Gearing for fire trails

[wrk2ride_ride2wrk]

Quick poll, the reality top speed of an FT, stock sprockets & tires, carb? I'd check mine but still running in the rebuilt motor. Net says 95mph?

I'm thinking now about the gearing I want for my purpose, fire trails this winter, but still need enough top end to get me the 100 odd klms to tum thar hills comfortably.
http://www.sprocketcalculator.com/

Working on what I have now;
Frnt 15  Rear 42
Web says top speed of;
95mph

If I drop just one tooth on the front
14T   42T   
Ratio; 3.00   
Torque; +6.7%   
Top speed;  -6.7%=88.5mph   

or
14T  43T
Ratio; 3.07   
Torque; +8.8%   
Top speed; -8.8% =86.7mph   


The second option seems to get me closer to the XL500 gearing and top speed
of ...85mph

[J6G1Z]

I'm running a 520 series chain on a mostly stock engined FT Ascot & pulling a 17/39 combination for the street with 17" wheels.

I originally intended to run a 16/39, but the sprocket company sent me the taller countershaft sprocket by mistake, so I tried it. It takes a bit more clutch to get rolling from a stop, but aside from that, I like the gearing. Not sure what it will top out at. I have one of the Rick's CDI units with the rev limiter set on the conservative setting & have bounced off of that a few times.

J.

[J6G1Z]

By the way... Your second option is the easiest to try.

Most folks are trying to increase the top end & run taller gearing.

J.

[wrk2ride_ride2wrk]

well..  I guess I'll put the 14 on frnt anyway see how that goes the I can add to the rear if I still need higher gears.

I want to be able to still sit on 80mph on the slab comfortably, the fire trails are not used for fire access just what we'd call them theyre called "rindo" here they're old mountain foot tracks used to link the old villages through the mountains, twisty and often sick inclines, declines, so street gearing is not going to work out

[J6G1Z]

Are you sure that you want to subject a bike as nice as an Ascot to off-road riding? There not really designed for that. Sure you don't want to locate an older XR or XL 500/600 for the off-road stuff? I don't think the Ascot is going to handle the dirt near as well.

Back to the gearing... I was once told that one extra tooth on a countershaft sprocket is equivalent to adding 8 teeth to the rear sprocket. I'm not sure if this is 100% accurate though. If it were me... I'd experiment with a 13 or 14 tooth countershaft & see how you like it. Sure is a lot easier & less expensive to change a countershaft sprocket then the rear sprocket.

Now that I think of it... I think that I have a 44 tooth rear sprocket that was removed from an '89 CBR600. I can check it out & send you a picture if you are interested in it. Please send me a PM if you are.

Good luck
J.

PS. Have you performed the carb jetting upgrade as explained in this post? http://ascot500.com/index.php?topic=10.0

PPS. If you end up changing both the front & rear sprockets, you may want to seriously consider converting the bike to a 520 series chain & sprockets just like the XR & XL. The Ascots 530 series chain is over-kill on an Ascot. You will remove several pounds of rotating weight from your drive train by swapping to a 520 chain.

[triguyracer]

One tooth on your countershaft sprocket works out to 3 teeth on your rear sprocket plus or minus a hair on almost all bikes.If you change from a 15 countershaft to a 16 countershaft it is like droping 3 teeth off your rear sprocket,if you change to a 14 its like adding 3 to the rear

[wrk2ride_ride2wrk]

Are you sure that you want to subject a bike as nice as an Ascot to off-road riding? There not really designed for that. Sure you don't want to locate an older XR or XL 500/600 for the off-road stuff? I don't think the Ascot is going to handle the dirt near as well.

Pretty sure I explained why I chose the FT for this build in my 1st post

PS. Have you performed the carb jetting upgrade as explained in this post? http://ascot500.com/index.php?topic=10.0

As I mentioned the carb's fine ATM pretty sure the Jpnese carb is not numbed down jet wise, as with US export models

PPS. If you end up changing both the front & rear sprockets, you may want to seriously consider converting the bike to a 520 series chain & sprockets just like the XR & XL. The Ascots 530 series chain is over-kill on an Ascot. You will remove several pounds of rotating weight from your drive train by swapping to a 520 chain.

Good idea, but I'll stick with it, with higher gearing in the pipeline and more than 6% increase of torque at the chain.

[wrk2ride_ride2wrk]

One tooth on your countershaft sprocket works out to 3 teeth on your rear sprocket plus or minus a hair on almost all bikes.If you change from a 15 countershaft to a 16 countershaft it is like droping 3 teeth off your rear sprocket,if you change to a 14 its like adding 3 to the rear

yup, I wanted to change out the frnt 1st (14T) then fine adjust with the back sprocket .. however... couldnt get a 14T, so ordered 45T for the rear..going to make it pricer to adjust if I need to,

 arh... WTH ...who needs two kids in college anyway $$$

[J6G1Z]

College is highly over-rated anyway. 

J.