Two Stroke Motocross

Two Stroke Motocross Forum => Technical => Topic started by: Twostrokepower!!! on March 11, 2012, 01:48:37 AM

Title: Rear sproket drop?
Post by: Twostrokepower!!! on March 11, 2012, 01:48:37 AM: Hello, i have a modded kx85. I have been wanting to experiment with gearing, i wanna gear up i believe. by dropping 2 teeth on the back sprocket. I want to do this because since it has aftermarket motor parts and stock gearing i feel like it revs out too fast in a gear and has so much more potential in each gear. I know this will be a pain for keeping it in the powerband and such. But will these changes aquire my desired results? Thanks
Dan
Title: Rear sproket drop?
Post by: SachsGS on March 11, 2012, 03:47:46 AM: Motor modifications, your weight and ability,and the gearing you are running now?
Title: Rear sproket drop?
Post by: Twostrokepower!!! on March 11, 2012, 10:53:59 PM: Pipe and silencer, high flow carb, reeds, ported, polished, lightweight piston, hot rod crank.
130lbs (heavy for it) expeirianced on the bike.
Stock gearing
Title: Rear sproket drop?
Post by: TotalNZ on March 12, 2012, 07:59:18 AM: Are you reaching top gear alot is more to the point, they gotta be quite low geared to stay on the pipe.
I take it you flat shifting it already? ie changing gears without backing off the throttle, this is key on the 80,s and 125's i reckon.
Title: Rear sproket drop?
Post by: Twostrokepower!!! on March 12, 2012, 09:52:36 PM: yes i power shift, and hmm well i think it will make each gear wider and i think it has enough powr for it...
Title: Rear sproket drop?
Post by: eprovenzano on March 13, 2012, 05:43:48 PM: Dropping two teeth will have a huge effect on an 85. One thing to also consider, where is the rear axle as far as chain adjustment goes? I lke to run mine as far back as possible as it helps keep the front wheel on the ground a little bit more. I thinking one tooth may be where you want to be. Plus you would most likely not have to remove a link from the chain and this would move your axle back more towards the rear. This option would allow you to switch between the two set-ups depending on the track and track conditions.
Title: Rear sproket drop?
Post by: Twostrokepower!!! on March 13, 2012, 08:38:19 PM: Thank you!! that was just the answer i was looking for. Ill let you guys know how she turns out!
Title: Rear sproket drop?
Post by: Twostrokepower!!! on March 15, 2012, 11:03:35 PM: So ive seen alot and people say they are already geared too high.. does anybody have personal experience? should i drop a tooth or add a tooth?
Title: Rear sproket drop?
Post by: Twostrokepower!!! on March 24, 2012, 02:46:27 PM: Well they sent me the 49t... with a 12t front sprockert now it does exactly what i was trying to get rid of... but worse!
Title: Rear sproket drop?
Post by: eprovenzano on March 26, 2012, 01:05:43 PM: I don't know what you had prior to the change, but it you went to a 12 front from a 13... its like adding 3 teeth in the rear. What was the sprocket size (front and rear) prior to the change?
Title: Rear sproket drop?
Post by: beaner on March 26, 2012, 01:54:17 PM: Quote from: eprovenzano on March 26, 2012, 08:05:43 PM
I don't know what you had prior to the change, but it you went to a 12 front from a 13... its like adding 3 teeth in the rear. What was the sprocket size (front and rear) prior to the change?

Do the math. It's like adding 4 teeth on the back.

IMO, 1 tooth on the back is a waste of time. You'll never notice a difference.
Title: Rear sproket drop?
Post by: eprovenzano on March 26, 2012, 05:52:28 PM: Quote from: beaner on March 26, 2012, 08:54:17 PM
Quote from: eprovenzano on March 26, 2012, 08:05:43 PM
I don't know what you had prior to the change, but it you went to a 12 front from a 13... its like adding 3 teeth in the rear. What was the sprocket size (front and rear) prior to the change?

Do the math. It's like adding 4 teeth on the back.

IMO, 1 tooth on the back is a waste of time. You'll never notice a difference.

If I read this correctly he felt it was already geared too low. Dropping to a smaller sprocket in the front is the equivalent of adding three teeth in the rear. Making a bike already geared too low, seem unridable.
Title: Rear sproket drop?
Post by: Twostrokepower!!! on March 26, 2012, 06:34:34 PM: it was 14/50, i wanted 14/49, and i got 12/49. yes it is too low now, revs right out in 6th
Title: Rear sproket drop?
Post by: beaner on March 26, 2012, 07:47:47 PM: Quote from: eprovenzano on March 27, 2012, 12:52:28 AM

If I read this correctly he felt it was already geared too low. Dropping to a smaller sprocket in the front is the equivalent of adding three teeth in the rear. Making a bike already geared too low, seem unridable.

How do you figure it's 3 when the ratio is 3.85 with the 14/50, and 4.1 with the 49/12?

Regardless, 1 tooth on the back is a waste of time. It won't make a noticeable difference.
Title: Rear sproket drop?
Post by: eprovenzano on March 27, 2012, 01:03:10 PM: A change of one tooth in the front is the equivalance of a change of 3 teeth in the rear. Its a cheap alternative to a new rear sprocket. Sorry Beaner, but depending on the bike, one tooth on the back can make a difference. No its not a huge difference, but when your in between gears and cannot find the sweet spot, one tooth may be what you need.
Title: Rear sproket drop?
Post by: MXLord327 on March 27, 2012, 02:24:01 PM: My YZ250 had 14/50 sprockets and I wanted to gear it down a little to get into 3rd gear quicker so I went to a 14/52, and it was too much - 3rd revs out too quickly now. I should have only gone 1 tooth, a 14/51 would have been perfect.
Title: Rear sproket drop?
Post by: Twostrokepower!!! on March 28, 2012, 02:00:11 PM: and especially on an 85 it should make a good chaange
Title: Rear sproket drop?
Post by: Charles Owens on March 28, 2012, 05:24:11 PM: Additional info if needed.

http://twostrokemotocross.com/2010/12/sprockets-and-gear-ratios-what-you-should-know