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Blow back through the carb on 314


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#1 shantzonpoint OFFLINE  

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Posted May 22, 2016 - 03:58 PM

I bought a 314 that's in pretty good shape a few months ago.  I've been going through it fixing little things like bushings in the steering system and various other things.  I'm really enjoying the learning experience.  After I bought it, I noticed a rattling sound after it warmed up.  Figuring it's probably due for an engine rebuild, I was planning to work with my friend who has a repair shop this winter.  

 

As I dug into the sound last week, I found the what I thought was an engine rattle, is actually air and fuel blowing out of the carb. It gets progressively worse as I get to full throttle.  It doesn't sputter when at idle.  

 

My question is what causes this?  Could it be a carb problem like the float valve seating?  Maybe an internal valve leaking and the air is escaping through the carb?  I can feel a significant amount of air blowing out of the vent tube below the carb.  I'm not very knowledgeable about the inner working of an engine. So if this doesn't make sense whatsoever, just ignore it........lol.

 

The engine runs really good.  It isn't missing or anything.  It's just sputtering out of the carb.  I will say the high and low speed mixture needles are set on the rich side compared to what the service manual suggests (both about one full turn past recommended settings)

 

I ordered a carb rebuild kit since they are so cheap.  I'm curious what your thoughts are.  I absolutely love this tractor.  I'm going to do whatever it takes to get it right.  

 

Here is a short video of what it's doing.

 

 



#2 stiemmy ONLINE  

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Posted May 22, 2016 - 04:33 PM

My GUESS without having it in front of me off the top of ny head would be intake valve not seating correctly, ignition timing is incorrect , sheared flywheel key, or cam timing is off.

A compression test is definitely needed!

Edited by stiemmy, May 22, 2016 - 04:35 PM.

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#3 Mtypython OFFLINE  

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Posted May 22, 2016 - 04:33 PM

Had wisconsin that did that,bad valve seat
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#4 Auburn David OFFLINE  

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Posted May 22, 2016 - 04:34 PM

I had one that did that..turned out it was running on one cyl..but it ran really good that way.


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#5 Auburn David OFFLINE  

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Posted May 22, 2016 - 04:35 PM

seems mine was a shear pin if I remember correctly.



#6 grattone ONLINE  

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Posted May 22, 2016 - 04:48 PM

Has it been setting for long?

Fresh gas?

Does adjusting the mixture screws out/in make any change?

 

Compression test would be in order

My 2 cents would be try the carb. kit before tearing into it, may save you a lot of work.

Good luck

Gratton


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#7 shantzonpoint OFFLINE  

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Posted May 22, 2016 - 04:50 PM

Thanks for the replies.  Looks like the rebuild will be happening sooner than I expected.  I take it it's not a good idea to use the tractor in this condition?  I bought it to mow grass at my cabin up north.  It will only be used about 4 times a year to mow.  



#8 shantzonpoint OFFLINE  

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Posted May 22, 2016 - 04:53 PM

Has it been setting for long?

Fresh gas?

Does adjusting the mixture screws out/in make any change?

 

Compression test would be in order

My 2 cents would be try the carb. kit before tearing into it, may save you a lot of work.

Good luck

Gratton

I bought it in March so I'm not sure if it had been sitting for long or not.  My guess is it hadn't been sitting because the guy I bought it from used it to plow snow and was rolling his yard with it when I went to look at it.  

 

Adjusting the mixture screws doesn't really help with the spitting.  It only spits when at full throttle.  At idle it seems to run fine. I'll rebuild the carb since I already ordered a kit but I'm leaning toward a valve problem. 



#9 stiemmy ONLINE  

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Posted May 22, 2016 - 05:01 PM

I bought it in March so I'm not sure if it had been sitting for long or not.  My guess is it hadn't been sitting because the guy I bought it from used it to plow snow and was rolling his yard with it when I went to look at it.  
 
Adjusting the mixture screws doesn't really help with the spitting.  It only spits when at full throttle.  At idle it seems to run fine. I'll rebuild the carb since I already ordered a kit but I'm leaning toward a valve problem.


Personally, I would start simple, and cheap.
1st id do a compression test, then if it passes, id check the key on flywheel, and go from there. Why tear it apart if ya dont have to?? Cheers!
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#10 propane1 ONLINE  

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Posted May 22, 2016 - 06:45 PM

Sticking intake valve maybe. If so, put some transmission fluid in the oil and run it. That will free up sticking parts. Just a thought. As was said, do the simple things first.

Noel
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#11 John Arsenault ONLINE  

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Posted May 22, 2016 - 07:05 PM

eeeeek sounds like a valve to me to....I would do as stiemmy suggested and do a compression test. That will tell you if its a valve or not and also give you info on the condition of the engine. From there I would look into the flywheel if all checks out. As far as running it ...yes you can damage the carburator gaskets and I have even seen a blown float bowl do to back firing though the carb worse case it can even catch on fire so if you run it just be aware and be ready to save your ride. 


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#12 ol' stonebreaker ONLINE  

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Posted May 22, 2016 - 08:06 PM

  If the intake is sticking feed it some marvel oil right in the intake to the point it is about to die. Do it for about 30 seconds( mosquitos won't be a problem,LOL), let it clean all the oil out and see what it does.

                                          Mike


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#13 lyall OFFLINE  

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Posted May 22, 2016 - 08:21 PM

while you have the carb off I would check the valve gaps

set valve gap when cold


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#14 olcowhand ONLINE  

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Posted May 22, 2016 - 08:29 PM

It is a points ignition which operates the points off the camshaft, so the flywheel key won't affect timing at all.  I'd say either intake valve doesn't have any clearance or the seat/valve face are damaged.


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#15 Trav1s ONLINE  

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Posted May 22, 2016 - 09:22 PM

Which carb is it?  Carter/Kohler or Walbro?  


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