Home Forums TaG Would it be stupid to run 11-66t on leopard to decrease RPM?

This topic contains 6 replies, has 4 voices, and was last updated by  Rod Hawkins 1 year ago.

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  • #5157

    Rod Hawkins
    Participant

    Since I will be switching my focus from my leopard to my KPV, I will almost exclusively be driving the KPV and keeping the leopard as a 2nd kart or for family or friends to drive when we have practice days.

    That being said, I want to improve the reliability of the leopard, so I don’t have to rebuild as much and also have less wear and tear on the kart in general and especially with regards to the starter.

    I also am wanting to decrease the performance a little bit so it is more inline with my kpv3, so when we are all together, we are on equipment that is more similar in performance.

    I am wanting to do this by bringing the rpms down by changing my gearing. Right now it seems like I am hitting right around 15,600 rpm along the long back straight away at Apex. I am currently running 11-81. By going by the theory of 1 tooth in the rear changes the RPMs by 200, and if my goal wold be to bring it down to around 12,600, then I would been to find the ratio to bring it down 3,000 rpm. With that theory in mind, that means I would need to decrease it by 15t or bring it down from 81t to 66t.

    I guess my question is, is there anything wrong with changing the gear ratio that dramatically?

    I also found this info online:
    Q: How do I prolong the life of my IAME Leopard RL motor?
    Answer: Above is the genuine IAME factory Dyno Power curve and Torque Curve for the RL engine. As you can see, its maximum power and torque is made between 10,000 and 12,000 RPM. There is no need to rev the engine beyone mid-15,000 RPM. By not revving the engine over 15,000 RPM the engine life will be prolonged between rebuilds. The starter motor brushes will last much longer as the engine will not have the high pitched harmonics vibration which breaks the starter motor brushes. By not revving the engine this will also be kinder to the main bearings, bigend cage and conrod. By revving the engine over 15,000 RPM you are risking a main bearing failure. The load on the drive-side crankshaft would be much less because it has the weight of the clutch hub mounted on the side of the crankshaft which may put excess load on the crankshaft if you are revving at high RPM’s.”

    #5165

    Tim Koyen
    Participant

    I don’t really see anything detrimental, other than the huge drop in performance.   The clutch might wear out faster from the starts.  If all you’re doing is joyriding, and not racing, then it should be okay.

    #5191

    12600 is really, really low max rpm for a leopard. You would have to lean out your low speed needles to get it to pull off of corners at all with that low an rpm. And since max torque is 10-12k rpm, right end the end of the straightaway just before you’re about to brake you’ll be in that max torque range the engine is suddenly going to take off like a bat outta hell. It will make for very sloppy driving. I think you are much better off revving it to 14,500 or so and just leave your high end needle on the rich side. You will be able to go 20+ hours without even touching the top end this way.

    Edit: you could swap on a JR header and carb and really have just about the same performance as the KPV

    #5257

    Jim Russell, Jr
    Participant

    As you stated its for non-karters to use as a play toy I would leave the gearing alone. Most likely they will not be able to maximize corner speed and would need the extra teeth to get decent acceleration. 15,600 is still fairly low on a Leopard. We routinely use them at 16,800 without any failures.

    #5416

    Rod Hawkins
    Participant

    12600 is really, really low max rpm for a leopard. You would have to lean out your low speed needles to get it to pull off of corners at all with that low an rpm. And since max torque is 10-12k rpm, right end the end of the straightaway just before you’re about to brake you’ll be in that max torque range the engine is suddenly going to take off like a bat outta hell. It will make for very sloppy driving. I think you are much better off revving it to 14,500 or so and just leave your high end needle on the rich side. You will be able to go 20+ hours without even touching the top end this way.

    Edit: you could swap on a JR header and carb and really have just about the same performance as the KPV<br>

    <hr>
    <div class=”bbp-reply-signature”>ActionKartRacing.com</div>

    It looks like there are a couple jr headers, a 25mm and a 30mm. Any idea what the HP difference is between these? Perhaps a better option would be to drop the rear sprocket 5 or 6 teeth and then put a jr header on there.

    #5418

    Rod Hawkins
    Participant

    Also looks like there is a jr restrictor plate available any idea if that would work?

    #5419

    Rod Hawkins
    Participant

    Another and perhaps the most logical thing to do would be to sell the leopard and throw a KPV on there. If it could be done without losing money on the deal?

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