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Old 05-12-2005, 12:11 PM   #46
txrider
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Quote:
Originally Posted by Loadedagain
so.... does that mean you combine the gear ratios with the primary ratio? for example..

1) 5th 22-18=1.22:1
2) primary = 30-81=0.37
3) an input to 5th of 6000rpm (* 22/18) gives you 7320rpm out...
4) then input to the primary is 7320rpm (* 30/81) and output to the counter shaft sprocket is 2708 rpm?
5) take the 2708 rpm and multiply with desired ratio to get wheel rpm.
6) divide by inches/rev for one wheel rotation... and we've got speed

the only thing here i don't understand is the primary ratio. is that on the output shaft of the transmission? it applies to all gears then.?
Well lets get this figured out as I'm going to be open for this pretty soon now. I've got the 625 SXC now and just ordered up all the DS parts for it so it'll be my main DS ride in about 3 weeks. :)

I'm about to pull the front end off the '96 RXC and change forks, add a fork brace, custom offset triple clamp and a scott's damper. Then I'll be ready to pull the engine and try this gear thing and replace the roller bearing while I'm at it.

I'll post up my gear ratios etc. and see what you guys think would be the best way to go both for narrowing my 1st to 2nd gap and making 5th a bit taller.

What LC4 has the tallest 5th gear btw? I would assume a Duke model but could easily be wrong.
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Old 05-12-2005, 01:39 PM   #47
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Quote:
Originally Posted by txrider
Well lets get this figured out as I'm going to be open for this pretty soon now. I've got the 625 SXC now and just ordered up all the DS parts for it so it'll be my main DS ride in about 3 weeks. :)

I'm about to pull the front end off the '96 RXC and change forks, add a fork brace, custom offset triple clamp and a scott's damper. Then I'll be ready to pull the engine and try this gear thing and replace the roller bearing while I'm at it.

I'll post up my gear ratios etc. and see what you guys think would be the best way to go both for narrowing my 1st to 2nd gap and making 5th a bit taller.

What LC4 has the tallest 5th gear btw? I would assume a Duke model but could easily be wrong.
Yes, the Duke supposedly does have the tallest 5th according to another thread I read somewhere.
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Old 05-12-2005, 01:50 PM   #48
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all information and manuals i can find indicate the duke has the same 22-18 5th gear as all other lc4 engines.

the change is in their final drive ratio (sprockets) which are 17-38 (2003) compared to 16-40 on the sxc (2003) and 16-42 on the 640 (2003).
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Old 05-12-2005, 03:23 PM   #49
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i'm doing up an excel spreadsheet for the hell of it... kinda like maxpowers, but lc4 specific... anything else you guys would like to see on it?

does anyone even want this?

yeah yeah... i know it's metric... i'll do an imperial one too

this is for the stock saharas for those of you who don't have excel:

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Old 05-12-2005, 04:32 PM   #50
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oh yeah.... the spreadsheet can be downloaded here.... lemme know how you like it, or if you want me to make changes.

http://www.ktmcanada.com/lc4_gearing.xls
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Old 05-12-2005, 05:09 PM   #51
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good job Loaded!

now, um, what do we do with it? change the sproket sizes and see what happens to the speeds? change the tranny cogs and... ah. Gotcha!
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Old 05-12-2005, 05:29 PM   #52
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Quote:
Originally Posted by Loadedagain
all information and manuals i can find indicate the duke has the same 22-18 5th gear as all other lc4 engines.

the change is in their final drive ratio (sprockets) which are 17-38 (2003) compared to 16-40 on the sxc (2003) and 16-42 on the 640 (2003).
I looked through the fiche and couldn't find a Duke that used that 583.33.008.006 "GEAR 5TH M/S 27T", but who knows. Did you ever get more information from steelhead on that thread?

http://ktmtalk.com/index.php?showtopic=107044&hl=5th
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Old 05-12-2005, 05:39 PM   #53
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Originally Posted by potatoho
I looked through the fiche and couldn't find a Duke that used that 583.33.008.006 "GEAR 5TH M/S 27T", but who knows. Did you ever get more information from steelhead on that thread?

http://ktmtalk.com/index.php?showtopic=107044&hl=5th
nope... nothin, but i gave it a bump anyway.
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Old 05-12-2005, 05:39 PM   #54
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Originally Posted by meat popsicle
good job Loaded!

now, um, what do we do with it? change the sproket sizes and see what happens to the speeds? change the tranny cogs and... ah. Gotcha!

what can i say? i'm an engineer.. we're wierd ass spread sheet lovin homos
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Old 05-12-2005, 08:57 PM   #55
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Ok here is what I've found/figured out so far.

My owners manual shows this...

Primary ratio 30:81

1st 14:35
2nd 16:24
3rd 18:21
4th 20:19
5th 22:18

I read that they changed the 2nd gear in 97 or 98 and the fiche shows a #56533010300 for a 15 tooth mainshaft. That would close the first to second gear ratio that me and others didn't like on the '96 RXC. Looks like most LC4's after 96 use this gear.

1st 14:35
2nd 15:24
3rd 18:21
4th 20:19
5th 22:18

The '95 shows a 15t first and a 16t second, would make a closer ratio overall without a gap from second to third I would have with a 14t first and a 15t second. They called the '96 a "wide" transmission. using a '95 first gear would give..

1st 15:35
2nd 16:24
3rd 18:21
4th 20:19
5th 22:18

I think that might be the best bet but I am not so up on the math to convert that to RPM and speed.

So what do you engineer geeks think?

Use a 15 first for close ratio and add the 27t fifth for overdrive?

Or leave the 14t first, go to a 15t second and a 27t fifth for ultimate wide ratio tranny with overdrive??

I have a 3 day ride in Wyoming June 10th, after that I'm free to go for it. I want to close up the first/second gear gap, have since the first single track I rode it on. If the fifth will fit I'll do it as well.
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Old 05-12-2005, 09:10 PM   #56
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I have a 40 tooth rear on now, and I have a 14 tooth counter sprocket in the garage... Does this look insane??

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Old 05-12-2005, 09:42 PM   #57
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Quote:
Originally Posted by txrider
I have a 40 tooth rear on now, and I have a 14 tooth counter sprocket in the garage... Does this look insane??
insane? define insane... i've got a 16, 17, 38, 40, and 45 on order... should be here tomorrow. i will get the perfect combo figured... i promise.

chains? well.... that's another story... i figure i can get all ratios combined into two or three chains. two of those coming too
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Old 05-12-2005, 09:52 PM   #58
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Well I've got a 48 and 52 tooth in the garage as well, I ran a 16/48 for a while but went back to a 16/40 for highways swapping out to a 15/40 for dirt.


So does that chart look like a the perfect LC4 gearset?
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Old 05-12-2005, 09:58 PM   #59
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Originally Posted by txrider
So does that chart look like a the perfect LC4 gearset?
define perfect.

i've got a dirtbike for dirt, so my 640's ideal gearing is ideally suited to 80 mph at a reasonable rpm... for road use. your gearing may be different.

for my 640's dirt wheels i have a 48 tooth sprocket that i ordered for my old exc and seems to work all right. if i ever use it in the dirt for long periods of time i'll prolly play with those sprockets.

for now i'm playing gear boy... arch set me on this course... it's all his fault. if i find the holy grail i will never tell.
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Old 05-12-2005, 10:00 PM   #60
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I am planning on running a 16/44 and swapping out for a 17/44 for highway use. These combos are just above and below stock gearing.

I want me one of those fancy STEALTH sprockets and the smallest they make is 44T.
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