hey what is up. alright, let me run down the bike....it is an 86 yamaha "yz" 250. just replaced the reeds, all seals, and oil. jets are cool, honed out the cylinder, replaced rings. got it all together, won't start. i have to end up kicking that pig a dozen times. then it floods, through all the kicking. i even re-set the floats. i took it up a hill the other day, and tried bum starting it. well it would start for a split second or two, i could even hear the expansion chamber ping a few times, then it would blub blub blub, then start, blub blub blub again, start...you get the picture. so to me, it sounds like a electrical problem. although, i had the bike running after all the repairs were made, and it sounded a little weird, even though i did have the pipes off. but it was high rev down to low up to high, and so on while i was at idle. when i got it into gear, all good. so that is my problem, she just won't atart anymore, and i'm afraid to keep kicking her over, cause i do not want to flood her out. i am that DIY'er type guy and don't want to take it to a shop until i have fully blown through all my resources. so any help would be much appreciated...since i'm heading up north at the end of the month and would love to go ride for a few days!. Thanks, Willie

 

I had a Honda 80 that did the same thing. The last year I had it, it was in the shop for a total of about 12 months and it still didn't run right. I eventually sold it and bought an atv to replace it. I miss riding the bike, but definately not the hassle of trying to get it started every time I wanted to ride it. I think that a warped head was the source of my trouble, but I'm not 100% sure of it.

 

well i know it is nothing like that. i did a thorough check over the heads and walls. but you are not worth the hassle everytime. i want to sell it, but i need to get it working right first!!

 

Just a quick thought...You said it ran with the pipe off? Did you try taking the pipe off again? Up here in the north, it is common for mice to nest in the expansion chamber of our snowmobiles, if you forgot to cap it off for the summer...

 

i sure as hell hope not!! if there was a mouse, it got toxic injestion!! and i only had it off for a little bit to chemical clean the inside.

 

I had a 50 yamaha y-zinger when I was a young boy. It ran fine for 4 or 5 years and then the magneto went out on it. It did the same thing you described. Don't know if your bike has one but it's worth a look.

 

now is the mag in the left side casing just opposite of the clutch?, or is it up on the frame by the tank? i have this black box under the tank that has wire in and out of it.

 

Is the gas fresh? Water in the tank or carb float bowl are going to make it difficult to start.

New spark plug?

Bad reeds and worn rings will also make it hard to start, but seems like you have replaced those.

Do you have any spark at all?

On an old '84 I had, the stator went bad and needed to be rewound. It is under the flywheel on the left side of the motor. It was about $100 at the time. IMO, this is more likely the culprit in the ignition than the black box (CDI). Places like www.rickystator.com can rewind it, or check with a local shop. With patience and the right wire, you can do it yourself (search
the internet for instructions).

Also, you should join www.dirtrider.net and ask over there.

 

Dave, i've been waiting for you man!! fuel is fresh, mix at 40:1, actually i think i went with 32:1 this time. as far as tesing spark, i know there is a safe way and an unsafe way, what is the safe way?, plug is new. how would i know if the starter is bad? is there a way to check it myself? thanks bro!

 

To test for spark, attach a good plug to the plug wire, and lay the plug on the outside of the engine. The plug needs to be grounded against a metal part of the bike for it to spark. Also, some say kicking the bike over without the plug grounded might damage the CDI, but I have never heard of this happening.

Kick the bike over - you should be able to see and hear the plug sparking.

Often it is easier to have a second person to either watch for spark or kick the bike over. Don't touch the plug while the motor is being kicked over - you could get a nasty shock. I suppose you could tape it down, but it will probably lie there allright.

FWIW, the bike will be easier to kick over (will spin faster) if you pull the spark plug out of the cylinder, Turn the gas off just to be safe.

If you have no spark, you have could have a variety of problems: Kill button shorting out (pretty common), bad ignition wire, bad coil wire, bad connection or ground somewhere, bad stator (common on old bikes in my experience), bad CDI, etc...Make sure there is no rust between any electircal connections and ground.

If you have a weak spark or cannot be sure how strong the spark is, it still could be the above. A stator going bad can give spark to a plug outside the motor, but not be strong enough to ignite the compressed fuel inside the motor.

There are a few other things to consider. Weather can effect jetting, and your bike will want to be jetted richer now than in warmer months. Turning in the airscrew (small brass screw near the left lower rear of carb) if the bike has one will richen up the jetting at low rpm and may aid starting.

Starting technique may also need to be adjusted after the rebuild, but the inability to bump start points to other problems.

Try the following starting technique:
New plug.
Turn the fuel on and put the bike in neutral.
Turn on the choke.
Lay the bike on its side for 5 or 10 seconds - let fuel trickle out the overflow tubes for a few seconds.
Pick the bike up. Don't twist the thottle!
Kick it over gently a few times to prime it - Don't touch the throttle.
Push the kickstarter very slowly and feel the resistance. As you are on the compression stroke, it wiill get harder to push the lever until you get to top dead center. STOP pushing the kicker the instant it gets easier to push. The piston is now at TDC.
Place your hand on the crossbar and don't touch the throttle!
Raise the kickstart to the top and kick as hard as you can.

If it doesn't fire, find TDC and kick hard again.

The point of getting the piston to TDC before you kick for real as it gives the motor a full down and up stroke to build speed before the next spark.

Good luck!

 

I use to be a bitch to start my CR 500 up. New reeds, new plug and fresh gas it started easier. but still a pain.

I would check the spark. My CR had problems like that. check the magneto, the coil and the spark plug wire (mine needed the boot replaced) kill switch shorted.

Do you have the right heat range on the plug. This made a huge difference on my cousins RM 125.

 

let me catch my breath first,.......... that didn't work! now what? i pulled the plug and hand cranked it, no spark, although i did see one after 20 cranks. as far as grounding it, just touch it to some form of metal on the bike right? so let's say it is not getting spark, faultly what? also, i'm flooding the plug too! after i did what you said dave, i pulled the plug and it was wet. like i said, all new seals.. head, cylinder, water pump, everything.

 

Rustbucket mentioned a few good places to start.

Best to begin with the free or cheap stuff first, such as the kill switch and all connections.

Your wiring is probably pretty simple, but if you have an owner's manual with a schematic, that will help you check wires one by one. If you don't have an owner's manual or shop manual, you may be able to find one or a reprint on ebay or by using google.

You are probably going to have to take the seat and tank off to get to the wires. Make sure there is no rust between the frame and any items grounded to it.

If you don't have an inexpensive volt/ohm meter, you can get one cheaply at radio shack or a hardware store.

On a dirtbike oriented site, you might be able to find someone who can post specs for testing the components of your ignition system.

If it is not a bad wire or kill switch, I would focus on the stator, underneath the flywheel/magneto. The wire in the stator can deteriorate over time and may need to be rewound with new wire.

BTW, once a plug gets wet and fouled, it may just not work well ever again. After you check the kill button, connections and go through the wiring, try checking for spark again with a brand new plug.

Another possiblity is the woodroof key aligning the flywheel to the crankshaft has sheared. This will throw your ignition out of whack and you will be unable to start. You will have to pull the flywheel to check or replace, but at least the part would be cheap. On most bikes you will need a flywheel puller; on some bikes an automobile steering wheel puller will work.

 

dave, your scaring me!! too much to handle. i will give it an all over check though. i did pop off some connections and wire brush them. but i will check it all out. i will be talking to you soon hopefully. Dave, thanks for all the help.

 

hey, i pulled off the kill switch and it is fine, put a newer plug in and got spark, got on the bike and kicked it over three times and whammo! it started!! hoo-ray for me! but hold the celebration. i wanted to open up the throttle a bit, and it stalled. sounded like a drowning bear! pulled the plug and i literally dumped fuel out of it, so i'm guessing it has to do with carbeuration. but what factor of the carb do i tweek? i got on that DRN site, wow, what a site. so much info, but it seems that all the members are always out riding, never home to reply to an e-mail! Lates Willie