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Engine Running Problem


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12-17-02, 05:53 PM   #1  
racer
bogging out

I have a single cylinder snowmobile it has a coil and cdi ignition on it.It will run fine and has alot of power until the engine gets warm and then it will die for power when you let off the gas.But if you keep it going at a steady speed and don't stop it will keep going with no problem.Would this be a carb problem or something to do with the fire?

 
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12-17-02, 06:35 PM   #2  
Racer...is this the same smowmobile mentioned in the other post? If so, we need to keep all this info in one thread so that we can view all aspects of repairs being done to the machine at one viewing. This is a perfect example of the reason for keeping it all in one thread, because the symptom you are describing seems to go hand-in-hand with the problem mentioned in the other post. The problems are most likely related. The engine is getting too much fuel via a leaking carb, and must run fast enough to burn enough fuel without flooding out. Once you decrease the speed, the engine can't burn the fuel as fast as it is getting it, and dies.

If this is the same machine, let me know and I will combine the two posts together.


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12-18-02, 04:00 PM   #3  
racer
I'm sorry I didn't mention that they are different machines.I have been repairing snowmachines for a passtime.So you figure it is getting too much fuel when it is running at a lower speed what would cause this?

 
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12-18-02, 06:03 PM   #4  
mastertekTN
It could be fire, fuel or compression related.

 
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12-18-02, 06:10 PM   #5  
mastertekTN
It could be fire, fuel or compression related. you will have to do some further testing to rule each of these out . If you need more help,I will need more engine info. Good luck.

 
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12-19-02, 02:08 AM   #6  
OK...different machines then .

If the 2 posts HAD beed about the same machine, I would tend to think that it was running too rich at low RPM since you talked about a spark plug problem....BUT...since it is not the same machine, that may or may not be the problem.

I doubt if it is an ignition problem, as that usually shows itself more at higher RPMs (if a coil were breaking down or shorting). It could be compression or fuel related though.

Keep in mind that I am going on basic 2 stroke operation to give you this info. I don't know much about snowmobiles, but I'll do the best I can to help. Sounds like Mastertek might know a bit about them though.

How does the spark plug look? Black and oily? Wet?

Another thing to check....many larger 2-stroke engines have a rubber boot that connects the carb to the head. This can develop cracks that cause vacuum leaks.


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12-19-02, 04:29 PM   #7  
racer
The spark is good and the plug looks wet and tonight when I went to start it it wouldn't start so I changed the plug and it started but it wouldn't idle on it's own.There was also fuel coming out of the muffler when it was running.It bogs really bad when you go to take off with it.It is a 1993 SKI-DOO TUNDRA with a 269cc single cylinder engine with oil injection and a MIKUNI CARB.

 
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12-19-02, 08:12 PM   #8  
So you do have a fuel delivery problem. You're getting too much fuel for some reason. If it is to the point of fuel coming out of the exhaust, then I'd say the float, neelde, and/or seat need replacement or adjustment. Remove the carb from the engine, but leave the fuel line attatched. Do you see fuel dripping out of it? Are you sure the choke is fully opening? Is the air filter clogged badly? Is the air tube from the filter to the carb pinched somewhere?


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12-20-02, 02:46 AM   #9  
racer
I'm going to check the air breather and the carb today and see if anything is blocked.The engine has a primer instead of a choke so that isn't the problem.I really appreciate the help you guys are giving me and I will keep you posted on how it goes.

 
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12-21-02, 05:59 AM   #10  
racer
I looked it over well and the rubber boot is cracked between the carb and the air box would this affect the engine performance?I also found that the cable to the oil injection is broken but I think by the looks of the fuel that leaked out of the exhaust it was getting too much oil.It was really black looking and oily.Would the extra oil harm the engine and will it burn the exess fuel out of the crankcase?

 
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12-22-02, 12:35 AM   #11  
The crack in the boot shouldn't immediately affect engine performance, but it will let unfiltered air enter the engine and can cause premature wear.

Excess oil will also cause running problems, and is not good for the engine at all. It clogs up everything with carbon.

The broken cable is probably controlling some sort of metering device to mix oil with the fuel. If the cable is broken, the metering device could be in the wide open position, causing a rich oil/fuel ratio.


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12-22-02, 08:27 AM   #12  
racer
I removed the exhaust and looked at the piston it is not scored or damaged at all.If the engine wasn't getting enough oil it would have burnt the piston right?If there is a hole in the piston would the engine still run?How do you get rid of the carbon in the engine if it was getting too much oil?I'm waiting for the new cable it will be in Tuesday and I cleaned the card and air filter.
THANKS FOR HELPING ME OUT GUYS

 
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12-24-02, 02:19 AM   #13  
Yes....you will have engine damage if you aren't getting enough oil. The engine may run very poorly if there is a tiny hole in the piston, but usually it won't run at all. If there is a hole any larger than a pin, it probably won't even begin to run. If you have a hole in the piston, it must be replaced. This is usually caused by either pre-ignition (timing too-far advanced), too hot of a plug, too lean of a fuel mixture, or a combination of any of the above.

The carbon in the engine will burn out once you get everything right. Get it running properly and take it for a ride...let it heat up good. It'll burn out.


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12-24-02, 04:00 PM   #14  
racer
I'm still waiting for the throttle cable before I can try it out.I tested the compression and it has 120PSI so that should be good.So once I get it running I will take it for a good rip to burn out the access oil.
THANK YOU CHEESE!!!

 
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12-24-02, 07:49 PM   #15  
Anytime! Let us know how it goes!


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01-03-03, 07:06 AM   #16  
racer
Finally got the new cable and put it together and took it for a good rip to clean it out.No more bogging and runs perfect.

 
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01-03-03, 09:34 AM   #17  
Good job racer! Glad you got it going!


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01-04-03, 03:52 PM   #18  
racer
engine dies

I have a 5hp techumseh engine on a snowmobile and once the engine has been running for about a hour it gets hot and quits. If I let it sit for about 10 minutes it will run fine again. It also is blowing some oil out of the crankcase vent. Any ideas what would be causing these problems?

 
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01-04-03, 04:26 PM   #19  
mikejmerritt
Hello racer, problems such as your with this engine can be the toughest to isolate. First, run it until it quits and loosen the gas cap and try to start it. If by some chance it will get a new cap, the vent is malfunctioning. If that doesn't do it I would look to the coil. Does the engine have an electronic ignition? About 1985 Tecumseh changed from points to electronic. Either way a failing coil is a failing coil and that may be the problem. My money is on a bad coil.....Mike

 
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01-04-03, 04:47 PM   #20  
Hello racer!

I bet Mike is dead on the money. The coil is most likely breaking down. The coil has tons of thin wire wrapped inside of it, and if that small wire develops a break in it anywhere, it may run until it gets hot enough for the wire to expand far enough to lose contact. A few minutes of cooling down usually lets it contract enough to fire again.

Check for spark when it quits...if there is none, replace the coil. If there is a spark, then the fuel tank cap may be the problem. Either of these 2 will most likely be the problem.

Let us know what you find!


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01-04-03, 06:32 PM   #21  
Tcumcman
5HP Tecumseh

Symptoms described sure sounds like either a bad coil, OR....
developing a vacuum in the fuel tank/fuel system. A "rest
period" allows the pressure built up inside a fuel tank to
subside. Then engine will start again. Got to be...one or
the other. As far as "blowing oil out the breather tube"....
VERY COMMON to "overfill" these with oil. I assume this
is an HS/HSSK50 or H50 ?? If so...19 ounces of oil is FULL
and it's very easy to put more than that considering MANY
other engines in this HP range take a bit more than this.

Tcumcman

 
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01-05-03, 06:14 AM   #22  
racer
Come to think of it guys the one time it quit I thought it was out of gas and I removed the gas cap and put it back on and it started again. I also noticed when it quits there is air bubbles going from the carb up to the tank in the fuel line. Is this normal?As far as a coil it has points since it is a very old engine. I figure the 70's since it is on a Alouette snowmachine. I filled the crankcase to the top of the filler plug like it states on the side of the motor.

 
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01-05-03, 11:13 PM   #23  
If it has a clear fuel line and you see bubbles going UP to the tank, then you probably have a plugged or bad vent in the cap. The reason for this: The tank starts off with say 1/2 gallon. You run it for a while and it gets down to 1/4 gallon. Air must displace the gas that left the tank. The cap should be vented to allow air to enter the tank for this reason. If air can't get in through the tank cap, then it will come in any way it can...in your case, through the bowl vent and up the fuel line. It's like trying to pour gas out of a gas can without releasing the little vent cap on the back side.

You may already know this, but other readers of this thread may not.


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01-06-03, 04:25 PM   #24  
racer
The guy that I fixed the machine for says that when it gets hot it still bogs and it blows out black oil and fuel on the snow but then it will run ok again.Would there still be oil and carbon in the crankcase doing this or could it be a bad coil?

 
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01-06-03, 08:47 PM   #25  
MODERATOR'S NOTE:

A troublemaker named Shibster replied to this thread. In his reply he embedded a site that would not allow you to escape. Sorry to anyone who was inconvenienced by this before I got a chance to get in here and figure my way around his cheap trick. The post has been deleted entirely.

Further measures may be taken.

Racer...I still think you have a fuel problem, possibly a sticking float. It seems as though your engine is flooding heavily for short intermittent periods. A float problem is the most likely cause.


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01-07-03, 02:03 PM   #26  
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a site that will not allow you to escape?


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01-07-03, 08:42 PM   #27  
Will not allow viewing of the thread in this forum, and will give trouble when getting out of the site. The other moderators on this board have had trouble also, in regards to your post. Do not embed another link.

I deleted the code you put in the previous post as well. Administrators have been advised of this, and will take necessary actions. What you are doing is violating your agreement.


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01-12-03, 05:25 PM   #28  
racer
still bogging

I'm still having problems with that snowmachine that was bogging it is the 1993 SKI-DOO TUNDRA with a 269cc ROTAX engine. It is oil injected and has a coil and CDI box.It is still bogging when it gets hot but it will sit and idle no problem and run perfect when I first start riding it. I cleaned the carb,changed the needle and seat,float is fine and tested the compression and it was 120PSI so all of that is ok. Do I start by changing the coil next or is there a way of testing the coil and cdi? I didn't post this with my other post because of that trouble maker. I really appreciate the help you guys give and info on this site.

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01-12-03, 11:16 PM   #29  
Just a thought...but what you are describing sounds like it could be restricted exhaust.

Another thing...try making small adjustments to the high speed mixture screw on the carb and running it to see if the problem improves/worsens. It could well be an adjustment if you haven't already done this. Low compression or bad reed valves (if equipped) could also do this.


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01-13-03, 02:51 AM   #30  
racer
I already checked the exhaust and it isn't blocked. It has good compression and it doesn't have reed valves. There is only one screw to adjust on the carb and that one is the air mixture screw and I have it adjusted to what the manual calls for. It calls for one turn out. I don't really think it is a fuel problem since it will only do it when it gets hot. When it is cold it has all kinds of power and no problem with it at all.

 
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01-13-03, 08:09 PM   #31  
Does it have a manual choke? If so, does puling the choke a little when it bogs help, or make matters worse? I still think it is a fuel-related problem. Try backing the air/fuel screw out 1/2 of a turn more and see if it gets better or worse. When you worked on the carb, did you check the float level? If it is too high, it can cause this kind of symptom.


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01-14-03, 03:02 AM   #32  
racer
The engine has a primer and I even took a carb off of a machine the same that is working on that machine and it still does it. The plug is wet and black looking when you pull it out. Should I start looking at the fire supply and change the coil? He also told me that it is getting harder on gas but there is no leak and the lines are fine. Would it not firing right make it harder on gas or what would cause this?
Thank you cheese for helping me narrow this problem down we will figure it out yet!!!!!!!!!

 
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01-14-03, 09:15 PM   #33  
Hmmm...lol.

If the plug is getting black and wet, it, of course, is getting more fuel than it can burn. Has it got the correct spark plug in it? Maybe it has a plug that is too cool. Maybe....but I think its gonna be something else. I suppose it could be in the coil or CDI, but if it runs fine at idle even when hot, well, ...that just doesn't quite fit with an ignition problem. In my few experiences with CDIs, they either work right, or they don't work at all.


When the engine gets hot and begins to give trouble, loosen the fuel cap. Do you hear air escaping as if it were pressurized?

Another thing...slip the rubber boot from the air cleaner box on without tightening it. When the engine begins to bog, pull the boot away from the carb to let it get as much air as it can. See if that makes it behave. That will narrow things down quite a bit.

Is this engine similar to an ATV engine? Does it have regular valves? Overhead? This thing has me scratching my head. I'd hate to keep saying I don't think it's an ignition problem only for you to find out much later that it was. I just don't think it is.

Does it pop and spit when it bogs, or does it just go "Blaaah", slowly dying while the throttle is wide open?


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01-15-03, 03:02 AM   #34  
racer
It has the correct plug in it. It doesn't have valves like a atv. I changed the coil to be sure that it wasn't that and it still does it. I pulled the exhaust off when it was hot and there isn't any unburned fuel or oil entering the exhaust. When it is hot and you go to give it the gas it will just go blahhh but if you pump the throttle 2 or 3 times it will keep going but if you just hold it to the bar when it does it it won't even move. Would this be fuel starvation when it gets hot because the oil is injected into the engine by a oil pump that has a cable that works together with the throttle cable? I thought maybe it was starving for fuel and only getting oil because when it bogs it is just blue smoke coming out of it. The fuel line has a filter in the tank I'm going to change that and it also has a vent tube for the fuel tank I will also check that. I checked the compression when it was hot and cold and it is the same. Hope to hear back from you cheese it has got me scratching my head to but I really appreciate the help!!!!

 
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01-18-03, 02:04 PM   #35  
racer
I think I may have found my problem. I changed the coil and it still did the same thing so I took it for a drive and I ended up walking back. I checked the plug and it wasn't wet so I checked for fire and there was none. So itried another one still no fire until I wiggled the wire that runs from the cdi to the coil. Put the plug back in and it fired up so I drove it about 100 feet and it died again. Anyways I went to check the connection when I got it home and it turned out that the wire was broken from the cdi to the coil. This would probably be the problem right? I guess when the wire would get hot it would seperate and not make a good enough connection to burn the fuel properly. Do you think I solved the problem guys? Thanks for all your help!!!!

 
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01-19-03, 12:08 PM   #36  
I hope so! LOL! Bad connections can do some really strange things. I don't really see where engine temp would be that much of a factor in a bad electrical connection unless the connection is pretty close to the engine...where it would expand a little when it gets hot.

I hope that's got it...let us know!


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02-03-03, 03:49 PM   #37  
racer
Well CHEESE!
The guy took it and drove it all day last weekend when it was cold and it worked perfect for him but he went driving it this weekend when it was milder and it still bogs when it gets hot.Would the compression be good if it was a cracked cylinder or would it not run at all? Also would it be any chance be the crank seals? Would it run if it had one of these problems? The machine also has an internal coil on this engine. How would you test the internal coil and the CDI? I am really stumped on this one I hope someone will try to help me out a little!!!!!

 
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02-03-03, 07:21 PM   #38  
It sounds like you've got a job similar to one I just got rid of today....a hair-puller! You run into this stuff once in a while and there's nothing like an engine that just won't cooperate.

I'll continue to help as much as I can, but as I said, these snowmobiles aren't my area, lol.

The coil should be able to be tested with an ohmmeter, but I don't know the specs for this model. I don't think it is the coil though.

Crank seals could do this...and might be the problem if the engine were leaning out....but if it blows smoke out, then it is probably flooding out rather than leaning. A cracked cylinder Would be a much more obvious problem I believe.

One way to check out the cdi box:....Connect a timing light with an inductive pickup. Turn the engine to top dead center. Make a mark on the flywheel that lines up with something like a casting mark or bolt on the engine. Crank up the engine and watch the mark on the flywheel with the timing light when it bogs. If the mark is jumping around and not staying in the same spot...lined up with the casting mark or bolt on the engine, then you have CDI problems. If the mark stays in the same place every time the light flashes, then your ignition is OK.


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02-04-03, 03:01 AM   #39  
racer
If it is a cracked cylinder would it not do it even when it is cold out? He drove it for about 4hrs when it was cold and it didn't do it so that doesn't sound right. As far as the CDI goes his brother has the same machine so I'm going to take it off of his machine and then try it. Should I use die electric grease on the wire connections or not? All the wire connections on this machine are covered in oil from him spilling it when he fills up his injection is this good or could it cause problems? Is there any way of checking for a cracked cylinder without ripping it apart? I'm just getting into the small engine repair but this engine is making me want to give it up already!!!!
I am happy you are trying to help me cheese!!!!

 
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02-04-03, 07:16 PM   #40  
No no...I'm not suggesting that you have a cracked cylinder. What I mean, is that a cracked cylinder would present a much more obvious problem... not in line with what the problem is on this machine you're working on. I don't think that it's cracked.

I would definitely clean all the oil off of the connections, and dielectric grease would be a good idea since it is operating in snow. You might use an ohmmeter to check all connections to make sure you don't have resistance across any of your connections.


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