Sprocket sizes for 650L - street-only config question . . .

[AZRoadRunner]

I know most folks go for lower gearing but has anyone experimented with higher gearing for the street? If so, can you go 16T on the front? Or is it better to go less than 45T on the rear? Is this sort of gearing change even advisable? I know thumpers don't like to be lugged . . .

[AZRoadRunner]

Found this in the FAQ (imagine that!):

Sprocket Specialists part number 514x-16 (16T) .Makes a great highway sprocket. Very easy to change. I've used one for 5 years.

Does this one extra tooth on the front sprocket require a longer chain? I think the answer is "no".

[akarob]

I think the stock gearing is best for the street. If you go with a higher ratio, you'll lose acceleration to gain top speed. What's more important to you?

Personally, I don't feel safe going as fast as stock gears will take me so I wouldn't want to go faster.

[AZRoadRunner]

I think the stock gearing is best for the street. If you go with a higher ratio, you'll lose acceleration to gain top speed. What's more important to you?

Personally, I don't feel safe going as fast as stock gears will take me so I wouldn't want to go faster.

You are most likely correct. I was reading an old thread and it stated that the oil temp rose when on an extended slab ride at 70 MPH but the temp cooled off when he slowed a bit. More than anything I'm just curious about higher gearing.

[Captain Midnight]

Found this in the FAQ (imagine that!):

Quote:

Sprocket Specialists part number 514x-16 (16T) .Makes a great highway sprocket. Very easy to change. I've used one for 5 years.

Does this one extra tooth on the front sprocket require a longer chain? I think the answer is "no".

I think that was me you are quoting. Stock chain works fine. The 16t lets you shift back and forth between 4th and 5th. It also pulls longer in each gear.

[akarob]

Yea, I was thinking that with the right street tires (sumo), balanced and all, the bike would run nice with a little higher gearing.

[Purcell69]

I never ran the 16 tooth, unlike Capt. Midnight. I did dabble with rear sprockets trying both a 42 tooth and a 44 tooth. The 42 was about equal ratio-wise to the 16/45 combination. I did not like the way the bike started from a stop and had to ride in 3rd gear in 35 mph city traffic. Also, in the Springtime Oklahoma winds, it did tend to rob the bike of power and did not seem to do much in added economy. The 15/44 seemed to be a better combination for me. I was running stock rims and not a sumo set-up.

YMMV.

-Joe

[AZRoadRunner]

I think that was me you are quoting. Stock chain works fine. The 16t lets you shift back and forth between 4th and 5th. It also pulls longer in each gear.

Thanks!

[AZRoadRunner]

Yea, I was thinking that with the right street tires (sumo), balanced and all, the bike would run nice with a little higher gearing.

I just purchased the Pirelli MT90 A/Ts - waiting for the 600-mile service for the dealer to install them.

[AZRoadRunner]

I never ran the 16 tooth, unlike Capt. Midnight. I did dabble with rear sprockets trying both a 42 tooth and a 44 tooth. The 42 was about equal ratio-wise to the 16/45 combination. I did not like the way the bike started from a stop and had to ride in 3rd gear in 35 mph city traffic. Also, in the Springtime Oklahoma winds, it did tend to rob the bike of power and did not seem to do much in added economy. The 15/44 seemed to be a better combination for me. I was running stock rims and not a sumo set-up.

YMMV.

-Joe

Thanks. I'm not sure I will change sprockets. I'm waiting until I get the Pirelli (mostly) street tires mounted and see how it feels on the slab at 60+ MPH.

[painter]

I am going to try 16T this spring. my bike is a commuter, 5mi @50mph and 30mi at 70. just wanna drop rpm on the freeway.

[HMFL]

I use 15/42 gearing currently with good results. If you ride interstate mostly, I would recommend 40 tooth rear.

[Onederer]

The XR650L gearing is optimized for the power. If you are going for a land speed record:) in perfect conditions, and the bike is stripped down, then taller gearing may be the ticket, but in the real world if you are traveling loaded, and facing headwinds, trying to sustain 70mph with taller than stock gearing will keep you wide open in 5th or higher RPMs in 4th. Just because the throttle is wide open doesn't mean the engine is turning max RPMs, it just means the engine is at maximum power. Sometimes, slightly lower gearing will increase top speed at the expense of higher RPMs because of mechanical advantage(leverage). When you climb a hill on the highway and have to shift down, same reason, limited power.

You already loose power in 5th gear anyway because it is over driven, meaning the output shaft is turning faster than the engine. 4Th gear is 1:1, after that you loose torque.

Just suggesting that unless you go to a shorter wheel like a 17", taller than stock gearing on a XRL is not the best route. Getting more power from the engine and going to taller gear would work, but you'll also increaes stress on the engine, so it won't last as long anyway and more than likely will get less MPG. The stock setup is about as good as it gets for economical transportaion use, of course substantinaly loweing the suspension, taking off the front fender and adding a full fairing would help, but then why not just buy 500cc sport bike.

[jakson]

I'm currently running 15/40, and feel there is very little discernible drop in acceleration or top speed. Speeds through the gears I calculated (@6000rpm) are: 31mph(1st), 51mph(2nd), 67mph(3rd), 84mph(4th), 99mph(5th).

As I hate fighting wind blast, my preferred highway cruising speed is 65mph. Which at that speed the motor is turning over 3925rpm (vs 4415rpm for 15/45). Simply rolling on more throttle in 5th provides adequate acceleration for passing in most all situations.

The only downside I found with this gearing is a greater degree of chain snatch striking the the swing arm's top chain guide which can be felt as a vibration through the frame.

BTW, the 40T sprocket is for a XR650R. I drilled out the 8mm holes to 10mm and purchased M10x1.5x35 countersunk bolts and matching lock nuts.

[Benesesso]

You already loose power in 5th gear anyway because it is over driven, meaning the output shaft is turning faster than the engine. 4Th gear is 1:1, after that you loose torque.

Power and torque are two different things. You don't lose any more POWER in 5th than 4th because 4th is still thru gears, even tho the ratio is 1:1.

[Horri]

I read a lot of threads here where people say they do extended 70mph plus freeway runs on stock gearing. All I can say is the engine must be screaming. I run all my bikes at 15/39 if I can find a 39..if not it's next size up on the rear..Never found a 16 front down here or I'd be using 16/39..I just like the lower revs at higher road speeds and don't care about having to ride the clutch a bit in lower gears if I run into a traffic jam,,We just do the "up the middle trick" down here should we run into jams..Sort of illegal but they don't bother enforcing it. I don't ride bikes to sit behind cars in traffic jams as it.kinda defeats the purpose of owning a bike for transport if you just follow the cage drivers around,,,freedom lost.

Edited January 31, 2010 by Horri

[AZRoadRunner]

OK. After riding my 08 XR650L on the street for 300 miles I agree with what several posters in this thread have stated: the stock gearing is just about right--no need for the bike to be geared any higher.

[Old Dog]

OK. After riding my 08 XR650L on the street for 300 miles I agree with what several posters in this thread have stated: the stock gearing is just about right--no need for the bike to be geared any higher.

... unless you're running a Sumo setup (17 inch wheels), then you're better off going a few teeth lower (40 or 42) on the rear sprocket.

[Captain Midnight]

I have an 17 inch rear wheel and 52hp. A 16-45 combo works good for that.