Kohler M8 Questions

[OverKnight]

I have a Kohler M8 on my Troy-Bilt Tomahawk chipper, a replacement for the under-powered 4 HP Tecumseh it came with. I bought this engine off of CL, and was told it came off of a blower. I have no further information about this engine; the silver sticker with the serial #, model #, etc is completely blank, as if someone used too strong a cleaner and wiped off all of the words. It runs very well, except if it hadn't been run for a few months or more, I can only get it started by using starting fluid. The carburetor has been rebuilt, and the fuel is fairy fresh and treated with B3C Ethanol Shield. Since this machine is used only a few times each year, the spark plug and air filter are changed every other year, and changed (oil is change yearly). The carburetor is Kohler #41 053 27 (is this the same as a Walbro #K1-WHL)? I always close the fuel petcock and run the carburetor dry when I'm finished using it. The choke is definitely closed during these initial starts.

Any ideas why this engine so difficult to start? Any suggestions towards correcting this? Also, why would a fuel pump be needed on this engine? Wouldn't gravity supply a sufficient amount of fuel?

Thank you.

[bgsengine]

If it has a fuel pump it is very common for those pumps to have check valves come loose when it gets warm your fuel pump may not be working right but if your tank is high enough above the carburetor for gravity feed you could bypass the pump. However if the tank outlet is not high enough (several inches) above the carburetor inlet then it would need fuel pump assistance. Of course you could rely on gravity feed but have to keep the fuel tank topped off. Also if you are using B3C Ethanol shield I would recommend instead keeping the tank topped off , and open the shut off every couple months , start the engine a few minutes and shut off then close the petcock. If you look on the carburetor itself you will see what model (WHL or WHG would be the base model if a walbro) and there should also be the model number *Stamped* (not cast or printed) into the carburetor body usually on a flange and you can get parts for them via walbro for much less money than from Kohler.

Fuel pump has 2 check valves that are notorious for catching bits of debris that holds the check valves open, and with the plastic body ones the check valves are also known to fall out (and sometimes they then pop back in place) There used to be a rebuild kit for them with new check valves, diahpragm and gaskets but as far as i have seen they are NLA so only option now is replacing the whole pump (have had very little success trying to clean them - when the check valve plates get worn they start to leak if they move around, or they can stick open randomly)

[KE4AVB]

That would be the question is fuel reaching the carburetor?

These M8 usually have a mechanical driven fuel pump can as BGS noted that go bad but there are couple other points that can also give problems and cause the fuel pump not operate. One is the fuel tank shut off valve and other is the fuel line itself where runs from the tank to the fuel pump. I had this line to clog couple times on my M8 on my TB horse tiller. The first time I replaced the fuel pump without fixing the problem then I notice no fuel was flowing thru the line. Well I check the tank valve and it was clogged with rust so I thought that all of the problems but still didn't have fuel flowing through the line so I pulled the line which is a pain to do and it was clogged too. The reason that it is pain on my M8 is that fuel line runs behind the flywheel. Once I got these problems resolved I was to get fuel to pump again.

One other that you need to check that I had several go bad on my tiller is the aluminum fuel bowl itself develops holes from water sitting in the bowl. I my last was a steel version. Fuel bowl is PN 20-180-1 and gasket is PN 92-301-8.

[OverKnight]

Thank you, Gentlemen.

Will a faulty fuel pump cause hard starting after a few months of non-use? It runs like a train once started, and if I use it again after one week, starting fluid isn't needed.

If the fuel line is disconnected from the carburetor, there is plenty of flow from the tank. My aluminum float bowl was replaced with a steel bowl last year due to corrosion and leakage. One modification I made was to the fuel line from the tank to the pump. I don't know what the stock configuration is, but this engine had a rubber fuel hose running from the tank, behind the flywheel shroud right next to the cylinder, and then out to the fuel pump. I didn't like the idea of a rubber hose contacting the cylinder cooling fins, so I replaced this with some copper tubing, which I bent and positioned it so it doesn't touch the cooling fins. I don't think this would affect cold starting (and does not appear to affect operation in any way), but I thought I would mention this, just in case.

I'd be willing to replace the pump, but without the serial number, spec code, etc. of this engine, how would I know which part number to order? I haven't removed the pump from the engine yet; would it have any identifying numbers, measurements, specific differences, etc. that would make specific part number identification possible?

While I'm writing, the muffler is pretty loud. Could anyone suggest something quieter?

Thank you.

[bobodu]

Have you looked at the valve lash?

[OverKnight]

Thanks, Bobodu. I believe I checked the valve lash when I first bought this engine, maybe six years ago, but not since. I use this chipper maybe three tines a year, so I'd think that there aren't enough hours on the 2011 valve adjustment for another to be needed. Why would this cause hard starting after a a few months of non-use, but not after a week or two?

[bobodu]

I do not keep a score sheet showing what you have done or how you use it so I really didn't notice whether it was a week or a day...but I have noticed that threads tend to chase down one possible cause and totally ignore others. I have seen threads run six pages discussing carbs when it turned out to be a spark plug. BUT....my M16 is doing the same thing and I have already done the carb and fuel pump....still takes 20 seconds to start. Just have other things going on right now...I swear I'll check the valves....someday.

[bobodu]

Holy crap....that pump is $100 even on Amazon !!! You might wanna try this...https://www.youtube.com/watch?v=aqZGWRJ66b4

[KE4AVB]

But Bob there is an aftermarket available. Primline 7-08012 or go through TEW and their 22-1007 which is the prime line pump.

Hard starting after sitting a few weeks or months is more likely a pin hole in the fuel bowl allowing the fuel slow seep out then it takes a little bit cranking to refill the fuel bowl. A pain when when using the recoil; usually easier just to prime it a few times. At least that what I found twice on my M8 on the TB Horse. That is one thing I like about my UC it opens up those pin holes.

On a side note does evaporate over time with some being more prone than others.

[OverKnight]

Thank you, Gentlemen, and sorry for the delayed reply. Replacing the mechanical fuel pump with a vacuum-driven pump is certainly a novel idea. Would a marginal/failing fuel pump cause the hard start condition I've described?