Home Forums Autocross / Solo 2 FJB/FJA World Formula

This topic contains 33 replies, has 4 voices, and was last updated by  Joe Ricard 4 years, 8 months ago.

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  • #15930

    Robbie Nelson
    Participant

    My kids have been running a Birel C28 w/ a KT100 in FJB for the past 2 years.  Next year I plan to move to a Briggs and Stratton World Formula for various reasons.  The purpose of this thread is to document the parts list, cost and dos/don’ts of the transition.  I will update this first post with new information as I get it.  This first post will be rather dry to start with, but will get better as the project comes along.  I may be over thinking this; we’ll soon find out.

    Parts List:
    Briggs and Stratton World Formula kit – $995
    Engine mount – $83
    Silencer – $75
    Silencer mount – $16
    Throttle cable
    Fuel line
    #219 Chain – $30
    #219 Axle sprocket set (4 total) $46
    #219 Chain breaker $25
    Battery – $??
    Battery mount – $??
    Battery wiring – $??
    Carb slide for JB – FREE

    Determined:
    #219 Chain – WF comes with 2 #219 drive sprockets 17 and 19 tooth (or is it 17 and 15?)

    Emailed Brian Harmer (bharmer@scca.com) with my member number asking for a slide.  He was quick to respond.  The slide was on it’s way within a few hours, free, with tracking number.  Awesome!

    Weights (w/ clutch, exhaust and motor mount):
    World Formula 30 lbs (w/ starter but no battery)
    KT100 21 lbs
    Weights taken with Intercomp car scales

    To be determinded:
    Gearing needs for typical autocross courses
    Chain length
    Battery and mount
    Starter wiring
    Will the seat need moved?

    http://youtu.be/JosoRLnXdcc

    Robbie Nelson

  • #15931

    Joe Ricard
    Participant

    Make sure the motor mount is 2 two piece so you can infinately adjust the motor outboard to keep clutch away from the seat support bars.    I used a Burris and it worked well.

    The cadet chassis is pretty small and is the exact one I used so it is possible.

    Chain length will be obviously determined by gear.  I think we were running 58 rear mostly but have used 53 up to 63.  fronts 15 to 19  It’s been awhile.

  • #15979

    Robbie Nelson
    Participant

    Hope this isn’t a dumb question…  219 or 35 chain?

    Robbie Nelson

  • #15981

    Scott Boito
    Participant

    219 chain is lighter but narrower.  I don’t have a good feel for why you’d run one over the other, but since we already had all 219 stuff, we stuck with that.  To switch after you’re already set with one or the other is expensive, so choose what you want first.

  • #16477

    Robbie Nelson
    Participant

    As for gearing ratios, I gear it between 17/73 and 17/65 for JB (#219 chain). Next season he moves up to JA and I’m getting a 19T clutch sprocket so he can get up to higher speeds with the same axle sprockets.

    Hmmm…  So, if I just simply swap the carb slides, one of the kids is going to be at a disadvantage.  That sucks.  I hadn’t considered that.  Argh….  My daughter turns 12 in May, so she can run JB until then.  I need to research that age/class rule again.

    As far as sticking with #35 (what’s on the KT100 now) or switching to #219.
    #219
    Chain $30
    Drive sprockets come with the World Formula
    Axle sprocket set $100
    Total $130

    #35
    Use chain I have
    Drive sprocket set $45
    Axle sprocket set $90
    Total $135

    Note: These are approximate values on economy units.

    So, it’s close to a wash.  I’m going to go with a new #219 setup.

    Robbie Nelson

  • #18211

    Robbie Nelson
    Participant

    Update:

    The KT100 is off the chassis.  Now it’s time to get the WF mounted.

    Note: This isn’t really hard work, but I’m making a video of the change.  So it’s taking a bit longer.

    Robbie Nelson

  • #18249

    Scott Boito
    Participant

    Sorry, I missed your question about the ages.  We clarified that sometime in the last 18 months in a FasTrack.  Essentially, 12 year olds can run either JB or JA.  So if your 11 turning 12 yr old wants to stay in JB all year, that’s OK.  Kieran will be starting the year in JB and making the switch to JA probably for Toledo.

    Be prepared to weight-balance the kart for the WF.  It will be completely different from the KT100 since it weighs more than 2x that motor.  Slide that motor as far inboard as you can to help.  Even doing that for Kieran he was pretty bad with the side to side weights.  Depending on the height of your kids, you may also have to move the motor pretty far forward to get it to turn (~42-43% weight in the front with kid on-board). Once we figured out to do that he had no problem turning, but the chain is so long now that we need to add a sprocket guard to keep it on the axle sprocket.

    We ended up getting him pretty well balanced overall, but still with a right rear bias due to the weight of the motor and his relative lightness.  Much better midway through the year, so I advise you to get that right from the start and everyone will be happier.

  • #18628

    Robbie Nelson
    Participant

    Regarding the clutch…  Does it matter if I run the drive sprocket inboard or outboard?  I read somewhere that it comes setup for outboard.  If it run it inboard, do I need to change anything internal?  I read somewhere that you have to flip springs or some such.

    I’d hate to give bad info in the video.

    Robbie Nelson

  • #18652

    Scott Boito
    Participant

    I’ve found that running the sprocket inboard is the easy way to get the axle sprocket to line up with the key slot in the axle.  I couldn’t get ours to line up otherwise.  There are ways around it, but the easiest is to flip the clutch.

    Instructions for flipping are provided int he paperwork with the clutch since it’s commonly done.  Basically separate the clutch assembly from the drum, reverse the screw things, then put it back together.  You need to add the additional washer against the crank at the case to make it work.  Overall pretty simple to make the change if your crank’s key slot isn’t too tight.  Videos are available on swapping for inboard running, I think.

  • #21005

    Robbie Nelson
    Participant

    I ran into a problem last night.  The bolt that holds the clutch on only seems to catch one turn worth of thread.  What gives?

    Note:  I’m installing with the sprocket inboard.

    To make sure I’m installing it right, here’s my install steps:
    – Flip clutch pack (remove clip; remove inner cartridge; remove screws; flip clutch pack; reassemble)
    – install radius washer with radius inboard
    – install clutch w/ sprocket inboard
    – install flat washer
    – install bellville washer w/ hump outboard
    – install bolt

    I never tightened the bolt, because I felt like it would strip the first thread of the bolt or crank.

    I’ve asked about this on the Briggs forum.  But I thought I’d ask here in case anyone else has similar experience and for future reference.

    Robbie Nelson

  • #21040

    Joe Ricard
    Participant

    Well it sucks you are faced with this issue.  But great on Briggs to have a fix for it and standing by to make it right.

  • #23281

    Robbie Nelson
    Participant

    Video tutorial added to first post

    Robbie Nelson

  • #23400

    Scott Boito
    Participant

    That’s a great video and I’m thankful (for future dads switching) that you included the mistakes, too.  Based on my experience, installing the clutch “backward” from the intended mounting got me twice, too.  Even after I was aware of what I should have been doing, I still did it wrong twice.

    The good news is that once it’s all together and mounted correctly, you shouldn’t have to worry about much else related to the motor.  It should run for years with only minor tweaks to the valves.

  • #23936

    Robbie Nelson
    Participant

    First autocross report:

    It was very cold and threatening to rain/snow.  Which makes for a miserable day.

    I believe the cold weather (high 30s) was affecting the carb jetting.  At high RPM and full throttle, the engine seemed to break up a bit.  Since I didn’t have a jet kit, I didn’t think I could make any adjustments.  However, in hind sight I think I could have.  Since we’re running the slide restrictor to about 1/2 throttle, I believe a needle clip position would help quite a bit.  Thoughts?

    Something is making a banging noise during launch and you can see the chain jumping around.  The kids both said that it made noises when you got on and off the throttle.  I think this is a symptom of the clutch needing broke in.  Perhaps a lapping day is in order?

    Robbie Nelson

  • #23978

    Joe Ricard
    Participant

    Sounda like your clutch might be backwards.    The Premier Titan will shudder a little bit as it getts to full lock up.  but it will sudder like a  MFer if backwards.

  • #23984

    Robbie Nelson
    Participant

    Can anyone recommend a battery and mounting method?  I can’t find any rules regarding battery type/size/mounting.

    Robbie Nelson

  • #23996

    Scott Boito
    Participant

    Mount the battery to the seat, not the chassis is all I’ve heard.  Vibrations on the chassis kill batteries.  Should be able to find something on LiPo batteries in the Briggs forum I think.  They are not cheap.  I recommend removing starter and battery anyway…

    For the clutch, what Joe said.  Also are you sure you have the axle sprocket lined up correctly?  I don’t ever remember Kieran’s chain jumping around.

  • #24079

    Joe Ricard
    Participant

    For batteries I always had a spare Rotax set up laying around.  Works well but pricey to buy new.     If you need to add lead anyway then keep all the self starting stuff.  Having your youngin be able to re-start the motor after jumping a cone make them grumpy peeps in grid more happier..

  • #24084

    Scott Boito
    Participant

    Pic not working.

    Stalling the WF will really take a lot of effort.

  • #24112

    Scott Boito
    Participant

    I’ll check our spare one tonight, but I think that’s correct for the inboard mount. Some folks actually run the shoes the opposite way on purpose, so that shouldn’t be an issue anyway, once the clutch is broaken in (with a load, preferably on a track with some time to heat cycle it).

  • #24126

    Scott Boito
    Participant

    Sorry, everything is packed up for Blytheville so I can’t get to it.

    Did you test it under load (as in sitting in the kart and throttling up)?  On the stand it can act a bit unpredictably until the clutch is broken in.

  • #24128

    Robbie Nelson
    Participant

    Today I learned that the choke works opposite of how I thought it worked.  I’m pretty sure we’ve been running it with the choke on.  I thought it was running rough due to jetting and 30 degree temperatures.  Guess I was wrong.  Runs and idles much better with the choke off.  Lesson learned…

    Robbie Nelson

  • #24491

    Michael Ball
    Participant

    Would you mind posting a picture of how your starter is wired? My kart and world formula came with a starter but, it was not installed. I am trying to figure out how to wire it. Also would one of these batteries work? http://www.amazon.com/gp/product/B0009GIKNE/ref=ox_sc_act_title_1?ie=UTF8&psc=1&smid=ATVPDKIKX0DER

    It meets the 12v 8 ah requirements.

  • #24492

    Joe Ricard
    Participant

    Yes that battery should work.   hot lead to starter, switch from solenoid to ground.  There is a detailed drawing in the WF owners manual found on Google  and the Briggs Web site.

  • #24845

    Robbie Nelson
    Participant

    Since we’re running the slide restrictor to about 1/2 throttle, I believe a needle clip position would help quite a bit. Thoughts?

    Nobody has any input on this?

    Something is making a banging noise during launch and you can see the chain jumping around. The kids both said that it made noises when you got on and off the throttle. I think this is a symptom of the clutch needing broke in. Perhaps a lapping day is in order?

    I believe the banging noise is/was due to an misaligned chain/sprockets.

    How much slack should the chain have?

    Robbie Nelson

  • #24846

    Joe Ricard
    Participant

    1/4″ with no tight spots when lifted in between the drive and driven sprockets.

  • #15980

    Scott Boito
    Participant

    Hey Robbie,

    We made this switch earlier this year after running the KT100 for 2 1/2 seasons.  After a few months of growing pains we finally got it figured out and it’s a dream to run now.

    Initial costs are higher than the KT100, but there are minimal hassles associated (no starter battery to charge, no charger to lug around, no tuning of the carb).  The weight of the motor is our biggest problem to overcome since it’s more than 2x the weight of the KT100.  Corner balancing is still impossible side to side due to Kieran’s size.  I had to move it pretty far forward to get the correct front/rear split, but the chain is super long as a result.  It will get better as he gets taller and heavier, but it is a real limitation.

    He’s on an older Top Kart SL28 chassis with a moveable seat stay and using a two piece mount easily allowed us to mount the motor without interference from the seat/seat stay.

    My advice: work that clutch early in the process.  The clutch was our only source of consternation those first few months.  It wasn’t until he ran it at a track that it properly broke in and started functioning as it should.  After that it has been a dream motor.

    As for gearing ratios, I gear it between 17/73 and 17/65 for JB (#219 chain).  Next season he moves up to JA and I’m getting a 19T clutch sprocket so he can get up to higher speeds with the same axle sprockets.  The 17/65 was perfect for Blytheville Summer Nats this year.  17/67 would have been the perfect choice for Wilmington.

    If you’re interested in running #35 chain, PM me as I acquired several fast #35 axle sprockets that we’re not going to use.

  • #16492

    Scott Boito
    Participant

    Don’t forget a new chain breaker for the 219 chain.  And I have a set of 35 axle sprockets for you.  PM me.

    You don’t need another drive sprocket, except maybe for really fast national courses.  I’m getting one just for the track and hopefully some of the fast courses at Wilmington and Lincoln.  That’s especially true if you run a 35 chain since you can get smaller axle sprockets with the 35 teeth than 219 (it’s a major challenge with the 219 that you can’t get smaller than 64T).

  • #16800

    Robbie Nelson
    Participant

    Hmmm… So, if I just simply swap the carb slides, one of the kids is going to be at a disadvantage. That sucks. I hadn’t considered that. Argh…. My daughter turns 12 in May, so she can run JB until then. I need to research that age/class rule again.

    I looked in the 2013 solo rule book and the age / class change rule isn’t very clear.  Can someone point me to the official rule on this?

    There seems to have been some movement as seen here, but it seemed to be something on facebook..??  http://eknclassic.com/viewtopic.php?t=116291&postdays=0&postorder=asc&start=0

    Robbie Nelson

  • #18710

    Robbie Nelson
    Participant

    For gearing / speed calculations, what max RPMs should I use?

    KT100 – 14,000?
    WF – 7,100?

    Was running a 67 and 9 gear on the KT100….

    Robbie Nelson

  • #18724

    Scott Boito
    Participant

    7100 is max.  We run a 17T with 65-73T axle sprockets.  So around a 4:1 ratio, plus or minus 0.3 ish.

    And from what we’ve experienced and what I’ve read, you ideally want to gear for hitting the rev-limiter ~2/3 down the straight(s) before braking.  So hitting the rev limiter is the best way to set your gearing.  Kieran hates when it happens, but it helps keep the gearing OK for digging out of the tight corners elsewhere.

  • #21013

    Robbie Nelson
    Participant

    Here’s the response from Briggs and Stratton:

    Robbie,

    We appreciate the e-mail and you have done NOTHING wrong with your installation.  Noram, who makes this clutch made a change to the thickness of the hub without notifying us.  This change impacts the fastener engagement so you are spot on in your findings.  We have a bulletin out to our dealers and have updated all of our inventories with a longer bolt to adjust for this manufacturing change.  It sounds like we need to help you out and we would be more than happy to send you a new fastener kit.

    Please drop me your mailing address – BriggsRacing@basco.com

    If you could, also give me an idea of how soon you plan on using the engine.  I will make sure we get this to you in that timeframe.

    Sorry for your inconvenience.

    Robbie Nelson

  • #24083

    Robbie Nelson
    Participant

    Correct installation or not?

    World Formula Clutch

    Robbie Nelson

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