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johanfalkman

wr400f -00 won't rev past 5-6000rpm

17 posts in this topic

Hi, new to the forum posting but I've red it "all" almost..

As the title says, my wr400f -00 wont rev past 5-6000rpm, it used to run smooth and hitting all the high rpm without a problem. It runs smooth and strong until then, starts fairly easy.

What I've checked:

Cleaned the carb 4-5 times, all is clean and everything is ok.

Measured all the electronics that the manual says, everything is within the correct resistance (ohm)

Tried running without TPS, neutral switch or kill switch. Still the same thing, no difference. Changed plug (which looks good). Grey wire is not an option since it is a EU model.

The sound is something like the rev limit hits it above 5-6krpm, almost like choking but not at the same time.. sound like a electric thing..

Not checked the timing, but shouldn't it be noticeable before or just idling/starting?

I've ordered a main coil, just to try something.. but meanwhile.. someone has any ideas?

br

Johan, Sweden.

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Ok,

Finally checked the valve clearance, and it was within limits.

But, when trying to set the motor to Top Dead Center. I could not get it 100%. The timing seems to be a bit "1-2mm" off. Should I worry about this? I have not done anything to it, it was running good as this. Could it somehow got "off" timing without me doing anything?

See the picture below. When the "I" is at center, the timing marks are alightly off. What to do? Check further for something else or how do I adjust this?

TimingSlightlyOff_small.jpg

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That timing looks good to me. There's quite a bit of play in there from the factory, so what your seeing is normal. As for not being able to get above 6000rpm's, I have no idea what might be causing that! Hopefully someone on here will chime in and give you some direction on where to look.

Maniac

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Thanks, what I was hoping for. So then my valves and timing is correct I guess. I'm now a bit worried if it could be something with the stator somehow.. guess it's hard to know since the resistance on the stator coil is according to manual.

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Don't know if it's related but mine wouldn't rev high till I took out the exhaust restrictor. Also if the air filter/intake/exhaust gets clogged up it will have a hard time revving . Did you clean the air filter ?

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Yes, cleaned and changed airfilter. Same exhaust as when it ran good. Even tried with stock exhaust.. Just put everything together after checking the timing/valves... still not reving past 6000rpm... :-(

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When it reaches approx. 6000rpm's, what does it do? What color is the exhaust out of the muffler? How are you checking rpm's? When did it start acting this way? Like after sitting all winter, etc..? We need more info.

Maniac

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The 6000rpm is very much aproximation from my side, could be in the range of 5000-7000 (but i've had some 2 stroke's and I'm used to engines (not this one though)) What's quite sure is that it's the same "rpm limit" every time. Aprox 70-80% throttle.

What it does is, "stuttering" and no matter of how much more throttle It doesn't rev more. I can hear that it's getting more air/gas (sucking noise) since it's kind of choking it's self.. not as it dies or anything just stuck there in the 6000'ish rpm's. I'll try to post a sound recording of it later. Also could compare to a 2 stroke with the wrong air/fuel mixture sound. Bu't ive tried adjusting the fuel screw and even changing for another one with the adjustment "nob" and still the same. No matter of how much I screw in or out. O-ring is also changed and it's all in the right order down there since I've not changed anything since it ran good (except new fuel screw, same problem with the old one though).

I've just bought it from my neighbour who had ridden it very little last 2 years.. It ran good for 2-3 rounds (1-3h). Then I just starting to notice, nothing dramatic but just wouldn rev as high as before.

I don't want to start re jetting or anything like that before I get it to run good again, the colour of the exhaust get's red/hot during high idle but not during riding. I then tend to adjust it down to low idle when the engine is hot and it then runs good on low idle and the exhaust dosn't get "RED", you could probably see it in the dark but not much. (which is normal I guess)

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I meant the color of the spent gases coming out of the muffler, not the color of the head pipe.

Maniac

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Sorry, i misunderstood. The spent gases are totally "clear". Neither white (Could indicate blown head gasket?) or black'ish (oil leak somehow?)

Could it somehow be a blown gasket somewhere, and how do I best check it?

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https://vimeo.com/44159613

This is a video of my wr400f warmed up, hitting WOT and you can hear the stuttering/stop at somewhere 6000rpm'ish.. it's in neutral here. But exact the same when going in gear, 1,2,3,4,5.

Edited by johanfalkman

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That sounds like the standard rev limiter to me, maxing out. Can't remember what the max RPM is, but its something like 12k. Maybe its hard to tell on the video. Get an inductive tachometer to measure what the actual RPMs are. Also, that thing is idling way high.

Edited by Pooley

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Yup, 11,500 rev limiter. Get the idle way down there too! If you pick up an hourmeter gauge and mount it like mine, you can see the rpm's as you ride. Set the idle at around 1900, and use the torque of the engine to move you around, not the high rpm power. I'm probably spending most of my time shifting gears between 6000 and 9000rpm's.

ManiacTT\'er Hourmeter 002.JPG

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Thanks for the help! Mostly been driving 2stroke so I might have my "ear" tuned in to listen to that high rev 2stroke sound. :-)

I'll hook up some meter just to tune it better then.. I'll for sure be newbie for some time. :-)

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Don't worry about it! As I said, I went from a 125 to the Yamaha YZ400 back in '98, and was bouncing off the rev-limiter the whole time because I didn't know any better either! We all started as Rookie's, at some point!!! Welcome to ThumperTalk!!!

Maniac

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Yikes! I'm scared to rev mine up!! Must be getting really old as I don't think I've hit the limiter yet..

Sounds like the limiter to me though.. Check out this video of what can happen..

http://vimeo.com/32887596

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I don't want that to happen to me! At least this mistake got me to check the valves, change oil/filter, order an hour/tachmeter read ALOT! So some work but then I'll know until next time!

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