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I have a late 1980s era John Deere SX95 riding mower with a Kawasaki FB460V single-cylinder, 12.5 HP engine that (gradually?) began to run rich in the last couple of months. It starts well, but has sooty exhaust and is rough at idle, and is even rougher under load, with poor power and poor response to throttle. The following is what I've done:
-New NGK-BMR4A spark plug, gapped 0.026,"
-Air cleaner cleaned, Compression tested = 87 psi.
-Good spark with spark tester; Coil measured & meets specs, gap to flywheel set,
-Valve clearance measured, both intake & exhaust are 0.005" (close to specs) at TDC,
-Oil changed; Fuel tank cleaned and fuel lines and filter replaced.
-Ignitor did not meet specs and was replaced with aftermarket brand,
-Disassembled and cleaned the carb twice, blowing out all ports with compressed air. Butterfly valve closes fully at choke position and opens fully in idle position. On the first cleaning, the float was elevated approx. 20 degrees to bowl mating surface when carb was held inverted, and I bent the clip to bring the float parallel. The needle valve had only a slight ring around it near the tip, but I later replaced it anyway. The air bleed (pilot) screw has a similar ring, was not replaced, and is backed out 1-1/8 turns, but turning it in or out doesn't make much, if any, difference.

None of these has made any difference, except for the development of lack of good throttle response during the time I was doing all this. I have not removed the flywheel to check the key. Could this be the timing is off? Can you tell that by the position of the magnet? See attached photo of magnet position at TDC.





Another question is about the positon of the float in the carb. I got a new spring clip with the new needle valve, and it had a 90 degree angle, which caused the float to be at a significant angle when installed (carb held upside down). Usually parts are supplied how they need to be used, not requiring much adjustment. I had to bend the new clip to get the float level again. Am I missing something here?

I hope someone can help, as I'm about to give up on this engine and ditch the mower.

http://www.mymowerparts.com/pdf/Kawasaki-Service-and-Repair-Manuals/

download manual & see troubleshooting section

https://www.youtube.com/watch?v=Jx7KMXQuP-A

good video your carburetor

Mark, I have, of course, looked at the troubleshooting section of the manual. That's why I'm posting here, because people with more experience with these engines might inform me beyond what is in the manual. I need specific suggestions or answers to the questions posed.

:anyone:

Firstly no you can not work out if the timing is off by the position of the flywheel unless you make a timing mark to check it with.
So pull the flywheel fixings off and have a good look at the key hole.
The two halves should make a perfect square.
Once you have verified this you can make an indexing mark on the outside of the flywheel to check in the future.

While I don't like using raw compression figures on engines with decompressors, yours looks a tad low.
You really need to do a leakdown test to confirm the condition of the rings & valves.
Cheap & dirty test for valves is to turn the engine backwards .
Once the exhaust valve closes turn the engine ( backwards still ) to TDC and listen for leaking through the exhaust , breather or inlet.
Going backwards defeats the decompressor so you are compressing a full charge.
If you remove the headder pipe and inlet manifold you can also squirt in some soapy water and look for bubbles around the valve heads.
I have a ColorTune and when I get stuck it comes out as does the manual & electronic tachos.
Over time the main jets do wear. They get bigger due to people poking things up there to clean it out.
Moving the idle jet 1/2 turn in either direction should cause the engine to stall out if the jet is clean and the engine is running on the primary circuit.
As such your carb sounds like it needs another clean

Your engine is getting a bit long in the tooth so worn out rings or leaking head gasket would be high on the list of prime suspects.

Thanks Bert, you've given me a lot to chew on. You've also clued me in to the Color Tune, which I've now been reading about. Pretty amazing!

I'll update after I do some stuff.

Bought my first one 40 years ago.
One of the best diagnostic tools you can get, particularly if you are a very occasional mechanic.
With the slop we get sold now days for fuel, many times you are looking at really weird colour flames.
But rich is always yellow and lean is always clearish and mostly white.

Used my colour tune plug to diagnose an old Kawasaki motorbike with a SU carburettor as it was also running rich. Manual said to turn mixture screw fully in, then undo three full turns out to start tuning. Ended up with the mixture screw 1/4 turn out from fully in due to worn screw. Colour was then blue in the plug (not yellow) and bike had much better performance.

Very interesting. I had never heard of Colortune, but now I'm intrigued. If the other things Bert suggested don't work, I may invest in one.

Grass Mower said:

Very interesting. I had never heard of Colortune, but now I'm intrigued. If the other things Bert suggested don't work, I may invest in one.

Click to expand...

It is a very good tool for the occasional mechanic.
I use it a lot with small 2 strokes that start the die in a few seconds, saves hours of checking things that are not broke.
Long time mechanics can tell by the sound & smell if an engine is missing rich or missing lean , something you learn with repetative occurrences.
On the web, all we have to go by is what the poster tells us and that is very much dependant upon their mechanical experience so something that tells you YES or NO is worthwhile.
Not as handy on mowers when access to the spark plug is very limited but I do use it a lot on chainsaws & trimmers.

Only two things to watch out for
1) don't shove your face in front of the pyrex window . I have never had one blow out, but if it does it will go right through your head.
2) don't play with it for too long, not a big problem on mowers but with motorcycles they can overheat quickly .

They are a lot easier to use in a dark place as the colours are not as bright as the video on Gunsens web site makes out.
I think they were outlawed in the USA so you will have to buy from Canada or direct from the UK.