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#25 Reply
Posted by
Dirtzilla
on 30 Apr, 2013 22:58
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zilla 273, if you go to one of the other atv sites, it has a gearing calculator, you just enter your tranny ratios, tire size and two sprocket sizes and it gives you the speed you " technically" should do.
there is no link, its on the web site only, it would be good if we could get one here, hint hint !!
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Bring the tire PSI up to 15psi or more and you'll see a big improvement in top speed...not only does it provide slightly taller gearing but rolling resistance is cut way down, and handling is improved at those speeds to boot.
I gained a solid 15mph by airing my tires up to 20psi with my LTR, and at least that much with my 250 running 30psi.
Higher speeds need higher PSI.
...and of course all of the tires say never inflate past something like 10-15psi, but who gives a damn LOL
Not going to buy street tires for 2 or 3 rides down pavement.
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#27 Reply
Posted by
Dezsled
on 30 Apr, 2013 23:15
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Get a pic... Those tires should look like pizza cutters at top speed!
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#28 Reply
Posted by
Zilla273
on 01 May, 2013 13:07
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jerry, im runnin the 87 transmission, 112 octane Sunoco, and its runnin really rich, its backed off on main just enough to pull 4th,5th gear with no sputter, i can already tel its gona pull the gear pretty easily.. I might end up having to lean it alittle for Saturday though, its callin for 75 degrees out and it was around 55-60 when i tuned last time
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#29 Reply
Posted by
Zilla273
on 06 May, 2013 11:46
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well I did my gps run again with the 38 rear, 12 lbs of air in tires, I got 92.6mph, its still pulling the gearing easily, I dropped 4 teeth on rear goin from 42 down to 38, does 2-3 mph sound right?
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#30 Reply
Posted by
Dirtzilla
on 06 May, 2013 18:43
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Nope, gearing calculator was dead on with ur 14/42 gears at 90 mph
14/38 sprockets you should be doing over 100 mph
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Nope, gearing calculator was dead on with ur 14/42 gears at 90 mph
14/38 sprockets you should be doing over 100 mph.
What RPM are you using for your calculations?
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#32 Reply
Posted by
Kyle T
on 06 May, 2013 19:45
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I use 8,000 myself.
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You might be slipping the clutch at those speeds, which can account for the speed difference and the feeling that the engine still has more in it.
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#34 Reply
Posted by
Dirtzilla
on 06 May, 2013 21:21
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I left it at 8500 rpm ,i used the 87 zilla gear ratios from my manual
Its the calculator on everything two stroke, you have to be logged
In for it to work.
I tried different tire sizes also just to see, it seems you could get almost 5 mph more for every
Inch taller in tire size .
Everyone knows its not going to be dead on all the time, but i think that
Calculator gives you a ball park as to what to expect when you want more
Bottom or top end speed
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I left it at 8500 rpm ,i used the 87 zilla gear ratios from my manual
Its the calculator on everything two stroke, you have to be logged
In for it to work.
I tried different tire sizes also just to see, it seems you could get almost 5 mph more for every
Inch taller in tire size .
Everyone knows its not going to be dead on all the time, but i think that
Calculator gives you a ball park as to what to expect when you want more
Bottom or top end speed
His engine will not make good power at 8500 RPM. His engine should make its peak power in the 7400 to 7800 RPM range at those speeds. Maximum top speed will be obtained when the gearing allows the engine to run at its power peak.
Aerodynamics, rolling resistance and the amount of peak power is what determines the maximum top speed any vehicle can obtain after the gearing has been optimized. The rider stance / position, front and rear fender cut is also a big part of the aerodynamics of bikes and quads.
Most gearing calculators do no account for tire growth.
Continue to take teeth off of the axle or add teeth to the counter shaft until it slows down.
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#36 Reply
Posted by
Zilla273
on 07 May, 2013 09:56
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I thought it coulda been clutch slip, bc it still pulls 5th fast, i can see what jerrys saying too, when I peaked at the gps it pulled to 92quick then as motor got above that particular rpm it droped to 88,
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#37 Reply
Posted by
Dirtzilla
on 07 May, 2013 10:42
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Motorgeek your absolutely right, when you do the calculation at 7500 rpm for example, Zilla273's bike is right on mark at 88 mph. another thing learned
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#38 Reply
Posted by
Zilla273
on 08 May, 2013 15:58
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Does anyone make a smaller rear sprocket then 37? Id like to gear up more but with the case saver i have i cant bring the counter shaft up more.. its quicker now then itwas with the42 rear, id like to continue gearing up to see how much more acceleration can be had along with top end numbers
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#39 Reply
Posted by
Dezsled
on 08 May, 2013 16:11
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14x37 should have you close to or over 100mph, find some 22" rear tires ill bet that would net a few more mph
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Does anyone make a smaller rear sprocket then 37? Id like to gear up more but with the case saver i have i cant bring the counter shaft up more.. its quicker now then itwas with the42 rear, id like to continue gearing up to see how much more acceleration can be had along with top end numbers
Put a case saver that is made for a 15 tooth. Increasing the tooth count on the countershaft reduces the parasitic losses in the chain and decreases the tensile load on the chain. A 15 tooth sprocket will also make the chain last longer.
If you found that a 3.00 final drive ratio was the optimum gear ratio, a 45/15 will deliver slightly more power to the rear wheels than a 39/13 sprocket combination.
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I dobt see how thats possible getting those speeds my bike only hitts 88mph with 15-40 gearing on a track.
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#42 Reply
Posted by
Stpltn250r
on 08 May, 2013 18:27
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14/37 gear with 22" tires on .863 5th @ 8k is 108mph.
you can go higher than 15t countershaft. they will be custom made and about 25 a piece plus shipping. I had some 16&17 made two years ago and that's what the cost me.
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#43 Reply
Posted by
Dezsled
on 08 May, 2013 19:04
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I got to race the Zilla in my avatar on some high speed courses. The Nevada 500 and Baja 1000 twice. We could reel in trx250rs easily (top speed approx 90mph) so I don't think that 100 mph is out of the question
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I got to race the Zilla in my avatar on some high speed courses. The Nevada 500 and Baja 1000 twice. We could reel in trx250rs easily (top speed approx 90mph) so I don't think that 100 mph is out of the question
maybe its because i gear.mine not to be a complete turd outta the hole guess if.you was just looking to go super fast its possible i dunno.
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#45 Reply
Posted by
Zilla273
on 09 May, 2013 04:58
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Cunningham, u shld try puttin alitt more gear to yours, mine is faster accelerating with the14-38 then with the 14-42, especially in loose traction conditions like sand
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I got to race the Zilla in my avatar on some high speed courses. The Nevada 500 and Baja 1000 twice. We could reel in trx250rs easily (top speed approx 90mph) so I don't think that 100 mph is out of the question
maybe its because i gear.mine not to be a complete turd outta the hole guess if.you was just looking to go super fast its possible i dunno.
Kevin:
Which transmission do you have? The later model transmissions have a slower 4th and 5th gear
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#47 Reply
Posted by
Stpltn250r
on 09 May, 2013 14:40
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hes got the 88-90 ratio trans.
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I dobt see how thats possible getting those speeds my bike only hitts 88mph with 15-40 gearing on a track.
Late model 5th gear
88MPH
15-40 gearing
20" tire has a theroretical roll out of 62.8"
Theoretical RPM would be 7687 for 88 MPH
Race track RPM would be higher because of some tire slip if there was not any tire growth.
Race track RPM would be lower if there was tire growth and not any tire slip.
None of these calculations are accurate unless all variables are known, but these calculation show that your gearing is allowing you to go through the lights at the engines approximate power peak
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#49 Reply
Posted by
Zilla273
on 20 May, 2013 19:09
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well I installed a 15 counter gear, that really jumped up the gearing. now gearing is 15-38 with 20inch tires(big for 20s). I did one pass, I got 93.5 just shifting fifth then I backed it down, I need to make it handle better for anymore then that! Im more impressed with how well it handles the higher gearing then anything, also we have a drag track that's about 400ft in a local sand pit, its faster on that track with this gearing then it was with 14-42! I launch 2nd gear with this gearing and the wheel speed just sends it, I think with paddles 15-40 would be perfect
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