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onan/simp 4040 questions?


john

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I am running champion H10c plugs in my ccka is there a better plug for this engine ? also the 4040 lugs down terribly in heavy grass and then takes a long time to return to normal, seems to run okay at about 3/4 throttle in light grass any ideas ? when it lugs down the charging also goes way down ? j.s.
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John my CCKB does the same [however] I checked the points and the gap was way shy of .020". After adjusting the points I definately had more power but still bogs real bad in heavy grass even at just a crawl. Check your governor make sure it's working ok. Also compression check for weak cylinder(s). Mine is low on compression on the right side.
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Haven't gottn to points yet, but know the governor works, the seller said it had new rings and valves last fall and it doesn't burn oil at this time. now ia am working on the air filter that may be god knows how old. the plugs were really sooty and it blew black smoke when lugged down. tried running it without the filter and it sounded better, but won't try it on mowing without a filter. an onan dealer wants 41$ plus for the filter. some found a contact at donaldson and may have an answer for their number tomorrow, ubless soneone out there has the donaldson # to share, it is and unusual filiter in construction. and my mechanic son isn't around to check timing and etc. I am a tin ear to listen to a motor, but he can hear things i never thought of . will post any results. thanks for the thought , haven't checked points yet either.
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John,

Sooty plugs means the mixture is too rich. Black (majority of the time) smoke means the same. Usually just a needle adjustment will do it but can also be a half dozen things. Sticky float valve, worn needle, worn needle seat, a couple other carb bugs, VERY dirty air filter. Electric fuel pump overcoming carb regulation .....

Stan
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I'm an Onan dealer and have been unable to find the
Donaldson air filter element available from any other
source but Onan..I believe it's a proprietary item.
The standard plug for that engine is Onan # 167-0241
(H8C). Using the H10 is about two steps hotter and
affect engine performance. I don't believe the
carb has an adjustable high speed circuit (needle) but
if it has make that adjustment for max rpm.
Also you might check to see that the choke butterfly
wide open with the choke cable full in. I quietly envy
you..I've been looking for a 4040 for over a year and
can't find one. If I can help any furthur contact me.
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Hey thanks you both gave me new ideas, I now know it is not the air filter, but the choke idea is great cause I did knock off the cable and then reset it, so tomorrow i will look again and re check. More details on the donaldson filter on my next posting after i check the choke tomorrow. stay tuned , thnaks again j.
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well, after all i did get it to run perfect, the donaldson filter is an onan only product, I have the donaldson print and it was last uo dated in 1998, but that filter from my onan dealer is $ 41.80 but it is in stock, the donaldson rep i ( from the factory ) said he had never seen aonther one like it. any way the choke is fine and the butterfly works fine. I did finally get two new plugs, they didn't help, but did go to ngk and the cross to champion h8c's i never have liked champions. so i apened up the casing for the points, i really no nothing about points or how to set them but the box was drenched in oil, so i sprayed it out with card cleaner and tried to dry it out and then sandpapered the points it took a while to start, but wheb it did i ran some carb cleaner through the carb, now best of all it runs great, took it out yesterday for about na hour and no prroblems, took it out today for about another hour in wet and humid grass and really heavy grass 2 or 3 feet tall and with the deck up ran and mowed just fine, only slowed it down when the mower almost plugged. the air filter is getting washed in mr clean and willl go back on when dry. i tried both carquest and napa for a replacement to no avail... Are I now HAPPY. UP. john
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John,

Now that your points are clean you'll never have to use sandpaper again to clean them. Every spring and fall and/or whenever you might pull the points cover, use common 20lb bond paper. Turn the engine so the points are fully closed. Slip a narrow single or double strip of paper between the points and (under the spring's tension) pull the strip out. Repeat 4 or 5 times. No need to go to more effort, this keeps 'em clean without wearing 'em out.

Stan
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John: I've read all of the other replies and realized that something was left out. If you want to adjust the carburetor, the main jet setting is on the bottom of the carb, very difficult to get at. I made a special hooked tool from an old screwdriver just for the purpose of adjusting the main jet. If you are still getting black smoke after you try everything else, try turning the main jet screw in a little bit to lean her out a bit. After that you may also need to readjust the idle mixture screw which is on the top of the carb.

One other thing that will cause black smoke under heavy load (actually bluish/black) is excessive blowby. I had this happen with mine several years ago before I rebuilt the entire motor. It would disappear if I squeezed off the crankcase breather hose, and it ran better too. The blowby problem also made it extremely difficult to get the carb set properly as the oil vapors would increase when the engine was hot, thus causing a rich mixture.
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