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Jr2 Purple Plate RPM?

1fasttiller

1fasttiller

Member
Hi fellas, We're running a pretty big 1/4 track here in Central Florida and I recently put a small tach with recall on my sons kart just to see where we are. We've been fast most nights, winning 5 out of 9 races in his rookie season so I just wanted to get some ideas of where I should be to begin really fine tuning the kart and gearing to move on to bigger and better tracks with more competition.

The motor is a Waller clone that I went through completely and refreshed. The cam is unknown, no markings on it so I can't say what I have. It just works!

We average 5880rpm all night. Once I've seen it turn 6000. Does this sound right for a purple plate? I'm an old flathead and 2 stroke guy so I'm still learning these clones and figuring out what works...
 
If this is a small pipe and your drops are less than say 600 ish, I wouldn't think twice about taking another tooth off the rear sprocket. Keep an eye on lap times, you'll probably find this will yield faster laps.
 
Thanks Chris, I've been contemplating dropping a tooth. He's getting smoother every race and really good at keeping his momentum up.
 
1fasttiller said:
Hi fellas, We're running a pretty big 1/4 track here in Central Florida and I recently put a small tach with recall on my sons kart just to see where we are. We've been fast most nights, winning 5 out of 9 races in his rookie season so I just wanted to get some ideas of where I should be to begin really fine tuning the kart and gearing to move on to bigger and better tracks with more competition.

The motor is a Waller clone that I went through completely and refreshed. The cam is unknown, no markings on it so I can't say what I have. It just works!

We average 5880rpm all night. Once I've seen it turn 6000. Does this sound right for a purple plate? I'm an old flathead and 2 stroke guy so I'm still learning these clones and figuring out what works...
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Hey 1fasttiller my friends son races red plate at Full throttle speedway in Cocoa FL and it's turning 5500ish with a 15/60 gear
the track is smaller than 1/4 mile. Can you tell me the name of this track and is it dirt or asphalt?
 
We are running at Marion County Speedway/AKA the BullRing with plans to venture down to Fruitland, Jasper and Callahan this coming year. All we race is dirt, don't know if much asphalt kart tracks around.


We are currently geared quite differently than anyone else in the class but it just plain works, I've got the new gears to change it but have been hesitant because of the success we've had!

We are running a 14/55, vast majority of the others are on 16/63. The ratios are almost identical but you get into that whole "momentum and larger driver is faster discussion"
 
1fasttiller said:
We are running at Marion County Speedway/AKA the BullRing with plans to venture down to Fruitland, Jasper and Callahan this coming year. All we race is dirt, don't know if much asphalt kart tracks around.


We are currently geared quite differently than anyone else in the class but it just plain works, I've got the new gears to change it but have been hesitant because of the success we've had!

We are running a 14/55, vast majority of the others are on 16/63. The ratios are almost identical but you get into that whole "momentum and larger driver is faster discussion"
Click to expand...


That track ive raced lots, its nowheres near a 1/4 mile. Fairly sharp turns, more closer to a 1/5.
14 tooth driver, with a 55 on rear, youre giving up lots of speed there.
 
How long ago has it been since you ran there though? I'm told it has changed very much from its older years. I'd say its well between a 1/4 and 1/5 mile.

I purposely geared the kart like this for my son to start out on, as I've always read it will help new drivers recover from mistakes better and get off the corners easier. It has worked well for us! I've had the 16/63-64 setting in the tool box but just haven't had reason to put it on. Our rookie season netted 5 wins, 2- 2nds and 2- 3rd place finishes (and 1 DNF because dad didn't tighten the fuel bowl...)
 
UPDATE: 4/12/19 races:

I went ahead and finally put the 16/63 gearing on as we had a big race Friday night for our Jr2 class (Points plus money race) and with 10 karts in the field I knew we'd have to bring our A-game!

The kart seemed to really like it! Peak RPM's were up from 5800 to 6000 and we won! He got a killer start from 3rd and when the 1st and second place karts tangled in turn one he took off around them and led almost the entire race. Had a couple cautions that worried me and there was a kart that pulled up beside him on a few occasions but once he found his line he stretched out a comfortable lead.

Thanks Earl for pushing me to finally try this gearing combo!
 
Great news, have you been watching and recording your lap times? How much time did you improve per lap? What was the lowest rpm per lap? Not just the best lap of the race, but a general average.
The reason I ask is b/c at 6000 rpm for a 1/4-1/5 mile, with a little pipe, I'd still be thinking about taking another tooth off the rear. I would continue to goto a taller gear ratio as long as lap times improved.
This is where a note book complete with data like: date, track, track conditions, weather, temp, lap times, gearing, kart scale numbers, tire choice, tire prep, tire pressures and any other data you can think of can really be useful.

Think of it like this: If you could shave .5sec/lap off your times, then in the end of a 15 lap feature, you would have improved by roughly 7 secs, which could be 1/2 lap.
 
All great points Chris! Unfortunately we don't have a Mychron with all that data available just yet. I only have a small tach on the Kart now which shows me peak RPM. I plan to get a mychron here very soon now that I know my son is invested and we want to take this all a little more serious.

I will certainly drop a tooth on it though and just see if it improves any for us. I was thinking about doing that any way as I didn't want to consistently see 6000rpm with this plate engine.
 
If you drop it to a 16/62 and it's real good, first time the track is real good meaning gripped up well I would switch it to a 17/65 ish and test that might just find even more. ;)
 
No offense, but without a Mychron to collect data you're kinda just peeing into the wind.
IMO this needs to be your next investment. The cheapo tach from the lawn and garden store may just be giving erroneous info............
And like Racing Promotor said above (he operates a local track here in Pa, and his advice is solid), you might be leaving speed on the table.
 
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Big Chris said:
No offense, but without a Mychron to collect data you're kinda just peeing into the wind.
IMO this needs to be your next investment. The cheapo tach from the lawn and garden store may just be giving erroneous info............
And like Racing Promotor said above (he operates a local track here in Pa, and his advice is solid), you might be leaving speed on the table.
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Oh I'm well aware that it is needed and plan to get one on the kart soon. Getting back into karting and seeing if a 10 year old is going to stay with it has made for a busy few months and the cost of a new Mychron has been better utilized in things such as new tires and preps first.
 
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1fasttiller said:
UPDATE: 4/12/19 races:

I went ahead and finally put the 16/63 gearing on as we had a big race Friday night for our Jr2 class (Points plus money race) and with 10 karts in the field I knew we'd have to bring our A-game!

The kart seemed to really like it! Peak RPM's were up from 5800 to 6000 and we won! He got a killer start from 3rd and when the 1st and second place karts tangled in turn one he took off around them and led almost the entire race. Had a couple cautions that worried me and there was a kart that pulled up beside him on a few occasions but once he found his line he stretched out a comfortable lead.

Thanks Earl for pushing me to finally try this gearing combo!
Click to expand...
Drop rear gear now, get even faster i believe. And you are very welcome. Congrats.
 
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