I am new to the forum, looking for some advice on getting some extra power out of a Leopard.
First of all, the goal is making the engine somewhat competitive with the X30’s.
The kart is not used in any competition so not bound by any specific rules.
I gave the engine an overhaul, hone, new piston, new bearings (the SKF roller type, not the standard ball bearings), clutch, rebuilt standard carb,…
I have a Tryton HB27 lying around which has a few mm bigger venturi.
Does anyone have experience using that carb on a Leopard ? Or perhaps a HW Tillotson ?
Shortening the flex pipe is also on the to do list since I’m measuring 422mm from the flange till the first weld, from what I’ve read I should go for about 407mm (16’) on tracks with long straights and no/few slow corners.
Now it’s topping out at 112 km/u @ 16200 rpm at the end of the long straighth, which is too high I was told, I was advised to put 83 tooth instead of 81. On the other hand I see several posts indicating that 17000 rpm isn’t unusual. In a bit of doubt on this, 17000 seems waaaay past peak power rpm.
The best X30’s reach 120 km/h at that spot.
Going beyond peak power into overrev is pretty normal. The optimal amount of overrev tends to depend on the difference between the tightest turn and longest straight. Ultimately the stopwatch tells the story because it’s a compromise between top speed while maintaining acceleration out of the tighter turns.
Overall, I’d say use gearing and pipe length same as x30 as a starting point and then work on the engine from there with compression, ignition advance and perhaps eve ln play with exhaust port height with base gaskets.
What fuel options do you have?
27mm I think was the spec for the leopard in some cases… long time ago though.
Other valuable information to have would be the min RPM, not just max. It does seem like the X30 has a lot on your leopard currently, knowing min RPM will give you more information than top.
Here in the US when we had the mixed TaG class at the national level, X30 and Leopard competed evenly with just a 5lb weight difference. Shouldn’t take much to make them even; they already are quite close. The Leopard will excel on tighter tracks with longer straights and the X30 will excel in more flowing tracks.
We regularly ran Leopard at 17k or more RPMs, no problem. 16k should be about the minimum you run.
I just had a peek into the stronger X30 data logs, their 120km/h claims were a bit optimistic, 117 was the highest speed were mine was 112-113.
The slowest corner on the track is about 50km/h where my Leopard is at 7780 rpm. I try to attach my rpm plot across the track to this post.
My ignition advance is stock, if I want to change it I’ll have to file the mounting holes of the stator or use an offset key. But that would shift the whole curve, which I don’t know would be safe/beneficial.
Fuelwise I have acces to 98 octane (sadly enough in Belgium it has 5% ethanol in it) to wich I add 1/16 (6%)two stroke oil as per Iame manual for the Leopard.
I use the thin base gasket, so my port openings are a bit retarded and compression a bit higher. Never done any port timing changes, since I haven’t got a clue what would be beneficial.
Fuel trim feels pretty spot on, EGT climbs constantly on the long straights without dropping to a max of 640 degrees C ( I read somewhere 660C is the limit before risking seizing the piston)
My airfilter box has the intake holes at the top, slanted about 30 degrees. I think having these vertical with sort of velocity stack shape would push in a bit more air at high speed, maybe minimal, but it would be an easy mod.
