I pulled forward through the parking space and started to turn left to head to the parking lot exit. I twisted the throttle and WOAH, the front wheel came off the ground. It was a very un-elegant wheelie since the bike was still leaned over a bit from coming out of the parking space, and I turned the bars a bit so that I could continue on my intended path once the front wheel regained contact with the ground. As I was coasting to a stop at the end of the parking lot, I reached down and flipped the throttle off since it starts to get too rich in a hurry after riding for a few moments with the choke on.

So here's the question - why would it have more power for a short period of time (sort of a transition period) as the bike is warming up when the choke is on? Here were my thoughts:

• it's not actually more power, it was just more abrupt
• the jetting is too lean, and the choke helps it run richer, but that only works in the transition period before it gets warmed up and is too rich. Change the jets to one size up, and you can have wheelie ALL THE TIME!
• the jetting is actually too rich, but it's still just the transition region where it's getting the right mixture
• the ignition system can only give out a few good sparks before it gets warmed up and only gives mediocre spark
• It's 2-stroke and there's a leak in the bottom end where it's pulling air.
• the carb needle [insert explanation here]
• when it's having wheelie-power, it's actually running in some condition where it would damage the engine if you did that long-term, so don't mess with anything.

So I guess I'm keeping all possibilities open at this point. Here are a few notes for reference:

• I typically run 91-octane ethanol-free gas.
• The carb has the round slide connected directly to the throttle cable, so it's not like the CV carbs on the XS11.
• this is a REED-valve bike, not ROTARY-valve like some of the earlier bikes. The carb is mounted right behind the cylinder, not burried on the side of the case like on those bikes.
• when I say "choke" I should really be saying "enrichener" - the only thing obstructing air flow into the engine (in the carb anyway) is the throttle slide.
• I have not messed with the jetting at all, and to the best of my ability to tell, it is factory jetting.

Thanks in advance! I know you guys have an amazing breadth of experience, so I'm sure that we'll be able to figure something out.

[rdmcguy]

A surprise wheelie

Am glad you didn't loop it!!!
Your best bet would be to do a series of plug readings especially on the pilot circuit.
It sounds as though you are a little lean on the low end(pilot circuit)
which would explain the need for prolonged choke.
Also most bikes run better after initial warm up especially two strokes.
once dialed in it will probably wheelie at your command.....
Don't loop it though...lol

[CRXSi90]

Yes, I am glad I didn't loop it also! It would have been a bad evening for the grapefruits on the back rack, nevermind my other fruits which were already at a higher than normal position.

Another thing that supports the pilot circuit being lean is that it takes a few moments for the idle to settle down.

So to do the plug readings, get it warmed up and then run at ~1/4 throttle, kill it, then read the plug? I have an Iridium plug in there right now. Do I need to be concerned about replacing the crush-washer between or after the plug readings? Or should I just put my old standard plug back in for this?

[MaximPhil]

The 5lbs of Grapefruit and a backpack full of groceries may have contributed to the wheelie.
Phil

[rdmcguy]

plug readings

The extra weight on back probably did contribute to the wheelie
(a new secret trick?)
Yes warm it up put a CLEAN plug in it and use less than 1/4 throttle
kill the engine....remove plug don't burn your fingers...
plug should be chocolate brown...white is lean.go up on jet size. black is rich
down on jet size..
good luck!!!

[motoman]

Also, when adjusting the air mixture screw(air, as it is located on air intake side not head side of carb), back it out to lean side, then gradually come in blipping the throttle from idle as you do so until it JUST reaches the point of NO stumble blipping throttle from idle. Actually, what's taking place is you come out with screw, setting on the lean side, then coming in richening mixture up JUST till there's no stumble. Any off idle stumble IS from a lean pilot circuit, whether it be pilot jet or a too lean idle mixture.

[CRXSi90]

Yeah, it's probably true about the weight in the rear - that's probably why it caught me off guard a bit more than usual.

I will round up a new plug and see what it says.

Unfortunately there are no mixture screws on this carb. The only adjustment is for the idle which controls where the slide stops. Here are a couple pics I just took...





and here's what happens when you almost get thrown off.