OK, what about running on the choke?

5 replies to this topic
  • ColoradoXR

Posted May 15, 2012 - 09:15 PM


I've been round and around with jetting, as discussed in my earlier thread. JD Jetting claims it's my 13 year old bike, something else other then their jet kit being a complete waste money for me. The kit is listed for 98-06 WR's, but the instructions show pictures and describe the AP mod that I can't do - it ain't my friggin' carb. To top it off, I thought I'd just throw in the 42 pilot jet included as pat of the kit as has been suggested and come to find out, apparently the pilot jets are different from 99 to 00 and the kit has the wrong one for me. Some of the worst $70 I've ever spent.

Anyway, I have the bike running GREAT with choke on, in spite of feeling like I pissed away $70. Power top to bottom, no bog, no backfire, idle's great. Runs hot, but they all do. No boil over or anything. With the choke off, it's missing a bit when steady on the throttle. Still has some good power, but very apparently still a bit off. Won't idle. I'm heading to Moab next weekend. No way I can stomp around on slick rock with a bike sure to die heading down steep stuff. Can I just ride it with the choke on? Knock off the choke and hit the hot start and it fires right up when hot. Am I going to damage anything or is it just a case of needing to smooth things out when I have time after the trip? Can I get by?

  • Stealth13

Posted May 15, 2012 - 09:36 PM


If its running better with the choke on it is too lean, saying you are running a 40 pilot makes it even leaner than stock. Think maybe you are going the wrong way on the jetting scale?

  • MANIAC998

Posted May 16, 2012 - 03:49 AM


Colorado, You won't hurt anything running with the choke on, it just makes your engine run rich is all. Something is definately wrong with your jetting, but if you want to run Moab with the choke on, you won't cause any damage. Then when you have more time, get it jetted better, later. Just wondering, does your bike have a different aftermarket carb on it? Some pictures, or a better description will help us to help you.

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  • miweber929

Posted May 16, 2012 - 04:31 AM


I know you are frustrated, but keep in mind you are buying a generic aftermarket kit that covers a pretty wide range of bikes with unknown mods to them. And the major cost to the JD kit is the jetting chart; if you bike runs that good, with the exception of idling, I think you got a pretty good deal at $70 and I hate to say it but un the world of still running WR's your model is getting to the end of a "supportable" range. I get it, I know my 04 is approaching that as well, sadly.

Sounds like your pilot is off then if you have to run with choke. Pull yours, take it to a shop and buy the recommended one from the JD chart that fits your carb, fiddle with the air screw and you should be golden. Might not be as huge of a deal as it sounds.


Edited by miweber929, May 16, 2012 - 07:58 AM.

  • RSanders

Posted May 16, 2012 - 10:46 AM



If your running well with your choke on then the jetting is way off. I wouldn't consider running a machine like that all the time, it's worth it to just start over and do it again to me. Also, you are running the risk of damaging your machine or getting stuck. Incorrect jetting can cause permanent damage to the machine. I strongly recommend spending the time to get it right or you will deeply regret rushing the job once you've pushed it 500 yards in the sand.

If your popping or running very poor with the choke off at mid throttle then your carburetor needle is either incorrect for your needle seat, in the wrong clip position, or both. From what you said above, this sounds like where the problem is. I am also assuming that the carb is clean and in good working order will all parts installed correctly. One little piece of debris in the system will cause these symptoms as well.

Also, everything has to work together in tune with each other or you will have problems. You can't just swap the mains and call it jetted, the pilot, needle, seat and main have to all work together and if one is off the bike will stumble on the overlap. For example, my FMF kit for my 2011 replaces the needle, needle seat and main but leave the pilot. If I were to leave out one change, i.e. the needle, it wouldn't be even close. It's possible there is an issue with the combo in your kit, you might want to look at starting from scratch with another vendor if you can't resolve the problems. Also keep in mind the kit will assume your starting from stock so anything that isn't in the kit needs to be OEM spec.

This is a drastically simplified explanation, you can get more details on the web.

The pilot jet and fuel screw controls your fuel when the throttle is closed to part open (~1/4). If your heavily popping on deceleration (a little is normal/good) then your pilot is wrong/gummed. If your bike stumbles off idle it could be the fuel screw being too rich or accel pump/leak jet being too lean. Once you twist the throttle this circuit isn't in use.

The needle and needle seat are in play at part throttle (1/8 - 3/4) and overlap with pilot and full main. If your popping or missing at mid throttle then raise the needle (lower the clip) to give it more fuel at that RPM. If your main is way off you won't ever be able to set the needle either. These two work together, the needle/needle seat and the main.

The main jet is in control at wide open throttle. If your wide open and popping/missing then your running a bit lean and need a bigger main. Also, since fuel flows through here at part throttle with the needle the main can influence other settings. Remember, it all has to work together smoothly, starting at the pilot to wide open on the main.

The accelerator pump is critical as well on the WR's. When you roll on the throttle there isn't enough venturi force to draw the fuel in because the air is still moving very slow. So, these components squirt some fuel to smooth the transition between closed and open throttle. If you don't address these, the bike will bog down really bad when you crack open the throttle momentarily. But, ignoring this change won't cause any damage it will just run like dog poop.

I know what it's like to want to ride really bad and can't because of a mechanical problem but it's better to miss a ride and fix it in your garage than to get out there and break down.

  • Mtn-Track

Posted May 16, 2012 - 11:13 AM


I'd be VERY careful running the bike with the choke on! I left mine on by mistake once and within a couple of minutes my pipe got so hot it melted my airbox all over everything. I smelled the problem before I figured out why it was popping so much and the pipe all the way back to the muffler was almost transparent. Best to fix the carb, IMO, as it's a lot cheaper than replacing an air filter, air box, drain lines, hoses, and wires.

The popping can happen if you're too lean but can also happen when you're too rich and the un-spent fuel is ignited in the pipe. Not sure about yours, but the new ones add air to the exhaust when you chop the throttle to lean out the A/F ratio to keep them from a rich-induced popping.

As for your JD-issue, well, their kit says I should be running a 160 main jet (or possibly larger) while riding above 9000'. I actually have a 152 main and run from 5000' on up to 12,000+.... no problem!

Edited by Mtn-Track, May 16, 2012 - 11:25 AM.


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