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Clone engine power drop, and RPMs to high.

M

MattRoss87

Member
So little contexts, my son races out at Indianapolis speedrome in the Jr fastkart division, we run a Honda clone with the blue restrictor plate and are open to any clutch and any sprocket. We can't do anything to the engine as far modification but we can change our own valve springs and set the lash, which I have done and have it set to . 0015 on both. My issue is I cannot get the RPMs down pass 3500 without killing it nor can I get it to stop dropping power off at 5700 RPMs. Now I am still very new at this and I barely know my way around how all this stuff works. I've talked with others at the track about their setups and they say that their RPMs are around 2700 and engaging the clutch around 3000 or lower. And peak RPMs should be around 5200. What am I doing wrong. Please ask any other questions and I will try to answer to the best of my ability.
 
first would be is the clutch engaging causing it to pull the engine down .
an inspection of theidle jet seems in order .
Power droping off after 5700 rpm sounds right .
 
MattRoss87 said:
So little contexts, my son races out at Indianapolis speedrome in the Jr fastkart division, we run a Honda clone with the blue restrictor plate and are open to any clutch and any sprocket. We can't do anything to the engine as far modification but we can change our own valve springs and set the lash, which I have done and have it set to . 0015 on both. My issue is I cannot get the RPMs down pass 3500 without killing it nor can I get it to stop dropping power off at 5700 RPMs. Now I am still very new at this and I barely know my way around how all this stuff works. I've talked with others at the track about their setups and they say that their RPMs are around 2700 and engaging the clutch around 3000 or lower. And peak RPMs should be around 5200. What am I doing wrong. Please ask any other questions and I will try to answer to the best of my ability.
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Can't answer your idle question, but if 5200 rpm is where your target should be, your gearing combo is off and your turning to many rpm. Do you know track size ? Describe shape tight turns out of throttle, or sweeping turns more momentum ?
What is your current gearing combo your running ?
 
racing promotor said:
Can't answer your idle question, but if 5200 rpm is where your target should be, your gearing combo is off and your turning to many rpm. Do you know track size ? Describe shape tight turns out of throttle, or sweeping turns more momentum ?
What is your current gearing combo your running ?
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Track is a 1/5 mile oval and we are set up to full throttle go from start to finish. And I have a 15 tooth on clutch and 58 on sprocket
 
MattRoss87 said:
Track is a 1/5 mile oval and we are set up to full throttle go from start to finish. And I have a 15 tooth on clutch and 58 on sprocket
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Then your 5 teeth off minimum to many, plus 95 % chance your gear bound and the 5700 reading is not correct, probably another 2 teeth could even be more, I'd try removing 8 teeth from rear, which you obviously can't do and stay on regular gears because you'd be down to a 50 rear gear, instead bump front driver to a 17 leave the 58 see what it does to rpm readings and adjust from there. Someone's going to point out that won't be the same ratio and 2 front driver size difference is only equal to 6 rear, but don't worry about that for now.
 
Speeddrome is asphalt i believe as well . Definitely do not want to be over spining the engine . Or have a tight chassis. Is this a different chassis style than a standard racing kart ?
 
flattop1 said:
Speeddrome is asphalt i believe as well . Definitely do not want to be over spining the engine . Or have a tight chassis. Is this a different chassis style than a standard racing kart ?
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I believe it's a standard racing chassis with a roll cage, and we try and keep the chassis as loose as possible for grip in the corners.
 
racing promotor said:
Then your 5 teeth off minimum to many, plus 95 % chance your gear bound and the 5700 reading is not correct, probably another 2 teeth could even be more, I'd try removing 8 teeth from rear, which you obviously can't do and stay on regular gears because you'd be down to a 50 rear gear, instead bump front driver to a 17 leave the 58 see what it does to rpm readings and adjust from there. Someone's going to point out that won't be the same ratio and 2 front driver size difference is only equal to 6 rear, but don't worry about that for now.
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Thank you, I was informed that I should go back to a 17 and see how that works.
 
Those new to our sport have a tendency to excessively worry about engine and gearing and not concentrate enough on handling. You may not be asking the proper questions. What kind of kart? Do you have scales and alignment equipment? If so post your numbers. Are you close to being competitive?
 
Screenshot_20220404-145838.jpg
 
Ten-4 . i also know someone else races there . They had trouble with gearing as well .
Rp gave you great advice.
I think a 17 is right .
 
We spent a lot of time at the beginning of the season setting the castor and camber on the front end and getting the toe corrected as well. With the way our karts are setup we try and keep the balance towards the mid front to help dig in for the turns. Best time we have ran was a 16. 1 with the top competitors 14.9 to 15.5. I run my tires on the front between 18 to 22 lbs, rear right at same and rear left at 10 lbs. The only time that left rear tire is touching is on the straights and it's not for long.
 
Looks like they make you purchase chassis and everything in house or at a sponsor. Definitely not a standard cage kart.
 
The wear patterns of the front tires seem to indicate negative camber on the left front, should be positive. It also looks like you have too much negative camber on the right front.
The rims look pretty narrow for the tire width. Are you allowed to change rim width?
 
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