my bike wont go fast anymore!

[my98xplorer]

I rode about 200 miles last weekend, no problems, but today i went for a ride and its fine at low speeds, but when i get up to about 90 it just wont go any faster. It seems like it just doesnt wanna rev up anymore, like past 6 or 7000 rpm. If you are in 1 through 3 gear, it will go all the way up to redline, but when you hit about 85 it starts acting up. Any ideas?

 

[rodcwer]

pull your plugs you probably aren't hitting on all cylinders.you'll probably find one plug either very black or wet compared to others

 

[duaneage]

I would bet on not enough fuel, clogged tank vent or dirty fuel filter? Petcock problems? try it on prime and see how it does, eliminating the vacuum controlled switch in the petcock.

Since it goes up in the first three gears the ignition system is cabable of delivering spark at that rpm. Higher speeds with greater wind resistance call for more fuel flow and maybe you not getting it.

That is one theory. Try cutting the engine at high speed, coast to a stop and yank a plug. Don't let it idle down or you won't tell whats going on.

Hey, your lucky enough to be riding in Florida with us looking at another &&$%^@# snow storm this week.

 

[KEITH KRAUSE]

I'd say fuel starvation too.
A dirty/clogged air filter would do this too, but you said it ran fine last week. Unless a rag was left in by mistake and moved around.

 

[my98xplorer]

I would bet on not enough fuel, clogged tank vent or dirty fuel filter? Petcock problems? try it on prime and see how it does, eliminating the vacuum controlled switch in the petcock.

Since it goes up in the first three gears the ignition system is cabable of delivering spark at that rpm. Higher speeds with greater wind resistance call for more fuel flow and maybe you not getting it.

That is one theory. Try cutting the engine at high speed, coast to a stop and yank a plug. Don't let it idle down or you won't tell whats going on.

Hey, your lucky enough to be riding in Florida with us looking at another &&$%^@# snow storm this week.

If i coast to a stop and yank a plug, what should or shouldnt happen? And yeah Fl is great, exept today its gonna rain all day

 

[duaneage]

I would bet on not enough fuel, clogged tank vent or dirty fuel filter? Petcock problems? try it on prime and see how it does, eliminating the vacuum controlled switch in the petcock.

Since it goes up in the first three gears the ignition system is cabable of delivering spark at that rpm. Higher speeds with greater wind resistance call for more fuel flow and maybe you not getting it.

That is one theory. Try cutting the engine at high speed, coast to a stop and yank a plug. Don't let it idle down or you won't tell whats going on.

Hey, your lucky enough to be riding in Florida with us looking at another &&$%^@# snow storm this week.

Well if the plug is fouled, too much fuel, white and cleaned off your lean. If you don't cut power and coast down, the carbs will load the plug upn when it idles, masking a problem with the high speed circuits. I don't think you really need to do this, just look around for something that impedes fuel flow.

If i coast to a stop and yank a plug, what should or shouldnt happen? And yeah Fl is great, exept today its gonna rain all day

 

[ard]

I had semilar problem, unfortunatly my problem was the igniter box I replaced the box and the bike ran fine

ard

 

[my98xplorer]

I had semilar problem, unfortunatly my problem was the igniter box I replaced the box and the bike ran fine

ard

is that the box that the plug wires come out of?

 

[RJ]

Does it run rough compared to when you didn't have a problem? If not then it might be something real simple like the throttle cable adjuster coming loose. Worst case scenario the camchain adjuster slacked up, chain jumped a few teeth and now you have 8 bent valves. Kinda unlikely though.

 

[my98xplorer]

Does it run rough compared to when you didn't have a problem? If not then it might be something real simple like the throttle cable adjuster coming loose. Worst case scenario the camchain adjuster slacked up, chain jumped a few teeth and now you have 8 bent valves. Kinda unlikely though.

actually i did have the throttle cable off cause i was gonna put some new handlebars on but they didnt fit. You think maybe something is screwy with that?

 

[RJ]

Yeah could be. Check how much slack you have in the throttle cable by twisting the throttle open while watching the cable connection at the carbs. Pretty much as soon as you twist the throttle, the shaft where the cable is connected to should start to twist as well. If there is a significant delay in that action then you've found your problem. All you need to do is adjust the cable to remove excess slack.

 

[my98xplorer]

Yeah could be. Check how much slack you have in the throttle cable by twisting the throttle open while watching the cable connection at the carbs. Pretty much as soon as you twist the throttle, the shaft where the cable is connected to should start to twist as well. If there is a significant delay in that action then you've found your problem. All you need to do is adjust the cable to remove excess slack.

great i will go try that now. Before i had a bike if i would have heard someone whining that theirs wouldnt do 100 mph anymore, i would have said aww poor baby! Now its driving me crazy that mine wont, funny how that works huh?

 

[my98xplorer]

btt

 

[Jethro]

Does it just feel weak at 90 mph or is it sputtering, coughing and misfireing/fouling at 90? Can you feel a surging at all when you have wide open throttle? Did you have enough road to be able to hold wide open throttle for a while?

 

[my98xplorer]

Does it just feel weak at 90 mph or is it sputtering, coughing and misfireing/fouling at 90? Can you feel a surging at all when you have wide open throttle? Did you have enough road to be able to hold wide open throttle for a while?

As far as i can tell its not sputtering or anything, it just wont rev up anymore to get going faster. I will ride it again tonight be able to tell you for sure. Once i got to 90 and noticed it wouldnt go any faster, i just let up and became aggrevated. Ill try again and see what happens.

 

[Jethro]

These are the things I would check:

1. Make sure the petcock is flowing well. Disconnect all the lines and keep the petcock at the "on" position and suck on the vacumm line. It should flow pretty good, maybe a pint a minute? Make sure that when it is on the "prime" setting it flows just as nice.

2. Check the fuel line. My bike came with 1/4" fuel line, it's supposed to be 5/16". This could cause a problem.

3. Make sure you don't have any leaks at the intake boots. This can feel exactly like fuel starvation. Some people will tell you to spray WD40 at the intake boots. Be warned, this doesn't always work. My bike had two badly cracked boots and the WD40 didn't cause any change in engine RPM's. You'll have to take 'em off and check them by eye.

4. As others have said, perform a plug read at all different RPM's. Your bike may be burning too lean at the high end. You should be able to tell if it's looking that way by 5 or 6k RPM's. Oh, and before you ask (like I did) apparently you can't just rev it in neutral, you have to be running in gear for a few minutes.

 

[duaneage]

These are the things I would check:

1. Make sure the petcock is flowing well. Disconnect all the lines and keep the petcock at the "on" position and suck on the vacumm line. It should flow pretty good, maybe a pint a minute? Make sure that when it is on the "prime" setting it flows just as nice.

2. Check the fuel line. My bike came with 1/4" fuel line, it's supposed to be 5/16". This could cause a problem.

3. Make sure you don't have any leaks at the intake boots. This can feel exactly like fuel starvation. Some people will tell you to spray WD40 at the intake boots. Be warned, this doesn't always work. My bike had two badly cracked boots and the WD40 didn't cause any change in engine RPM's. You'll have to take 'em off and check them by eye.

4. As others have said, perform a plug read at all different RPM's. Your bike may be burning too lean at the high end. You should be able to tell if it's looking that way by 5 or 6k RPM's. Oh, and before you ask (like I did) apparently you can't just rev it in neutral, you have to be running in gear for a few minutes.

Beware of contamination if you decide to suck on the vacuum line.

The fuel line size is probably not an isue, this happened suddenly and unless he replaced the 5/16 with 1/4 line recently it is probably not the cause. might be a intake boot but if one was bad it should still get up there without too much trouble. All four would most likely not go bad at once.

How about the choke? Is it rally on when you think it is off? A choke that is slightly stuck on will cause similar problems.

 

[my98xplorer]

These are the things I would check:

1. Make sure the petcock is flowing well. Disconnect all the lines and keep the petcock at the "on" position and suck on the vacumm line. It should flow pretty good, maybe a pint a minute? Make sure that when it is on the "prime" setting it flows just as nice.

2. Check the fuel line. My bike came with 1/4" fuel line, it's supposed to be 5/16". This could cause a problem.

3. Make sure you don't have any leaks at the intake boots. This can feel exactly like fuel starvation. Some people will tell you to spray WD40 at the intake boots. Be warned, this doesn't always work. My bike had two badly cracked boots and the WD40 didn't cause any change in engine RPM's. You'll have to take 'em off and check them by eye.

4. As others have said, perform a plug read at all different RPM's. Your bike may be burning too lean at the high end. You should be able to tell if it's looking that way by 5 or 6k RPM's. Oh, and before you ask (like I did) apparently you can't just rev it in neutral, you have to be running in gear for a few minutes.

Beware of contamination if you decide to suck on the vacuum line.

The fuel line size is probably not an isue, this happened suddenly and unless he replaced the 5/16 with 1/4 line recently it is probably not the cause. might be a intake boot but if one was bad it should still get up there without too much trouble. All four would most likely not go bad at once.

How about the choke? Is it rally on when you think it is off? A choke that is slightly stuck on will cause similar problems.

My choke cable broke some time ago, and it used to idle around 3 grand, which is high i know, but now the idle seems to have gone back down to about 1500 to 2000, ranging on how hot the bike is. I guess i could check that too. Keep the suggestions coming please!!

 

[KEITH KRAUSE]

My choke cable broke some time ago, and it used to idle around 3 grand, which is high i know, but now the idle seems to have gone back down to about 1500 to 2000, ranging on how hot the bike is. I guess i could check that too. Keep the suggestions coming please!!

Regarding this "high idle when hot".
Is this what your bike has done recently?...Start the bike cold, idles OK, say 1,200 rpm. Once completely warmed up the bike now idles much higher, say 2,000 rpm. You turn down the idle by using the idle adjuster knob. All seems OK for the moment. But the next time you cold start, it won't hold an idle until you turn up the idle adjuster again. Once warmed up, the idle's too high again.
If this has happened, you have an intake leak. Most likely the manifold o-rings (if you have them) or the manifolds or loose clamps. An intake leak can happen anytime, and it only takes one effected cylinder to cause your problem.
If not an intake leak, fuel starvation.

 

[my98xplorer]

My choke cable broke some time ago, and it used to idle around 3 grand, which is high i know, but now the idle seems to have gone back down to about 1500 to 2000, ranging on how hot the bike is. I guess i could check that too. Keep the suggestions coming please!!

Regarding this "high idle when hot".
Is this what your bike has done recently?...Start the bike cold, idles OK, say 1,200 rpm. Once completely warmed up the bike now idles much higher, say 2,000 rpm. You turn down the idle by using the idle adjuster knob. All seems OK for the moment. But the next time you cold start, it won't hold an idle until you turn up the idle adjuster again. Once warmed up, the idle's too high again.
If this has happened, you have an intake leak. Most likely the manifold o-rings (if you have them) or the manifolds or loose clamps. An intake leak can happen anytime, and it only takes one effected cylinder to cause your problem.
If not an intake leak, fuel starvation.

It has always idles high, its just recently idling lower and its so much nicer. Some other people said to check the intake boot?? Where is that on my bike and what is it?