Adjusting Comet Tav2 engagement RPM

[Sprocket86]

Hello there.

I'm in the process of fine tuning my Lawn Boy Powered Tav2 equipped mini bike and I'd like to change the stall or engagement RPM in both the driver clutch and the driven clutch to a higher RPM value.

My driver clutch is a genuine Comet part but I see no colour markings on both of the tension wrap around springs. What "colour" would these be from the factory and what about the two weights, how many variations are there available?

My driven clutch is a china knock off and the torsion spring has no colour. I do have it installed in the far left hole (no#3 position) but it will shift into high range almost right away. Are my only options the green or yellow spring?

I pretty much want this Tav unit to engage and shift at a much higher RPM then it currently is set up for.

Thanks for your input and help.

 

[FirePowerMinis]

Stock driven is supposed to be green. Yellow is stiffer. On a knockoff, hard to say what is on it.

Drives have more tuning options.
Replacement Springs for 20 & 30 Series Driver | 011188 |

 

[yalipito]

Don't bother with the torsion spring. Get the garter springs and weights needed for the rpm engagement that you want.

 

[Sprocket86]

Don't bother with the torsion spring. Get the garter springs and weights needed for the rpm engagement that you want.

Is the yellow torsion spring not really all that much stronger? I have a plain natural colour one in my driven pulley and I wonder if it stronger or weaker then both the green or yellow Comet torsion springs?

What type or material are the weights that would come on a stock 30 series driver clutch? I thinks it's the heavy Zinc ones but I'm not sure.

If I'm correct, a stock 30 series driver clutch comes with the blue 2200 rpm springs?

 

[Sprocket86]

Stock driven is supposed to be green. Yellow is stiffer. On a knockoff, hard to say what is on it.

Drives have more tuning options.
Replacement Springs for 20 & 30 Series Driver | 011188 |

I really had no idea that there were several different driver clutch garter springs available. If I'm correct, a stock 30 series driver clutch has the blue 2200 rpm springs?

 

[FirePowerMinis]

I really had no idea that there were several different driver clutch garter springs available. If I'm correct, a stock 30 series driver clutch has the blue 2200 rpm springs?

Seems to be, according to this, that zinc and blu make 22
http://www.bmikarts.com/PDF/Comet_30series.pdf

 

[yalipito]

Is the yellow torsion spring not really all that much stronger? I have a plain natural colour one in my driven pulley and I wonder if it stronger or weaker then both the green or yellow Comet torsion springs?

What type or material are the weights that would come on a stock 30 series driver clutch? I thinks it's the heavy Zinc ones but I'm not sure.

If I'm correct, a stock 30 series driver clutch comes with the blue 2200 rpm springs?

I dont know how the unmarked spring compares to the yellow but from green to yellow it did not make a big difference. Light weights and garter springs made a huge difference in engagement rpm.

 

[FirePowerMinis]

Stiffer rear spring/winding allow faster backshift/downshift when letting off then nailing it again, as well as upshift delay.
Drive clutch mostly controls engagement revs.

 

[Sprocket86]

I placed an order with BMI karts and I got the white and yellow garter drive clutch springs (3100rpm and 3300rpm), 10T #35 drive sprocket and the yellow driven clutch torsion spring.

I hope this gets me in the ball park. My current rear tire is a 13x5.00-6 with a 60 tooth sprocket and went from a 12t drive sprocket to a 10T.

 

[super nate]

my stall speed is 4100 with a 7inch driven sheave,13tooth front sprocket and a 70 rear with a 13 inch tire...does 53mph at 7700rpm in the eighth mile

 

[Sprocket86]

my stall speed is 4100 with a 7inch driven sheave,13tooth front sprocket and a 70 rear with a 13 inch tire...does 53mph at 7700rpm in the eighth mile

Sweet! What engine are you running?

 

[super nate]

predator 212

 

[Sprocket86]

Well my Tav springs came in from BMI Karts as well as the 10t #35 sprocket.

I got them installed the other day. I have the yellow 3300rpm drive clutch springs in and the yellow driven spring installed in the 3rd hole. Man that was tough getting that reassembled lol.

I'm really hoping this gets this engine up in RPM's and into the meat of the power band.

 

[super nate]

if your running a six inch driven pulley you may have the engine hit a rev limit. I have found that the .9% overdrive seems to stop engines from reving higher. I use the seven inch driven pulley which has a one to one high gear with no overdrive, that made my engine rev on up to 7700 no problem

 

[Sprocket86]

Yeah I have the 6 inch driven pulley and interesting, I did not know this. One thing for sure is that the new yellow driven torsion spring is a hell of a lot stiffer than my natural colored one that came in this 6 inch china driven pulley. I'm hoping I'll be able to test it out today.

 

[FirePowerMinis]

I'm of the thought that overall ratio is what one should tune too.
Gotta fill in ALL the blanks in the equation to get the right answer.
Merely swapping the 6 and 7 inch drivens changes both ends of the range. Drastically.

The web sez:
30 series 6" driven: 0.90:1 high ratio, 2.68:1 low ratio, 2.98 overall ratio range
30 series 7" driven: 1.12:1 high ratio, 3.13:1 low ratio, 2.79 overall ratio range

All 3 factors listed for the units, comes in play.
Final drive would have to be altered for them to be comparable.
The wider overall spread of the 6" would need a steeper final drive, regardless of which end you optimize for.

 

[Tom S.]

...does 53mph at 7700rpm in the eighth mile...

:thumbsup::thumbsup::thumbsup:

 

[super nate]

I haven't found a motor or a combination yet that would allow the motor to rev with the six inch pulley. that overdrive seems to stop the motor reving in its tracts. soon as I swapped over to the seven inch pulley it spun right up to 7700. I did have to change the rear sprockets to find whats the best time and speed it would run in the eighth. so far 13/70 is all it will pull. I'm sure if the motor made a crap load of power like over 20 it might rev on up but I'm sure that 3/4 inch belt in the 30 series wont handle it.

 

[FirePowerMinis]

I haven't found a motor or a combination yet that would allow the motor to rev with the six inch pulley. that overdrive seems to stop the motor reving in its tracts. soon as I swapped over to the seven inch pulley it spun right up to 7700. I did have to change the rear sprockets to find whats the best time and speed it would run in the eighth. so far 13/70 is all it will pull. I'm sure if the motor made a crap load of power like over 20 it might rev on up but I'm sure that 3/4 inch belt in the 30 series wont handle it.

Did you lower final drive gearing 24% to compensate for the 1.12 to .9 difference in converter ratio?
I'm not doubting your tests, just curious if it was a level field.

 

[super nate]

I ran 9/70 gearing #35chain ...still hit a rpm limit...smallest gear I have...I am using the stock db30 rear tire which is 15 inches tall..i have never tested the idea but I think the six inch pulley might work with a much smaller tire/rim combination along with a short gear