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Archive through December 18, 2013
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JIM HARDER - The ONAN in my 982 started surging exactly when I shut the mower deck off when I finished mowing the lawn and mulching leaves a month ago. But I think my issue is the condenser.
The intake manifold on the B48G Onan is a two piece assembly, cast runners with a thin steel top bonded onto the runners. They are very prone to vacuum leaks. Get the engine running and warmed up OUTSIDE... Carbon monoxcide in a closed shop can kill you! Then use a propane torch that is NOT lit and turned on and move the end of the torch around as much of the intake manifold as you can and see if the engine smooths out. If the engine still surges, your intake is problably O-K, if it snooths out, you're sucking raw air into the intake with no gasoline and are running lean, that's why pulling the cloke out smooths the engine out. An aerosol like starting fluid, WD-40, etc, anything flamable would work too, but keep a fire extinguisher handy.
Some guys on another forum have had some success taking the cover off the intake and re-sealing it.
The governor on the Onan twins do have issues, but surging really isn't one of them. The governor is a ten-fingered plastic finger wheel pressed onto a hub on the camshaft driven gear and as the engine gets hot the plastic expands and the finger wheel slips on the hub of the cam gear which causes the engine to not increase the throttle to hold engine RPM as the load increases, then when the load is decreased, the engine RPM's race.
I really like my 982, I really HATE my Onan engine in my 982. Makes you really appreciate the K-series Kohler engine!
The intake manifold on the B48G Onan is a two piece assembly, cast runners with a thin steel top bonded onto the runners. They are very prone to vacuum leaks. Get the engine running and warmed up OUTSIDE... Carbon monoxcide in a closed shop can kill you! Then use a propane torch that is NOT lit and turned on and move the end of the torch around as much of the intake manifold as you can and see if the engine smooths out. If the engine still surges, your intake is problably O-K, if it snooths out, you're sucking raw air into the intake with no gasoline and are running lean, that's why pulling the cloke out smooths the engine out. An aerosol like starting fluid, WD-40, etc, anything flamable would work too, but keep a fire extinguisher handy.
Some guys on another forum have had some success taking the cover off the intake and re-sealing it.
The governor on the Onan twins do have issues, but surging really isn't one of them. The governor is a ten-fingered plastic finger wheel pressed onto a hub on the camshaft driven gear and as the engine gets hot the plastic expands and the finger wheel slips on the hub of the cam gear which causes the engine to not increase the throttle to hold engine RPM as the load increases, then when the load is decreased, the engine RPM's race.
I really like my 982, I really HATE my Onan engine in my 982. Makes you really appreciate the K-series Kohler engine!
jdiederichs
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- displayname
- Jim Diederichs
Jim H,
Along with what Denny said,
I'd drain the gas and dump it in your truck or whatever. Buy fresh gas (higher volume station) and use only the good stuff, no ethanol blends.
Remember that ethanol requires MORE fuel than gasoline; results in a leaner mixture.
Does your Onan carb still have a high speed mixture screw? Probably not, but hoping it does. If you back out the h.s. mixture screw you can enrichen the fuel and eliminate the surging/hunting. That symptom is 99.9% a lean condition.
1) Fresh non-ethanol gasoline
2) Adjust H/S mixture screw if present
3) Locate the fixed H/S jet if no adjustment screw. Have a machinist buddy open the hole ever so slightly (he will have the super small drill bits so as not to overdo it)remember, you can remove more material but it is a pain to "put it back"
4) If the carb has a shut-off solenoid on the main jet, be sure the carb is absolutely grounded so the valve opens fully. Later units used a separate ground wire from carb body to known good ground on engine.
Along with what Denny said,
I'd drain the gas and dump it in your truck or whatever. Buy fresh gas (higher volume station) and use only the good stuff, no ethanol blends.
Remember that ethanol requires MORE fuel than gasoline; results in a leaner mixture.
Does your Onan carb still have a high speed mixture screw? Probably not, but hoping it does. If you back out the h.s. mixture screw you can enrichen the fuel and eliminate the surging/hunting. That symptom is 99.9% a lean condition.
1) Fresh non-ethanol gasoline
2) Adjust H/S mixture screw if present
3) Locate the fixed H/S jet if no adjustment screw. Have a machinist buddy open the hole ever so slightly (he will have the super small drill bits so as not to overdo it)remember, you can remove more material but it is a pain to "put it back"
4) If the carb has a shut-off solenoid on the main jet, be sure the carb is absolutely grounded so the valve opens fully. Later units used a separate ground wire from carb body to known good ground on engine.
Dennis,
I am with you. I relly like that 982 but sure am getting tierd of that onan. The parts price alone and nobody haveing anything in stock for it. Some may have a heart attack when I say this but I truly wish it had a bigger version of a kt 17. I am a Die hard x82 fan. But this one sure is testing my love for them. Thanks to all that have gave advice I will try it all on friday I hope. Thanks again Jim
I am with you. I relly like that 982 but sure am getting tierd of that onan. The parts price alone and nobody haveing anything in stock for it. Some may have a heart attack when I say this but I truly wish it had a bigger version of a kt 17. I am a Die hard x82 fan. But this one sure is testing my love for them. Thanks to all that have gave advice I will try it all on friday I hope. Thanks again Jim
sblunier
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- Steve Blunier "Mr. Plow" (Central IL)
Jim(s), Denny, Mike,
As hard as that 20hp Onan pulls, I still think the best motor in that frame is the 20hp Kohler Mag......power without the headaches!!!!
Snow thrower speed up.....
With the recent talk about thrower performance and speed up pulleys I thought I'd add an observation. The melting snow left nice windrows in the yard corresponding to the thrower passes on my driveway. I put the tape measure to them this afternoon and got an honest 20' throwing distance (center of chute to center of pile). This was in 6" of medium wet snow with a QA-42A on my 782 (18hp Mag) and 4" speed up pulley (~1/2" undersize). Doesn't look very impressive in print, but lay out a tape beside your thrower some time......that's a fair distance to chuck snow!
As hard as that 20hp Onan pulls, I still think the best motor in that frame is the 20hp Kohler Mag......power without the headaches!!!!
Snow thrower speed up.....
With the recent talk about thrower performance and speed up pulleys I thought I'd add an observation. The melting snow left nice windrows in the yard corresponding to the thrower passes on my driveway. I put the tape measure to them this afternoon and got an honest 20' throwing distance (center of chute to center of pile). This was in 6" of medium wet snow with a QA-42A on my 782 (18hp Mag) and 4" speed up pulley (~1/2" undersize). Doesn't look very impressive in print, but lay out a tape beside your thrower some time......that's a fair distance to chuck snow!
That maybe a option if it keeps it up. Or maybe even a Honda. Allthough I doubt I could bring myself to actually do it. I am kinda of a stickler for keeping what came with. Like puttig a sbc in a ford. That just isnt for me. (although I truly have a deep seeded hate for anything GM)Hopefully tomarrow I will get it figured out.
akleyla
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- Amy J. Kleyla
Harry, yes my tires now are BF Goodrich 23x8.5x12 on the rear an they are really badly cracked and have been plugged so many times . Im sure if I just added tubes they would be fine but I have been wanting new tires on the rear for a few years.
Kraig,ty for the lubrication table that shows im doing the right weight of oil in winter
Donald, I have heard the ATV tires are basically the same size with a different tread which is more aggressive. I agree about the chains leaving marks on concrete,I have left a few and dont like doing that thats why I wondered about how well AGs or ATV tires would do.
Nic,I agree they look good in the pic but they really do have a lot of cracking an have been plugged too many times. Ive been having problems with air leaking out when its cold so ive considered just adding tubes but I also have wanted new tires for awhile.
Dennis,I have chains on my cub right now,but also have the set I used on an old truck years ago. So no need right now to cut down any chains yet. I agree that chains are better traction no doubt,but just trying to keep from marking up my driveway if thats possible ? I too an curious how an ATV tire would work?
Richard, I bought a smaller pulley yesterday so I have it ready to change. I am waiting on a good snow just to see how its working now before I change anything. I will change the pulley though just to see the difference I get.
So it sounds like window washer fluid is whats used so now I wonder how much to add to each tire any clues ?
Ty for all the replies they do help....
Kraig,ty for the lubrication table that shows im doing the right weight of oil in winter
Donald, I have heard the ATV tires are basically the same size with a different tread which is more aggressive. I agree about the chains leaving marks on concrete,I have left a few and dont like doing that thats why I wondered about how well AGs or ATV tires would do.
Nic,I agree they look good in the pic but they really do have a lot of cracking an have been plugged too many times. Ive been having problems with air leaking out when its cold so ive considered just adding tubes but I also have wanted new tires for awhile.
Dennis,I have chains on my cub right now,but also have the set I used on an old truck years ago. So no need right now to cut down any chains yet. I agree that chains are better traction no doubt,but just trying to keep from marking up my driveway if thats possible ? I too an curious how an ATV tire would work?
Richard, I bought a smaller pulley yesterday so I have it ready to change. I am waiting on a good snow just to see how its working now before I change anything. I will change the pulley though just to see the difference I get.
So it sounds like window washer fluid is whats used so now I wonder how much to add to each tire any clues ?
Ty for all the replies they do help....
