YZ450F 2010 running problems!

Hi guys and girls...

Have a 2010 YZ450F and she is running bad...

Bought her like it would seem, long story... she will start up from cold just fine, sometimes popps and bangs out of the silencer, sometimes not, will idle mainly when cold, but will again sometimes when hot, then not and just cut out when revs drop low, hard to re-start, have to give her gas to get her to fire up again, when running if you hold the throttle still say 1/4 will try and keep there but will go up and down the revs slightly, she's just all over the shop, have had her on the power tuner and no faults on that one, "0" mapping on the tuner, now waiting to see if the Yamaha F1 diagnostic will pick anything up....is there anything else that i can try that could be making her run so poor?, not sure if electrical or fuel?, or worse!!...:thumbsup:

Anyone had the same thing happen?, have cleaned fuel tank out and new fuel, checked timing marks for a jumped tooth and all fine, just dont know what to try next!?

Any helpwould be great, thanks.

sounds like a sensor could be bad, you really need the diagnostic tool and observe the sensor readings

Hi, yes will get it on this week hopefully.....

I started to strip her down and found this :

Any ideas?, its well corroded/furred up, looks like a type of fuse maybe that all the wires in a big block plugged into, and then a "watertight" < not, cap was over the lot!....if you look to the left, you will see a white plug in the other pics, and a red/orange "seal" that what this was plugged on the end of, there's another one too that was on the opposite side of this one, but was not as furred up, looked like something had burnt a little on it too?, had a look into the Manual and could'nt find any info on it at all, nice!.

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Those symptoms sound just like vacuum leaks. Un-metered air entering the system, most likely the rubber boot that connects the throttle body to the head. I would check that for cracks, I would also check to make sure that any gaskets/o-rings for that part are replaced.

Check your MAP sensor connecting hose as well for cracks, it is the right angled hose on the throttle body, over time it will harden and probably crack being so close to the head and all...

Check your valves while your at it, super easy to do on this bike and you should have no reason not to.

btw

Not sure where that connector comes from, but that grease is non-conductive and is meant to keep water out from shorting. I see it all the time in the harness's for my truck for rear lights etc.

wow is that connector melted? maybe a short on that circuit?

Those symptoms sound just like vacuum leaks. Un-metered air entering the system, most likely the rubber boot that connects the throttle body to the head. I would check that for cracks, I would also check to make sure that any gaskets/o-rings for that part are replaced.

Check your MAP sensor connecting hose as well for cracks, it is the right angled hose on the throttle body, over time it will harden and probably crack being so close to the head and all...

Check your valves while your at it, super easy to do on this bike and you should have no reason not to.

btw

Not sure where that connector comes from, but that grease is non-conductive and is meant to keep water out from shorting. I see it all the time in the harness's for my truck for rear lights etc.

Hi, thanks for the input, yes i thought the very same but sadly no cracks or leaks found, have checked valves and timing and all spot on, and yes, the grease is MENT to keep water out lol!. The strange thing is i cant find anything out about this connector/plug, anywhere!?...

wow is that connector melted? maybe a short on that circuit?

Hi, the mystery plug its not melted as such, just how i pulled it out and found it!, lots of furr and corrosion tho, so that could not have helped matters i think!, must of been happening over a period of time i would say?, and i'll say too that it must be causing a problem somewhere?, fingers crossed it might have something to do with this whole issue i have atm!, so i'll be cleaning up and re-fitting/checking everything today so will post back findings.

Any update? Thanks

I had similiar symptom with my 2011 YZ450F. Started great when cold, but very hard to start when hot without opening throttle or cold start/idle knob. I changed spark plug and noticed it was wet, so I read some more and found a case where a problem was dirty injector that made carb-flood-like-scenario. I have now run 30 min with 110ml Red Line SI-1 injector cleaner in full tank and I could swear that this problem already got solved, I will test it more - but atleast it had not got any worse.

Update: I can recommend to try injector cleaner. I drove over a hour today and no hot start issues.

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