Alrashid2 355 #1 Posted January 26 (edited) Hey guys. Have 2 different little digital tachometers that I had used in the past for some chainsaw tuning. My 312-8 with a Kohler K series K301 runs well, and by ear sounds good at both idle and full throttle. However, thought I should double check the RPMs just to be safe. Programmed the tach for 1P2R based on the paper instructions which said that is what should be done for a 4 stroke 1 cyl engine. However, after doing that, my RPMs just did not seem correct. They hovered around 3500 RPM at idle and 6000 RPM at full throttle. Based on my reading, idle should be 1200 RPM and full throttle should not exceed 3600 RPM. I know the tach is off, so I'm thinking that maybe this engine isn't quite the same as a modern 4 stroke single cyl. Any idea how I should program this? Thanks all! Edited January 26 by Alrashid2 Share this post Link to post Share on other sites
ebinmaine 69,414 #2 Posted January 26 What does it read at 1P1R? Share this post Link to post Share on other sites
Alrashid2 355 #3 Posted January 26 3 minutes ago, ebinmaine said: What does it read at 1P1R? I'll go back out tomorrow, ran out of daylight today. I think it was reading around half - maybe 1700 RPM at idle and 3300 RPM at full throttle. Anything wrong with idle being slightly higher than 1200 RPM? I figured if anything that'd be better for lubrication/cooling. Likewise, anything wrong with a slightly lower max RPM? That one may be due to my throttle control not staying up in the highest position very well. Tends to slip from vibration... Share this post Link to post Share on other sites
lynnmor 7,451 #4 Posted January 26 4 minutes ago, ebinmaine said: What does it read at 1P1R? Sure sounds like he has the system that sparks on every revolution. 1 Share this post Link to post Share on other sites
Alrashid2 355 #5 Posted January 26 Is that how K series engines are setup ? Share this post Link to post Share on other sites
lynnmor 7,451 #6 Posted January 26 Just now, Alrashid2 said: Is that how K series engines are setup ? Not an expert on those, but I believe the electronic fire on every stroke and the points style fire every other revolution. 2 Share this post Link to post Share on other sites
Alrashid2 355 #7 Posted January 26 Interesting. Pretty sure mine has points... I did some googling and another forum post mentioned that K series spark on every revolution and just "waste" the spark on exhaust stroke. If that is the case, I guess my K301 is 1 spark per rev Share this post Link to post Share on other sites
ebinmaine 69,414 #8 Posted January 26 8 minutes ago, Alrashid2 said: I'll go back out tomorrow, ran out of daylight today. I think it was reading around half - maybe 1700 RPM at idle and 3300 RPM at full throttle. Anything wrong with idle being slightly higher than 1200 RPM? I figured if anything that'd be better for lubrication/cooling. Likewise, anything wrong with a slightly lower max RPM? That one may be due to my throttle control not staying up in the highest position very well. Tends to slip from vibration... I'm open to correction here. ... Idle speed is IMHO a moot point. An air cooled and oil splash lube engine should NEVER be operated at an RPM lower than about half throttle unless immediately before shut down. Even then it really isn't necessary for most. My idle speeds tend to run a little high. 1300 to 1500. Upper RPM is necessary for a hydro machine so the transmission is properly lubed as well. On my manual transmission tractors I often run at half to 3/4 throttle. 3 Share this post Link to post Share on other sites
Alrashid2 355 #9 Posted January 26 Thanks @ebinmaine good points. I don't run idle often but unfortunately I need to for a minute here and there when I need the beast to not wake the neighbors! No hydro here so I think my tractor is good. Will test out the 1P1R programming tomorrow and report back Share this post Link to post Share on other sites
Bar Nuthin 859 #10 Posted January 26 52 minutes ago, ebinmaine said: What does it read at 1P1R? I have a similar tach. It is set on the 1P1R setting to get the correct reading. I checked it against a digital tachometer and only had a variance of ± 100 rpm, which I can live with since neither of them is probably 100%. One thing I discovered was if I wrapped the conductor wire about twice the recommended 4 or 5 wraps, the reading is more consistent. I have it stuck on my dash for now. Now that I'm accustomed to the tractor and have it running well, I'll probably remove it and store it away. 1 Share this post Link to post Share on other sites
squonk 41,783 #11 Posted January 26 K series Kohlers fire once every other revolution. 2 Share this post Link to post Share on other sites
ebinmaine 69,414 #12 Posted January 26 51 minutes ago, Alrashid2 said: I don't run idle often but unfortunately I need to for a minute here and there when I need the beast to not wake the neighbors! Get away from the habit of idling. The engine will be a very similar decibel level at 2400 RPM and it's better for it. 1 Share this post Link to post Share on other sites
RED-Z06 2,368 #13 Posted January 27 Virtually every small engine is 1 spark per Revolution, 2 strokes, 4 strokes, points, magneto, solid state, CDI. Share this post Link to post Share on other sites
Handy Don 12,957 #14 Posted January 27 1 hour ago, squonk said: K series Kohlers fire once every other revolution. Makes sense to me. Never having been inside one of these, I always assumed that the points lifter is on the camshaft which turns at ½ the crankshaft speed. The magneto engines would fire on every revolution? Share this post Link to post Share on other sites
lynnmor 7,451 #15 Posted January 27 Read about the 3 types of ignition systems on the K series engines, manual. The breakerless system uses the crankshaft and the others use the camshaft. Only the points systems operating off the camshaft would fire every other revolution. 1 Share this post Link to post Share on other sites
Alrashid2 355 #16 Posted January 27 Hmmm is there an easy way to figure it out? Pretty sure I have points and they are to the left of the camshaft cover... Share this post Link to post Share on other sites
RED-Z06 2,368 #17 Posted January 27 I use an optical tach for the most part now, got tired of having to switch modes for cars, hei, small engines. I cut up a few dozen little ashesive squares and keep them in the pouch, stick one on whatever im trying to tach out, point and shoot. Only thing its not quite so useful for is saws, trimmers...there the spinny bits are covered. 3 1 Share this post Link to post Share on other sites
Alrashid2 355 #18 Posted January 27 (edited) 14 hours ago, ebinmaine said: Get away from the habit of idling. The engine will be a very similar decibel level at 2400 RPM and it's better for it. That is definitely true and actually what got me thinking about checking RPMs with a tach. I noticed that being slightly higher than full idle was still pretty quiet in comparison to full throttle, so I thought I should check various RPMs. That is what makes me OK with my lowest throttle position being around 1700 RPM rather than 1200 RPM - should only help. Also seems like a lot of conflicting opinions here. Some saying K series fire every other rev, others saying every rev... based on my tach readings, mine sparks every revolution. And I have a points system. So not sure. Edited January 27 by Alrashid2 1 Share this post Link to post Share on other sites
ebinmaine 69,414 #19 Posted January 27 35 minutes ago, Alrashid2 said: Also seems like a lot of conflicting opinions here. Some saying K series fire every other rev, others saying every rev... based on my tach readings, mine sparks every revolution. And I have a points system. So not sure. Have to admit that's confusing to me too..... 1 Share this post Link to post Share on other sites
Alrashid2 355 #20 Posted January 27 Glad it's not just me! Guess I'm happy she's working 1 Share this post Link to post Share on other sites
squonk 41,783 #21 Posted January 27 (edited) If you have points that are driven off the camshaft with battery ignition the plug fires EVERY OTHER REVOLUTION!!! Camshaft turns at half the speed of the crank and only has 1 lobe for the points. Your K301 engine does not fire every revolution unless it uses the breakerless ignition. Your tach readings are not accurate. I went thru the same thing. Had to use a phototach. Spark happens when the points open and the magnetic field in the coil collapses. There is only 1 points lobe so 1 opening per CAMSHAFT revolution so 1 spark for every 2 crankshaft revolutions Edited January 27 by squonk 3 2 Share this post Link to post Share on other sites
Alrashid2 355 #22 Posted January 27 Interesting...thought I had points? I've got a little points cover to the left of my camshaft... But both tachs I have are showing one spark per revolution Share this post Link to post Share on other sites
ebinmaine 69,414 #23 Posted January 27 3 minutes ago, Alrashid2 said: Interesting...thought I had points? I've got a little points cover to the left of my camshaft... But both tachs I have are showing one spark per revolution You have pictures of your engine tag? What year is the tractor again? 7 minutes ago, squonk said: phototach That's what I bought and posts like this may be why I did so. I don't recall. Share this post Link to post Share on other sites
squonk 41,783 #24 Posted January 27 Take the cover off and see what's in there. Is the coil a std. looking coil? 1 Share this post Link to post Share on other sites
Alrashid2 355 #25 Posted January 27 I'll snap some photos and post at lunch. Sorry, I've worked on engines for a while but new and confused on the various ignition/electrical systems so not sure what I'm looking at 1 Share this post Link to post Share on other sites
