Carb help on 1989 416 Onan twin

[KREP 15]

I bought this tractor new when the house was built. It runs decently with no smoke or other issues. I missed a little during startup but straightens out after a minute or so.
 

I decided to clean out the carb to see if that would make it idle better at startup.  A friend that used to work at the WH dealer said pull the top off the carb, remove the brass rod, clean it out and replace. Did that, and sprayed the passages on the upper and lower parts with carb cleaner. 
 

when I re-assembled it, it started easy and I pulled outside where it died.  I had a heck of a time getting it started again. I took it all apart and saw the needle valve sitting sideways in the hole, and not connected to the float. So I slid the nub on the needle valve into the slot on the float (black plastic floats). A bow shaped wire connects the floats to the upper. Then I reassembled again.
 

Tried to start it again without the air cleaner bottom pan.  No luck. I put some starting fluid in the carb, and it started but was blowing out black smoke. After it ran a moment it cleared up but didn’t sound right. And gas was blowing out of the 4 holes at the mouth of the carb and getting sucked into the carb, causing a bad “rich” condition. Then it died again. 
 

So I took it apart again and the needle valve was sitting in the bottom not connected. I reassembled carefully and tried to start and same result. It is ok when I assemble and install it, but not when it starts the rough running and blowing out black smoke.  I don’t know what to do next. I didn’t bend the parts on the float (tab), and the needle valve is ok  

 

what’s the next step? Should I try bending the tab with the slot so the needle valve can’t escape??  It didn’t have a retainer spring. ???

 

thanks for the help. 

[lynnmor 7,815]

You aren't putting it together correctly, also the float level is difficult to adjust with the carburetor in place.  Page 7-3 has the information.

[KREP 15]

[KREP 15]

Above are pix of carb. The only removable parts are the float,  needle valve, and pin. They only go together one way, and that is what’s confusing. When I assemble it runs fine for the first minute or so. Then the overgassing starts. When I just took it apart, the needle was not hooked to the float. Again. What’s causing it to fall off ?  There was no spring clip holding it on originally. Maybe I need to bend the tab so it can trap the needle in place m

[KREP 15]

I downloaded the file. Thank you. I compared parts with illustration and everything matches fine. I’ll go out in the morning and try again. 

[lynnmor 7,815]

Was the needle ever replaced?  Some of the cheap Chinese kits have two needles and maybe the short one was used.  Also, check both the float height and drop, if there is too much travel maybe that allows the needle to pop out.

[kpinnc 14,632]

I would exercise caution "bending the tab" that connects the float to the plunger. I've wrestled with one for weeks after changing the angle of that tab, because it changes how high the fuel is allowed into the bowl before the plunger shuts it off. 

 

Make small adjustments is the best thing I can suggest. If you let too much fuel in, the tractor will choke off every time you move or turn, too little it won't run at all. Vanguards use those carbs on the smaller twins, and I think that is the only manual I've seen with the adjustment procedure in it. I don't think they are online, but I will look at mine and get a screen shot if I can find it.

Edited April 30, 2021 by kpinnc

[KREP 15]

Needle looks ok and I don’t think I ever replaced it. 
 

I’ll take care when looking at the tab. 
 

thank you n

[kpinnc 14,632]

This got me thinking- because I've done this: if the D shaped retainer was out of the slot on the top half of the carb when you put it together, it could have been crushed just enough to fall out during operation. I measured a good one at .550 as shown below:

 

Edited April 30, 2021 by kpinnc

[kpinnc 14,632]

There are a couple procedures that cover the carb float adjustment in the vanguard manual. Since this is not specifically for Onan, I would just use it as a guide. The Mikuni carbs are identical on Vanguards with the exception of the throat diameter. Also, I apologize for these shots, as I've never seen a soft copy online. This is from my manual.

 

 

Edited April 30, 2021 by kpinnc

[KREP 15]

Needle looks ok and I don’t think I ever replaced it. 
 

I’ll take care when looking at the tab. 
 

thank you n

 

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kpinnc, thanks for the carb file

 

i bent the tab down a touch without crushing the bend. It started up good and ran ok. It still is running real rich, but I think I’m in the right direction because it stays running at an idle. 
 

I’ll have to put in some new fuel. That helped my surging issues in ALL my gas powered tools. I was an automobile engineer for 24 years and noted that the new fuels turn to crap in 2 months or so. Then you get poorly burned fuel that emits black smoke, surges and pops,  and backfires.  I have even had it do all that with stabilizer in it.  I usually run it with non-ethanol, but I can’t always get it, and that’s when the symptoms come up. 
 

Anyway, I may bend the tab a little more too. 
 

thanks. 

[onanparts.com 185]

Immediately after installing the float, are you checking for free movement? Pushing gently on the float tang directly above the needle? It should come up to nearly horizontal and then drop down easily when you let go. Do it several times. Smooth full movement up and down? When installed correctly it is not possible for the needle to come loose from the float retaining notch/slot. It is possible to install and "think" it's right.....but it's wrong. No bending is normally required on the float tang.

[Chestnut 315]

I see that it's a plastic float. It's uncommon but possible that it's absorbed enough gas so it's not floating. With the top off the carb and float installed you could hold the float assembly down by the pivot pin and fill the float bowl with gas from a squeeze bottle to see that it's floating correctly.

Alternatively, if you have one of the outboard engine type squeeze bulbs you can feel the needle shut off flow when the bowl is full. 

18 hours ago, onanparts.com said:

When installed correctly it is not possible for the needle to come loose from the float retaining notch/slot. It is possible to install and "think" it's right.....but it's wrong. 

Amen to that. I installed it wrong the first time through. The needle fell off as I was putting the assembly in the carburetor. In my case the needle completely sealed off fuel flow leading to no start.

[KREP 15]

Yup I rocked it up and down with fuel in the carb. It’s ok now. I just mowed a couple acres with.  Thank you