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post #1 of 67 (permalink) Old 05-31-2019, 08:43 AM Thread Starter
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Back for more advise on my 98 450ES, blowing smoke

OK need some more advise, she is now blowing smoke out the muffler. It has been running swell since the timing chain replacement and had her out last couple weeks pulling some logs for cutting. She did a great job. A couple days ago I was helping my son pull some brush out that was overgrown and on one pull I looked back and had smoke behind me. It is the whitish I guess blue smoke. Still seems to run fine and doesn't smoke right away when starting until I give her some throttle or slight load. I have tried adjusting the carb with no success. I pulled the plug and it was wet and pretty cruddy looking. The air filter is clean and no fuel in that area which is good. I am now going out to check the valves, but probably figure it is something worse. After I check valves where should I start? I surprised myself with the timing chain replacement and would like to do what is needed this time also. I will post results from the valves later.


Also the color of smoke, if it was fuel related would it not be a darker blackish color? This much lighter in color....Fun times....


Update: valves are good at .006, so any ideas much appreciated....

1998 Honda Foreman 450ES

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post #2 of 67 (permalink) Old 05-31-2019, 07:57 PM
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Either valve seals are leaky, or its in need of a topend rebuild, or both. Is the motor oil blackening up quickly? Checked the compression yet?
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post #3 of 67 (permalink) Old 05-31-2019, 09:34 PM Thread Starter
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Oil looks good changed a month or so ago. I have to get a compression tester, nobody I know has the right size adapter.

1998 Honda Foreman 450ES
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post #4 of 67 (permalink) Old 05-31-2019, 09:46 PM Thread Starter
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Looking at testers online, is the plug size on this Honda 12mm? Want to get one that works for me...

1998 Honda Foreman 450ES
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post #5 of 67 (permalink) Old 06-01-2019, 12:05 AM
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Ya, I think the adapter it takes is 12mm. When you buy an adapter it won't have a schrader valve in the end of it so your readings will be slightly lower than reality, but close enough that you can make a decent judgement call on the condition of the cylinder.
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post #6 of 67 (permalink) Old 06-01-2019, 08:03 AM Thread Starter
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Quote:
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Ya, I think the adapter it takes is 12mm. When you buy an adapter it won't have a schrader valve in the end of it so your readings will be slightly lower than reality, but close enough that you can make a decent judgement call on the condition of the cylinder.

OK thanks, will do some reading here on how to test, never tried before...should give me an idea of what is wrong hopefully...

1998 Honda Foreman 450ES
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post #7 of 67 (permalink) Old 06-01-2019, 09:22 AM
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Its easy... warm the motor up to operating temp, yank the spark plug and ground the plug wire, screw in the compression gauge, hold the throttle wide open and hold the starter button down until the gauge stops climbing.

Make sure you are getting a good pressure seal where the adapter meets the head and mates with the pressure hose. I use an old spark plug gasket on those wherever possible, cause rubber o-rings squeeze out and can't be trusted.
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post #8 of 67 (permalink) Old 06-01-2019, 10:02 AM
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Almost certainly a worn top end unless it is too full of oil and or fuel leaked into the crankcase and overfilled the level. I can't imagine a worn valve stem seal leaking that much oil to make that much smoke.
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post #9 of 67 (permalink) Old 06-01-2019, 12:33 PM Thread Starter
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Almost certainly a worn top end unless it is too full of oil and or fuel leaked into the crankcase and overfilled the level. I can't imagine a worn valve stem seal leaking that much oil to make that much smoke.

Oil level is good, right at top of fill stick mark when placed on top, not screwed in.

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post #10 of 67 (permalink) Old 06-01-2019, 04:10 PM
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Quote:
Originally Posted by bcsman View Post
Oil looks good changed a month or so ago. I have to get a compression tester, nobody I know has the right size adapter.
Following your recent oil change did you use a similar grade oil or maybe a thinner viscocity? Is your motor original spec or has it been rebuilt/rebored in the past? Cylinder/piston ring age/mileage related wear maybe making itself known.
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