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I have a weird problem.
It is a FB460V engine 12.5 HP.
All summer the engine would start right up every week.
Now, it is getting into the 30s at night. When I go to start it during the day, it doesn't want to start. It kind of sputters, but never starts. Here is the weird part: if I put a brand new spark plug in it, it will fire right up. However, the next day, nothing, unless I put a brand new plug in it then it will start. Here is what I know:
-fuel system is clean and is supplying sufficient fuel
-fuel is fresh
-Correct oil level
- carb is clean
It runs great once it is running.
I am leaning towards a compression problem, since it ran fine in hot weather. I do not have a tester, but plan on getting one soon to check it.
The engine was made in 1985, and to my knowledge has never been rebuilt. It has a lot of use on it.
Do you know what the compression should be for this engine, and what compression tester do you recommend?
Thank you in advance

It sounds like your spk plg is fouling out. Next time, with the old spk plg still in, try starting without using the choke.

You might want to try to borrow or rent a compression tester from your car mechanic or where you buy your small engine parts. If you have worked with them in the past, they may be willing to help you out. I would not purchase one unless you figure on using it at least once a month or just starting in working on units.

I have tried no choke with old plug. It won't start without a brand new one in it.

I do work on engines, especially during the summer, so I may buy a tester.

If that is the case I would buy the best one I could afford. Make sure that the hose is stiff and Gage is easy to read. A hose that flexes, will expand under pressure and give you a false reading. If you a afford it, I would recommend purchasing a cylinder leakage tester instead. It is far more useful and will give you a better diagnosis of where the problem are. Just an old wrench monkeys opinion.

Rivets said:

If that is the case I would buy the best one I could afford. Make sure that the hose is stiff and Gage is easy to read. A hose that flexes, will expand under pressure and give you a false reading. If you a afford it, I would recommend purchasing a cylinder leakage tester instead. It is far more useful and will give you a better diagnosis of where the problem are. Just an old wrench monkeys opinion.

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Ok thanks for the information. I appreciate it :thumbsup:

jakesmurray said:

I have tried no choke with old plug. It won't start without a brand new one in it.

I do work on engines, especially during the summer, so I may buy a tester.

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I find it interesting that replacing the spark plug "always" allows it to start. Usually, a spk plg shows the health of an engine. When it doesn't start, and you R&R the spark plg, is the old one oiley (as in black oil)? Is it wet (as in fuel)?

chance123 said:

I find it interesting that replacing the spark plug "always" allows it to start. Usually, a spk plg shows the health of an engine. When it doesn't start, and you R&R the spark plg, is the old one oiley (as in black oil)? Is it wet (as in fuel)?

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I know, a very odd problem.

Yes when I pull the old one, it is very black and very wet with gas. It looks like it has been there for 10 years, even though it has no more than an hour on it. :confused2:

jakesmurray said:

I know, a very odd problem.

Yes when I pull the old one, it is very black and very wet with gas. It looks like it has been there for 10 years, even though it has no more than an hour on it. :confused2:

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OK! Now we're getting to the root of the problem. You "might" have a collapsed oil ring on that cylinder. To get you by for a while, try increasing the spark plug gap on your next new spk plg. .035 or .040

Ok so you are thinking oil is getting past the rings?
I will try that gap next time.
Thanks

jakesmurray said:

Ok so you are thinking oil is getting past the rings?
I will try that gap next time.
Thanks

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Let us know

chance123 said:

Let us know

Click to expand...

Ok, I will
It may be a few days

Alright guys, I finally got around to checking the compression on the Kawasaki. The mower is 30 miles from me, so I am not near it all the time. Anyway, the compression reading was 30 psi. I researched and ofund that this engine needs at least 43 to start, so 30 is way too low. I do have a theory though...
During the summer, the engine ran great and fired up every week. Now that it is getting cold (20s and 30s at night), it is acting up. Is it possible that the air in the cylinder is contracting from the cold and causing it to have less compression? During the summer it was in the 100s around here, so the air would expand, causing more compression. This would make sense to me as to why it seems to want to start better on the warmer days.
Nevertheless, I do think I have some worn rings, or a collapsed ring, so I believe the fix would be an overhaul. Can you guys confirm or deny this?
Thanks

Rings are a definite possibility, but not the only possible problem. Could be a sticking valve or a head gasket. Each of these would be affected by engine temp. You could test the rings by squirting a small amount of oil into the cylinder and then retaking the compression test. If the compression goes up, you know that the rings are part of the problem. A valve that is sticking, could get worse in the cold, as the lubricant does not allow it to move as freely. Your head gasket may have finally shown itself in the cold and finally blown. The only way I know to find out which one is the cause, with out tearing into the engine, is to do a cylinder leak down test. Otherwise you are going to have to start disaasembly to find the problem.