Sticky throttle on XR650R


7 replies to this topic
  • Kirk_Moon

Posted September 20, 2004 - 03:34 PM

#1

I have been trying to use my '01 XR650R as a street bike with 17" wheels. I like it and have been having fun, but I have had a problem with the throttle response and I'm not absolutely sure where the problem is.

My problem is that the transition from power off to power on is quite abrupt. The throttle feels sticky and I feel a fair amount of resistance to turning until I actually crack it open a bit, then I get this abrupt power surge. Once I am back on the gas, the throttle response is smooth. I am having a lot of trouble getting back on the gas without messing up the balance of the bike in mid turn, which kind of messes up the whole supermoto thing.

I have taken off the throttle tube and cleaned the handlebar and lubed the cable attachements at the handlebar. I haven't been able to lubricate the throttle cables themselves, and I haven't looked at the carb yet. I don't think this is a cable problem, though.

Is this common? Is this resistance to the initial cracking open of the throttle a "feature" of the stock carb?

I have an Edelbrock carb on backorder. I think this will come with new cables and I really hope this solves the problem.

Has anyone else experienced this?

Thanks in advance.

Kirk Moon

  • qadsan

Posted September 20, 2004 - 03:57 PM

#2

It could be mechanical if something truly is binding. Try loosening the throttle/grip and reposition it slightly to the right of its current position and re-test it. Make sure your throttle cable routing is smooth and isn't binding as it enters the frame. Sometimes these cables can be pinched by the fuel tank mounting bolt if you're not careful when installing the fuel tank, so make sure nothing is binding there. If there's nothing mechanical binding the cables, then my guess would be it's either related to your jetting or the 'ACV' Air Cut Valve (AKA coast enricher) on the carb. I think the ACV on this carb may be the source of trouble for a number of people, particularly those who notice snatchy throttle reponse (abrupt power surge) while on the street during decel/accel transitions. There are ways to modify / disable the ACV, but I would try the Edelbrock first as your throttle response can be tuned to be smoother.

  • gav_114

Posted September 20, 2004 - 04:18 PM

#3

check the cable, turn your bars to the left and see if it sticks then turn to the right and see if it does the same thing, on mine the cable was wrapped under tha bars causing them to clamp in when turning left try that

  • tirebiter

Posted September 20, 2004 - 06:22 PM

#4

check the cable, turn your bars to the left and see if it sticks then turn to the right and see if it does the same thing, on mine the cable was wrapped under tha bars causing them to clamp in when turning left try that


I think I found the reason the throttle cables "stick" when hard turning to either side..As mentioned, they can be mis-routed when installing the tank, but I think the cables get held tight after installing the tank, allowing no 'flex'. This causes the cable to grind against the inside of the cable housing on one side, all along it's travel- creating friction.
I loosened up my cable adjusters a little at the carb, problem solved. Allowed the cable itself to float freely in the housing at any bar angle..

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  • Old_Man_Time

Posted September 20, 2004 - 09:11 PM

#5

check the cable, turn your bars to the left and see if it sticks then turn to the right and see if it does the same thing, on mine the cable was wrapped under tha bars causing them to clamp in when turning left try that


I think I found the reason the throttle cables "stick" when hard turning to either side..As mentioned, they can be mis-routed when installing the tank, but I think the cables get held tight after installing the tank, allowing no 'flex'. This causes the cable to grind against the inside of the cable housing on one side, all along it's travel- creating friction.
I loosened up my cable adjusters a little at the carb, problem solved. Allowed the cable itself to float freely in the housing at any bar angle..



It sounds like you have your cables routed underneath the left tank mount (you know the mount that you bolt the tank to the frame). The tendency of the cables is to fall below (underneath) the left tank mount. When you lower the tank into position reach up underneath the tank on the left side and push the throttle cables above the tanks rubber mounts. They must be routed this way or you will have the problem you describe. When routed properly you will not need to loosen the cables as you have done.

  • gav_114

Posted September 20, 2004 - 09:49 PM

#6

interesting i may have to check that out,
p.s old man how do the ktm 525 and the 650 stack up to each other? have always wondered

  • Old_Man_Time

Posted September 21, 2004 - 08:18 AM

#7

The 525 will walk away initially but if there is enough room to keep them both pinned the 650 will catch and pass the 525. I personally never ride either bike that fast.

The 650 is 20 to 25 pound heavier and carries its weight a bit higher so you feel the weight a lot more than you do on the 525. You can go faster in the tight stuff on the 525 because of the fact that the weight it distributed much better. The 650 can be ridden sitting or standing but the 525 is too hard on you when you sit. For me its hard to really compare the two since they both have their strengths and weaknesses. They are both awsome bikes. The 650 is easier to keep up the routine maintenance. It is closer to a ride and park bike. The 525 is a pain to maintain but a joy to ride.

As I've said many times I prefer the 525 in the tight stuff and the 650 in the more open terrain where you cover a lot of ground for a long period of time (Desert/dirt roads).

If I were purchasing one bike which needed to last for many years and did not have alot of cash for upkeep I would choose the XR650R over the 525. It is very capable in the tight stuff as long as all you care about is getting the job done. In other words it is an all around bike which will take a beating and keep on ticking. I'm glad I didn't have to make that choice at this point in my life. :cry:

It's hard to say anything bad about the 525 and it's only flaw is in the area of longevity. But that is the price you pay to have a nice handling, powerful relitively light race bike with an E-Button.

  • tirebiter

Posted September 24, 2004 - 06:38 PM

#8

Nope, cables were routed correcty.
I just tested my theory on three 4strokes, a honda, yamaha and a Kawasaki. All push/pull throttles.

I made sure all the front wheels were facing forward and took all the freeplay out of the throttle cables, all the time making sure every throttle snapped back home.
After cranking the handlebars to the left, the throttles on all three were in a state of bind.

On all three I made sure the cable was still sticking while it's the bars were still cranked to the left. loosened up the cables a tad on each one, throttle snapped home.

Don't believe me? Try it- I'm an old fart too....





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