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RacerDad

2011 YZ450 bogs at high RPM's

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New crank & top end 3 weeks ago...ran great the next day at WORCS race & ran fine last weekend. Yesterday started bogging at high R's. Switch fuel pumps with a friend last night. Practice before race today...same problems.

Any ideas on what to check next??????

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If the symptoms are that it runs fine up to a certain engine speed and load level and then won't take anymore throttle, that would be a classic FI symptom for a clogged filter, but as there really isn't one apart from the pump screen, the next thing might be the injector. It shouldn't be too difficult to swap them.

But you should test the TPS with the GYT-R tuner or a VOM to see if it's OK, too.

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the injector is easy to remove. pope the seat, lift the tank and remove the plastic plate above the cylinder head. Full access to the injector is available at this point

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if it ends up being the injector or you just want to try it, go to one of your local auto repair shops and buy a can of BG 44k. Add 1/3 can to full tank and run it hard. This would be a rather concentrated mix so try to run out a full tank. The stuff is magic!

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my sons was doing that and would have a low speed bog,and was hard to start.took the fuel pump out and one of the wires were very loose.used pliers and crimped it together a little more and he rode it and said all bogs and hesitations are gone.

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Well it's not the fuel pump since we switched one from another bike.

Not the fuel injector. Put a new one in.

Not loose connections that I can find as we put in a whole new wiring harness.

Not a mapping issue that I can see as we put it back to stock.

Thinking valves/cams. He has Hotcams in there that may need to be put back to stock.

Edited by RacerDad

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glad you fixed it, what led to finding the problem?

Good question.

I just checked the price of a fuel pump online - $239. Ouch. (probably why you were banging your head)

I have a feeling that we are going to see some growing pains related to the additional components needed for fuel injection. (just like we did when more cars started going to it) Overall though, I think it will help bring the sport to another level in regards to tuning capabilities and the ability for the bikes to adapt to different air density and elevation without the need for manual intervention.

I remember everyone hated it when the Mustangs went to FI in 1986, but within a few years, it was the $hit. I had a 500rwhp 92 Mustang that ran great, passed the California smog test, and ran mid-11's on sticky street tires. Lots of tuning possibilities.

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Well I'm banging my head cause It's my son's bike but he had tried to check this by borrowing a whole tank with fuel pump/filter from another bike. He said that wasn't it. Well then I bought the injector NOT IT, then I bought wiring harness looking for bad connection NOT IT. Changed the Hot Cams & mapping back to stock NOT IT. So I went back to fuel pump & that solved it.

So the $239 jcm3 mentioned was a drop in the bucket. We do get a very good racer discount but sh!t I spend too much.

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Well I'm banging my head cause It's my son's bike but he had tried to check this by borrowing a whole tank with fuel pump/filter from another bike. He said that wasn't it. Well then I bought the injector NOT IT, then I bought wiring harness looking for bad connection NOT IT. Changed the Hot Cams & mapping back to stock NOT IT. So I went back to fuel pump & that solved it.

So the $239 jcm3 mentioned was a drop in the bucket. We do get a very good racer discount but sh!t I spend too much.

Of course I'm stating something that you know for certain, but you can't generally return anything electrical or any used fuel system component.

Again, obvious, but keep the parts that didn't fix anything as spares.

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