Kohler M18 skip - Page 9

ol'George · #81 02-03-2018, 07:32 PM

Quote:

Originally Posted by DieselDoctor

George - I checked the coil mounting bracket and it is installed correctly with the arrow pointing towards the top of the crankcase.
When I ran the engine this last time after doing the valves and rings. I installed new plugs, this time using AC's. There was no change in the skip but I wanted to read the plug color. Mixture was pretty close as I had mentioned. After running the engine for about 5 minutes on and off, I shut it down, frustrated. I just pulled the plugs and cyl #2 which is left bank facing the flywheel is noticeably darker than #1. This is the plug furthest from the coil too. Now seeing as the motor isn't smoking from a rich condition, is the dark from the misfire or is the #1 plug more white from lean? I know I have said the other fuel system from the 2072 made no difference so what is causing the difference in plug color from side to side?
Anybody got a known to be good coil they're willing to loan for a test? I don't really want to shell out $100 for another coil until we pinpoint the problem.

Doc,
I don't know why one plug reads darker than the other.
Since both plugs fire @ the same time, swap the plug wires to the other sides.
You will have to stuff a old plug wire in the short side boot to get it long enough, just as a test and see what happens,and if the dark plug follows the wire to the other side.
I remember you swapped complete fuel systems, but what carb is on there now? an adjustable one or a non adj walbro?
I have seen some walbro's just cantankerous and exhibit one side giving problems while other side running fine, it defies logic, as it is a log manifold.
I'm assuming you are using the same flywheel in this testing, as the other one has not arrived yet?

DieselDoctor · #82 02-03-2018, 09:18 PM

It skipped with the original Kohler carb (not a Walbro) which was adjustable. I had a new, never installed China carb in stock so that is what's on it now. It is fully adjustable as well. My 2072 is the same thing. Nothing in the fuel system has had any effect in changing the symptoms. I like the idea of swapping plug wires side to side. I have another set of new AC plugs in stock. I'll throw the questionable flywheel back on and run it with the wires swapped tomorrow. The coil is new, but in today's world new isn't necessarily good. What really pisses me off is these engines just aren't that complex. I have missed something somewhere.
Side note - the M16 opposed twin shows to use a different flywheel from the M18/M20. Anyone know what the difference is? I've never seen a M16 twin.

If we get a good weather forecast for a couple of days, I'll pull the M20 out of the 2072 and start swapping pieces until I find something. I wish you could get the fan shroud off in the chassis a big fight.

J-Mech · #83 02-03-2018, 10:32 PM

On H twin and V twin engines that share a carb, it is common for one cylinder to run leaner than the other. Don Vogt and I talked about it before. When they set up the twins for pulling, it's not unusual to use two carbs. On a Harley, they found the same to be true. One cylinder will run just a bit stronger than the other. On a stock set up, it's not an issue. But in the pulling world, it makes a difference. I wouldn't worry about it Stan. It's normal. After a bit of run time, you won't be able to tell.

Get you're old timing light out again and check the flash....

DieselDoctor · #84 02-04-2018, 12:10 AM

Thanks Jon. I'll play around with the test light again. Too bad I don't have an oscilloscope, I'd like to be able to see coil output voltage, etc.

J-Mech · #85 02-04-2018, 12:18 AM

Quote:

Originally Posted by DieselDoctor

Thanks Jon. I'll play around with the test light again. Too bad I don't have an oscilloscope, I'd like to be able to see coil output voltage, etc.

Oh, I know what you mean. My Snap-On Modis has an oscilloscope built into it. I've used it a lot. (But it is limited on what types of ignition systems you can do. Or I am limited, as I only have certain "adapters".) Most guys think that tool is obsolete. Most techs nowadays don't even know what one is. Sometimes that is the best tool for the job. Found a lot of issues really quick using an oscilloscope. Have any "old" auto shops around you? I used to know of a few that still had the old Sun machines in the back with a cover on them. As obsolete as they are, they can be bought cheap!

This is what people use them for now.....

https://www.youtube.com/watch?v=w68qZ8JvBds

DieselDoctor · #86 02-04-2018, 01:04 AM

Passed up an old big blue Sun machine at auction this summer. Went for around $100. Auctioneer claimed the scope worked but most of the cables were bad. I should have bought it, trashed the cabinet and fixed the scope. Oh well.
If you're used to using one as I was years ago, you really don't want anything else. Every ripple had a meaning and you understood what the ignition was doing. Points closing, points opening, condenser discharge, coils saturation, discharge voltage, everything was there. Of course kids today don't even know what points are !! Unless they mess with old Cubs!

jaynjeep · #87 02-04-2018, 01:23 AM

Quote:

Originally Posted by DieselDoctor

Of course kids today don't even know what points are !! Unless they mess with old Cubs!

I know what you mean Doc.. I've run a shop for the past 30 years with my Dad.. Haven't had a mechanic in the last 20 years that wasn't scared to death of points or carburetors!

J-Mech · #88 02-04-2018, 01:47 AM

Quote:

Originally Posted by jaynjeep

I know what you mean Doc.. I've run a shop for the past 30 years with my Dad.. Haven't had a mechanic in the last 20 years that wasn't scared to death of points or carburetors!

You can say that again Jay!
NONE of the guys who worked for me wanted to touch either of them. I had to do every carb and point ignition..... and magneto for that matter. The boys would watch me tear down a carb like I was performing brain surgery. Before working for me, they had never even seen a mag. Do you know they don't even cover that stuff in the tech schools anymore? I don't understand way. Simple systems. They should cover it.

Oh well..... it gives us guys who have the knowledge an advantage I suppose.

Since we're off topic anyway, the same is true for the old 2 stroke Detroits. Hey Stan, how many of those you work on? I got some good money from Norfolk Southern Railroad a few years back. I was the only guy they could find that would work on them. They called a diesel shop in Evansville that I did business with and asked for recommendations. He gave them my name. After literally days of watching this piece of rail equipment run, I told them the engine was fine and never even opened it. Well..... that's a long story. But a valuable one. Maybe I'll tell it another time.

DieselDoctor · #89 02-04-2018, 12:12 PM

Jon - yep work on them and all the other old diesel stuff. My business name is Vintage Diesel and Gear. I do a lot of drivetrain work for a couple of antique truck clubs in my area and one museum. I just finished rebuilding the blowers and running the rack on a 12V-71 in a Brockway cabover. Currently working on one with a 903 V8 Cummins. The owners can't find anybody that wants to work on this stuff, let alone know anything about it.

J-Mech · #90 02-04-2018, 12:27 PM

Quote:

Originally Posted by DieselDoctor

Jon - yep work on them and all the other old diesel stuff. My business name is Vintage Diesel and Gear. I do a lot of drivetrain work for a couple of antique truck clubs in my area and one museum. I just finished rebuilding the blowers and running the rack on a 12V-71 in a Brockway cabover. Currently working on one with a 903 V8 Cummins. The owners can't find anybody that wants to work on this stuff, let alone know anything about it.

That's cool Stan! I haven't seen a 903 V8 since my first job. Ever run across the old 378 V6's? I wish I still had the piston and rod I pulled out of one. Detonated the piston with ether. Piston came off the rod, hammered the crap out of it and the valves until it bent the end of the rod in a "U" and rotated the wrist pin (still in the rod) 90 deg, then jammed it sideways in the top of the block and stuck. Had to torch it out. Never seen a rod bent in a small "U" and twist 90 deg like it did and not break. Coolest thing I ever saw!

I kept it for a long time. Lost it somewhere along the way. We fixed the motor.

Sorry.... we can go back to your engine now, lol.