250 2c jetting question
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Thread: 250 2c jetting question

  1. #1
    Member
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    chris
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    250 2c jetting question

    Hi

    I have fitted Higgspeed expansions & now looking at jetting on my ally barreled with 25mm Dellorto's running 40:1 mix.

    I had to reduce idle jet from 45 to 40 as it was 4 stroking on part throttle, this is better now.

    3/4 to full throttle seems fairly ineffective, went from a 90 main back up to a 95, do I need to go bigger or have I got another issue?

    What are other people running?

    Cheers
    Chris

  2. #2
    RUSSBUS
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    RUSS
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    Mine has no air box just Cone filters, I've ran right upto #140s and down to #130s it seems happiest at #135#s but is still a long way off from running right it loses buff the moment I go from third to 4th.
    I have not bothered with the idle jets yet I just wanted to get the main jetting right first, even with the 140#s it seems lean I might have to ask for advise from Dave Higg but don't want to trouble him until I've tired stuff out myself plus he builds the pipes to work with original airbox and Ive binned mine.
    Ill keep posting and hopefully you will to, Ill try the smaller idle jet that you've put in yours next weekend.

    Russ

  3. #3
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    Hi Russ, I'm runningfaoam pod filters with 25mm delloto's, i didva plug chop friday & was weak on 95 mains, ive drilled out to 110 but not tried yet, hopefully this week if we get a dry day. The higgspeeds didnt have a stand stop so i coobled something up. What did you do?

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  5. #4
    RUSSBUS
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    The filters came from Dellorto's with the new 25mm carbs they are the normal corricated with mesh type not unlike the foam filters from a air volume resistance point of view.
    We ran upto #115 jets on the dyno and it was really lean so we quit the testing.
    I'm now doing it the old fashion way of tearing up the road for 2 miles and then hitting the kill button and checking the plugs.

    I'm sorry but I do not know what a stand stop is, I'm guessing you mean for the centre stand if so I made my own plus I raised the pipes a touch because I'm using the rear pegs to get that 'arse up head down 17 year on his first bike look' !

    I hope to do more runs at the weekend but between the weather and the fact I have started to redo the kitchen not sure how long I will get to sort it out.
    I got one of those weird wives who thanks getting the bike sorted is more important than the kitchen (she hates cooking) so should be able to report after the weekend.

    Russ

  6. #5
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    Hi Russ. Are your dellortos the std VHB25 like mine or a modern equivalent? I thought you had mikuni from previous posts? Gives me a main jet size indication if VHB's

  7. #6
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    Quote Originally Posted by RUSSBUS View Post
    The filters came from Dellorto's with the new 25mm carbs they are the normal corricated with mesh type not unlike the foam filters from a air volume resistance point of view.
    We ran upto #115 jets on the dyno and it was really lean so we quit the testing.
    I'm now doing it the old fashion way of tearing up the road for 2 miles and then hitting the kill button and checking the plugs.

    I'm sorry but I do not know what a stand stop is, I'm guessing you mean for the centre stand if so I made my own plus I raised the pipes a touch because I'm using the rear pegs to get that 'arse up head down 17 year on his first bike look' !

    I hope to do more runs at the weekend but between the weather and the fact I have started to redo the kitchen not sure how long I will get to sort it out.
    I got one of those weird wives who thanks getting the bike sorted is more important than the kitchen (she hates cooking) so should be able to report after the weekend.

    Russ
    Russ Iím running 125 mains on mine with an X2 needle, top notch. However Iím on spannies and 30mm Dellortos. Iíve got a buddy who has gone down to 118s. It does seem to be very temperamental with the mains. I went from 130s to 123 in a single weekend.

    Going well this year with the BHR. Seems well matched with the other 250s and also in the BEARS class against 500s

  8. #7
    RUSSBUS
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    Hi
    New version of Delorttos, they are like the originals but plastic float bowls etc, I am running at this blind because I'm not 2 stroke competent.
    I'm going to do a complete leak down test this weekend just to confirm I am air tight and ship shape.

  9. #8
    RUSSBUS
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    Hi Colin
    Keep me posted of your meetings dates I will pop along and see you.

    Best regards

    Russ

  10. #9
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    Quote Originally Posted by RUSSBUS View Post
    Hi Colin
    Keep me posted of your meetings dates I will pop along and see you.

    Best regards

    Russ
    here you go Russ...
    British Historic Racing, VMCC Ltd - Race Program

    next one is Darley Moor in a few weeks time then the road trip begins with Lydden, Angelsea and Pembrey. Thatís got to be a 1500 triangle for me

  11. #10
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    Tried 110 mains, seems ok, not too rich looking at the plug, may try 120's. Still to rich on the needles(one notch from leanest & 40 pilots, still rich as 4 stroking part throttle unless under a bit of load. Tested with new plugs running 40:1. Feels flat full throttle ad if weak but rich everywhere else. Float hieght as spec.

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