Kohler CV Carb tweaking?

[SmilinSam 4,157]

I have a CV Kohler single cylinder like used on the later Broadmoors. I was wondering if there are any "tricks" that can be done to enhance the carb to add some power and performance to the engine? I have spare carbs for these that are sacrificial for experimentation.

[HubbardRA 19]

Sam, Unless the carb is running lean, there is not much that can be done to a carb that will help. If the carb is lean, then the main jet can be opened up about .001 inch, just to richen it slightly and get closer to an optimum mixture for maximum power. Most of the later model engines with fixed jets are set to run right on the lean edge to help emissions. Just a bit more fuel will increase the power. I had a Vanguard that was running too lean. Richened it .001 and it ran fantastic. In the summertime, on a hot day, it would start and run without a choke. You can usually get some added power by putting a longer tube on the exhaust, in other words getting closer to the tuned length. Shaving the head will always yield more power. I have a head on the 14 Hp Kohler that has been milled .060 inch. Believe me that was noticeable when we changed it. If you do something like this, you must make sure you have sufficient valve clearance. I measured the head and valves and compressed gasket thickness, so that I knew what could be done. I didn't want to bend a valve. Sometimes some porting around the valves and in other areas to eliminate sharp corners can help. Been there, done that too.

[SmilinSam 4,157]

This engine needs full throttle and full choketo start. Runs Ok at light loads, but as the governor kicks in and the load is increased it just ascts like the fuel is not sufficient for the load. Cleaned the carb out and thats not the problem. Electric fuel pump is delivering more than adequate fuel. This is what sparked the thought anyhow.

[HubbardRA 19]

Sam, that is normally how they act when they are slightly lean. I am sure that is a fixed jet carb and not adjustable. That is why I have that very little set of drill bits. I would have to look up the sizes, but the whole index with about 20 bits in it is no larger than a book of matches. I check the jet with the smooth part of the bit, then just open the jet up to the first size that will not go thru. That is usually about .001 inch and is never enough to make the engine too rich to run right. It isn't doing the emissions any good, but sure improves the performance. Sometimes when I do this, I find out that I am not removing any material from the jet at all, but just cleaning out some un-noticeable varnish buildup inside the jet, and putting it back to factory size.