help!! Top speed 85mph on 650L

[Xr650LMartin]

I dont know whats wrong, i cant get over 85 mph on my 00 Xr650L, its desnorkelled, slide drilled, uni filter, needle shimmed, stock exhaust with baffle out, rejetted 158/55. The bike has 6000 miles on it and I believe valves never been adjusted. Could that be it?? I'm not a great mechanic but i think rpm's dont get as high as they should. the bike sounds the same at WOT in 3rd gear as it does in 5th at 85 mph! Thanks for any replys! ?

[NukBoy]

It could be the valves or it could be your jetting. To get my XR650L over 100mph I have to be going downhill with one arm behind my back, and the wind behind me. One other consideration is wind. That bike has low end torque but the high end is weak. If you have recently gone to a bigger floppy winter time jacket you may be experiencing DRAG. Have you Checked your Plug? Why haven't you run your valves yet? Are you rich or lean? Are you using your choke or not to start it up?

I recommend if you wan't help, do not admit you are French.

[Xr650LMartin]

I havent check the valves cause i just got the bike 2 months ago and have no clue on how to perform a valve check. Ill try gettin a new plug first, its probably the original one still on. the previous owner was an old man who did only road with it..thanks for the clues

[cheff]

My XR will do 85 90 when heading home from work. That's with the coastal wind behind me. In the morning on my way to work I can hardly keep it at 75, against the coastal wind. This bike is just not a fast bike, it has tons of low end torque but the wind drag at anything over 65-70 can really affect the top speed.

If you went with a 15-43 or 16-45 gears you might be able to get it up to 100.

[jamesp]

If you went with a 15-43 or 16-45 gears you might be able to get it up to 100.

You wouldn't go any faster because the XRL won't pull 5th gear with stock gearing....but it will go 100mph according to the speedo.

[jamesp]

What gearing are you running? Does it feel like its winding tight when fully revved out or does it feel weak? Is it a Keihin 158 main or one of those dynojet mains? Does it feel like it is running hot? What is your top speed in 4th gear?

Definitely check the vavles.

[Xr650LMartin]

i run 14-45 sprockets for last 2 weeks but it didnt go any faster with stock gearin (15-45) The main is a 158 keihin and yes the bike feels weak on high rpms and no its not running hot. top speed in 4th is about 72 mph

[cheff]

i run 14-45 sprockets for last 2 weeks but it didnt go any faster with stock gearin (15-45)

Actually with 14-45 you will lose top end compared to stock

[jamesp]

Actually with 14-45 you will lose top end compared to stock

No you won't. A stock or slightly modified XRL will generally go the same speed or slighly faster in 4th because 5th is too tall for the horsepower available with 15/45 gearing.

[jamesp]

i run 14-45 sprockets for last 2 weeks but it didnt go any faster with stock gearin (15-45) The main is a 158 keihin and yes the bike feels weak on high rpms and no its not running hot. top speed in 4th is about 72 mph

It sounds rich on the main jet but 155/158 should be about right for the mods you have done. I forgot to ask your elevation.

Anyway, definitely get the valves checked. That can make a tremendous difference and 6000 is too long. Also, you can check to make sure your carb slide can go all the way up and that nothing is interfering. You can disconnect the rear boot and get your finger in there to do this. I am not sure how much you know about bike maintenance so I'll just mention that you don't want to over oil your air filter. I wouldn't bother with jetting changes until you have checked these things. Also, I doubt replacing the spark plug is going to get you 10-15 mph more.

If everything checks out, you can go 160 on the main to see if you lose even more speed. If so, go to a 155 and see if that gets better without causing excessive heat. If you start getting too lean, it will feel like it is winding tight.

Other than the lack of top speed, how does it run? Very responsive off start? How does it accelerate from 35-50 in third gear? How easily does it start?

[Dual_Dog]

i run 14-45 sprockets for last 2 weeks but it didnt go any faster with stock gearin (15-45) The main is a 158 keihin and yes the bike feels weak on high rpms and no its not running hot. top speed in 4th is about 72 mph

Two things to consider. Crank rpms and countershaft sprocket rpms. A larger css spins faster at any given crank rpm. A smaller css spins slower. Slower rotation speed equals slower mph. Now acceleration is a different matter. That will increase.

Go back to the 15-tooth. That's what the bike was designed for, unless you plan on riding more off-road than on. I swap between 14- & 15- depending on the type of riding. My $0.02.

[NukBoy]

You must understand that there is not really much you can do to get it faster than that. 100mph is really the max, maybe 105mph with Mods. And not to mention the whobble the bike can get over 85mph. High speed wheel wobble and endshake on that bike is no joke. It will quickly get more severe if you do not let off or quickly get all your weight on your pegs. It has killed more than one person.

I have been able to add an extra 5mph using Sunoco GTplus racing fuel. It is 104 Octane and is three times higher oxygen then VP. The gain does not outweigh the cost though.

If you want a faster motard just trade it in for the new KTM 800cc coming out in 05. You need to change the gears for greater torque at low speeds instead of higher top end speed. From the factory it a wheelie monster. Dropping a tooth on the front sprocket increases that more. ?

[cheff]

Actually with 14-45 you will lose top end compared to stock

No you won't. A stock or slightly modified XRL will generally go the same speed or slighly faster in 4th because 5th is too tall for the horsepower available with 15/45 gearing.

Maybe you wont, but in theory you will lose top end. I run 13-45 and can go just as fast as I did with 15-45, and feels more responsive at the top end. I am sure it feels more reponsive since I can now use the power in 5th. Before it just did not have the pull in 5th with the high gearing.

[NukBoy]

One last thing. Make sure you check the speed rating of your tires. Stock tires are for not exceeding 82mph for a sustained amount of time. If you are spending more time on the street get street tires. The factory 50/50 tires are greasy as hell if you are carrying any speed through corners on concrete.

[DesertWill]

The powerband on the big single is different than most motorcycles, it's a torque machine and max torque is found at only 3800 rpm. I short shift mine on the front side of the torque curve when I run it up through the gears as it doesn't accelerate any better when I get on it. At top speed, it's reving past max torque. Therefore, going to a 14 tooth sprocket won't help the bike be on the power curve (at max speed on flat highway).

On flat ground my XRL goes 88 w/ a 14 tooth cc sprocket & 92 w/ the stock 15 tooth. It vibrates a lot more at 65 w/ the 14. After running w/ the 14 a while I went back to stock as it wasn't an advantages for me. The 14 worked better for slow 1st gear stuff like deep sand washes as the bike is a pig. Here's a link to a dyno chart.

http://www.motorcycle-usa.com/Article_Page.aspx?ArticleID=71&Page=7

[jamesp]

I don't see what torque peak has to do with top speed really. If the gear ratio is too tall for it to pull at max RPM, it isn't going to pull it no matter where the torque peak is. You are obviously going faster at 8000 rpm than you are at 4700, so regardless of your sprocket combination, you aren't going to be in the strongest part of the powerband when running top speed. At 55mph, I can see where you might have a point.

But there's no sense in continually arguing about it. Everybody who wants to know only needs to top it out in 4th and then top it out in 5th and see for themselves. If your bikes are like the two I own, it will probably go the same top speed in 4th and 5th, maybe even faster in 4th. It helps to tuck in to reduce the wind resistance.

It is obvious that they geared it taller than the xr600 for MPGs and to preserve the engine on the highway, but if you don't care about that, and want the acceleration, then there is nothing wrong with running a 14 tooth front.

Thanks for the link to that article, I was curious how those two bikes compared ?

[smashinz2002]

Well, maybe this suggestion will end all those arguments: Get rid of the XRL and get an XR650R, uncork & re-jet it. Then you will have a bike, with stock gearing, which will do 100mph even if you're wearing a jacket and going against the wind.

And it won't wobble or shake, it runs true and straight at 100mph.

However, a lot of people complain that the 650R does not have e-start, requires an effort to make it street legal, and for many people, produces way too much power to be comfortable with.

Personally, I think it's worth it to get an "R" and make it street legal. However, the intense power takes some getting used to, especially on pavement where you get full traction. A loose grip on the bike is not recommended. Full attention is required at all times, and this can be tiring to many riders.

LL.

'00XR650R/uncorked/jetted/street legal

'04KX500/fmfgnarly/radvalve/illegal

[DesertWill]

Jamessp, As you can see on the Dyno chart peak horsepower is at 6000 rpm. At 90 mph or so, with stock gearing, the bike must be turning more rpm than that. Lowering the gearing, for top speed, seems like the wrong way to go.

[jamesp]

If the bike had unlimited power, it wouldn't make sense to lower the gearing for top speed. But it doesn't have unlimited power, and at some point, you will quit gaining top speed by gearing taller. On a stock or desnorkled and rejetted XR650L, it seems like that point of no return is right about 14/45.

Think of it another way, 14/45 may give it the mecahnical advantage to be able to turn the full 8000/8500 rpm with the 20hp available that high in the powerband. But if you make the gearing taller, it loses the mecahnical leverage it needs and may not even make it to 8000 rpm because it only has enough horsepower to pull that gearing lower in the RPMs.

To demonstrate, try 15/39 gearing and see how fast you go in 5th gear on flat ground. It won't be any faster than stock gearing of 15/45 and I'd bet it would be significantly slower.

[budinsac]

I have a 2000 with similar mods, and I have found that with a 155 it will rev much higher, than with the 158. It is much smoother at high speeds with the smaller jet. I'm running 15/48 gearing and have had it up to 90 with some pull left over(fast enough for me). I'm 6'4" 230lb and was not tucked in. It seems that everyone is running a 158 main, but it is just too rich for my bike.

Bud