my cold weather jetting experience- carb guru's read this



12 replies to this topic
  • MikeOK

Posted December 30, 2001 - 12:21 PM

#1

After reading some cold weather starting experiences lately, I finally decided on a cold boring day to go out to the shop and try re-jetting my bike since it is a little hard to start in the cold. My bike also tends to have more decell pop when it's cold too. I replaced the stock 42 pilot jet with a 45. Then I took it outside and kicked it about 10,463 times and no start. A few fires when I first tired then down to nothing. I then went back in the shop and watched Dallas until I was mad enough to try again and still no luck. I changed the plug (old one was black and sooty but not wet). No luck. I move it in the warm shop (it's 25 degrees outside here today). Still no luck. I tinker with the air screw (now 1 3/4 turns), no luck. All this time I was trying with the choke on, so I decided to try one more thing out of desperation, I pulled the hot start button. Starts first kick. Again and again. Runs great with very little decell pop. I used to think I understood this carb but not today. One thing I might note, my bike has always been a good starter, and I have rarely needed the hot start before unless it was really hot outside, even after a stall. Makes me think I'm too rich now but that doesn't make sense either...

Confused Mike

  • lc426jean

Posted December 30, 2001 - 03:05 PM

#2

it feel like to rich because it is.gaz in oil .....gaz in oil.

  • mikeolichney

Posted December 31, 2001 - 08:08 AM

#3

once you have it idling, see where it runs fastest:

1. FS 1/2 turn out
2. FS 1 3/4 turn out
3. FS 3 turns out

If 2. is fastest, you have the right pilot jet (if everything else is OK, air filter, etc).

  • Boit

Posted December 31, 2001 - 01:18 PM

#4

MikeOK: Your description is pretty much what I have found to happen with my '00. Generally, what I have found to works best on my machine is to try and start it without the choke no matter what the ambient temp is. If it won't start after a few kicks, I use the choke. Either way, it ALWAYS starts easily. If I must use the choke, I only let it run for a few seconds before taking the choke off. My '00 is only on the 4th spark plug since new and I only change them as a course of routine maintenance and never because one has fouled.

  • MikeOK

Posted December 31, 2001 - 02:02 PM

#5

Hi Boit- I guess i just somehow flooded it yesterday, because after I posted I left it outside in the 25 degrees for about an hour (shop was about 75 degrees), then I tried to start it after the cylinder was cold to the touch. It started right away while choking it just as if it were 90 degrees outside. I think the jetting change did it some good as I've always thought it was just a little lean. You might be interested in this- i have a 13.5:1 Wiseco piston on the way. My bike still has good compression but I know it's due for a re-build, and since I have this new shop I figured I would re-build it this winter to keep the cabin fever away. I'll let you know how it turns out. Seems like me, you, Hick and mikeolichney are about all the old-timers left on this board... I've learned a lot from you guys.

  • Mxer303

Posted December 31, 2001 - 05:52 PM

#6

MikeOK-do you have to do any work to the head for the 13.5 piston? I'm going to rebuild mine and thought about trying one of them. Do you know what kind of performance gains to expect with the piston?

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  • ksp

Posted December 31, 2001 - 06:10 PM

#7

The hot start button lets more air into the mixture-therefore making it leaner. if it starts with the hot start and won't start with the choke on it tells me it's too rich. Also the black plug reaffirms it. Why don't you try a #40 pilot? or 38? I don't know what elevation NE Oklahoma is but it sounds like sea level so that shouldn't be a problem.

KSP

  • MikeOK

Posted December 31, 2001 - 06:34 PM

#8

Kxer- somewhat vague at this point but I posted this over at DRN and got several responses, everyone tells me that I can still run pump gas but none of them are exactly under the same conditions as me so I think I'm the guinee pig lol. But no, as long as you stay with the 95 stock cylinder you can use the 13.5:1 piston so no cylinder work (I hope, anyway). Some guy that goes by SFO over at DRN went with the 97mm cylinder, 13.5:1 piston, but he did lots of other work along with it. Anyway he says he is very pleased with his results. My parts should be in this week so I'll post my results after I'm finished, probabaly in a couple weeks because I plan to do a trip or 2 before I tear it down.

ksp- this is what I thought also so see my previous post... Hey You should be out at Taos skiing anyway instead of posting on dirt bike forums hehehe...

  • James_Dean

Posted December 31, 2001 - 11:17 PM

#9

MikeOK,

You may need to reevaluate your startup procedure. If it doesn't start in 2-3 kicks with choke on, something is wrong. Turn the choke off and try another 2-3 kicks, then straight to the hot start to clear if needed, pull the compression release and kick it through 6-10 times.

Changing the pilot jet will require adjustment of the pilot(fuel) screw.

Part of my setup and evaluation of the pilot screw has been to check the throttle response by slowly rolling the throttle open after the choke is off. The choke is off after only 20-30 seconds. Doing the throttle roll-on at about 1 minute after startup will test if it's on the edge of lean or not. A hesitation is lean, a steady increase in speed is plenty rich. A very slight hesitation will go away as it warms up and usually works best for me. If you run through a cold start-up 2 or 3 times it will become clear where it needs to be.

James

  • Taffy

Posted January 01, 2002 - 02:08 AM

#10

mikeok

you do make me smile. you say other old chums taught you a lot = so you got it wrong.

you tell ksp "that's what you also thought!"

ANYONE WHO HAS HEAVILY MODIFIED THEIR JETTING HAS AGREED ON GOING DOWN ON THEIR PC JETTING.

FYI. if you go up on the PJ try going in 1/2 to 3/4 turn on the PS automatically so that the bike starts and runs pretty much how it had been. you richen the jet so you lean the screw. get it running and then you can adjust it as you run.

start jetting
you were rich on your start jetting but lean perhaps on your PC area.

the answer was to go down on your PJ to 40 but to pop the PS out 1/2-3/4 turn. then adjust as you need. this will lean the starting but keep the same at low revs.

Taffy

  • MikeOK

Posted January 01, 2002 - 07:46 AM

#11

James Dean- another old timer hehehe. I have done some tinkering and I think it's dialed in now. I kept the 45 PJ, and used somebody's method (think it was mikeolichney) to adjust the AS. I let it idle and cranked both up and down and left it in the middle, which ended up being slightly under 2 turns out. I also noticed that my head pipe didn't get quite so hot. I was riding around the other night in the dark and I noticed that the head pipe was staying red even under speed which surprised me. You wouldn't notice it during the daylight. Anyway, I have a new WB pipe and a piston kit coming so I'll probably get to do it all over again after that...

  • Mxer303

Posted January 01, 2002 - 10:10 PM

#12

I just got through kicking my 00 426 about 500 times. It's not been started in about a month, and has been very cold here. I've never had any problem whatsoever with starting my bike-always started in 2-3 kicks hot or cold. I tried the choke/hot start method as suggested with no luck. I've got it setting in front of the heater now, but this would be of no help if I were out somewhere trying to ride. Could my jetting be off this much?(45 pilot, fuel 2 1/4 turns out)

  • James_Dean

Posted January 01, 2002 - 08:07 PM

#13

Good to hear MikeOK.

Mxer303,
If it always started easily before, then it must be close. The cold temps may need minor richening on the pilot screw and maybe a slight increase in idle speed. That or your bike is getting back at you for not having been riding. :)





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