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Here is where i get frustrated. Onan BF 16hp


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#1 coldone OFFLINE  

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Posted June 20, 2011 - 05:35 PM

Well now is the time when i get frustrated with engines, its running but just not quite right. I have had the engine running for 3 weeks now. I have pulled and cleaned the carb, installed new intake manifold, set the timing with meter, and adjusted the valves. I thought with the new manifold all of my problems would be solved, but when i got it on and tried adjusting the carb, the idle screw still does nothing. I know that the passage is clean, and it still has a extra louad pop every now and then in the exhaust. You can hear it run and it will be just purring away, as much as straight pipes can purr, then it will sound like one cylinder is hitting hard.

I think my mistake was reusing the 30yo intake gaskets. I guess my next steps are to pull the heads and decarbonize them, get a new upper gasket set, and a carb kit. The PO had already replaced the coil, points, condensor, and wires.

One thing I noticed when i adjusted he valves was that the intake valve had alot of carbon build up on the stem and underside of the valve. I am guessing this has come from improper timing, or misadjusted valve clearance, or bad valves. I am guessing timimng since it was on both intake valve equally.

#2 olcowhand OFFLINE  

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Posted June 20, 2011 - 05:38 PM

If you haven't already, while you have the heads off, I would do a full valve job.

#3 coldone OFFLINE  

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Posted June 20, 2011 - 08:47 PM

Can you walk me through a valve job?

#4 olcowhand OFFLINE  

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Posted June 20, 2011 - 09:00 PM

I have no pics to show you, but maybe someone here does. You have to remove the valve keepers using a valve spring depressor, then the valve slips right out. Be sure to put each valve back in the same spot it came from when finished. I have never had to do more than lapping valves & seats. If valve faces or seats are too rough, they may require grinding, which you'd need to take to a shop to do, as the tooling is expensive.
The best way to explain is this youtube video I found. It starts with showing how to cut the seats, then finishes with lapping them in. Usually lapping only does the trick.


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#5 DH1 ONLINE  

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Posted June 20, 2011 - 09:08 PM

Just finished fixing the neighbors Toro wheel Horse with a 16hp onan in it, has had fuel problems, surging, hard to start, on and off now for 2 yrs, I pulled the fuel tank cleaned and flushed it out, new gas cap to keep as much water out as possible, this thing live outside in the rain. Cleaned out the carb, main jet, fuel lines, put on a new filter and had to change the fuel pump, old one would not work any more unless you got it running by pouring fuel down the carb. $180. for the pump, no time to shop around, had to be fixed now. It cranked over 10x and fired right up with dry fuel lines and filter, runes smooth and steady, for how long???
I told the owner best thing he can do for his tractor is keep it inside and dry.

#6 coldone OFFLINE  

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Posted June 20, 2011 - 09:24 PM

So just lapping should be enough, unless i get in there and find the seats are too bad?

#7 coldone OFFLINE  

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Posted June 21, 2011 - 11:42 AM

Upper gasket kit has been ordered. I hope to get time this weekend to get it fixed.

#8 MH81 ONLINE  

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Posted June 21, 2011 - 09:43 PM

Lapping will often fix your issues like this will always at least try to use a power tool (drill) to turn the valve because I hate running those sticks. I have had several old timers tell me they owed to use old fashioned abrasive white toothpaste as a lapping compound in a pinch.

I have heard of other things, but I won't repeat them as I don't want to sound too redneck LOL.




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