Help with 140 looper igntion

[joezek]

I have a '85 140 Looper with one dead cylinder. I've narrowed it down to the stator, but need to get in the water this weekend.....So my question is if the ignition system on this engine fires a spark more than once per cycle. What I'm thinking is that it might fire once normally, and once again on the exhaust stroke- at the same time as another cylinder compression stroke. If that's the case then I'll temporarily connect the coil power lead of two cylinders that normally fire at the same time. I've done this before on another engine and it ran perfectly.

 

[racerone]

Sorry there is no EXHAUST stroke on this motor.------And no 2 cylinders fire at the same time !!---.----Each plug fires once during one revolution of the crankshaft !----And how did you determine the dead cylinder.----Which cylinder is dead ?------How did you determine that the stator is at fault ?---And what engine did you try your tricks on ?

 

[flyingscott]

Did you do a compression test. What about a spark test. DO NOT CONNECT COILS TOGETHER. I doubt the stator is dropping one cyl I would look at the cdi boxes. Just because 2 cyl are at the top of the stroke doesn't mean they are on the same stroke. And remember 2 stroke motors combine the strokes they are not seperated like a 4 strke motor.

 

[racerone]

On that motor you never have 2 pistons at the top of the stroke at the same time ??-------------And a 2 stroke like that is realy 4 seperate motors as far as processing the air is concerned.

 

[flyingscott]

My comment was meant as a generality to not connect the 2 coils together ever. Some motors do have 2 cylinders at the top at the same time and people will mistake that for being on the same stroke. And the Op seems to indicate that he is working off of 4 strk experience as they will have 2 cyl at the top at the same time on a 4 cyl motor. I apologize for any miscommunication I just did not want you to connect the coils together as that would lead to possible engine damage..

 

[sutor623]

I have a '85 140 Looper with one dead cylinder. I've narrowed it down to the stator, but need to get in the water this weekend.....So my question is if the ignition system on this engine fires a spark more than once per cycle. What I'm thinking is that it might fire once normally, and once again on the exhaust stroke- at the same time as another cylinder compression stroke. If that's the case then I'll temporarily connect the coil power lead of two cylinders that normally fire at the same time. I've done this before on another engine and it ran perfectly.

If you are losing spark on one cylinder, then the stator is not at fault. There are two power leads off of these stators (not including the charge coil), and one goes to each bank. Typically you wont have spark on 1 and 3 or 2 and 4 SIMULTANEOUSLY if the stator is at fault.

If you have erratic firing on one cylinder, then your timer base may be at fault. Best way to check timer base is to index the flywheel in white marker at each cylinders TDC (Write the number right where the timing arrow is located for each separate cylinder. Should have 1-4 spaced evenly around the flywheel). Then when you place the timing light on the spark plug lead, you should ONLY see the number of the correct cylinder flashing at the timing arrow. Another thing you can do is attach an inductive tachometer to each lead and see if the RPMS are the same on all 4 cylinders.

Let us know what you find.

 

[joezek]

Thanks for your advice everyone. It has 4 new coils, plugs and wires, and CDI box just replaced. I'm not getting a power pulse to one cylinder most of the time, especially at low rpm. There's a second cylinder (same bank) that is intermittent as well, but gets power more often. When trying to get the boat on plane, it starts off with 2 cylinders and bogs horribly. Then as the boat starts to slightly plane and pick up a little speed (5 mph tops) the load lessens on the engine and like an on off switch you feel another cylinder kicking on/off. After about ten seconds of that I get the 4th cylinder doing the same thing. It's like a shot of nitrous each time, and suddenly the boat launches like a cannon and runs perfectly until shut down. At full speed it runs 5,800 rpm @ 56 mph (with GPS), so I'm assuming the prop is fine.

I did use a spark tester, and see that the two cylinders on the right side will not spark during cranking. Then after it starts the bottom right cylinder starts firing, but not when it's under a load in the water. The top right cylinder really takes a long time to wake up and fire. The compressions are all in the 120's and I just rebuilt all the carbs.

I'm obviously not too familiar with this engine design but the last two stroke I had with this problem on was a Polaris 1050. Those engines had a well known problem with the stator and there was even a recall on them because it would internally short and take out one individual cylinder. In that case it was easy to troubleshoot with an ohmmeter, but it sucked because I had to pull the engine to change the stator. I've also read on a CDI troubleshooting write up that in rare cases you can have a weak magnet on the flywheel that could take out just one cylinder, but at high rpm's the magnet will be strong enough since this type of ignition gets stronger as the RPM's increase.....not sure how accurate that write up was.

Anyways, I was for some reason thinking the timer base and stator were an assembly together- but I guess not.

 

[sutor623]

This may also point to a loose wire on the timer base. If I were you I would do a stator output test (with a DVA meter) while cranking the motor over. (spark plug leads OFF of plugs) You should have around 150V DVA coming in from EACH lead of the brown wire of the stator. While you are at it, check the DVA and resistance of the timer base.

Most stators that fail at low rpms will fail MISERABLY at WOT, especially after the boat sets for 30 mins or so after a long run. If you end up pulling the flywheel, check it for loose magnets, corrosion, cracked magnet in timer base, melted epoxy on the stator. Visual inspection may help narrow it down.

 

[joezek]

BTW, which cylinder is which as far as cylinder number? I don't see a stamped number anywhere other than the head bolts numbers.

 

[racerone]

Upper cylinder is always # 1 on these.---Bottom cylinder is # 4

 

[joezek]

After using the troubleshooting guide from CDI I found two bad leads on my Timer Base. Replaced it, now I have 4 cylinders all the time. BUT it still will not make any power with the carburetor cover on. It completely bogs down horribly. I take the cover off, runs perfect, instant power. I'm wondering if it has the wrong cover and how to tell if I have the right one or not. I rebuilt the carbs and set the floats. I don't see any numbers on the jets, and most of the jets won't come out because the threaded base just spins inside the carb. I'm also wondering if bad reeds could cause this problem.

 

[sutor623]

When you say runs perfect, have you ran the motor down the lake without the intake cover? Or is this just in the driveway at idle?

If it is in the driveway at idle, you may simply have to richen up your idle screws in the carbs, but sounds like something bigger is 'a brewin.......

 

[joezek]

It runs awesome in the river at almost 60 mph, according to the GPS, but not with the air cover installed. With it installed it completely bogs down. I did the voltage output check on the stator and now I'm thinking it's bad as well. The Brown and Brown/yellow leads are putting out 18-19 volts a/c. I think it's supposed to be 150V or more according to the CDI troubleshooting sheet I have. Hopefully someone here can let me know for sure.

 

[sutor623]

Yup 150V is the ticket. This is the big question. When you remove all of the spark plug leads from the engine, does each lead produce a nice deep blue spark that jumps 7/16"??

Heres the thing. If you are just setting your multimeter to AC volts, you will NOT see the correct voltage value. You NEED a DVA adapter/peak voltage meter to determine this value.

 

[joezek]

I get a small orange spark from each plug, very weak IMO. I have one checklist from CDI that says measure from brown to ground, and another checklist saying from brown to brown/yellow. When measuring from brown to brown/yellow I get 80 volts. Still nothing close to the 150. I'll try and borrow a DVA today from my avionics guy here on the airport. When this is all said and done I'll have a used $500 engine with $1500 worth of new parts in it. At least it's got a crap load of power and gets me to the sand bar every weekend.

 

[sutor623]

Hey man, thats not too bad. If you can keep these old girls up and running it will save you a pretty penny. Just be glad you have the desire to fix it yourself.

Now, back on track. If you are getting weak orange spark, at least you have narrowed it down to ignition. That 80V that you measured is USELESS. Get a DVA meter on that stator, or don't even worry about checking it. The AC spikes are so fast, that you need the capacitor in the DVA meter to find peak voltages.