Jetting help please

91 replies to this topic
  • MANIAC998

Posted February 08, 2012 - 10:04 AM


Because one of us is wrong, that's why. Maniac

  • Leardriver

Posted February 08, 2012 - 10:14 AM


165 sea level
162 2000 feet
160 4000 feet
158 6000 feet
155 8000 feet.
That is for summer temps.

In the winter, one size richer.

I don't guess, I measure them on the dyno with a wide band.

Those sizes are really one size conservative, giving you closer to a 12.5-1 a/f ratio than the desired 13-1, but the bike will run fine, and you can rule out jetting as a cause of any driveability issues.

These bikes will run ok with the main jet 5 sizes wrong, but they run really nice when it is correct.

Edited by Leardriver, February 08, 2012 - 10:16 AM.

  • Stealth13

Posted February 08, 2012 - 10:24 AM


If stock is 165, at my elevation according to your chart I'm too rich? It seems too lean to me

  • MANIAC998

Posted February 08, 2012 - 10:51 AM


Stealth, I can't help but notice your having all kinds of issues with your bike, as you've been posting all kinds of subjects on it. At this point, I think you need to take it to a dealership to have them fix any and all issues that your having. Do you own a manual for this machine? Maniac

  • Stealth13

Posted February 08, 2012 - 10:58 AM


Yes I have a manual it doesn't tell
Me what jet I need for my elevation though. Everything else is working great on the bike I rode it for a couple hours on the weekend

  • Leardriver

Posted February 08, 2012 - 10:58 AM


Warm up your bike and run it wide open down the road with the choke pulled out. Better or worse? I am guessing worse.

Armed with that bit of info, take out the main jet and report back what you have in there. This is a ten minute exercise.

The manual is written by lawyers, who don't want your bike to ever blow up, so they make the jetting charts pig rich. There aren't too many jetting secrets any more. It's not a black art. All the info is available and willingly shared here. Now, you have to do your part and let us know what main jet you have installed right now.

Edited by Leardriver, February 08, 2012 - 11:53 AM.

  • Stealth13

Posted February 08, 2012 - 11:32 AM


Its the stock jet from 2006 wr450. Bike was never touched

  • Leardriver

Posted February 08, 2012 - 11:53 AM


And what jet is that? You have to help yourself out here?

  • Stealth13

Posted February 08, 2012 - 11:55 AM


I was told its a 165

  • Leardriver

Posted February 08, 2012 - 12:11 PM


You are spending a lot of time guessing and hoping, when a few minutes of your time could verify that you have the correct settings. Jetting is easy stuff.

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  • Stealth13

Posted February 08, 2012 - 12:22 PM


Not to me I've never done it before, I'll look into it once the weather is nicer again

  • Leardriver

Posted February 08, 2012 - 12:27 PM


I took the time to explain it in detail to you, and it's even easier than it sounds. I can change a main jet in 3 minutes. You can pull one out in a similar amount of time.

You are getting lots of competent advice, but no one can fix it for you over the computer. You are going to have to try some simple things, so that we can help you, or pay someone a lot of money.

  • Stealth13

Posted February 08, 2012 - 01:09 PM


Yes thank you for the help, I'll try it this weekend and report what I see

  • Stealth13

Posted February 08, 2012 - 04:37 PM


Took it for a rip and I tried ripping it with the choke open and it was in fact worse. So I need something richer than whats it in right ?

  • tech857

Posted February 08, 2012 - 05:14 PM


The choke makes the mixture richer. So if its worse you need to go leaner with a smaller main jet.

Edited by tech857, February 08, 2012 - 05:14 PM.

  • Leardriver

Posted February 08, 2012 - 05:46 PM


No, like tech says, you are too rich. When you added more fuel via the choke, it got worse. You are drowning it in fuel, hence the top end blubber. I suspect you have a richer main jet in it than a 165.

  • MANIAC998

Posted February 08, 2012 - 05:50 PM


On one of your other posts, you were told to check your valve clearances. Have you done this yet? It doesn't matter what jetting you use, if the rest of the engine isn't in it's proper tune. You'll be chasing your tail until you get the valves in the proper spec. Maniac

  • Stealth13

Posted February 08, 2012 - 06:09 PM


The valves were checked a week ago. Bike only has 850 kilometers on it too

  • Stealth13

Posted February 09, 2012 - 07:22 AM


Hmm maybe it is too rich, my header doesn't glow red like most people. Do I need a 162? Would that make enough difference from a 165?

  • tech857

Posted February 09, 2012 - 10:02 AM


Have you checked to see whats actually in your carb for jets right now? The header usually glows at idle due to a lean pilot jet. That would be normal. So ya your rich.


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