300ex wont start

[brooksto]

Bought a 96 300ex, knowing that it didnt start as a winter project. Hadnt been started in probably 10 years and the person I got it from couldnt (or wouldnt) tell me the history of it.

Soo... that being said, it will crank and crank but wont start,

has new battery and carb rebuild kit and spark plug. good spark. Cleaned out lots of crud from the carb and fuel tank. Fuel seems to puddle up between the carb and motor, or at least you can see its wet when you remove the carb. plug doesnt seem to be getting wet. pilot screw is 2 1/4 turns out. tried putting some gas in the cylinder, also tried spraying starter fluid into the intake pipe.

I think I should check the compression next (what size fitting do I need?) But is there anything else I could be missing or somthing I can try? Ive already had to charge the battery twice because we keep trying things and cranking and cranking but nothing....

[SAMM250ex]

Squirt or pour 2 tablespoons of oil down the spark plug hole.. reinstall spark plug and spray starting fluid into the rear of the carb. while cranking at half throttle...... I had the same prob with my 300 after setting for years !!

[ss420ex]

another thing to look for is to make sure u hav a good connection on all wiring... mainly the 2 wires on the right (by the brake lever on the motor.) also a compression test and a spark test might tell you something... im not sure on wat size fitting it takes for the compression test....
do u know how to test for spark?

[brooksto]

ok thanks for the ideas, Im guessing putting oil in the cylinder would raise compression if it was low? I found in the manual that the spark plug is threaded for 12mm so I will try to locate an adapter for that, check the wiring and report back.

[dbc112]

Check electical 1st.. did you do the good ole spark test, put a screw in the spark plug boot (or an extra plug) and hold it close to the engine, crank it over. You should have spark.

If you have no spark PM me. I went through months of electrical BS. I can wire these things blindfolded now. I also have a clymer manual.> get one, well worth the $30.

Also, is it all stock? Pistons? Did you change out the oil, air filter? Are you running the stock airbox lid (you should to run richer for now).

[brooksto]

i held the plug against the engine and saw it had spark. Also tried with a known working plug. I have the factory manual, not the clymer though I figured out that most of the clymer is available for free on google books preview :)

Im not sure about stock as I dont know the history of it, There are no exterior aftermarket parts so I doubt any engine work has been done. I did change the oil and oil filter....

air filter is some kind of oiled foam thing, dont know if its oem. There was some sort of rats nest in the airbox, (full of animal hair) when I first starting taking things apart, got it all cleaned up, filter was on then so I dont think it sucked up anything. We have tried starting it with and without the filter on (have tried spraying starting fluid into the intake also) We had the airbox lid off when we were trying to start it,does this make a difference?

[stevenroberts]

check timing thats a common problem i have with
most old quads

[dbc112]

Airbox lid off allows for more airflow.. I was saying to leave it on to run richer.

You tripple cheked the carb? I would think the spray would be plenty of bang to start her up.


Try the old jump start and listen to the engine crank over.. Also how charged is your battery? Sometimes it needs a really good push.


Also the compression test would be my next recommendation..

[brooksto]

Hey guys thanks for the help. Heres an update:

I finally got the compression gauge adapter (12mm), and I only was getting 50psi! Should be 185 according to the manual. Did a kind of ghetto leakdown test where I put it at TDC and hooked an air hose up to the spark plug hole, heard air leaking out of the oil filler so im thinking rings....

tore the motor apart and found this:

http://img188.imagevenue.com/loc908/th_19117_0217092102_122_908lo.jpg (http://img188.imagevenue.com/img.php?image=19117_0217092102_122_908lo.jpg)

The whole intake side of the piston is eaten away, bottom lip of piston is broken off. clinder sleeve is toast.

Soooo.... now I am trying to decide do I part it out and cut my losses or try to fix it. Head is in good shape, pulled the clutch cover and everything in there looks really clean. Cam chain has some metal in in it and the guide is a little torn up. I was thinking of pulling the engine and splitting the case and trying to clean out any metal bits as best I could. Any opinions on this, is it saveable? Or better yet, should I even try to save it?

[glatf70gg]

dude that is narley, never seen one that bad. you can get a new cylinder kit on ebay for a couple of hundred. i'd rebuild it. as long as the crank is cool. i just bought a 330cc kit from moto-man.com for $289 included new cylinder with sleeve installed, piston 11.5:1, and gasket kit. gotta clearance the cases but other than that it is a bolt on kit.

[Grimzella]

i just made it. i got my quad right around the time i joined this site. one day while riding at wellsville.. a buddy behind me said i would periodically blow smoke. the quad was already 5 years old so i figured i would tear it down and replace the rings. After ripping it down.. i noticed the crack and bad scoring\burning on the piston's intake side just like that one above. another ride or 2 and it might have busted off, and then right down into the crankcase. so an aftermarket wiseco piston is now in its place.

[Grimzella]

the otherside looked fine exhaust side. i would assume the person who i bought this from either did not clean the filter or oil it.. or it was torn, or the boots were leaking. that stuff was all checked and fixed after repair.

[SAMM250ex]

Ouch !! I hate to split cases !! to many parts to fall out... Take the engine out of the frame and feel the bearings in the crank. If they are good run water through the case and clean out the garbage...then run solvent through to double clean it... Buy a cheap piston and cylinder and go again and enjoy !! Just my 2 cents..... Im a cheap sob tho hehehehe

[SAMM250ex]

Just a question ..... Could this problem with the piston be from running a hot dog exaust and not richening up the mixture... (Running to lean and overheated) ??? Thanx

[Studster]

i know a guy that put the oil filter in backwards on a rmz250 which stopped circulation of oil and the piston looked exactly like that ...

[dns1764]

YIKES!! sure looks like a good canidate for a 330 kit

[brooksto]

A little update for you all, I have been slowly gathering the parts I need to rebuild. I got a 250x cylinder and a new oem piston and wrist pin and gaskets. I am still trying to figure out how to flush the case since I am too afraid to split it.

A friend suggested sloshing around some kerosene in it. My main worry is if there are large pieces of the skirt somewhere inside how to get them out without splitting.

Well I may get to resume this project this week so I will let you know how it goes.

And it had the stock exhaust on it when I bought it, looked like it had never been removed.

[SAMM250ex]

I still say pull the engine and turn it upside down and rinse the case with water, solvent, karoseen whatever and wash the broken parts out.... Put it back together (with new parts) and go again....... :D

[brooksto]

thats not a bad idea, would be much easier to get them out of the cylinder hole then the drain plug hole!

[SAMM250ex]

Yes it will.... You must have missed that part on my first post heheheheh Have fun :D

[SAMM250ex]

P/S Use the garden hose and spray a hard stream of water into the case to wash out the crap !! Be sure to get all the water out !! and replace the oil filter !!! We did this one time with a Volkswagon to wash a broken skirt out and it worked great !!

[Grimzella]

i have to agree with the top hole over the bottom hole.. lol cylinder hole is bigger, and many more broken pieces will come out much easier. take your time to make sure everything is out. you and a friend grab an end and shake around, see if you can maybe here some inside.