Vibrating K241

[JoeM 7,874]

I have been tinkering with an 1979 C81. I wanted to check out the transmission and take it for a ride so I installed a k engine from a CUB. 

 

Before I get to deep. Some background on the engine. The seller said a fellow that did some pulling had it and it was in great shape and solid. I could not hear it run. It was in long block form and no carb or starter. Not a lot of money so I took a chance. Ran okay with choke smoke and if you left it idle for a while it would burp a puff of blue smoke. Not so solid....but the leak down test was not real bad. Leaked through the crankcase mid 20% range.

And going form memory when I had the head off it was actually a K301 with a K241 bore. Kind of unique with a 1 inch output shaft, 20 over piston. 

Put it on the side that was 4 years ago?

 

When I installed it on the C81 it would vibrate your filling out. 

Looking around I decided to put solid motor mounts, for EB that would be solid engine mounts, it helped but still not to good. low Ided nice and vibrated pretty good at full tilt. 

This is one of those CUB engine that doesn't have the anti vibration gears. 

 

So now I am looking at the point setting and timing. Lined up the S mark and used a continuity test for open and close. She would not even try to start. In the beginning I installed new points using the old compression stroke with the pin out and set them at .020. I went back to this method and set them a tight .018. It ran and the vibrations are much less. 

 

Now to my question, I put a mark on the flywheel at the place where the points are fully open and that mark it not even close to the flywheel timing marks. Could this motor have a special camshaft for pulling??

That mark I put on the flywheel lines up with key way on the crankshaft. I wanted to change the flywheel but it looks like the guy anti seize it and tightened up good. Had the big puller and some heat and a rap from ball peen. no go just let it go. 

 

Even with a little smoke this motor seems to have balls! 

 

Did I miss something? Anyone shed some light on the matter?

 

 

[squonk 41,150]

I'm thinking hot cam or cam timing changed a few teeth.

[ebinmaine 67,592]

12 minutes ago, JoeM said:

Looking around I decided to put solid motor mounts, for EB that would be solid engine mounts

 

 

I appreciate the mention.  

 

 

 

I'll be curious to see the answers...

[953 nut 55,298]

My guess is that a spark advance cam is being used rather than a compression release. Perhaps the cam was reground for more valve lift or duration. Here is a write-up I did that explains it. I doubt that the cam timing is off or you wouldn't be able to idle it.

 

Ignition timing on Kohler engines.

 

Gapping the ignition points at .020 has always been the standard answer to how points should be set. That probably will get you into the ballpark where the engine will run, but with a bit of additional effort you can improve the engine’s power and performance.

The Kohler engine manual in the Red Square files section covers two methods for setting the ignition timing, Static Timing and using a Timing Light. This manual is a relatively new manual and it overlooks the fact that many of our engines were built prior to the ACR (automatic compression release) camshaft.

Earlier engines (mostly 1965 and earlier) had a Spark Advance camshaft that can not be timed using Static timing. At rest (and very low RPMs) the timing is retarded to fire slightly after TDC. The timing mark (SP) on your flywheel is at twenty degrees before top dead center but at rest the points on these engines break about ten degrees after top dead center. The only reliable way to check or set the timing on these engines is with a timing light.

There are a couple ways to determine what camshaft you have. Presuming the camshaft in your engine is the one it was born with the data plate on the engine has a suffix that can tell you what camshaft was used. The table below will tell you the suffix applicable to your engine. The other way to determine what camshaft you have is to remove the cam gear cover and take a look. If you see a mechanism attached to the cam gear it is the ACR cam.

 

 

The following engines have the spark advance camshaft;

K-141, Suffix prior to “C”

K-161, Suffix prior to “J”

K-181, Suffix prior to “D”

K-241, Suffix prior to “D”

[JoeM 7,874]

50 minutes ago, 953 nut said:

My guess is that a spark advance cam is being used rather than a compression release

good info. unfortunately I don't have the original cover or spec. 

The biggest problem lack of any timing marks I'll have to take the cover back off and make sure.

[Ed Stoller 19]

"where the points are fully open and that mark it not even close to the flywheel timing marks."  The spark fires when the points just open electrically not when they are fully open.

 

Ed

[953 nut 55,298]

12 hours ago, JoeM said:

I don't have the original cover or spec.

That is what the pictures are for. pull the cam gear cover and take a look to see what type camshaft you have.

19 minutes ago, Ed Stoller said:

"where the points are fully open and that mark it not even close to the flywheel timing marks."  The spark fires when the points just open electrically not when they are fully open.

 

Ed

Rolling the flywheel over in the clockwise direction while watching the points you should find that the points open near TDC. If you have the ACR cam it will occur at twenty degrees before TDC, with a Spark Advance  cam it will be about ten degrees after TDC. Setting your points also sets your ignition timing.

With a battery ignition system, the ignition points are closed the majority of the time. With the points closed and the ignition switch ON the primary windings of the ignition coil have current flowing through them and are developing a magnetic field in the iron core of the ignition coil. The moment the ignition points open the magnetic field collapses and induces a momentary high voltage pulse in the secondary windings of the coil which goes through the spark plug wire and arcs across the gap of the spark plug. If this occurs in the presence of a compressed fuel/air mixture of the proper ratio an explosion will occur within the cylinder. If this explosion occurs at the proper time in the engine’s cycle there will be pressure applied to the piston forcing it downward on the power stroke. The ignition points will continue to open further after this has occurred. How far they open is immaterial, their work has been done for that cycle of engine operation. What is important is when they open relative to the position of the piston on its compression/power revolution. If it occurs too soon there will be backfiring, too late and there will be a reduction of power. In the case of our Kohler engines the sweet spot is twenty degrees Before Top Dead Center, that is what the “SP” mark on the flywheel is set. At the moment the points open the condenser quenches the arc across the points extending their life, the rest of the time it just sits there.

Static timing can be done with Kohler engines that do not have a Spark Advance camshaft. The instructions in the Kohler Engine Service Manual for static timing of the later ACR camshaft engines calls for an Ohm Meter to be used. I prefer a 12 Volt Test Light. The light will be connected between the battery “+” terminal and the lead that connects the points to the coil (disconnected from the coil). When the points are closed the light will be on, the moment the points open the light will go off. You don’t have to be focused on it like you would on a meter. With the test light situated near the sight hole for the flywheel (spark plug out so the engine will turn with ease), turn the flywheel slowly by hand in the clockwise direction (counter-clockwise if on the PTO end) until the moment the light goes out. If the “SP” mark is centered in the hole you are done, if not you have a little work to do. If the points are opening too late, they need to be opened further, if it occurs too early they need to be closed up some. Make gradual adjustments until the “SP” mark on the flywheel is centered in the sight hole at the moment the light goes out. Now tighten the screw securely and turn the engine over several revolutions to be sure the points are consistently opening at the proper moment.

[ranger 1,750]

1 hour ago, 953 nut said:

 Make gradual adjustments until the “SP” mark on the flywheel is centered in the sight hole at the moment the light goes out. Now tighten the screw securely and turn the engine over several revolutions to be sure the points are consistently opening at the proper moment.

Then make a note of the points gap you arrive at. It may save a bit of ‘fiddling’ in the future?

[JoeM 7,874]

I did not get to much time to work on it today but was able to put a timing light on and the S mark was just a smidge below center. Right now points are set at a snug .018.

[RED-Z06 2,221]

Some K series shook, like an uncomfortable resonant vibration that could be incredibly uncomfortable...ive said before the K series prominence in the GT community is probably what gravitated the market to boxer twins..Naturally balanced.  

 

Ive had K series you could sit on concrete and go from idle to 3800 and they barely move...and ive had them shake the shake the sheet metal off and bust mufflers from the vibrations.