'94 KTM 620 EXC Need Jetting Advice.

Discussion in 'Thumpers' started by gravityisnotmyfriend, Feb 25, 2013.

  1. gravityisnotmyfriend

    gravityisnotmyfriend Long timer

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    Last summer I bought a used and badly neglected LC4. I got a great deal on it and am enjoying the process of bringing it up to snuff. I'm replacing all the high maintenance parts that I'm sure (based on the state of the bike)that the two previous owners neglected.

    Tomorrow, I'm putting in an order to KTM-parts.com for seals/bearings/orings and decided that I need to get the right jets for the bike as well.

    The bike seems to run fine, but it's drinking a lot of fuel. I'm getting about 25 MPG just doing in town commuting and brief 30 mile cruises at 60-65 MPH. The bike is stock, except for an FMF exhaust. Now, I realize that an aftermarket exhaust requires a little fatter jetting, but I think this bike has been jetted way too rich.

    The main jet is a 195 and the pilot a 53.

    So, this is where I need advice. I've read a ton on this bike and I'm thinking I'd do well with a 160-170 main jet. But, I haven't read much of anything on the pilot. Any advice there? Maybe a 40? 42?

    I've got the stock dell'orto PHM 40 carb and am in the central midwest at about 1000' MSL.

    I really want to get these parts ordered so I can get my bike back together. Any advice on the jets would be greatly appreciated!
    #1
  2. slackmeyer

    slackmeyer Don't mean sheeit. .

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    Wow that seems rich, but I have a BST, and not a Delorto. I'm running 162.5 and 47.5 pilot, which many here say is too rich for the bst, but it works well for me, both in power and mileage. That may be a starting point for you. I think jumping from a 53 to a 40 is way too big a jump, unless you have very good info that those jets in that carb is a good starting point.
    #2
  3. gravityisnotmyfriend

    gravityisnotmyfriend Long timer

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    Thanks for the post. 162.5 and 47.5 sound pretty consistent with what I've been reading. Which bike are you riding?

    The only info I have about the jetting is that I'm getting poor mileage and I've got a dark, sooty plug. I know it needs to be leaner - just not sure how much.

    I'll probably go with a 165 MJ and maybe a 46 pilot?

    The jets are only a few bucks a piece, but I don't want to sit around waiting for new ones to get in if these are wrong.
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  4. Kawidad

    Kawidad Long timer

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    Have you considered junking the Del Orto and replacing it with a better and/or more modern carb, even the BST-40?
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  5. gravityisnotmyfriend

    gravityisnotmyfriend Long timer

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    Yeah, I've considered it. If this bike had the Edlebrock, I would definitely be replacing it. But, there's nothing wrong with the Dellortos if they're jetted correctly. I just have to take care of that.
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  6. biensur22

    biensur22 litigious poster

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    I've got a dellorto take-off from my '98 620adv. let me run out to the garage and see what jets i had in it.
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  7. gravityisnotmyfriend

    gravityisnotmyfriend Long timer

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    That'd be great!

    No rush, though. I couldn't wait and submitted the order.
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  8. biensur22

    biensur22 litigious poster

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    200 MJ and 50 pilot.

    I'm down in San Diego and ride up to 6,000 feet. Mind you, it was probably running rich but I was still getting 40-45mpg. Either way, I was unsatisfied with the dellorto and strapped on an FCR39 off a polaris outlaw. Totally changed the bike's characteristics, and I'm still getting 40+mpg.
    #8