overdrive sheave

Overdrive YES or NO

I originally beleived OD had merit. Then after this thread progressed I thought maybe it would not be worth the effort for very little benfit. Matts cracked sheath and 1-2 mph gain seemed as though if would not be worth the trouble. A big thankyou to Bufalo Bob, Scott , MrViper Who all contribute to this board and we certainly respect their testing and field experiances. I dont have timers to prove the benifits positive or negative. Maybe I will call the Mythbusters. Anyone know of timing lights that dont cost a fortune? I'm guessing a radar gun would be worthless for a test? With timers I may attempt overdrive and report the results here. I purchased a brand new Apex clutch with 50 miles on it from Ebay about two weeks ago and it may go in the lathe. Thanks everyone.
 

mac:

never be afraid to think outside the box. a lot of great products were developed by people who were told " it can't be done that way ".
the fissure cracks are normal on yamaha primarys, cut or uncut. if you can't afford timers or a radar gun buy a gps ( they're cheap ) a pen & notepad & start testing. none of this stuff is rocket science but it does take time.

bob
 
taller gearing

mrviper700 said:
mac,

I will say 1;1 ratio is well before the clutch closes the sheaves together.1:1 is with the belt about 1/2 to 5/8 up the sheaves in the front, you can see exactly what ratio your in if you use this formula: engine rpm x sprocket pitch diameter divided by your MPH x gearing x 336

Lower gearing is faster on take off but only out so far and that depends soley upon the traction available! In the grass race example we are talking 60ft times, some sleds gain more by gearing taller in the 60ft because less time is spent spinning the rpms and more time spent moving the sled forward.
Like madmatts sled example, he got better traction from the taller gearing which improves your 60ft time(take off) if you have more engine power taller gears can be even faster if the sleds power to weight ratio is in check.

The trick is too gear as tall as you can without losing your acceleration, thats your decision on how far you go, remember the steeper the gear the less traction youll most likely get from excessive spinning of the track.
Click to expand...
Without solid traction good luck gearing down because you'll be spinning worse and the person next to you will be driving away.Ran 3 years on the tar and i found a lot of good things gearing for more topend.All my testing was done on lights with a full racepack download system. More topend gear starts showing up right around 500ft your mph goes up. Gearing down can sometimes be like advacing your timing it all depends track conditions and the distance of the track your racing. In the end TALLER GEARING works for me i've had great results and beat a lot bigger cc sleds then mine!!!!!!
 
oh no srx1000, you cant be right according to these 3 guys they dont need anything but overdrive and deep gears,,,,,,,LOL!! Glad to see other people dont live in a fantasy world and know how to apply the power to the ground and more of it, faster......Obviously you have done your homework!


Scott, prove you right...LOL.....your applying less power in O.d. 10hp less in your example.......LOL :rofl:

buffaloBob, I know how you got to work, it was on a 10 speed bicycle, so you can backpeddle......I see you again "know too much to simply read something you dont know how it works... You bypassed answering someone offering you real free information, but when you "think" you know it all, I guess its hard to swallow your pride and open your mind.
"Make sure you have a good belt cover" -as the belt likes to explode in O.d. due to excessive belt spped.....thats the best one yet, lets promote something dangerous on here for others to be injured by..... :Moon:

Go on with your comments................LOL
 
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mrviper:

my results using o.d. clutching:

NBSSR IS700 ( SRX ) undefeated 4 years in a row & record holder @ 135.2 mph. sold sled 2 years ago to jim marsten from maine.

NBSSR Trail IS900 ( 835 SRX ) undefeated & record holder @ 126.9 mph with 1" camo track, 240 megabites & reverse.

IS700 @ lancaster speedway 1/8 mile @ 760# with driver ran consistant 1.35 to 1.39 60' & 6.2's @ 108 - 111 mph. stock suspension, stock rear wheels.

bob
 
Bob - not to steal the thread, but how much difference is there in the IS700 and Trail IS900 classes? - what kind of mods are allowed in the IS700 class? - obviously the 700 must of had more hp and not stock?!?! - to look at it on the surface, it does not make sense that the 700 would be faster than the 835, but I know nothing about this racing!!
 
yammiman:

good questions.
the IS700 & the Trail 835 had about the same peak h.p. ( 190 ). the 835 has 118 lbs. ft. torque & the 700 had around 105.
the 700 was a race sled: lowered, high comp., hi rpm bender pipes, race cdi, 10 tooth proline alum. drivers, 1/2" closed window track, no hifax & on & on & on.
both motors were built by bender racing & have never had a problem to this day. there was more speed left in the IS700 - i believe around 140 mph would have been possible, i just got bored & sold it.
the 135.2 mph was @ 13% o.d.. & the 835 has already ran 15% o.d..

bob
 
srx102.That one the alcan 200 a few years ago witrhh a 175hp cpr 780 in his srx ran 141mph with gearing up and no over drive.It's all in the set up I guess.Yes gearing up get you mph so does overdrivebut when your drag racing and using overdrive your not putting as much hp tothe track because it's not as ifficent.Please lets this go to rest or this thread will be locked.Thank's
 
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