Gearing.

[evo550]

I need to tighten up my gear spacings, am I right in assuming 1 tooth smaller on the front sprocket equals approx 2 teeth larger on the rear?

[frostype400]

yeah that ratio sounds right you can always alter i would try 1 smaller on front and 2 larger on back thanks Michael.

[mike1948]

Divide number of teeth on the rear sprocket by the number on the front to get the the right ratio.  1 tooth down on the front could easily be equivalent to 4 or more up on the rear.
Mike

[mx250]

I always worked on 1 at the front was about 3 on the rear, not that it matters.

Changing the f or r sprocket won't have much effect on the gaps between gears and even then I think to drop the gearing accentuates gaps. The high gears you hold the gear longer and gain more speed per gear change (provided you have the horsies to pull the gear).

[evo550]

I'm actually trying to lower the gearing, there is a huge gap between gears and top is only obtainable on an airstrip, sprocket gearing is standard for a Husky 250 cr but the bike has been fitted with a xc 6 speed box, great for the finke not real good for an mx track.

[LWC82PE]

1 tooth on the front is equal to about 3 teeth on the rear. If you want to lower the gearing then fit a smaller sprocket on the front and larger on the rear which will lower the overall top speed in each gear, but give quicker acceleration. The only way to change the spacing between each gear is to change the ratios internally.

[motomaniac]

I'm actually trying to lower the gearing, there is a huge gap between gears and top is only obtainable on an airstrip, sprocket gearing is standard for a Husky 250 cr but the bike has been fitted with a xc 6 speed box, great for the finke not real good for an mx track.

What is your current gearing? I tooth on the front can be 3- 4 depending on the current ratio.Some older Euro bikes had a very small front sprocket to start with and a large rear egBultacos.
Get a calculater and divide the rear teeth by the front ,get the ratio and then calculate again with different combo's ie. 1 less on the front same rear or same front 1,2 or 3 more on rear.Dont make too big a change because you just get wheel spin.

[lukeb1961]

a handy gearing, sprockets, chain calculator
http://www.sprocketspecialists.com/SprocketOptimizer2.aspx

[Moto]

Husky six speed boxes were designed to be used as five speed boxes(MX)in a broad way.ie by changing the sprockets you used 2nd to 6th or 1st to 5th to get the desired ratios for different tracks.This gave the bikes a huge range of gearing options. Some owners manuals have gearing charts to show how different sprockets can acheive this.

[evo550]

1st gear is already quite low, the problem is the spacing between the higher gears, 4th, 5th and 6th is very wide, I don't know if sprocket changes will fix the problem without effecting the lower gears

[Nathan S]

It doesn't sound like changing the sprockets will help you much.

A few minutes with a scrap of paper and a calculator will tell you everything you need to know, without having to lift a spanner.

The ratios of most gearboxes get closer together as you get into the higher gears - the gap between 1st and 2nd is usually huge compared to the gap between 4th and 5th. This is because wind resistance increases with speed, so it becomes harder for the engine to pull the next gear. This is particularly apparent in car gearboxes (ignoring late model manual Commodores, which commit crimes against good engineering to neatly deal with emissions issues) - rally cars regularly use this technique to close up the gaps in crappy standard road gearboxes - you lower the diff gearing right down so that you're using the higher (closer spaced) gears for any given road speed.
Obviously, it compromises top speed but top speed is rarely an issue for rally cars - you gain a lot more with the improved acceleration through the gears.

I have a suspicion that the old WR/XC Huskys have odd gear spacings: Big gap from 1st to 2nd, 2nd to 5th are all fairly tight, and then another big gap from 5th to 6th. The advertising of the day claimed that 1st would get you anywhere, 2nd/3rd/4th/5th were the racing gears, and 6th was an 'overdrive' for transports.

This might mean that the gap between 5th and 6th is actually larger than the gap between 4th and 5th. If this is the case, then you should look at gearing it UP, so that you never (want to) use 6th in a race.

If you want to know how to do the maths to quantify all of this, then just ask (its a lot of typing if you DNGAS).

[Lozza]

Yes the pen is mightier than the sword and with this problem, sprokets will help but not cure the issue. I would have to ask why persist with the wide ratio box? Also your rpm drop with each shift might be dropping out of the meaty part of the torque band. A smaller primary drive crank gear will increase torque to the clutch.

[Nathan S]

A smaller primary drive crank gear will increase torque to the clutch.

...and ultimately have exactly the same effect as changing sprockets. Yeah, it might make a difference to your gearbox (XR600/Dominator style), but as far as the rider is concerned, it won't make any difference at all.

(I know that Lozza knows this, just wanted to make it clear to others who might not know).