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Old 04-14-2015, 03:32 PM   #1
yamaham OP
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KLX 650 not hitting redline

Hey everyone, I've got an issue that has me stumped on my bike, it's all stock except a jet kit and dg exhaust. When I rode today it wouldn't hit redline, it's as if the redline was 6k rpm, so I took it apart, took the intake boot off, started it up and tried it, works perfect, but if I put the boot back on it goes back to 6k redline. It's as if the intake boot is restricting it, but I removed the air filter so there is no restriction at all. I can't figure this one out any help is appreciated

Edit: when I say intake boot I mean rubber boot between Carb intake and air filter

yamaham screwed with this post 04-14-2015 at 03:59 PM
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Old 04-14-2015, 05:15 PM   #2
lobolator
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Was it jetted and then running ok, or was it jetted and then the issue popped up?
Is the air filter clean and oiled?
Air box lid on/off?
Snorkel or not?
Do you have an inline fuel filter before the carb?
Sounds like you need to clean the carb or check the air box.
Up north here, bikes that sit over winter can provide nice snug homes in an airbox for mice and the like...your running fine with the boot off points to your airbox, or running way too rich.
But more concise info is needed.
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Old 04-15-2015, 07:40 AM   #3
yamaham OP
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Originally Posted by lobolator View Post
Was it jetted and then running ok, or was it jetted and then the issue popped up?
Is the air filter clean and oiled?
Air box lid on/off?
Snorkel or not?
Do you have an inline fuel filter before the carb?
Sounds like you need to clean the carb or check the air box.
Up north here, bikes that sit over winter can provide nice snug homes in an airbox for mice and the like...your running fine with the boot off points to your airbox, or running way too rich.
But more concise info is needed.

The jet kit was installed and it ran well for a few days. The air filter was clean and oiled. Airbox lid is off along with the snorkel. No inline fuel filter. I thoroughly cleaned it when I rejetted it. I don't understand why it runs fine with nothing on the intake, but even if you put the boot on with no filter it messes it up.

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Old 04-15-2015, 07:45 AM   #4
yamaham OP
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With the intake disconnected, you can see the slide move very easily all the way to WOT, it seems as tho the intake restricts the slide from going all the way up so it sits at 6k rpm
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Old 04-15-2015, 09:23 AM   #5
markk53
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Look up the TRUE redline - aka peak horsepower figure - and you will find it is at least about 1000 rpm below that red mark on the tach. It's a waste of time to rev beyond where the peak rpm is for anything other than just over-reving to avoid shifting when one is a very short distance from a corner entry if play racing or racing. The KLX250 is even worse - 10,500 red mark on tach, but peak horsepower is at 8200 rpm! The horsepower signs off 2700 rpm before the supposed redline.

I can't remember the last time I redlined my 650... or 250 for that matter. If your 650 pulls strong to about 6500 rpm that is about it, considering Kawasaki claimed 39 hp at 6300 rpm.
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Old 04-15-2015, 10:10 AM   #6
yamaham OP
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Look up the TRUE redline - aka peak horsepower figure - and you will find it is at least about 1000 rpm below that red mark on the tach. It's a waste of time to rev beyond where the peak rpm is for anything other than just over-reving to avoid shifting when one is a very short distance from a corner entry if play racing or racing. The KLX250 is even worse - 10,500 red mark on tach, but peak horsepower is at 8200 rpm! The horsepower signs off 2700 rpm before the supposed redline.

I can't remember the last time I redlined my 650... or 250 for that matter. If your 650 pulls strong to about 6500 rpm that is about it, considering Kawasaki claimed 39 hp at 6300 rpm.

Mark, true, i do not run to redline on a regular basis, hardly ever really, but it doesn't pull like it used to when i could crank it all the way up. It's down on power throughout the range, and I have no idea why
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Old 04-15-2015, 10:22 AM   #7
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If the slide is not opening all the way, my guess is the slide diaphragm is not seated in the groove, it has a tear or the little O ring under the cap is missing.

If the jet kit came with instructions to drill the bottom of the slide, that can prevent it from opening all the way if the hole is too large, at least make it bounce up and down.

What jetting are you using? R or C model?, the jetting is different. I ran without the lid or the snorkel. It was persnickety about jetting and what ever gains I got on top, came at the expense of low and midrange.
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Old 04-15-2015, 10:31 AM   #8
yamaham OP
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If the slide is not opening all the way, my guess is the slide diaphragm is not seated in the groove, it has a tear or the little O ring under the cap is missing.

If the jet kit came with instructions to drill the bottom of the slide, that can prevent it from opening all the way if the hole is too large, at least make it bounce up and down.

What jetting are you using? I ran without the lid or the snorkel. It was persnickety about jetting and what ever gains I got on top, came at the expense of low and midrange.
its a C model. I just got a new slide and diaphragm (the old one had a tear in the diaphragm), it is seated properly I am sure of that. I did not drill the slide. I got the dynojet kit, running a 155 main jet, needle is at 3rd position down from the top. So are you saying the hole in my slide may be too small and I should look at drilling it out a bit?
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Old 04-15-2015, 10:55 AM   #9
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Quote:
Originally Posted by yamaham View Post
Hey everyone, I've got an issue that has me stumped on my bike, it's all stock except a jet kit and dg exhaust. When I rode today it wouldn't hit redline, it's as if the redline was 6k rpm, so I took it apart, took the intake boot off, started it up and tried it, works perfect, but if I put the boot back on it goes back to 6k redline. It's as if the intake boot is restricting it, but I removed the air filter so there is no restriction at all. I can't figure this one out any help is appreciated

Edit: when I say intake boot I mean rubber boot between Carb intake and air filter
To much wind drag on the milk crate I would guess.......

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Old 04-15-2015, 10:56 AM   #10
itsatdm
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The hole in the slide thing, is a hot rodders trick to open the slide quicker. I drilled mine 7/64". If you haven't done it, it is not the problem.

I don't see a 155 Dynojet. Their numbering system is different than either a Keihin or Mikuni jet. Our carbs are Keihin. The C model main jet is much smaller than the R model.

A 155 Dyno jet would be the equivalent of about a 170 Keihin. That is way too rich for the C model and marginal on the R model.
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Old 04-15-2015, 11:02 AM   #11
yamaham OP
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The hole in the slide thing, is a hot rodders trick to open the slide quicker. I drilled mine 7/64". If you haven't done it, it is not the problem.

I don't see a 155 Dynojet. Their numbering system is different than either a Keihin or Mikuni jet. Our carbs are Keihin. The C model main jet is much smaller than the R model.

A 155 Dyno jet would be the equivalent of about a 170 Keihin. That is way too rich for the C model and marginal on the R model.

Well the kit comes with a 144, 150, and 155. The instructions say to use 155 if you take the airbox lid off and have an aftermarket exhaust. Do you think it's worth a shot to try them?
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Old 04-15-2015, 11:19 AM   #12
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They gave you a wide selection. The richest I ran, was a 148 with stock needle with washer under it, when I removed the lid. The bike also has a big bore, which I think sucks more fuel through the smaller jets.

I would go down a size. Take a look at your sparkplug. Does dyno jet have different jet kits for the R model vs C model. BTW that needle is probably no different than the stock needle in a R model.

I am not a big fan of the jet kits. I don't think you get much HP gain. Nothing that can't be duplicated with going up one jet size. Now you get to fiddle with jet size and needle position.

I put the lid and snorkel back on. With out the lid, the air box turns into a vacuum cleaner if you ride any desert or loose dirt. Removing the snorkel added top end, but came at the expense of bottom end power. I am running a 142 mj and it is a little rich.

I would check and see if the kit you have is meant for the R model. All the jets you have are richer than the 148 Keihin jet I ran.
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Old 04-15-2015, 11:28 AM   #13
yamaham OP
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They gave you a wide selection. The richest I ran, was a 148 with stock needle with washer under it, when I removed the lid. The bike also has a big bore, which I think sucks more fuel through the smaller jets.

I would go down a size. Take a look at your sparkplug. Does dyno jet have different jet kits for the R model vs C model. BTW that needle is probably no different than the stock needle in a R model.

I am not a big fan of the jet kits. I don't think you get much HP gain. Nothing that can't be duplicated with going up one jet size. Now you get to fiddle with jet size and needle position.

I put the lid and snorkel back on. With out the lid, the air box turns into a vacuum cleaner if you ride any desert or loose dirt. Removing the snorkel added top end, but came at the expense of bottom end power. I am running a 142 mj and it is a little rich.

I would check and see if the kit you have is meant for the R model. All the jets you have are richer than the 148 Keihin jet I ran.

It is a kit specifically for the c model. I checked the plug it looks a little on the rich side but not super black. But would running rich cause it to stop revving so soon?
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Old 04-15-2015, 11:32 AM   #14
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I would. It is rich if it gains revs/speed by backing off a
WOT throttle a bit (1/8 of a turn)
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Old 04-15-2015, 11:36 AM   #15
yamaham OP
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I would. It is rich if it gains revs/speed by backing off a
WOT throttle a bit (1/8 of a turn)
Backing off the throttle makes it go down as it should. The only factor that affects it from running normal is when you put the intake boot on the carb, it will only Rev up properly when there is no cover on the intake side of the carb
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