'02 426 Idle Issue

13 replies to this topic
  • polybash

Posted March 02, 2009 - 09:43 AM


I replaced my head gasket this past weekend because of coolant in the oil. After a couple of attempts to get the timing right, my buddy and I finally got it figured out properly so it would kick through properly. The bike will kick over fine, it actually started first kick when we tested it out. However as the title states, it won't idle properly. Could this still be a timing issue or is it a dirty idle jet in the carb? Before the gasket was replaced it stuttered a little bit while idling, but it wasn't this bad. Additionally, we revved the engine up some and once the bike got down to idle it died. And, the bike will idle properly while choked. I'm thinking as the carb was being moved around during assembly/disassembly some dirt got knocked around and plugged a hole. I appreciate your help and information provided.

  • Birdy426

Posted March 02, 2009 - 12:27 PM


Sounds like it might also be a vacuum leak...are you sure the clamps on the intake and carb are tight? Also, did you have the slide out of the carb? It's easy to put in backwards, which will cause idle (and sometimes starting) problems...

  • polybash

Posted March 02, 2009 - 02:17 PM


That is a possibility and an easy check. As far as the carb is concerned, we haven't pulled it apart yet. So I don't think any of the pieces could have gotten dislodged. Are there any other places to check for a vacuum leak besides the two rubber couplings on either side of the carb? I will post what I find when I get home tonight.

  • polybash

Posted March 02, 2009 - 06:42 PM


I checked the clamps for the carb and one of them was slightly loose, so it got tightened. I got it started and it ran fine choked, turned the choke off it started to idle a little bit better. I revved the engine up a little bit, it went up fine and pops some coming back down. After it came down to idle again it stuttered a little bit then died. After doing some searching for similar problems, I'm going to check to make sure the hotstart isn't partially open. If anyone else has any other ideas as to possible problem I would appreciate the input. Thanks.

  • 642MX

Posted March 02, 2009 - 07:12 PM


Check the hot start first and if it feels fine, then pull the 17mm nut off the bottom of the carb. If you see any particles, then its time to clean the carb.

  • polybash

Posted March 03, 2009 - 03:58 PM


I pulled out the hot-start, cleaned it up a little bit with rubbing alcohol and reinstalled it. I also pulled the nut off of the bottom, there was a little bit of grit and sludge in the bottom. I also talked to the local shop and he was saying it sounds like it is running super lean, so I guess a new jetting kit is in store for the bike. What would you recommend for jetting as the bike is pretty much totally stock. I'm from southern CA (magic mountain area) usually, but I'm on the central coast for school. Thanks for the input, I appreciate the help.

  • 642MX

Posted March 03, 2009 - 04:42 PM


I also pulled the nut off of the bottom, there was a little bit of grit and sludge in the bottom.

Nothing worse than dirty nuts... :p

In all honesty, I don't think you need to rejet it to make it run right. I think a good carb cleaning would solve your problems. When the pilot jet sucks dirt up to it, it restricts the flow of gas and will cause your idle problem.

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  • polybash

Posted March 03, 2009 - 07:24 PM


Nothing worse than dirty nuts... :p

You are absolutely correct, lol. Talking with the guy at the shop he was telling me the bike is jetted lean to pass CA emissions laws, and I don't doubt that at all based on what I've heard. Also in reading the jetting sticky, most guys went from the 162 main up to the 165 main and had good results. I was thinking of trying that. But if all it takes is a good cleaning, then that is definitely the cheaper and easier way to go. Thanks for help.

  • grayracer513

Posted March 03, 2009 - 08:27 PM


Just to put a myth to bed, there is no emissions test for closed circuit race bikes.

  • polybash

Posted March 04, 2009 - 06:28 PM


Got the carb pulled this morning and the jets pulled out this afternoon. The jets weren't too bad, but they got blown out. One interesting thing I noticed was a small crack along the threads where the hot-start screws in. This may have been the problem as too much air was seeping in through the crack. So I got some JB Weld from Home Depot and will get that applied to the crack either tonight or tomorrow morning. I'm hoping that will help seal it up and prevent it from growing.

Gray, thank you for the clarification. I was under the assumption CARB regulated all emissions for all vehicles in the state.

  • Birdy426

Posted March 04, 2009 - 07:12 PM


Make sure you put some white grease onthe hot start plunger when you put it back into the carb. If you don't, it will corrode in the bore and then stick. You will have to perform major surgery to get it out!

  • polybash

Posted March 04, 2009 - 09:56 PM


Make sure you put some white grease onthe hot start plunger when you put it back into the carb. If you don't, it will corrode in the bore and then stick. You will have to perform major surgery to get it out!

Does it have to be white grease? I have a can of normal automotive grease, will this work just as well?

  • grayracer513

Posted March 05, 2009 - 07:43 AM


A grease containing moly is better, but I found with our 250F (same hot start layout) that it doesn't need greasing at all.

We had that one stick a time or two and become a bit of a problem. In cleaning it out, one needs to use a good corrosion killer and something on the order of a .35 caliber rifle brush to clean the bore. ALL of the corrosion found there needs to be completely removed, or it will return.

As far as keeping it free, I determined that the cause of the problem was water coming in while washing the bike (we had a DRD remote setup, and the water was entering via the cable), no matter how careful we were not to wet the area. What I started doing about it was to run the bike after washing and play with the hot start while the engine ran, holding it open in order to draw athrough, and moisture out of the plunger bore. Once I began doing this, I had no more trouble with it sticking.

If you wash your air box with the rest of your bike, you should of course not run the engine until a clean, dry air filter is installed, since foam filters don't stop water, and some could be drawn into the air jets.

  • polybash

Posted March 06, 2009 - 08:52 AM


Well I got it all put back together and she runs like a charm, almost. Just a little bit of tuning is required so I can get it to start first kick again. Thanks for all of the replies/help, I greatly appreciate it.

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