Home Forums Road Racing LAGUNA SECA

This topic contains 21 replies, has 8 voices, and was last updated by  Roger Miller 4 years, 5 months ago.

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  • #37041

    FREDDY SANDOVAL
    Participant

    I’m planning to make it to laguna seca by January, with my 99 stock Honda CR125 shifter kart.
    Currently comes with the pump around fuel system, and I recently melted a piston by the exhaust side, destroying the jug.
    Any recommendations on good jetting to the carburetor for this long track, and to keep it from happening again?
    What is a good jet set up for that track?

    Thank you all in advance. Fast Freddy. ;)

  • #37059

    Ray Chiappe
    Participant

    I used to run the pump around. Could not get it to work well. What I run might not work for your setup. You have to consider an Air Box in the equation, which is mandatory at Laguna. What jet were you using when you stuck it?

  • #37061

    FREDDY SANDOVAL
    Participant

    Thanks, Ray

    55 and 170 when I stuck it

    And yes, of course I’m planning to run an air box also.

    Thank you in advance for all the help

  • #37074

    Larry Dobbs
    Participant

    Hey Freddy, you could always tune it up at our Sears Pointe Sonoma race on Saturday November 29th ;)

  • #37076

    FREDDY SANDOVAL
    Participant

    Thanks. Larry.

    I would love to, but I have a race here locally that falls on the 29th and 30th for our year end shootout KT100 YC Heavy Pipe.

    Do you know what jet size is needed for Sonoma, also? Main and Pilot? Sprocket size/gear ratio

  • #37084

    Ray Chiappe
    Participant

    I’m on the heavy side. Last time I ran the shifter at Sonoma I ran a 18/22. Prob would try a 17/21 next time. Both Laguna and Sonoma have good air. Not sure what to suggest because of that pump around. But I have run 55/175 at both tracks. With a 178 main in practice.

  • #37086

    FREDDY SANDOVAL
    Participant

    Ray
    Thanks. Pump around should only affect fuel delivery, with out having fuel starvation, as it keeps the bowl full
    As for the jetting goes I really don’t know what happened, but my piston got melted at the top edge by the exhaust port ( never stuck ) just lost compression, I opened it up and found a big chunk missing at the top down to the ring.

    Any Idea?

  • #37094

    Larry Dobbs
    Participant

    I would recommend you talk to Jason at Swedetech.  Joseph Hollinger runs stock moto.  Email him off of our website http://www.nckroadracing.com for a second opinion.  Your description makes me think that you have a problem more than just too lean of a main jet.  Maybe an air leak.

  • #37096

    FREDDY SANDOVAL
    Participant

    Thanks, Larry
    I think you may be right
    I think I’ll contact him
    Thank you, so much.

  • #37107

    FREDDY SANDOVAL
    Participant

    Well
    Swedetech is closed till December, so I won’t be able to get any purchases or questions answered.

    Thank you, every one who had inputs in trying to help me. Fast Freddy. ;)

  • #37388

    Kerry Matthews
    Participant

    18/22 is a good gear, I’ve been using it for the last several years there.  Almost impossible to say what the jetting would be, as it’s going to be dependent on so many things.  I use a SwedeTech fuel system, so my notes wouldn’t be accurate for you, but the weather at LS is the biggest determining factor.

  • #37401

    FREDDY SANDOVAL
    Participant

    Thank you, Kerry.
    Very good info, and yes, you’re right with weather conditions and elevation in Laguna Seca. It will still cold in January, and jetting may be a factor for me, but I’ll start fat, and then work my way down, and see what works best.

    I just don’t wanna stuck the top end again, while the motor is screaming down the hill, or up hill. :)

  • #37861

    Roger Miller
    Participant

    I will get to my jetting notes tonight – one comment about the fuel system, have used a pump around for several years at all of the road race tracks, and never had a problem.  And Ryen grabbed a couple of club championships during that time.  So it works.  170 does sound a little lean, but it is all about the air.  I have a table built from all of the races, where I have noted the best jet (plug, EGT, and piston top inspection) for whatever the air reads, and now all I do is read the air gauge and go to my table and jet.  Never an issue.

    That said, one engine and driver is one jet, and another engine/driver at the same time, could be different.  I know that several folks are usually a jet or 2 smaller than when we run.  I know Ryen is a bit over the class weight, so that may be a factor heavier, needs more power, needs more fuel….

     

  • #37864

    FREDDY SANDOVAL
    Participant

    Thank you, Roger

    I appreciate this very much

    I have always respected a gentleman and his notes/book keeping

    Thank you.

  • #37932

    Roger Miller
    Participant

    So looking through my notes – Laguna air is often between 500′ and 1000′ relative air density.   And we have run 182, 180 and 178 – 182 for around 500 and 178 at 1000 and higher.  Again – I am always checking plug color and EGT behavior and adjusting around that.  Laguna is also not very much on long straightaways.  For same air, at places like Thunderhill and Sonoma, I stay on the richer side as the long WFO sections need the fuel.

    I don’t have access to the kart to verify the pilot, but I believe we have a 60 in there and the needle I don’t remember either – but there is pretty much just one needle all the road racers use.  This is all on a PWM, without airbox.

     

     

     

     

  • #38181

    josh martin
    Participant

    For what its worth, i use the cr125 jetting app regularly. I find it to be highly accurate for sprint track racing, but have discovered (the hard way) that its suggested jettings are way too lean for big road-race circuits. It is still useful, as long as you understand its limitations. For large road-race tracks, i have found you need to add nearly 20 jet sizes (if it says 178, you need about a 198), otherwise a 100 mph piston stick is in your future. That being said, it is dead-on for about any size sprint track.

  • #38211

    Chris Hegar
    Participant

    If your needing near a 200 main your probably a little lean in another part of the carb.

  • #38503

    Roger Miller
    Participant

    I think you are on to something there Chris – sprinters use a leaner pilot – and a bit leaner needle as well to get it to pop out of corners, and they rarely rev out.

    Josh – as I said, in my post above we are not anywhere near a 200 (195 even) at the RAD for LS and Sonoma for usual air.  Over the next week or two I will get out there and verify my pilot and needle and report back.  Like I also said, I have run successfully with the engine, never cooking the piston or anything, and, so have a reliable set of data up to 6000′ like at Miller Motorsports down to sea level.  And about every 400′ is the next size.  But still one engine is not the same as another, so plug color, egt, and piston have been my guide and now more folks are using o2 sensors and that will be even more accurate as to how “right” the jetting is.

  • #38582

    Chris Hegar
    Participant

    Fuel type/oil and plug heat range are also variables to consider.

  • #38585

    FREDDY SANDOVAL
    Participant

    Yup, fuel, pre mix, plug, tires, radiator type, pipe, etc. I agree.
    Hey guys, thank you for all your help
    Unfortunately I’m not gonna be able to make it, as I sold the kart in broken condition. Sad
    A buddy of mine came over to my shop, saw the kart and fell in live with it, made me an offer and bought it.

    He will be seeing you guys up north in January at Laguna Seca, and Willow Springs, Button Willow, and Infenion.

    Thanks so much for all your input. God bless you all. Fast Freddy. :)

  • #38817

    Mark Morrison
    Participant

    The Winter Classis at Laguna Jan 24 2015 is approaching fast. Registration will open on Jan 1 2015. This will be a rain or shine event. Due to restrictions the field is 35 karts per run group. Noise is 92 db you get one warning. This year’s format is a practice session, qualify session and the Main you must use the same set of tires from qualifying in the main. Stay tuned for more info here as will at our website nckroadracing.com

    Mark Morrison, President NCK

  • #39410

    Roger Miller
    Participant

    Finally got out to the trailer and got into the carb – pilot we use is a 60 and the needle is a DGH

    And we have never messed with either at any track from sea level to Miller Motorsports park.  Not to say that is always golden, but it has been reliable and given me good tuning indications on the main jet.  Perhaps more extended time at higher altitude, I might try a leaner needle, or try a 58 pilot and see what changes.  At most though, maybe moving the clip up one slot might all that is needed to correct a mid richness or something.

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