rmz fuel injection problems

When was the last time the valves were checked? You said a new head but when assembled was it and cam timing checked?

I'd ask #1- did it start fine before you installed all the new parts.

If yes, #2- what do you mean you moved the cam timing around? Did you move the chain a tooth or did you re degree the sprockets? Hot Cams have been known to be off on the timing from China. If you haven't already, put a degreeing wheel on the motor and verify if your cams are set with the proper timing.

Not to argue but unless there is a problem with the injector/fuel pump it still sounds like a tight valve or low compression.

A broken timing chain tells me you may have bent a valve. Why would you put on a new head and not put on a new timing chain? You may want to also check the fuel pump.

Have you tried a leak down test?

I've seen injector issues(CRF450 & KTM250) similar, but not the same, where the bike would only fire with starter fluid. The bike wouldn't run clean through the RPM 's though and I see yours runs fine after started. Had an ultrasonic cleaning done and the bikes fired and ran fine after.The flow bench test showed increased flow after cleaning, but % increased with higher flow readings. You could have a possible injector issue except I'd think if it's clogged enough to not start, I'd run poorly at higher RPM's as well.

It's a long shot, but if you don't figure it out you can always find an injector cleaning shop local if you run out of options. I'd do the leak down test for sure, like X said so you know where you stand.

Try using the ECM off the donor bike.

My buddy had the same problem with his CRF450. Turned out to be a bad ECM. There is a circuit in the ECM that supplies the voltage to the capacitor to fire the injection for starting. Once the bike is running the injection gets it's voltage direct from the stator, or something like that. Bottom line it was a bad ECM.

Double and triple check your timing. A local pro's dad called me a year or so ago with a very similar problem. His bike was hard to start and would seem to hit the rev limiter early. We checked everything. Turned out the cams were marked weird or wrong. Instead of the timing marks being level with the head, the intake cam had to be turned one tooth clockwise, hiding the dot below the head. The bike ran great that way. I'm not sure what kind of cams he had then.

Recently, he had a similar issue where the timing was off at a race. We pulled it down after practice and set the timing, this cam was correct. When we put it back together it wouldn't fire. After a brief discussion the dad told me the bike had shocked the crap out of him while adjusting on it a day before. A few more questions and I found out it had had a propensity to blow the plug cap off while running hard. We ended up finding a broken place in the insulation and spark plug wire. We splinted it to get through the day and the bike fired and ran fine. He got a new coil and wire the next week.

This may sound stupid but did you replace piston and rings too? Have you checked the compression.
People bring me bikes all the time that they can't kickstart but can bump start or start on starter fluid and all it needs is rings that actually seal to the cylinder.

I have the same issue with my 2012 Rmz 250.
What did you find out?

Old thread I know, but did you ever find out what the problem was? My 11 Rmz 450 is doing exactly the same thing, simply will not start no matter how many times I kick it, but as soon as I spray aerostart or something like that straight into the throttle body it will start second kick. I have replaced the fuel pump and the stator, valve clearances are all in spec, timing is spot on, new piston and rings, all this done after the problem started and still does exactly the same thing. Fuel injector works perfect on the bench with a 9 volt battery but once it's in the bike it won't spray while being kicked over, so no fuel no start. Why would no power be getting to the injector on initial start up. When the bike is started with aerostart bike runs perfect, doesn't miss a beat. Frustrating.

Any advance on this? I'm getting a very similar thing after shipping a bike from NZ to the UK

Not from me there is not, I have replaced everything with brand new parts. The only thing I haven't replaced is the TPS only because the manual says a bad TPS won't stop the bike from starting.I even tore the head and barrel off just to check everything out, and its all perfect. Still my injector will not fire enough fuel for the initial start up. The only thing left to replace is the Tps, at least that way I can then rule it out. Lucky I have shopped around and got a lot of brand new parts from all over the world of eBay and for a hell of a lot less than I would have paid for retail in Australia. But it still won't start cold.

I had similar symptoms with my rmz after a rebuild. Tore it back down and double checked timing. Looked right. Put it back together, still not right. Tore down again to triple check timing and found I was off a tooth.. wtf. It's ran great ever since. Starts first or second kick.

The timing marks on these bikes aren't 100% accurate

after some messing i found my problem to be the TPS. I only adjusted it crudely as i didn't have a voltmeter to hand but i got it to start perfectly (*hot or cold).

Thanks for the replies though guys

Looking forward to it. My 97 Cr125 is out but my oldest boy will be racing the '02/96/15 CR125 hybrid. Looks to be a fun weekend..............

Hi i need help with my rmz 450 2011 mod it will not start unless you spray fuel into throdle i have cheecked timing valves in spec new stater its doing my head in please help

Please any help

My problem ended up being a bad flywheel, its magnets became weak and didn't supply enough power for the injector to fire fuel into the port. I put a used flywheel I got off eBay and my bike has run perfect ever since. It's a strange problem that's rare but it does happen I spent a shit load of money on parts before I tried the flywheel. Good luck.

I have a similar issue!! Bike started good when I got it. Was smoking though burning coolant, so i redid the top end. New piston, rings, gaskets. Valves reshimmed in spec. Bike is in time! But will not start at all no bump. No kick. No ether. After many kicks I start smelling gas so it's getting fuel. This is a 2012 rmz250. Please help!
Are you supposed to do anything special after you unplug the electrical.
Also the flywheel timing mark will not line up I can get there but it jumps forwards. I even tried just bumping it clockwise to line it back up and itll jump passed the timing mark.

Mopar
If marks don't line up on flywheel the woodruff key may broken allowing wheel to be out of alignment
and timing off