2007 Honda Rancher TRX420 4x4, Cuts out above half throttle similar to rev limiter

[Sha35297]

So I rebuilt this engine completely with all factory parts. Transmission was damaged, so customer wanted to replace crank while I had it apart. After putting everything back together, everything worked great. Customer picked up bike and ran it for about two months (he uses it daily for work in crawfish ponds). Brought it back to me because it was overheating and would rev up to about half throttle and the cut out over and over while holding the throttle at anything above half throttle. Radiator was plugged. Everything with ignition tests good. I never loose fire while this is happening. ECM is brand new, fuel pump is new, injector is new, swapped TP Sensor with known good one. Fuel pressure is at 51psi at idle and its hard to tell because of vibration, but seems to drop to about 42psi while its cutting in and out at high rev. Any ideas on what could cause this?

[Ajmboy]

My first thought is fuel pump but you mentioned you replaced that. Is that OE or aftermarket? Was it assembled? Sounds like a fuel pressure issue.

[MarkinAR]

I'd check the timing.  I put a 300 together once and got the timing a tooth off and it had all of the symptoms you mention above.

[Mech]

The dropping off of pressure at the same time it's missing , might be a dirty filter.. fuel filter. Even though the pressure's good at idle, it might not have a good flow. It always pays to check flow and pressure, because you can have one without the other.

[Kevin Connors]

2015 had same problem sold it. 420 just have to many problems. 

[Sha35297]

So the fuel pump I replaced was aftermarket. I only replaced the pump itself and used original can. It came with new filter and seals. I'm not sure how the pressure regulator works on this system. It is only a spring valve. So what exactly tells the ECM when to cut the fuel pump on and off? Timing is set and valves are adjusted correctly. I guess the next step is to just replace the whole fuel pump canister. I will place the order for the new one and update once its installed. I am pretty certain that its a fuel pressure issue. Just not sure if its an electrical issue causing the pump to cut off when its throttled up or something else.

[Mech]

Are you sure it's not running in safe mode since the overheating issue ? Some of those things, if there's a problem that could damage the engine, they restrict the revs until you've fixed the problem, and in a lot of American stuff, taken the bike to a dealer to cancel the safe mode.

I suppose you have read the manual regarding this problem ..

[Sha35297]

I completely forgot to give an update on this issue. It was the timing. It had jumped a tooth. I must have missed it when I had checked it the time before. I replaced the chain and tensioner. The bike has been in use for over a year now. The guy uses it daily for work. Thanks everyone for the help.