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1974 SS16 Onan Carb questions


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#1 Captain OFFLINE  

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Posted November 06, 2015 - 12:10 AM

Hey All,

 

I have a 1974 Sears SS16 with a twin Onan and I want to take the carb apart to clean it and replace the float with a brass one. And I would also like to take the fuel pump apart and replace its gaskets and diaphragm. I had a couple questions since this is my first GT and my first time taking a carb apart. I have watched some videos and it seems pretty simple but I want to make sure I'm not missing anything. The motor is model number BF-MS/2666c if that helps.

 

-As far as replacing the gaskets and the float, its seems to be pretty much "screw off, replace, screw back on". Nothing too intricate or needing any specific tuning. Is that correct? 

 

-Someone recommended I might want to replace the high speed jet while I'm at it. What exactly is that? I have a diagram of all the carb and fuel pump parts in the tractor's manual but it doesnt list that part.

 

-This tractor has been very well kept but it has been sitting for at least 3 years. Are there any other parts in the carb I should replace when I take it apart?

 

-Lastly, where would you recommend I find the carb gaskets, brass float, and fuel pump gaskets? I can buy a carb/fuel pump repair kit from Sears but its $273 and it has other parts in it like the float valve assembly and the valve plate assembly for the fuel pump. That's a little pricey since I don't know if I even need those 2 parts. I was just planning on doing the gaskets, diaphragm and float and see how it does. 

 

-Ok, I have one more question but its off topic... My manual says you should change the oil when the engine is warm. Since its been sitting for years, do I really want to run it to get the oil warmed up? I was thinking it would be best just to drain it and change it before I even start it once. 

 

Any advice is much appreciated!

Thanks!

 

 



#2 Jazz OFFLINE  

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Posted November 06, 2015 - 12:26 AM

Wait for the experts to wake up,,Sears kit is way too much.  .  Pretty sure the vendors here have it for much less. The carb is pretty simple, I have identical tractor.  I had mine apart and the tractor started again.....amazingly.


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#3 dthomp17 OFFLINE  

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Posted November 06, 2015 - 09:07 AM

I'm not an expert by any means but I have worked on that carb before.  If the tractor has been sitting for three years and you plan on replacing carburetor gaskets and float, I would go ahead and flush everything out while its apart.  I rebuilt one of those about two years ago and it's a relatively simple carb to work on. Aftermarket carb kits are available on ebay including the fuel pump kit.  Can't remember what I paid but I'm thinking in the $25-$35 range.  Are you sure the $273 price from Sears was only for a kit and not the complete carburetor?   That price sounds way out of line to me.  Don't see the need to replace any of the jets unless they appear damaged when you take them out. 

 

I think you should be able to run the engine enough to warm it up with the old oil as long as there is a sufficient amount of oil in it.


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#4 Captain OFFLINE  

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Posted November 06, 2015 - 09:24 AM

I'm not an expert by any means but I have worked on that carb before.  If the tractor has been sitting for three years and you plan on replacing carburetor gaskets and float, I would go ahead and flush everything out while its apart.  I rebuilt one of those about two years ago and it's a relatively simple carb to work on. Aftermarket carb kits are available on ebay including the fuel pump kit.  Can't remember what I paid but I'm thinking in the $25-$35 range.  Are you sure the $273 price from Sears was only for a kit and not the complete carburetor?   That price sounds way out of line to me.  Don't see the need to replace any of the jets unless they appear damaged when you take them out. 

 

I think you should be able to run the engine enough to warm it up with the old oil as long as there is a sufficient amount of oil in it.

Thanks for the reply. If you remove the jets, do you just screw them back in tight? There isnt any specific way or depth they need to be screwed in? 



#5 toppop52 OFFLINE  

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Posted November 06, 2015 - 10:10 AM

Is it a Zenith carb, or a Marvel Schebler?

#6 Captain OFFLINE  

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Posted November 06, 2015 - 10:19 AM

Is it a Zenith carb, or a Marvel Schebler?


I have no idea... Will it say which one it is on it somewhere?
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#7 toppop52 OFFLINE  

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Posted November 06, 2015 - 10:29 AM

Yes it will, especially the Zenith. Zenith kits are all over the net for $25-$35 dollars less float, and the floats from a lot of different applications will work, just use the measurements, they're $5-$15 on eBay. If it's a Marvel, I'd suggest calling Onan ASAP in PA, they have a nice website. The Zenith is online new for $225, ASAP has the MS carb for about $299. I used a Tecumseh float in my Zenith.

Edited by toppop52, November 06, 2015 - 10:30 AM.

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#8 Bolens 1000 OFFLINE  

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Posted November 06, 2015 - 10:35 AM

If its the DD series Marvel Schebler , the kit should look like this:

 

$_1.JPG

 

Last time I ordered one for a customer it was in the $70 range I believe


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#9 wahoowad OFFLINE  

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Posted November 06, 2015 - 11:04 AM

I did mine last winter, pretty easy carb to work on. I soaked it first in a bucket of parts cleaner which cleaned it up pretty good. I then used carb parts from onanparts.com to do the rebuild. I can't find my order but think I had to get a carb kit, order one of the jets separately, a fuel pump rebuild kit and a separate brass float.


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#10 Captain OFFLINE  

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Posted November 06, 2015 - 11:31 AM

I didn't see either name on the carb but I could make out "model no. DD". I've seen carb kits for DD carbs on a few websites. I wondered what they meant by DD carbs. Now I know!

#11 bbuckler OFFLINE  

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Posted November 06, 2015 - 12:33 PM

I didn't see either name on the carb but I could make out "model no. DD". I've seen carb kits for DD carbs on a few websites. I wondered what they meant by DD carbs. Now I know!

Your onan should be a BF Series. The service manual will help you http://gardentractor...-16-hp-engine/ 

Onan has very helpful manuals 


Edited by bbuckler, November 06, 2015 - 12:42 PM.

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#12 MNGB OFFLINE  

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Posted November 06, 2015 - 02:15 PM

Hi, first I would start the engine  and run  to warm it up good for the oil change, at this time you'll find out how the engine runs if it starts idles and throttles up nice, I would do nothing with the carb (don't fix what isn't broke) on the Onan to do a complete carb cleaning and kit install you'll have to remove the intake and that means new intake gaskets are needed. Run the engine to find see how it runs, I've got many older Suburban and I have a SS16 I always run them to find out how they run before starting any fixes.

PS the Onan I have tends to be a bit cold blooded and needs choke for about a minute before it will stay running after that it idles and runs up good.


Edited by MNGB, November 06, 2015 - 02:17 PM.

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#13 bhts OFFLINE  

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Posted November 06, 2015 - 04:04 PM

I have the kit for the carb in stock if you need it http://bobsgardentra...570?search=carb  As for the float is there a reason you need to replace if not I would leave it.


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#14 dthomp17 OFFLINE  

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Posted November 06, 2015 - 04:08 PM

Thanks for the reply. If you remove the jets, do you just screw them back in tight? There isnt any specific way or depth they need to be screwed in? 

No, don't screw them in tight.  Before removing them, screw them in until they just bottom out and count the number of turns needed.  Be very careful because if you screw them in too tight they can be damaged.  After cleaning and during re-assembly, you will need to adjust each jet so they are screwed out the same number of turns that you screwed them in before removal.  This should get your carb jet settings close and then you can do some fine tuning while the engine is running.  Hope this makes sense.


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#15 JBRamsey ONLINE  

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Posted November 06, 2015 - 04:47 PM

Hi, first I would start the engine  and run  to warm it up good for the oil change, at this time you'll find out how the engine runs if it starts idles and throttles up nice, I would do nothing with the carb (don't fix what isn't broke) on the Onan to do a complete carb cleaning and kit install you'll have to remove the intake and that means new intake gaskets are needed. Run the engine to find see how it runs, I've got many older Suburban and I have a SS16 I always run them to find out how they run before starting any fixes.
PS the Onan I have tends to be a bit cold blooded and needs choke for about a minute before it will stay running after that it idles and runs up good.


I agree. Try and get it running first. Then determine, what, if anything, is wrong. You may find that all is ok, saving you a bunch of time and money. Plus, if you start tearing stuff apart before you have it running, if it doesn't run after you fool with it, then you won't know if it was a previous problem or something you inadvertently created.

At the end of the day, have fun and good luck.
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