Hi Kevin,

I’ll share our recent experience as it seems relevant. My son’s JB WF is essentially brand new and rebuilt (twice, unfortunately) by Eric Nelson at 7th Gear. The motor is strong, but Kieran was having exactly the issue you describe: terible launches and terrible recovery from slides and sharp turns. Gearing didn’t matter and we tried several different ones. Importantly he experienced the same things when he briefly drove a loaner motor while his was being rebuilt. The only common piece between the two motors? The brand new clutch. That’s foreshadowing.

After a few events where he wasn’t improving, I decided that a track day was in order to get us both back in the swing of driving fast. It worked wonders for two reasons: we got more seat time that one day than we’d had for the previous year combined, and his clutch finally came in. My guess is that either the shoes had to be scrubbed some or the drum needed to be heat-treated as we did at the track. The result? Kieran went out and was faster than all of the JB and JA kids at Summer Nats and finished the Champ Tour paxed 13th out of 213, his best finish in a National event ever by a long shot. His launches at the Pro were great and his clutch didn’t falter all weekend. He said it was a dramatic change for the Pro and we were able to gear him all the way down to 17/65 for the Tour.

So my hypothesis, right or wrong, is that autocross doesn’t allow the clutch drum to heat up enough for a proper break-in/coating. The answer for us was a track day to allow that to happen. Alternatives might be to sand down the clutch shoes a little to get to the good material and/or rough up the inside of the drum to make material transfer or heat-treatment to more readily take place.

I was almost ready to ditch this motor and head back to the KT100 (and would have if we’d still had them around). Kieran was not having fun until this change and constantly asked about going back. Now he’s VERY happy with the motor and we’ll work on weight-balancing the kart better now that I know we’ll have it for several more years.

Good luck!

Scott

I’m happy that Scott was able to get Kieran’s problem solved.  And, the clutch was where I was going to suggest looking as well, when I heard of the issue with slow launches and spin recoveries.

The clutch we got with our WF had Yellow springs.  I bought another clutch without checking what was in it, only because it was CHEAP.  Since we run the sprocket inboard, I took the unit apart and swapped the direction of the pucks, noting that it had orange springs, which are supposed to be the stiffest?

Colin immediately noticed the improvement in launches, and it got better as the clutch wore in.  Yes, we also did several track days for him and brother Connor.  I’d suggest reading up on the expected engagement RPM for the various springs.  If the clutch is engaging shortly off idle, and/or locking well before the designated engine speed, then there is an issue.

FWIW, the only time we experienced the issue both of you described was when an outrageous gear was selected for an event in Oscoda.  Colin was in charge of choosing his own gears, and I let him put the 56 rear on (16 or 17 front, I forget…) although I knew it was not going to work.  Was it slow to get going?  Ouch!  Tight corners meant it took way too long to get up to speed again.  After the event, we devised a method of checking for his actual top speed capability with a run down the long taxiway.  67 mph when the limiter kicked in.  After that, I handed him a calculator and had him first estimate his actual top speed potential, based on course design, then choose the gear based on what we knew the other one could achieve.  That is when the wins began.  Good times……

Sounds like that washer is the shield for the needle bearing piece of the assembly (officially named the thrust bearing).  Check out the exploded view here: http://www.noramclutch.com/go-kart-clutch/premier/titan-sp2.html

Kevin,

Do you have to run the clutch with the drive sprocket “outboard” in order to clear the chassis properly?  From what I have seen since we got our WF many years ago, the general consensus is that running it “inboard” places considerably less strain on the crank and drive-side bearing.

Another option might be to reconsider what is being used as an engine mount.  Many of them are fixed laterally, with the only adjustment being fore and aft along the frame rails.

The one we began with and still use is flat, and allows side-to side adjustment as well.  That came in handy when getting the proper  clearance.  The frame we have was designed as primarily for outer right drive (such as the 2-cycles, KT-100, etc) where the rear sprocket is inside the RR wheel.  Mouting the WF was not all that tough, though.

The Gold chassis does not have the 3rd bearing hanger.  I thought only the frames built for higher power engines used those?  That must be some beefy frame you have there.  Are you sure it is for a kid?  ;-)