5 dealer mechanics later and still cannot find the issue of this bike not starting. I am also a small engine mechanic that restored this bike from the ground up. I bought the bike that was not running because it needed a new water pump shaft and impeller. So decided to restore it. The engine rotated and compression was good. I restored everything but the bottom of the engine, buttery smooth and only had about 40 to 50 hours on it so it was a great candidate. Rebuilt top end including valves checked with dial indicator and lapped. Springs, seats and keepers all good. Reassembled with new out seals and flat sanded head to clean up mating surface. Cams are original but installed new cam chain and tensioner. Piston looked great, typical carbon and no rubbing on piston or its skirt. Timing is perfect, no spun cam and carb is delivering fuel. No start. Compression checked and good at 72 psi @ 5 kicks with engine never started after top end rebuild. 120 total psi with throttle open at highest psi. Still no start. Need help bad.
Do you have spark?
Also, I'd be amazed if an FCR carb that old did not need some decent attention. Likely clogged pilot and or fuel screw passage, leaking AP diaphragm, etc.
Carb Vapor blasted and completely rebuilt including mid body. All new jets to manual. Air/fuel screw out 2 turns to manual. Has blue spark with oem coil and boot and new CDI. Carb does not need any attention as it is brand spanking new now.
Has the machine key been checked on the ignition rotor? Possibly sheared and ignition timing is off. Other possibility is bad stator.
Side note, lapping valves is not really a thing on 4-stroke MX bikes since most are coated titanium valves and lapping ruins the coating. Possible with aftermarket stainless valves. Not saying this might be a cause of your no-starting. Only way to know for sure is a leak down test. More beneficial than a compression test on these 4-strokes.
I want to say "kick it more than 5 times" but i feel like you've probably done that by now.
Did you ever take the flywheel off? Maybe spun.
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You are 100% correct on the valves they are titanium coated and plan on replacing them in the near future with new. Just wanted to get a little more life out of them for now. Did liquid text for exhaust and Intake and they are sealed with no leaks
As for the rotor woodruff key, yes the flywheel was pulled and it is like new and keyway is perfect.
CHECK SQUIRTER IN CARB PULL CARB RUN FUEL THRU IT OR BAD ECU
Negative!
It's not a squirter and would hope nobody would listen to you for calling something that has an actual name for a function on a bike.
It is called a primary accelerator pump. If you knew your bikes which I would think since you are on this forum and you already identified I have a carburetor it's not called a ECU but a CDI.
ECU is for FI.
Clean out your bong..... Bro!
Not to be a dick, and I don’t know Factor E personally but he’s helped me along with tons of others on this side of the forum. I don’t think I’ve seen him even post anywhere else on the site, he knows his way around bikes. Kind of a stupid response for someone offering their advice.
Did you powder coat or paint anything motor mount or chassis related? How’s chassis ground? Are you sure the passages in the carb body are clear; vapor blasting media loves to pack into orifices... Lapping Ti valves is a huge no go and honestly those valves are dead now... even if they seal right now they’ll last very minimal run time. A Liquid test for checking valve to seat seal can be a good quick test; but can also be misleading depending on liquid used... always run a true leakdown test to check valve condition...What’s the current valve clearance? if you have clean spark like you say... then your problem more than likely lies with fuel delivery or top end/ valve condition... If you mist fuel down the bore of the carb into the intake can you get it to fire? Slide height looks low to me... get a pin gauge around 2mm and reset your slide height this will be close to right for correct idle speed... if Unplug your TPS this will make it so the “Capacitive Discharge Ignition” will only have Base Timing which is smart to check if the TPS was remove... Did you check and reset the TPS voltage When you completely disassembled the carb and reassembled it? Also not to be a dick, but I don’t think you understand how many very intelligent mechanics refer to the accelerator pump as a “squirt or squirter” and a CDI vs ECU really? You know damn well what he was referencing.. It sounds to me like 5 other Mechanics, including you, are out of their element and possibly dealing with something above their pay grade...
You are absolutely right Rickyisms.
I want to apologize to Factory E for being a complete asshole. In this time of such division and people being so damn defensive I am admitting I was wrong to comment on your post the way I did. I hope you truly except my apology. Unlike most out there in the world I am not too big to know when I was wrong and I am truly sorry. There is no but either.....
I was wrong and you are just helping and I do sincerely appreciate it. I wish everyone could step back and realize or have a little self awareness sometimes.
Thank you Rickyisms for setting me straight on my attitude as it was totally uncalled for and calling me out on it.
I hope both of you and anyone else reading my thread will forgive me for my unnecessary sharp tongue.
We are all in this together, right?
The chasis was not powder coated. The chasis is bare aluminum and was acid washed and scrubbed with a prime pad to bring out brushed aluminum look. The coil has a ground lead to the frame and coil is new and was ohm checked with new boot and was good for test. Spark is blue and has strong jump when testing spark gap for distance. Every bolt and metal component was buffed with prime wheel, this includes cases to all mounts and bolts. I have a strong ground and good spark. I don't think spark is an issue. Plus several ohm tests at the coupler for stator primary and secondary resistance ohm test. Within service manual test readings. It has a new oem CDI and prior old CDI used to check start as well.
CARB: Yes, I blew out every port with air compressor and breakclean. As for the configurations of the carb I went strictly by the service manual. Needle 4 down with C clip, main 175, starter 72, leak jet 70, slow jet 42 and slow air jet 100. Fuel screw is 2 out. Bench tested the accelerator pump jet and squirts great. Yes, I did remove TPS but not before marking it from casting to plastic head and was installed matching markings. Hotstart nipple was replaced with an aluminum one. Btw, all new jets from Allballs rebuild kit, this included all new gaskets for the midbody too. All jet sizes in ket were dou le checked to SM as I heard sometimes these kits make mistakes with jet sizes.
Someone told me I should change the Leak Jet from the stock 70 to a 55 but not sure how that effects starting.
I did not reset or do a voltage check on the TPS, it was stated the bike ran great before teardown. Will a bad TPS prevent a bike from starting?
Morgan from Highland Cycles (YouTube) out in Colorado and I have been communicating on troubleshooting this bike for a while now. Going thru a hit list of things to check and he pretty much gave up. Everything he suggested checked out good. So I don't think it's about pay grade.
Valves: Yes, I knew they were titanium coated and did look stock but the carbon was so bad. The valves wouldn't even seal all the way and they were straight as an arrow so there was no hang up just carbon build up. Buckets, shims, valve guides, dual springs and seats wear all good. I did reshim after lapping and installed new valve oil seals. Intake 1 is .10mm / .11mm no go, 2 is .10mm / .11mm no go. I also went down on the intakes one shim size that brought to clearances .15mm for the other end of the spectrum and still no start.
Exhaust 1 is .19mm / .20mm no go, 2 is .20mm / .21mm no go.
Intake spec - .10mm to .15mm
Exhaust spec - .17mm to .22mm
I did pull cams out to check if I could see if intake or exhaust cam spun a gear and here is what I found.
They are stock oem cams, as I know it the hole on the intake gear should line up to the last lobe hole. This being said there is no info out there to confirm this though and not in the SM. Visually the holes are off. Measuring the difference with a laser it is about a tooth and a hair more. It may be just off enough, if my theory is correct about the holes are suppose to line up that it won't start and a valve doesn't hit the piston. The exhaust may be spun too but there is only a screw hole for the decompression mechanism once removing the actual screw that in theory lines up with its last lobe hole. If this theory is correct then looking at it that gear to last lobe hole is off too. Just as much as the intake is off. About a tooth and a hair. Does anyone know if this is how you check kx450f oem cams for spun gears? I only heard of how to check them from other people with kx450f on other forums but no facts anywhere. Suggestions or knowledge of this?
I knew lapping the valves I was shorting the life out of them but was planning on installing new valves this winter. I figure I wouldn't even put 5 to 10 hours on them before changing them out. Doing what I did how long do you think they will last? I am curious and would like some advice on what new valves should I purchase. I heard to stay away from titanium valves because of the light weight therefore you have to change to stiffer springs. I heard to go with stainless steel because you use the stock springs and have to shim way less often and they last longer. Any suggestions?
For reference, the white painted dot that you see on the inside intake gear is the position on the other side of gear where the manufacturer's dot marking is.
To determine whether or not the cam gears have spun, I'd search the web for good pics of cams and compare orientations.
I do know that 1.5 teeth off time can definitely be enough to keep the bike from starting. I've seen KXF's assembled 1-tooth off that would not start.
I did exactly that, searched every pic I could see. Nothing definitive though for kx450f cams to what mine are showing. So I ordered new Hotcams stage 2 to compare, will be here by Saturday supposedly.
Did you ever find the solution? I'm in the exact same situation with a 08 KX450F. It also has stage 2 INT/EX cams. Everything on bike checks out still no fire.
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