1985 yz250 stalled on me

[snowskater101]

my bike had ran good all day... on the way home it just stalled amd sounded like it ran out of gas. it still had good compression so i dont think it seized but it wouldnt start up at all so i had to push it for 3 miles. later i tried starting it, the kick starter seemed to not grab until about halfway; every once in a while it would fire a couple strokes and stop. i cleaned off the plug but it didnt help. after about 20 or so minutes of trying to start it, a part on the end of the kickstarter shaft broke out of the crankcase!!! HORRIBLE... I KNOW!!!
i put the bike away for a week and then came back to it to realize the bike was leaking gas out of the magneto cover, i opened it up and got about a quarter gallon of gas to came out. i can also hear about a quarter gallon of gas in the exhaust too. i left the gas on by accident for the week but still, it should have came out of the overflow tube unless it was blocked or something.
i changed the oil after all this and it was a nice grey metally color. the engine had just been rebuilt and that was the first oil used.

does anyone have any help with any of these problems. im about 99% sure its not seized. i havnt had a chance to take the crankcase cover off yet though. im thinking the idle gear that connects with the kickstart gear got caught or something and stopped the engine and thats why the kickstarter shaft was so easy to break out of the crankcase.

any help would be great!!!

 

[whenfoxforks-ruled]

Load it up and bring it over. I hope you have a manual before pulling the clutch cover. If the kickstart mechanism is not installed correct it can cause similar issues,but gas in the magneto cover,yikes! That one calls for a leakdown test,crankshaft may be gone.

 

[j.lawson]

it's not seized if you said you kicked it over for twenty minutes. and pulling the clutch cover is no biggie. but i'd start with the small stuff bro, take off your carb, see where all that gas is coming from??? check your reeds, and maybe even pull the head and cylinder? I'v never heard of gas? flooding out of the side case of a non-running bike...

 

[snowskater101]

yeah the crazy thing about the gas coming out is it wasnt discolored in any way, it looked exactly like the gas in the tank.

 

[snowskater101]

i took the crankcase cover off to get to the kickstarter this weekend... it turns out part of the kickstarter shaft broke off and pushed a hole through the crankcase. i put a new k.s. assembly in and it kicks fine now.

it turns out the grey and flaky oil was from the peice that broke off the k.s. and it was grinding against the case when i was kicking it over.

i also emptied all the gas out of the exhaust, there was about a third of a gallon:-/

i tried getting it started after all this, it didnt want to though. i didnt clean the plug off though, its probably still wet and fouled. im gonna try the plug next, maybe it just needs to be cleaned or maybe it is ruined??? i hear of people fouling plugs, does that actually make them totally uncleanable and unusable? i thought i fouled one before on a different bike but i was able to clean it up and still use it.

if its not my plug i think im gonna check all my connections and make sure im getting a good spark.

oh i also took the carb apart, everything seems perfectly fine. there were not jets in the bottom of the bowl like i was hoping.

i have no idea at all if it doesnt start up after all this. does anyone know much about fouling plugs or have any ideas??

 

[whenfoxforks-ruled]

Have you done a seach on that subject?

 

[76GMC1500]

I've seen gas fill a crankcase and pipe when the fuel valve is left on. If that happens, there is a problem in the carb and you need to replace your float valve and seat as well as clear any vents and overflows. You'll have to pull the pipe and drain the gas out. The gas in the flywheel cover indicates your crankcase seal is blown which could also explain the bike stalling. On a bike that old, both crankcase seals are likely out.

 

[rmc_olderthandirt]

It sounds like there is a combination of problems.

You shouldn't get any liquid gas from the tank into the engine. For that to happen, two things have to have gone wrong. First, the float valve had to have stuck open or leaked excessively. In addition to that, the over flow tube had to have been either blocked or routed upwards so that it was higher than the intake port of the engine.

If liquid gas made it into the crankcase your engine would be flooded and it would stall and not restart until you got all the gas out. If it was still leaking during that time you would never get it to start.

The gas getting into the magneto indicates that in addition to the above problems the crank seals are shot.

Fix both the problems with the carb: I suggest installing a new float valve and then make sure that the over flow tube is routed properly.

I recommend that you take the gas tank off the bike entirely as well as the exhaust. Turn the bike upside down, resting on the seat - handle bars. Remove the sparkplug. Now turn the engine over, either with the kickstarter or by turning the rear wheel with it in gear. If there is any liquid down in the crankcase this will get it to run out fairly quickly. Contine until no sign of liquid comes out the spark plug hole or exhaust then turn the bike back upright and reassemble with a new plug.

Now try to start it again.

Rod

 

[snowskater101]

it was the plug!! :-D i took it out and it looked like it had a smaller gap than it should, i put in a older one that i had and it fired right up. right when it got going some oily gas came out of from the exhaust where it meets up with the cylinder, only like a tablespoon though. hopefully that was just the little bit left in the bottom of the cylinder. i ran it for a couple miles and it seems to be back to normal, plus a few new leaks from me putting it back together though :-/

 

[snowskater101]

so i fixed the kickstarter and figured out the fouled plug but... i went riding the yesterday and my bike fouled another plug at the end of the day. i took it out and cleaned it off and tryed to start it up; it started but i didnt give it enough gas. i kickstarted it again and it fired one time then stopped(not enough gas again) but since it fired and stopped right away it pulled the kickstarter back up REALLY fast. i immediately knew what had happened, it pulled it back so fast that the kickstarter stopper broke again. this was a perfectly good kickstart shaft as well.

this shouldnt be happening right??? the engine like i said was just bored out for the second time when i got the bike, do you think it might have too much compression? thats what im thinking, and also that i need to give it a lot more gas and kick it harder instead of trying to go easy on it.

does anyone have any idea on why ive broke the stopper on two kickstart shaft in two rides?

the kickstarter worked totally fine until it fired once, stopped and pulled it back up super hard.

if it is too much compression, would a larger head gasket make it have a little less compression?

 

[rmc_olderthandirt]

it fired and stopped right away it pulled the kickstarter back up REALLY fast. i immediately knew what had happened, it pulled it back so fast that the kickstarter stopper broke again.

Let me see if I am understanding this:

You kicked it, it fired, then the kick starter returned to the top with significant force and broke the kickstarter or what the kick starter stops against.

First question: Wasn't your boot still on the kickstarter? Did it lift your foot up as well? Or had you let your boot slide off the kickstarter at the end of the stroke?

If my understanding is correct then I would say that you may have a serious timing issue, or perhaps you are running way too low of an octane gasoline.

When the kickstarter forces its way back like that it is because the engine was actually running BACKWARDS! While it is possible (in general) for a two stroke engine to continue to run backwards any engine can fire once and rotate backwards.

This will happen when the air/fuel mixture ignites way too early on the compression stroke. The piston is still coming up, the fuel ignites. The flywheel doesn't have enough momentum to force the piston the rest of the way up so it stops the piston and sends it back down, turning the crank backwards. This can happen on a two stroke or a four stroke.

When the engine stops and then rotates backwards and the kickstarter is still engage it will force the kickstarter back up with a vengence. If your foot has slipped off the front you could end up getting the kickstart lever snapping into the back of your leg. At best it would hurt and at worse it could break your leg. In your case it seems like it broke the kickstarter.

One reason that this would happen is if the spark was advanced too much. Another possibility is that the gas has too low of an octane and it ignited without any spark at all.

If you have modified the engine to get a greater compression ratio then you need to run a higher octane gas. A YZ in its stock configuration would probably require 91 octane to start with so any increase in compression ratio and you may need to run racing fuel.


Another way that the problem could be happening is if the timing is too far advanced. I would check it to make sure that it is within spec and working properly.

Rod

 

[snowskater101]

how do you check your timing? i have the manual but ive never looked into timing.

i took this kickstarter shaft out and replaced it with one i refurbished. i noticed on both kickstart assemblys that a retaining washer was bent(it lets the gear move only so much) so i machined a thicker washer for it. they have a circlip thing i think it is that is suppose to pull the kick gear away from the idle gear as the kickstarter lever travels back to the normal upright position. on the last one it seemed very weak but the one i put on this time seemed fine, im kind of thinking that those clips are weak and maybe its not pulling back away from the gear when it should.

i really hope this new larger washer will solve the problem.

if the engine was to rotate backwards with the kickstart gear still engaged wouldnt it spin it downwards. i really have no idea though.

im gonna try a higher octane gas and cross my fingers.

 

[snowskater101]

my foot was coming off of the kickstarter at the end of the kick. i use 91 in it now but ill get some octane booster and try again.

if the timing was off, i would probably be able to tell when i was riding around right?

 

[whenfoxforks-ruled]

If the gear and spindle are not in proper sequence it will do this. If you leave your boot on top of the kick starter,it can also do this. And all the engines that I have seen run in reverse,did not have kick stater issues,just a priceless look,roost and then shut it off and restart. On yours I am not for sure about the gear needing to be in time,its almost like I remember having this same issue on this model,seems to me it was a matter of loading it properly. It would go in seemingly fine,and when I messed with it it would reload further. Getting it all the way back was the ticket!