Xjchief 128 #1 Posted April 29, 2013 I need help i have a 4hp k91 that i have done points condenser coil new plug carb tune up kit cleaned flywheel magnets everything is gapped properly compression is good. Once its running it runs like a champ idles the whole bit but to get it started takes alot of pulling with the old style rope start sometimes i have to put a drill on it to do most of the turning. If anyone has other ideas i am open to ne suggestions thanks Share this post Link to post Share on other sites
MarkPalmer 81 #2 Posted April 29, 2013 What color spark do you have with the engine cold? Other than a weak coil, or if the choke isn't closed up fully or there is an air leak at the intake, I can't think of any reason why it shouldn't start on the first or second pull. I encountered loads of these engines at a go-cart track in the early 1980's, and they always started up quick. -Mark- Share this post Link to post Share on other sites
Xjchief 128 #3 Posted April 29, 2013 Its a nice bright snappy spark i replaced the coil due to inconsistant spark but now its much better. There is fuel on the plug so i know its getting there Share this post Link to post Share on other sites
Fordiesel69 271 #4 Posted April 29, 2013 Is the flywheel magnets getting weak? Share this post Link to post Share on other sites
WH nut 553 #5 Posted April 29, 2013 You say compression is good, What is good, Need PSI Share this post Link to post Share on other sites
MarkPalmer 81 #6 Posted April 29, 2013 That is a good idea to get a compression reading. The K91 doesn't have a compression release so a standard compression tester can be used to get a good indication of the internal condition of the engine. -Mark- Share this post Link to post Share on other sites
VinsRJ 723 #7 Posted April 30, 2013 You said the plug Its a nice bright snappy spark i replaced the coil due to inconsistant spark but now its much better. There is fuel on the plug so i know its getting there Initial carb adjustment correct? The plug should not be wet with fuel. Share this post Link to post Share on other sites
Xjchief 128 #8 Posted April 30, 2013 Ill check that i figured the old 1.5 turns should b good jus to get it to pop but im gonna play around with it today. Thanks Share this post Link to post Share on other sites
Xjchief 128 #9 Posted April 30, 2013 90 psi compression Share this post Link to post Share on other sites
MarkPalmer 81 #10 Posted April 30, 2013 I'm drawing at straws now, but one thing that has me wondering is that it does start when you spin it over with a drill. This is telling me the problem might be in the spark timing. Try setting the points gap a little tighter, to say .015-.017. There could be some wear on the cam for the points push rod. See if this helps. -Mark- Share this post Link to post Share on other sites
Xjchief 128 #11 Posted April 30, 2013 Is that the only timing adjustment here? Share this post Link to post Share on other sites
MarkPalmer 81 #12 Posted April 30, 2013 Yes, that is the only way to make a small adjustment in the ignition timing. You usually have to set the points a bit tighter if there is any appreciable wear on the cam lobe that drives them. If this doesn't make any difference, set them back to .020. -Mark- Share this post Link to post Share on other sites
WH nut 553 #13 Posted April 30, 2013 It might not hurt to pull the flywheel and check the key. If its dinged or bent even a little it will throw the timing off. 90psi should run it Share this post Link to post Share on other sites
Xjchief 128 #14 Posted May 6, 2013 Still nothing im going nuts here replaced the coil under flywheel got a new plug nice spark at plug. Coul someone tell me the wiring diagram / order of operation of the ignition system? Share this post Link to post Share on other sites
Hodge71 665 #15 Posted May 6, 2013 If you have spark at the plug then your ignition is operating correctly... at least I think so.... Share this post Link to post Share on other sites
wallfish 18,226 #16 Posted May 6, 2013 I had one K90 that would fire off spark at the plug when it was laying on top of the head (so It would pull over easier). When the plug was installed, no spark (using an inline spark tester). It turned out to be the points gap setting. An old timer told me to close the points and then open them just a hair each time you pull it over until it fires up. It didn't make sense to me either,how it would spark out of the cylinder and no spark when it was installed but... The old timer was right because it worked. ????? Share this post Link to post Share on other sites
buckrancher 2,695 #17 Posted May 6, 2013 is your float level set correctly and when you rebuilt the carb were the all small holes in the main needle open and is your carb mounting flange flat (check for air leaks) also when you rebuilt the carb did you blow compressed air thru all ports and passage ways? Share this post Link to post Share on other sites
WH nut 553 #18 Posted May 6, 2013 Have you tried dumping a little gas in the plug hole to see is he fires, that will narrow things down quite a bit. Share this post Link to post Share on other sites
Don1977 605 #19 Posted May 7, 2013 Try a different spark plug I have found plugs that would not fire when installed under compression. Not all new parts are good. Share this post Link to post Share on other sites
MarkPalmer 81 #20 Posted May 7, 2013 One other thing I can think of, have you checked the cold valve stem to tappet clearances? Should be .005-.009 intake and .011-.015 exhaust on the K91. -Mark- Share this post Link to post Share on other sites
Xjchief 128 #21 Posted May 7, 2013 Is it possible to install the magneto coil wrong cus there were no instructions and i cant seem to find ne thing online? Share this post Link to post Share on other sites
MarkPalmer 81 #22 Posted May 7, 2013 You can download PDF manuals from this page: http://www.kohler-engine-parts.opeengines.com/kohler-engines-parts/manuals/free-engine-service-manuals/free-kohler-service-manual-downloads You'll see the link for the K series singles manual there, it discusses magneto installation in section 8 Electrical Systems and Components. -Mark- Share this post Link to post Share on other sites
Xjchief 128 #23 Posted May 9, 2013 Well I got it to run today I did a new plug and it started with the drill. Once running the motor couldn't run any better its strong no smoke idles from full throttle to the lowest of low idle and any where in between. I'm baffled!! Once running I checked for air leaks on the carb and carb gasket got nothing. Now I think it's safe to assume that if I installed something wrong it shouldn't run but it does it just doesn't want to start. Share this post Link to post Share on other sites
stevebo-(Moderator) 8,541 #24 Posted May 9, 2013 I have a 58 RJ with a k91 and OIL BATH !!!! I believe the float level may be off because the oil bath fills up a bit with gas when it sits a while. When this happens i cannot get it to start at all. What i found is that the gas is preventing the air into the carb which is why it does not start. When I pull the oil bath off it fires right up. So..... do you have an oil bath ai cleaner on it? Share this post Link to post Share on other sites
Xjchief 128 #25 Posted May 9, 2013 No standard round air cleaner Share this post Link to post Share on other sites