I wish I was not sorry I bought this bike

[henrysdad]

I had lots of fun when it ran.

I reek of gas,lost count of the number of times I had the plug out checking for spark.or flooding. the carb is spottless on the inside and apparently working properly. I just kicked this piece of crap all over the garage.Literally, it scoots a 1/2 inch every kick.I almost puked,200 300 kicks!!!!!!or more.

It will not run.(2000 426)

I have spark.it is weak . there is new gas.I just put in a big bore piston,had the cylinder plated ,and installed the 450 cam.

early this year ,the bike started the first kick. then got really hard to start and lost most of it's compression. Meaning I suddenly did not need the decompression lever,where I did before.and then it would not start at all.All this happened in a day.

I overhauled the top end. the valves were perfect,didn't leak fluid before,but I lapped them anyway.now that I installed the 450 cam there is no judge for compression.

it has an electrex 45watt lighting coil. I get numbers way off from what the manual gives for the magnito source coil tests.I wonder if I have magnito failure?I hate to buy a new one for that not to be the problem. I don't need lights I need the bike to run.swaped a good coil,and cdi box.

I'll be missing my third race because the bike does not run. why Do I own it? I bought a newer bike because I want to race not fix the damn bike.I may not own this thing for long.

I am at my witts end.

[mnovarossi]

You may want to recheck your cam timing.

[kizzle426]

Man.....sorry to hear all that. I had a problem getting mine to start and i solved it by leaning out the fuel mixture. I moved the clip on the needle up one position and turned out the throttle screw a half turn. It started right up. You might try that. It could possibly be that simple.

[chequamie]

check out motoman393.com there are some suggestions for hard starting bikes like removing the neutral sensor wire to improve spark flow and coil/sparkplug setup tips.

[mj2412]

Last time i tried to start my bike Yz426 01 for about 1 hour. We were three guys and kicked the bike all time, tried to start it by pulling behind a car. No way. I ripped the spark plug out 4 times and every time i had a spark. Then i tried a new spark plug NGK CR8E and couldn´t see a spark. I was driving crazy and in the end tried the new spark plug without a seen spark. Heureka. The bike runs with the second kick. My 2 cents. My fault before this starting problems was to use the kill switch with still the choke on. This will kill your spark plug.

[kizzle426]

Another tip about starting it: Before you ever kick the bike, turn the gas and choke on and give it two quick snaps of the throttle, then procede with the starting drill. Mine starts on the first kick just about everytime I do this. If you don't start it the correct way it will take forever. Just in case you didn't know these things.

[Chris_from_Oz]

I have spark.it is weak .

My guess is you need a new plug. Try an NGX CR8EIX. ?

[ovrrdrive]

Definitely try a new plug first... It's the cheapest solution.

[Yamaguy4Life]

It sounds like it's time for the professionals. Not to challenge your technical prowess, it sounds like you really know your stuff, but there are so many intricacies to the modern 4-stroke, and they are so hard to start even when everything is working, that it's sometimes just easier to let the pros do it. I too hate to pay someone else to do something that I should be able to do myself, but I own an MX bike to ride not to wrench.

Luckily I live in OH and Yamaha of Troy isn't that far away. They have some real good tuners that can really make the bike sing a high note. I'm always amazed at how much better it runs when the pros have given it a go.

Don't give up. It's a machine. Once everyting is back in order, it will fire on the second kick.

[00YZ426FMRCD]

How did it run before doing all your Mods? Not questioning your ability but if it ran fine before the Cam mod and Big Bore kit, then there has to be something such as the Carb, jetting or something else that should have changed with the new Mods....

[henrysdad]

Early april the bike started after sitting for a few months. I changed the oil and was going to have at it. It used to be a 2 kick bike. that same day It became hard to start.10 kicks. the next day 20 kicks then it would die after 1 minute. then no start . the next day no start ,then loss of compression.Like not needing the decompressor,where before you could stand on the kicker all day and it would not move.

Now the spark does not hit every revoloution and is really weak. it will shock you some times. If you kick the bike real fast for a while it will spark a few times then go away.if you kick it over lazily it will maybe spark once then not for a while .this is why I am suspicious of the lighting coil.

I pulled the top end hoping to find horrible things,the worst of it was the head gasket was coming appart. the head and valves are fine,really nice actually. the bore was scratched so I went overbore while having the cylinder repaired. and everyone raves so much about the 450 cam mod I figured I could not go wrong. Wrong.

I am going to buy a yamaha magnito coil and give up the lights.I am confident the bike will run like a champ.

[phat_450f]

thats the only thing i hate about doing mods to engines. makes them less reliable. I think anyways. but indeed go for the cheapest solution first.

[John_Lorenz]

If the Spark is weak enough to not act as a refibulator when you grab it then there is an issue. Things to look at

1: Remove your Kill Button from the Bar or disconnect it (Test Only)

Sometmes the Kill button goes bad or is shorting

2: The Plug cap is hosed or needs replacement, buy a new one for dril whats 5 - 10 bucks

3: There is a short or there is bad connectivity in the wiring harness / plugs

Go over these with a fine tooth comb, take a wire brush to the ends to get rid of any corrosian then seal using silicon

The CDI is a funny thing since you swapped this out, I woudl venture to say the Lighting coil is part of the issue.

Outside of that I think your savvy enough to start the bike and know the drill to doing this. If you dont know the drill here it is The Drill

The other aspect I know you said the carb is clean , when is the last time you took it apart and cleaned the snot out of the pilot.

Last

Hard starting may be a sign of Valve adjustment, Check these specs

[Slowmotion426]

Sell it.

[Jeremiah]

Don't sell it, it's a great bike! My bike was an absolute bitch to start when I bought it. Turns out the idle circut was clogged. Now it starts on the second kick...no matter how long it has sat.

I know you said you checked the valves and they looked good...does that mean you checked the clearance?!? You sound saavy enough, so I would guess you did, but your problem sounds either like valve clearance issues or carb problems. I've checked my spark and it always seems weak, virtually no spark there, but it runs great and starts wonderfully.

Don't give up on it yet.

[Florida_426]

Henrysdad,

If I understand you correctly you kept the decompression set-up from the stock cam. If so check the decompression lifter for sticking the exhaust valve open. My '02 has great compression with a 450DCM. I have no offerings on the spark and coil voltages. I have a coil, black box, plug wire and cap you can try to see if they help.

I would first go through the electrical steps John outlined, then try a magneto if you need. I guess you got rid of the stock one so I would try to borrow one again. Good luck. P.M me if you want to try the box and other stuff.

Bill

[fatmancantfly]

Before you go any further. Change the plug!!! When you did the cam change, did you count the pins between the timing marks? Put the intake cam same as stock and count 14 pins between the top intake cam mark and the top exhaust cam mark. Change the plug first!

I had lots of fun when it ran.

I reek of gas,lost count of the number of times I had the plug out checking for spark.or flooding. the carb is spottless on the inside and apparently working properly. I just kicked this piece of crap all over the garage.Literally, it scoots a 1/2 inch every kick.I almost puked,200 300 kicks!!!!!!or more.

It will not run.(2000 426)

I have spark.it is weak . there is new gas.I just put in a big bore piston,had the cylinder plated ,and installed the 450 cam.

early this year ,the bike started the first kick. then got really hard to start and lost most of it's compression. Meaning I suddenly did not need the decompression lever,where I did before.and then it would not start at all.All this happened in a day.

I overhauled the top end. the valves were perfect,didn't leak fluid before,but I lapped them anyway.now that I installed the 450 cam there is no judge for compression.

it has an electrex 45watt lighting coil. I get numbers way off from what the manual gives for the magnito source coil tests.I wonder if I have magnito failure?I hate to buy a new one for that not to be the problem. I don't need lights I need the bike to run.swaped a good coil,and cdi box.

I'll be missing my third race because the bike does not run. why Do I own it? I bought a newer bike because I want to race not fix the damn bike.I may not own this thing for long.

I am at my witts end.

[Guest RIDE_for_RED]

Timing, kick it /w/ the plug removed, check for spark when its surposed to.

[grayracer513]

If the spark is that weak, and it went downhill that fast, you might be looking at a CDI module or coil failure. It happens. With the plug out, you should get a good blue spark every time, and you should also be able to strobe it and find the timing consistently at the right time. If you don't see that, consider running it down to a dealer and have the electricals checked.

[Guest RIDE_for_RED]

may even just be a dirty connection, drop the tank and have a look-see.