11 yz450f stumped....

I bought a used 11 a while back and have been working on getting her running right. Unfortunately I have not gotten to the bottom of it. Here's the list of things I have done in an effort to get it to run right:

Adjusted valves

New fuel filter

New air filter

Clean throttle body

Remapped it

Oil change + filter

New spark plug

Played with idle screw

The problem: it will start but takes 5-10 kicks. Has trouble idling, I can ride it up and down the street but has a bad miss mid throttle. If you keep it alive it will miss in the mid of the throttle range. Needs a relatively high idle to stay running 26-3k is what I have noticed. Has anyone had anything similar happen? Unfortunately it's used and don't have any info on its previous life or maintenance.

I got a second opinion from a local shop yesterday and was told it could be an electrical problem. Was instructed to remove stator cover and see if there's any metal shavings, 2x valve adjustment and timing, and to test stator/coil. Is there anything else I should look for? Any ideas? Thanks in advance.

Throttle position sensor. Just replaced the one in my tacoma due to same issues.

It's a possibility, but your Tacoma system is maybe just a little different. 

 

Any trouble codes in the '11? 

True but it sounds like the issue has to do with throttle position rather than engine speed

It's a possibility, but your Tacoma system is maybe just a little different.

Any trouble codes in the '11?

No codes, have hooked up my tuner multiple times and it doesn't spit anything out. If the tps was out of wack would it throw out a code? Gonna have a look at the bolt holding it in place and see if it's been tampered with.

Im not sure that it would if its just out of adjustment.

You said it stumbles at mid throttle? Does it seem to run right at 1/4 or wot?

Another Thought is to check for an air leak on either side of the throttle body

I'd approach it like I would a car. Get a little ignition tester. Its a little plugwire section with a light built in. Install it inline between the coil pack and the spark plug. You could rig it up with another longer plugwire to get it up where you can see it while you run it down the street. You'll have to use duct tape or tie wraps to hold it all in place. If the light stops flashing as it cuts out you'll know its the ignition. If it doesn't cut out, you can then forget about all that and move to the fuel system. Report back with findings and I'll give you the next step. Good luck

Thank you guys for the replies, I did find some good material in checking coil and stator with ohms meter. Going to do that and re-check valves and timing to start with. Then move on to remove stator cover and see if there's any metal shavings on the flywheel or stator. Once I get thru all this i will check back in with my findings(this wknd sometime). I'm not saying it can't be fuel related but it seems to get fuel down low and up top when I do get it going, just mid Mis Fire and hesitation, if riding it will like buck back in forth a little when you get in the mid range and if you twist the throttle to full it will snap out of it and run like a raped ape. Also takes a more than average 5-10 to maybe even 15 kicks to start. So don't know if spark or fuel but going to go after spark first and like you said fuel will follow up if I can't detect anything. Anyone know if by chance the rectifier/regulator, or condenser could be the culprit or what job the posses in the system? A way to check these?

Edited by Dexter42

Thank you guys for the replies, I did find some good material in checking coil and stator with ohms meter. Going to do that and re-check valves and timing to start with. Then move on to remove stator cover and see if there's any metal shavings on the flywheel or stator. Once I get thru all this i will check back in with my findings(this wknd sometime). I'm not saying it can't be fuel related but it seems to get fuel down low and up top when I do get it going, just mid Mis Fire and hesitation, if riding it will like buck back in forth a little when you get in the mid range and if you twist the throttle to full it will snap out of it and run like a raped ape. Also takes a more than average 5-10 to maybe even 15 kicks to start. So don't know if spark or fuel but going to go after spark first and like you said fuel will follow up if I can't detect anything. Anyone know if by chance the rectifier/regulator, or condenser could be the culprit or what job the posses in the system? A way to check these?

I'm no real expert but it seems that the issue has to do with the position of the throttle. I would think that the stator and rectifier and most all the other electronics other than the throttle position sensor would have more to do with engine speed rather than throttle position. I would still check the throttle position sensor. If you have the manual in the back of the manual it gives you all the test parameters for the throttle position sensor. You can check it with an ohm meter or volt meter. I would check that and also check your air box to make sure that the fittings on both sides of the throttle body or tight and that its not sucking in air. Those are the only two things I could think of that would directly relate to the position of the throttle rather than the speed of the engine. my experience has been that when something in the ignition system is going out the issues are relatively inconsistent and happen randomly regardless of what you are doing. Your issue seems to be pretty consistent with half throttle.But like I said I'm not a real expert so I could be wrong. Edited by Goforaride

I'm no real expert but it seems that the issue has to do with the position of the throttle. I would think that the stator and rectifier and most all the other electronics other than the throttle position sensor would have more to do with engine speed rather than throttle position. I would still check the throttle position sensor. If you have the manual in the back of the manual it gives you all the test parameters for the throttle position sensor. You can check it with an ohm meter or volt meter. I would check that and also check your air box to make sure that the fittings on both sides of the throttle body or tight and that its not sucking in air. Those are the only two things I could think of that would directly relate to the position of the throttle rather than the speed of the engine. my experience has been that when something in the ignition system is going out the issues are relatively inconsistent and happen randomly regardless of what you are doing. Your issue seems to be pretty consistent with half throttle.But like I said I'm not a real expert so I could be wrong.

I do appreciate your reasoning and defiantly something I forgot to mention but will be checking as well while I'm in there. It is a used bike and I don't want to rule anything out, it also doesn't hurt to check while I'm in there. Thanks again. I will probably won't have time till this weekend to check it out so I'll report back as soon as I start digging into it. I also did remove the throttle body to clean it so an air leak is possible, will check all intake clamps. If you come up with anything else please post.

Throttle position sensor. Just replaced the one in my tacoma due to same issues.

And there you have it folks, we got a winner!!!!! Not really sure how it fixed itself or what I did to fix it if anything to be honest. But either or I went thru everything in my previous post and check ohms on just about anything the book had ohms measurements for. Stator check out perfect, coil was perfect, kill switch was good, spark plug gap was good and valves where all in spec, timing was on point. When I got to the tps sensor is when the ohms meter was wiging out big time, it gave me a good measurement on one of the checks (upper left and bottom) but a bad out of spec measurement(reading was over limit) on the other (upper right and bottom) and when I would open the throttle the numbers bounced around everywhere and wouldn't go up and down gradually. So I took it off completely, cleaned the inside and for shit and giggles check it again rotating the inside with a flat head. This time around the reading was still good on left but now it was under the spec on the right and it went up and down gradually like its suppose to, thru me for a loop. So again for shits and giggles I said let me try putting it back on and see if it will work now, eyeball center of the slot to the best of my eye and bolted her up, tested again and what do you know- measurements where dead on!! Everything checked out good and when twisting the throttle it went up gradually and did not default and hit all the ohms measurements right in the middle of the tolerance. Put everything back together, warmed her up and just from idle I knew this thing was different. Rode her up and down the street for over 10 min no problems/ hesitation misfire or anything. Thing rips just like my 13 if not harder!! Again thank you guys, this forum is a blessing! God bless all the knowledgeable people that actually come here to help others. Thank you all..

 

when I would open the throttle the numbers bounced around everywhere and wouldn't go up and down gradually.

 

...And, of course, that check is NOT in the manual.  It's always a good one to do when looking at the TPS, though, as you can see from this.

 

But I would be somewhat surprised to find out that it is permanently fixed.  It might be working now, and I wish you luck with it, but while faults like this are often intermittent, they are rarely transient.  The TPS may act up again.  Replace it when it does.

...And, of course, that check is NOT in the manual. It's always a good one to do when looking at the TPS, though, as you can see from this.

But I would be somewhat surprised to find out that it is permanently fixed. It might be working now, and I wish you luck with it, but while faults like this are often intermittent, they are rarely transient. The TPS may act up again. Replace it when it does.

Yeah that check is something I saw on you tube and picked up. I too am skeptical that it's fixed but for the time being its working like is suppose to so gonna ride it till it starts acting up again and then replace. Pricey little sensor...

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