16 HP ONAN CARB HELP NEEDED

[dbartlett1958 96]

Happy New Year to all at Red Square!

 

I need a little guidance regarding the Carb on my 1990 416-H with Onan twin. I am having some surging when running which smooths out a bit with some choke, so I know I have some crud where it shouldn't be.

 

I have changed the fuel filter.'

I am anal about keeping my fuel fresh and clean.

I use Seafoam in all my gas.

I have taken the top off the carb and cleaned what I can see. (There was some sediment in the bowl that has been there a while and I am sure I stirred it up and sent it where I can"t see while cleaning things as best I could with the carb on the engine.)

 

Which brings me to my question: Is there an easy way to remove the carb from the manifold without major disassembly?  It appears to be held on by two cap screws from below, which I might be able to get too if someone else has done this before.

 

I know the carb needs a good soak overnight in Carb cleaner. Just want to get it off without doing more than I need to.

 

Thanks for listening.

 

David

 

[Martin 2,131]

you may be able to get it clean without removing it.......

 

have 2 416s that needed carb cleaning, as of today both are running very well without removing and soaking the carb.......

 

416 #1

 

 

and 416 #2 ( this one took 2 goes to get it right)

 

 

[dbartlett1958 96]

Martin,

 

I will give it another go tomorrow. When I had the top off, I did not unscrew the jet as you did. I bet I have some crap in mine as well.

 

Thanks for the great pic's and I am enjoying your 416 threads.

 

David

[Martin 2,131]

make sure to try and remove the main jet as well. you need to remove the hex head plug on the side of the bowl first, then use a nice tight fitting screwdriver to remove the jet. i found on of those larger insulated electricians screwdrivers had the perfect size tip. had to remove some of the insulation on the shaft so that it would pass through the hole in the side of the bowl.....

 

 

 

 

 

[dbartlett1958 96]

OK, will do, but that might be a bit tight with it on the machine.

[Martin 2,131]

you have enough room, i was able to get in there on both engines......

[dbartlett1958 96]

Martin,

 

Thanks for the encouragement. I'll report back tomorrow night how things go.

 

Right smack in the middle of snow-blowing season, I need to keep things running right.

[JackC 617]

You might be able to remove the carburetor with crows foot wrenches to get to the bolt heads under the manifold.  Last time I did one I took the muffler and both intake and exhaust manifolds off in order to remove the carburetor and soak it.  Gaskets and a carburetor kit were needed. 

[tbarnhart 240]

Intake leaks were somewhat common on the P-series Onans as well.  I had one acting exactly like that on a miller welder that I had cleaned the carb several times.  Finally began pulling the intake and carb and discovered the sealant between the two halves of the intake was deteriorated. I drilled out the rivets and resealed the intake with a fuel resistant sealer called Permatex Motoseal.  Ran great, never did work on the carb again.  Tbarnhart

[Wishin4a416 2,190]

I have an 18 on a JD and it surged real bad. I never could figure it out. Took it to the dealer and it was a 34 cent welch plug that had gotten blown out on the carb. Just something else to check out.

[Martin 2,131]

good point Jack. that plug could be missing and/or leaking. the plugs are also easy to blow out with compressed air when you are cleaning out all the passages from the top of the carb too. that plug is located  just above the idle mixture screw.......

 

the manifold leaking is also another area to look at.

 

all good tips here guys......

Edited January 1, 2014 by Martin

[JackC 617]

Surging and carburetor issues are so common with the P Series engines that I now have spare carburetors to swap in to reduce down time. Ordering gaskets and kits and disassembling and soaking overnight takes too long.

 

On the newer engines I replace the emissions carburetors with non emission.

[dbartlett1958 96]

Well Guys........

 

I had another go at the carb today. Took off the top, took out the drain plug and the idle jet and power jet. Nothing obviously wrong, so sprayed everything with carb cleaner and then blew it out.

 

It idles better now, but still surges at WOT with no load.  With a load it smooths out pretty good.

 

Tomorrow I plan to give it another go, will remove the carb and give it  a thorough cleaning.

[Martin 2,131]

check the governor spring position while you are playing with it tomorrow, not saying this is at fault, but it was a problem i had with it being too sensitive. spring was in the wrong hole in the arm. don't forget about the other tips in this thread too.......

[dbartlett1958 96]

Martin,

 

I don't think it is a governor issue, as the tractor ran fine for two years before I went mucking about in the carb that first time. I will check the manifold for leaks while I am at it, and for missing plugs.

[Martin 2,131]

yeah, i figured it was a good runner before, just thought id throw it out there......

I've heard others have found junk in and behind the main jet, thats why i mentioned it yesterday. i think a good soaking is the only true way of cleaning them properly though..........

the other stuff is worth checking out. good luck with it.......

[wheeledhorseman 574]

Been there with this issue myself. I can't remember how many times I removed the carb for cleaning but the hunting / surging call it what you will wouldn't go away. As mentioned in the thread mine would run sort of ok under load until it got really hot in summer.

 

In the end I bit the bullet and took the inlet manifold off for resealing after that and new gaskets the problem hasn't surfaced again. I did a thread on it with photos etc here

 

If you've tried everything else then the answer to the problem could lie here. Good luck, I think the 16 hp is a good engine and worth the effort to get it running well. Others may disagree but that's my opinion. 

 

Andy

[woodchuckfarmer 333]

I bent an open end box wrench to get at the bolts under the carb.

[dbartlett1958 96]

Update,

 

Last Thursday I took the exhaust, intake manifold, and carb off the tractor. I disassembled the carb and gave it a good soak in Berrymans, then hosed it all off with spray carb cleaner, and blew it all out with air. I re-sealed the intake gaskets with some anaerobic gasket sealer as I did not have any new gaskets. 

 

The intake manifold did not appear to have any leaks in the seam, so I left that alone.

 

After putting it all back on the tractor, it started and ran great at first, but after a bit it did still "hunt" a bit at WOT with no load, but much better. Idle was perfect.

 

Today, I used the tractor again, and it started and ran perfectly at all speeds. Seems to have fixed itself.  

 

The difference between today, and last Thursday is about 40 degrees.  Today it is above freezing, last week was below Zero.   I am thinking I had a frozen gas cap vent issue on top of a dirty carb. Cleaning the carb, and today being milder allowed the vent to open up.

 

Time will tell, but for now I have 16 horses of slush blowing power.

[JackC 617]

Good to hear.  The ONANs start and run beautifully when their carburetors are clean.

[Tankman 3,516]

Today I tried Berrymans, gas additive. We shall see.

 

I've been cleanin' the carb little by little and, what a difference! From now on, Seafoam and / or Berrymans for the 20 hp Onan.