who knows something about 2 stroke engines?

[pegscraper]

I'm not real familiar with 2 stroke engines. I'm better with 4 strokers. I have a 1980 Yamaha snowmobile that won't start. It literally ran fine one day, and wouldn't start the next. It almost acts like it's flooding itself. It will start and sputter for a few seconds and then die. Then I have to blow out the cylinders and spark plugs to get it to sputter like that again. I've been into the carb a couple times and can't find anything wrong. This model has an oil injector, meaning I don't have to mix gas for it. It mixes oil and gas itself. How might I check to see if the oil injector is working? Will a two stroke motor run without oil in the gas? Or course I wouldn't want to do that for very long, but the question is, would that be giving me the symptoms I have? Where, oh where has manic mechanic gone so fast? I'm sure he could tell me what's wrong with it.

[jonesy]

spark plugs foul easy on 2 strokes, have your tried spray ether right in the carb to see if spark is there. oil mixer could be bypassed by premixing the gas, not sure of mix but I'm sure you could find it.

[FreezyRider]

First, put NEW sparkplugs in. A 2-stroke can foul a plug and keep it from firing under compression, and the plug will still "look" good. No amount of cleaning it will help.

If that does not fix the problem, get a compression tester and check to see if you have sufficient compression.

If the plugs are good (and firing under compression) and the engine is producing sufficient compression, then it is most likely fuel related. Yes, it will run without oil in the gas....but not for long!!

[pegscraper]

I have new plugs in it. I can also connect the plug wires and hold the plugs to a ground outside of the engine and watch them spark when I crank it. I'll check the compression just to verify it, but that doesn't really explain an instantaneous overnight change like that, does it?

[FreezyRider]

Pegscraper,

 

Whether a plug will fire outside the cylinder has nothing to do with it's ability to fire properly under compression. I have a small spark tester that clips between the plug wire and the spark plug (plug installed in the engine) that allows you to see if you are getting spark under compression. I think those are available at most autoparts stores. They are really valuable when trying to diagnose a problem like this.

However, if you replaced the plugs at the beginning of this process, that probably isn't the problem. Not seeing your engine, it's hard to diagnose...is it a twin cylinder? You've been into the carbs....have you had them off? Are there reed valves behind the carbs? If so, I'd be looking to see if some foreign material has gotten in there and is keeping the reeds from sealing.

Will it run if you continue to squirt fuel into the intakes? I used to use a squirt-type oil can filled with gas or gas/oil mix to do this. If it will run by manually supplying the fuel, then you know that the fuel system is the problem. If not, then it's either ignition or compression.

 

Good luck.

[RPG]

If it has a choke and not a primer, I'd check to see that the choke was operating correctly. It sounds like it could be a stuck choke or maybe broken choke cable.

[MikeM8560]

many time when id try to start ahd the motor would act likes its flodded, I would hold the throttle wide open and pull start it, It is pull not electric?

then it would clear up anf one a a few pulls and clear out/ if that dont work get a POLARIS:rotf:

[dray]

if you have the fuel pump working spark and compreson then it is most likey the center seals are shot and they will not show in a comp test it will just push air back and forth in the crankcase this will cause the vacum that is needed to pull the mixture in the cylinder!

you could pull one plug and see if it will run on the one with the plug in it if it dont switch and put the plug in the open cyl. and pull the first one if it will run on eather one the center seal is good unless you are running a triple this would give you one good cyl. it could also be a end seal. if you ran without oil it could be a hole in the piston or a scored jug. I would check simple things first change fuel lines for cracks pickup in tank filters:080402gudl_prv:

[GeorgeS]

How old is the gas in the Tank?

 

Maby drain and refill is in order ??

[BOO]

We use to race snowmobiles but it's hard to figure out what's going on unless you are in front of the machine itself.

The low end may be flooded with gas, this happens sometimes when you transport the sled with the gas turned on. Also can happen when the sled is just setting if the float got stuck for some reason and let gas drain into the low end.

The way to clear the low end is to drain the gas out and you do that buy taking the drain plugs out of the bottom of the engine and then holding the rear of the sled up high so the gas can drain out.

Another way to clear the top end of gas is to hold the spark plug over the hole of the cylinder with the key on and pull the starter over+++++WARNING***** DO NOT stand over the engine while doing this, you loose your eyebrows and possibility some hair.

Like someone else said, be sure to have some new plugs. That is very important.

Jerry

[Snarley Bill]

I'm not real familiar with 2 stroke engines. I'm better with 4 strokers. I have a 1980 Yamaha snowmobile that won't start. It literally ran fine one day, and wouldn't start the next. It almost acts like it's flooding itself. It will start and sputter for a few seconds and then die. Then I have to blow out the cylinders and spark plugs to get it to sputter like that again. I've been into the carb a couple times and can't find anything wrong. This model has an oil injector, meaning I don't have to mix gas for it. It mixes oil and gas itself. How might I check to see if the oil injector is working? Will a two stroke motor run without oil in the gas? Or course I wouldn't want to do that for very long, but the question is, would that be giving me the symptoms I have? Where, oh where has manic mechanic gone so fast? I'm sure he could tell me what's wrong with it.

the oil injection will not create the symtoms your having.sounds like you don't have adequate crankcase compression.if you have reed valves, they could be slightly warped and not sealing when closed. or you could have a leaking crank shaft seal.both very common problems on two cycle engines with age on them.check to see if you have a blue spark.if it is orange it will not fire under compression.if you do not have adequate crankcase compression it will fire, but will not run or idle.there is a way to test crankcase compression.you will need a shop manual to tell you how and give you the specs.i repeat it will not run without adequate crankcase compression.so check this out first and then,go on from there..bill:2133:

[Kurt]

I quite wasting my time on sleds years ago. Work on them for hours for a 5 minute ride.

[pegscraper]

Thanks for all the ideas. There are some things here I didn't know about 2 strokers. I have some investigating to do. I have thought for a long time that the guy who invented the 2 stroke motor never deserved to get the thing running. I don't like them.

[rod]

Don't know about sleds but I had an old 2 stroke motorcycle when I was 15 that did that. After trying everything listed here I took it to the dealer (much to my shame). They pulled the baffles out and it ran great. the baffle was totally plugged with carbon. Rode it home and it was LOUD. Heated the baffles and tapped them with a hammer to remove the carbon and ran like new. Rod

[Eck]

Freezyrider,

Hey bud, I'm not trying to doubt you to much here, but I would like to, (in a respecful way please), challenge your below comment.

I was a state certified mechanic for years. Went to many a state scheduled training class, and several manditory state held seminars over my years, and I built many an engine from scratch, and I not once EVER heard of this.

Please endulge me for a minute.

If a spark plug fires while being grounded on the outside, then it will / should fire the same on the inside unless there is an actual break in the spark plug wire and the "spark" is shorted or grounded out, prior to it reaching the spark plug.

Engine compression can do nothing whatsoever to stop the "spark plug" from producing or creating "spark".

Compression is a required ingredient of the actual "combustion" process, but it alone can not stop or alter the plug from producing "electrically produced spark".

The engine cylinder can not "fire" (produce combustion) if the gasoline and air is not "compressed", but the compression alone can not stop the spark from coming in through the plug or change it in any way.

A plug will fire the same on the outside the cylinder as it would on the inside of the cylinder whether it is under "compression" or in a state of zero compression.....Spark is spark...

Ok,

I have been corrected many times in my life, so here is your chance.

Eck

 

 

 

 

 

 

Whether a plug will fire outside the cylinder has nothing to do with it's ability to fire properly under compression.

[pegscraper]

Don't know about sleds but I had an old 2 stroke motorcycle when I was 15 that did that. After trying everything listed here I took it to the dealer (much to my shame). They pulled the baffles out and it ran great. the baffle was totally plugged with carbon. Rode it home and it was LOUD. Heated the baffles and tapped them with a hammer to remove the carbon and ran like new. Rod

 

I haven't had a chance to do anything with this yet. I may have to try this one. My very first thought when this thing wouldn't start was that mice had built a nest in the exhaust pipe. They had obviously been all around the engine. After two or three attempts to start it with it sputtering and stalling it will literally blow the exhaust pipe right off the engine with a loud bang (it's held on with springs, for whatever reason). To me it acts like it's having too much trouble getting rid of its exhaust. But I couldn't come up with a way to move enough air through the pipe to see if anything would blow out. I even attached it to the one inch water drain pipe on my 80 gallon air compressor and opened it wide open... nothing. The shape of this pipe is such a snake there's no way to run anything through it or try to look through it. I've been afraid to cut the thing open for fear that the metal is too thin to weld back together. I suppose replacements are going to be hard to find and expensive, and this old sled is probably not worth it anyway. But pulling the baffles out, I can't believe I didn't think of that. I'm not convinced that the pipe is or isn't plugged, either way. I may have to try this one and see what there is to see.

[Marcarl]

One thing that has not yet been mentioned is that the timing may have gone off. This can happen if the engine backfires, or is brought to a sudden halt, or the when the cord is pulled the engine kicks back. Most 2 cycles run on a magneto and this is governed by the flywheel which is attached to the crank shaft and held in position with a key made from soft metal. The slightest little bit off this key may be will give the symptoms discribed earlier.

[FreezyRider]

Freezyrider,

Hey bud, I'm not trying to doubt you to much here, but I would like to, (in a respecful way please), challenge your below comment.

 

I was a state certified mechanic for years. Went to many a state scheduled training class, and several manditory state held seminars over my years, and I built many an engine from scratch, and I not once EVER heard of this.

 

Please endulge me for a minute.

If a spark plug fires while being grounded on the outside, then it will / should fire the same on the inside unless there is an actual break in the spark plug wire and the "spark" is shorted or grounded out, prior to it reaching the spark plug.

 

Engine compression can do nothing whatsoever to stop the "spark plug" from producing or creating "spark".

 

Compression is a required ingredient of the actual "combustion" process, but it alone can not stop or alter the plug from producing "electrically produced spark".

 

The engine cylinder can not "fire" (produce combustion) if the gasoline and air is not "compressed", but the compression alone can not stop the spark from coming in through the plug or change it in any way.

 

A plug will fire the same on the outside the cylinder as it would on the inside of the cylinder whether it is under "compression" or in a state of zero compression.....Spark is spark...

 

Ok,

I have been corrected many times in my life, so here is your chance.

 

Eck

 

 

Hey Eck,

I have also been wrong many times in my life, but I have to respectfully agree to disagree. A fouled plug creates resistance to the spark jumping across the gap. The more fouled the plug is, the greater resistance. And, believe it or not, a plug that is seriously fouled CAN fire outside the cylinder where there is no compression, but not when installed. I have seen it with my own eyes.

I owned and operated (chief cook and bottlewasher type of position ) an outdoor power equipment business for 8 years. During that time I sold and serviced just about every type of engine imaginable....gas, diesel, electric, 2-stroke and 4-stroke. Even though I sold that business in 1991, I still have the tester that plugs in between the plug wire and the plug, and allows you to get a visual of what is actually happening. I saw many instances of a plug fouled enough to not fire under compression, but a spark would still jump the gap when the plug was just held against the engine block. Seems to occur most often on chain saws and Lawnboy mowers.

I did not have state certification, although I DID have factory-level training from Briggs & Stratton, Kohler, Tecumseh, Husqvarna, Dixon, and other minor players that I've since forgotten. But, my best teacher was experience.

 

I'd love to be able to actually show you a situation like this sometime...maybe that will happen. Meantime, we'll disagree with mutual respect.

 

Joe

[V7Goose]

Hey Eck,

I have also been wrong many times in my life, but I have to respectfully agree to disagree. A fouled plug creates resistance to the spark jumping across the gap. The more fouled the plug is, the greater resistance. And, believe it or not, a plug that is seriously fouled CAN fire outside the cylinder where there is no compression, but not when installed. I have seen it with my own eyes.

I saw many instances of a plug fouled enough to not fire under compression, but a spark would still jump the gap when the plug was just held against the engine block. Seems to occur most often on chain saws and Lawnboy mowers.

Joe

OK, maybe not the mirrors - with no apologies to the TV commercial. Heh heh . . .

 

It sounds to me like you two are in violent agreement, just not using the right terms. You are both right on what you are trying to say. Compression itself can have little to do with the ability of the spark plug and coil to fire, but any liquid introduced into the mix (such as fuel) can! A perfectly dry carbon-fouled plug will usually still fire, but if that carbon layer gets wet it becomes a good path to ground for the charge instead of being forced to jump the air gap. Technically the problem is not increased resistance across the gap, but a lower resistant path to ground through the wet carbon coating over the ceramic insulator. Always best to have some new plugs available when troubleshooting a problem like this. Good luck,

Goose

 

BTW - that exhaust pipe blowing off with a bang proves that you do have spark (at least some times). You are just getting a backfire from the unburned fuel building up in the pipe, then getting ignited by partially burned fuel being blown out on one of the exhaust strokes. That does not prove the pipes are plugged, but certainly worth checking.

[Eck]

Joe,

Ha..........I love it.......

I have to respectfully agree to disagree.......Now thats cool!!!!

 

One thing I notice in your below post is you are now speaking of a fouled spark plug.

 

In the previous posts, I didnt see or notice mention of anyone speaking of a fouled plug.

However, I may have missed that point, i will go back and re-read them all.

 

So if we are now speaking of a fouled plug, then I too will agree with you in that a "fouled plug" can have the effect of a ground, and thus short the plug out where it will not fire.

 

However, if we were talking about a GOOD spark plug, I will have to respectfully agree to have to disagree...

 

LOL with you Joe and dont think I am mad or trying to get under your skin..

 

Looks like V7Goose thinks we are having it out!!!!!

 

Now stop that, ouch, quit, your hurting my feelings, stop now, sniff, tear, sniff..

 

Doesnt really matter, as Pegscraper said ;he has new plugs installed.

 

 

 

 

Hey Eck,

I have also been wrong many times in my life, but I have to respectfully agree to disagree. A fouled plug creates resistance to the spark jumping across the gap. The more fouled the plug is, the greater resistance. And, believe it or not, a plug that is seriously fouled CAN fire outside the cylinder where there is no compression, but not when installed. I have seen it with my own eyes.

I owned and operated (chief cook and bottlewasher type of position ) an outdoor power equipment business for 8 years. During that time I sold and serviced just about every type of engine imaginable....gas, diesel, electric, 2-stroke and 4-stroke. Even though I sold that business in 1991, I still have the tester that plugs in between the plug wire and the plug, and allows you to get a visual of what is actually happening. I saw many instances of a plug fouled enough to not fire under compression, but a spark would still jump the gap when the plug was just held against the engine block. Seems to occur most often on chain saws and Lawnboy mowers.

I did not have state certification, although I DID have factory-level training from Briggs & Stratton, Kohler, Tecumseh, Husqvarna, Dixon, and other minor players that I've since forgotten. But, my best teacher was experience.

 

I'd love to be able to actually show you a situation like this sometime...maybe that will happen. Meantime, we'll disagree with mutual respect.

 

Joe

[FreezyRider]

Don't worry, my dander was far from being ruffled out of place! Yeah, I was talking about a fouled plug....problem is, I tend to not be detailed enough in my communications. I even do that in person! Sorry fer the confuscating!

 

And the GooseMan would make a good arbiter, too!

[Redneck]

A new plug is only new for 1 stroke a badly flooded cylinder can foul a plug on the first stroke. I would clean and dry the plugs crank the engine with the plugs out to blow the cylinders out. install the plugs and lay the plug wires on the plugs let the fire jump about a 1/4 inch from the wire to the plug that will give you a hotter spark. If you suspect the exhaust is plugged just take it loose at the cylinder that will answer that question. The reason the exhaust is healed on with a spring is to keep the exhaust from distorting and breaking the cylinder.

[pegscraper]

The problem is that two strokers won't run without the exhaust pipe on them. The expansion chamber in the pipe somehow greatly increases exhaust flow, which is really needed when the exhaust and intake stroke are the same thing and the engine won't generate its own exhaust flow. Without the expansion chamber keeping the exhaust flow up they won't run.

 

If exhaust heat distorting and breaking a cylinder is an issue on a sled, I wonder why it isn't on our bikes. What's the difference?

[Ol Erns]

If I may, and maybe you already replied to this, but honestly this sounds like a fuel problem. Old gas, whether you stabilized it or not will cause the conditons you described. I have owned several sleds and currently have three for my riding pleasure. Each season, which will soon be upon us, I go through the same ritual of getting the sleds started for the first time.

 

I will have previously drained or removed almost all of the gas from the tank and resupplied it with fresh, 92 octane fuel. The other fuels have a shorter "shelf" life due to the additives. I will always try to start on the plugs left in it, but always have a fresh set on hand.

 

I will remove the plugs and with either 40:1 ratio gas, either with spray bottle or filler put approx. 1/2 oz in each cyclinder. Put the plugs back in and pull. It will most likely start and run until it runs out of gas. I will repeat this three to four times until it has had the opportunity to to draw fuel from the tank on its own. The fuel pump works off the engine, creating vacuum, pulling fuel from the tank, to the fuel pump and then to the carb(s).

 

Now the warning....as always when dealing with gas in this fashion, it is easy to spill it, possibly onto the exhaust and you could have a flash fire. That is why I like the spray bottle. Four or five squirts in each cyclinder will usually do it.

 

On my 340 fan, it usually only takes one series as described. My 700 twin moutain sled will take two to three of the series.

 

I also maintain our Departments 7 sleds, and every fall, which we just did yesterday, is started the same way for the first time.

 

And when you put it away for the season, don't forget to fog the motor.

 

If you think you've ate a piston, two ways to find out. 1. you will have aluminum on the spark plug 2. a flashlight and looking down through the spark plug hole. 2- strokes will have a heavily carboned piston. If its got a whole in it you will easily see the shinier aluminum.

 

Just my two cents, good luck and when you get it running enjoy. For us Northerners it "almost" makes up for the inability to ride the bike.

[Snarley Bill]

hate to disagree but it takes more voltage for a spark to jump a given distance under compression than at atmospheric pressure. a plug can fire out side a cylinder and not fire under compression this is due to the fact that as you compress air, the molecules are forced closer together and the resistance between the electrodes increases.that is why racing engines use high voltage ignition systems in access often times of 40,000 volts or more.an orange spark, which is a very weak spark will usually not jump a spark plug gap at all under compression.this is one of the reasons the new cars start so much easier in the winter than they once did.they have a much higher voltage output on the secondary side of the coil than the older cars to fire the ultra lean mixtures being used now.