2 stroke wont run

[crashinmatt]

Ok, I know this isn't a quad, but my brothers dirt bike won't start. Now, I know my wat around any part of a 4 stroke motor, but 2 strokes I'm not as good at. Ok, now for the details. He was riding it today, and then it started to die. Just as if it ran out of gas. But it didn't, gas was just filled. The motor was just rebuilt, and broken-in with 2 rides after break-in. Everything was cleaned at time of rebuild from carb to bottom end. Now, it won't start. Nothing not even a sputter. It does have compression, good spark, and everything is put together right. From what i can tell it is not getting gas into the cylinder. I took the carb apart and made sure all jets and everything looked good, and it did, but I still can't get fuel throught to the top. Any suggestions?

[SnowFlake]

Check the reeds. See if they are flush wiht tha cage. If they are bent up a bit replace them. and check the fuel line going to the carb from the cas tank, see if its clogged or kinked. Thats only thing i can think of at this monent.


-snowflake

[crashinmatt]

I checked the reeds, they look fine. Actually they were just put on before it needed to be rebuilt. And, the gas is getting into the bowl from the tank. I know this, because i took the bowl off several times after I thought I had it figured out, and everytime the bowl filled back up. Thanks for responding, anyone else have anything? This thing has me stumped.

[JDiablo]

lol maybe the piston is seized...that would suk...that all i could think of...that a tough one if you ask me

[James Parent]

My friend rode an XR250 for like 2 years ( 4 stroke) and then recently got a YZ125 (two stroke, bad ***) Well it ran for the first two weeks, and didn't work again.. he checked everything like 4 times, took the carb apart, checked spark and all.. but never actually double checked the fuel/oil mixture in his tank.. he put a little too much oil and it caused all this concern.. i don't know 2 strokes either, but try some totally new gas .. mix it yourself

[crashinmatt]

The piston is good, and everything seems good, but thanks for trying. At this point I think my brother is either gonna tear it down and split the cases and replace everything, or he may sell it, which I know he won't get much out of it not running. But, if anyone can think of anything else, it would be much appreciated.

[ewalker302]

I've had this happen a few times w/two strokes.

It may be that the exhaust is clogged or just has too much build up inside the pipe.

I don't know why exactly, but this will cause a 2 stroke not to fire even if it isnt conpletley clogged.

Try unbolting the exhaust from the head, just let it be cracked open there, and see if it will fire.

Once, dirtdaubers had gotten into my pipe, and another time the exhaust was just clogged up w/ carbon. I had to take the pipe off heat it w/ a torch & wail on it till all the junk fell out.

Have you tried starting fluid?

:bandit:

[JDiablo]

ewalker i have read on here of problems with some people like that to with the exhaust being clogged that sounds liek that might be the problem...starter fluid works good....just stand back a lil when you try to start it...or push start it down a hill or seomthing

[Aallron]

Any internal combustion motor requires certain things to happen at certain times in order for it to run. It has spark... but at the correct time? The shear key on the magneto could have sheared and altered the ignition timing, hence spark and no run. The reeds are ok and it has compression, that leaves the exhaust. If the motor cant clear the exhaust a NEW charge of air/fuel cant come in... try taking the exhaust off and see if it will start then. Very rare but it does happen. To check the ignition timing remove the inspection screw from the mag side, take the spark plug out and insert somthing nonmetalic that will project out of the spark plug hole and not hit the frame or tank and roll the motor over slowley by hand untill the mark is aligned with the indicator ( each manufacturer is a little different ) , while this is going on watch the TDC indicator you have inserted into the spark plug hole and guestimate TDC. Most of the time if the shear key is sheared it is very obvious, either the TDC incdicator has rotated past TDC and you are no where near the "T" mark on the mag.

Dont throw in the towel just yet... these things arnt that difficult to fiqure out.

[F-16Guy]

Try a new plug. 2-strokes are pretty famous for fouling spark plugs during or shorlty after break-in. A 2-stroke is one of the simplest engine designs, and if you have spark and fuel, they will at least sputter. If you've checked the carb and it's fine, chances are good that the plug is fouled. Also check the connection inside the spark plug wire boot. When you pull it off, the wire can pull away from the connector causing intermittent or no spark. One other thing to think about is the stator. When I was younger I had a KX 80. It wouldn't start so one of the first thing we checked was spark. It looked like it had spark, but appearently the spark was intermittent and pretty weak; it turned out to be a bad stator.

[BUILT TO RIDE]

Make sure the Air filter is clean. A two stroke will not run with an assed up airfilter. make sure the spark plug wire is connected to the plug solid. Like E walker said, get that sh*t out of the pipe. What i did with my old bikes stock* pipe was poured a lil gasoline in there, lit it with a lighter and let it burn it till it was dry. and it burnt out all the grease and oil. Watch ur legs when u light it, cause mine was in front of the outlet of the pipe and a fireball blew out there and burnt all my leg hairs off:eek2: :blah: :devil:

[crashinmatt]

I tried startin fluid, and that dont work. And I know I did it right, cuz I've done it plenty of times before on other motors. Air filter was cleaned right after rebuilt. Stator was replaced about 6 or 7 short rides ago, and it is getting spark. Spark plug was replaced, but now when you take the new plug out after trying to kick it over, it comes out clean and dry. I haven't checked the exhaust yet, but it was open before the ride. My brother said it just slowly died like it ran out of gas. We even took the head off and looked at the cylinder and piston, and it all looks fine. The only thing that is left is possible seal in the bottom end went bad and isn't letting fuel to get around and up into the cylinder, or something is keeping it from getting there. The bike ran good for like 5 minutes that ride, and great the previous 4 rides since the rebuild. Thanks so far, I'll check the pipe, but if anyone can think of anything else let me know.

[Syrus]

Check spark plug, sounds like the problem.

[AndrewRRR]

How old is the gas/oil in it? I'd put in a fresh spark plug (gapped properly), throw in some fresh gas/oil, clean out the carb really good with some carb cleaner, and try it again.
How did the bike run when it was running?

[cgamla]

You need to pay close attention as to why there is no fuel getting to the cylinder. I have seen a piece of rubber fuzz from a fuel hose land right on top of the needle and seat assembly in the carb. That blocked the fuel flow for sure. To test this just pull the bowl off the carb and reinstall it the carb.--- then turn the gas back on--- then lift up the float---you should have gas pouring everywhere-- if you don't then pull the line off the carb and see if gas comes out there---if no gas comes out of the tank there might be a clog there. My daughters pw50 actually had a serious case of microbial growth which clogged up everything and was really nasty to clean up. Good luck

[cgamla]

sorry if your float is hinged on the bowl. still find a way to check fuel flow for sure.

[crashinmatt]

Well, gas and oil is new and mixed right, the carb has been thoroughly cleaned twice, new spark plug, gapped, was put in and nothing still. I took the pipe off, and there was some antifreeze in there. But I dumped that out and cleaned the pipe and tried it again, still nothing. Now, not only is there a problem with the bike not running, but theres also an antifreeze leak. I just wondering if the 2 aren't some how connected? Thanks for all the replies.

[hollywood43]

Antifreeze in the pipe isn't right. How does the fluid level look in the radiator? Could possibly be a failed water pump seal.

[crashinmatt]

The antifreeze level was good, but it was just filled a couple days before. That was when we finished the top end. But, we took the side cover off, and the the bearings on the crank seem to have some slop. So, it looks like it's gonna have to be torn down, and while we are at it, we might as well do all the seals. Thanks for the replies guys.

[04'400ex'er]

take the airbox lid off. take the pipe off. get new plug. spray starting fluid in the airbox. if that dont fix it its ignition.id bet its the plug.

[EX_Junkie]

My buddies 250r just did the same thing about three days ago. Take the side cover over the stator off. Pull the flyweel off and check the woodruff key. I'd almost bet u money it sheared off. If it's sheared off it's not firing at the right time. It's a very cheap fix.

[crashinmatt]

Well, we tried the starting fluid and we tried several different plugs, and took the pipe off. Still nothing. We took the side cover off to check the stator, and everything was good there. But, as i said before the crank bearings had some play in them. So, we are gonna tear it down.