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Blow back through the carb on 314


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#76 Trav1s ONLINE  

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Posted June 28, 2016 - 06:19 AM

The carbs used on the larger K series are as follows:

 

K241/k301 - Carter 26 or Walbro

K321 - Carter 28 (very rare carb and not common)

K321/k341 - Carter 30 or Walbro

 

The bore of the carb is smaller on the 26 but I don't recall the difference. Kirk talks about it here:

Killer Kohler Part 1

Killer Kohler Part 2

 

Killer 241 Part 3



#77 shantzonpoint OFFLINE  

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Posted June 28, 2016 - 06:36 AM




The carbs used on the larger K series are as follows:

K241/k301 - Carter 26 or Walbro
K321 - Carter 28 (very rare carb and not common)
K321/k341 - Carter 30 or Walbro

The bore of the carb is smaller on the 26 but I don't recall the difference. Kirk talks about it here:
Killer Kohler Part 1

Killer Kohler Part 2

Killer 241 Part 3

I replaced a carter/kohler 30 with the same size. If the previous owners installed a K301 as a replacement, how can I tell? I didn't see any type of ID when I tore it apart.

I will say this, I replaced both valves. I ordered them for a K321 and they fit perfect. Not sure if the valves on other size K series are the same size tho.

This theory is honestly a long shot. I'm just curious if this could cause the symptoms I'm seeing. I'm grasping at straws at this point. The engine runs really good other than this popping. I want this thing to run right tho.

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#78 Trav1s ONLINE  

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Posted June 28, 2016 - 02:44 PM

Valves are smaller on the k301 but I'd have to check the Kohler manual.  The info from Kirk talks about the size difference.  

 

IIRC the k321/k341 use different exhaust valves than the k241/k301 but don't quote me.



#79 New.Canadian.DB.Owner OFFLINE  

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Posted June 28, 2016 - 05:47 PM

I've read the whole thread and I have to ask: why won't you just pull the bottom off and check the cam timing?  It has been suggested and ignored a dozen times.  The stuff you've tried, repeatedly, hasn't worked and you've ignored the one suggestion that bears any hope of taking down a different road. The points dial in the timing by a microscopic amount.  The cam being off by a full tooth is not going to be cured by a points adjustment.   All the carb cleanings in the world aren't going to stop the piston from forcing air backwards out the intake.  Pull the carb & spin the engine.  The air will still come out.  It isn't the carb.  You've replaced,  lapped & adjusted the valves.  The are riding on the cam.  They only do what the cam tells them to do, when the cam tells them to do it.  They aren't doing what they should do when they should do it, therefore the cam is not in the right spot.

 

Just my two cents worth.  



#80 shantzonpoint OFFLINE  

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Posted June 28, 2016 - 07:08 PM

I've read the whole thread and I have to ask: why won't you just pull the bottom off and check the cam timing? It has been suggested and ignored a dozen times. The stuff you've tried, repeatedly, hasn't worked and you've ignored the one suggestion that bears any hope of taking down a different road. The points dial in the timing by a microscopic amount. The cam being off by a full tooth is not going to be cured by a points adjustment. All the carb cleanings in the world aren't going to stop the piston from forcing air backwards out the intake. Pull the carb & spin the engine. The air will still come out. It isn't the carb. You've replaced, lapped & adjusted the valves. The are riding on the cam. They only do what the cam tells them to do, when the cam tells them to do it. They aren't doing what they should do when they should do it, therefore the cam is not in the right spot.

Just my two cents worth.

I haven't ignored anything. Everybody has been a great help on here. If you've read the entire thread, then you know how limited I am in experience. I'm not afraid to tear into things but something that is that that in depth, I want to make sure it's the problem. I guess what I'm saying is it needs to make sense to me.

When I had the head off, everything looked spot on to me (once I spun it the right way). The "T" mark on the flywheel was dead on the mark on the engine case at TDC as it should be. I had to adjust the point gap about .002 to get the "S" mark (spark) on the fly wheel dead perfect with the mark on the case. The point gap is .022 instead of the recommended .020. From what I've read, this is acceptable.

Wouldn't the problem be evident from the time it starts if the timing was off? It usually took like 10 seconds when I had the air cleaner off. With the air cleaner on, it takes minutes for it to start.

With what I explained above, if this still sounds like the timing being off by a tooth, then please tell me (with an explanation so I can learn about it), and I'll tear into it.

#81 New.Canadian.DB.Owner OFFLINE  

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Posted June 28, 2016 - 08:51 PM

I have attached some photos of the inside of an engine.  Yours will be different as these are Briggs engines, but you can get the idea.  The two dots/dashes are the timing marks. The first shows the crankshaft & cam shaft gears aligned properly, the second shows them out of alignment (different engine).   The second engine still ran but just barely.

 

The cam gear (bigger gear) is driven by the crankshaft gear (the smaller one).  As the piston rises and falls, the crankshaft rotates and turns the cam shaft which raises and lowers the valves.  There are 4 stroke in your engine: suck, squeeze, bang, blow, also known as intake, compression, ignition, exhaust.  It is not enough that the piston and valves rise and fall, they must do so at specific times.  That timing is controlled by the alignment of those gears.  If they are not aligned properly, then the valves may LOOK like they are opening and closing at the correct time, but they ARE NOT.  The intake valve MUST be closing on the compression stroke and fully closed at spark, or the engine will blow fuel / air mixture & / or fire out the carb. 

 

The cam gear is twice as big as the crankshaft gear.  The cam gear goes around once for every 2 rotations of the crankshaft gear. The cam shaft drives the points, which means they open once for every two revolutions of the crankshaft (4 strokes).  It must happen just before TDC on the compression stroke.  If your gears are out of align, your spark will arrive when the piston is somewhere other than short of TDC of the compression stroke.  It may happen 17 degrees early, or 17 degrees late (720 degrees / 42 teeth). You cannot fix that with the points gap and your engine may run, but it will be firing while the intake or exhaust valve is still open.  It can't be 180 degrees out, or it would firing at TDC on the exhaust stroke, and it would not convert fuel to noise.

 

To further complicate matters, some engines have a compression release mechanism that cracks opens one of the valves on the compression stroke at low RPMs in order to facilitate starting by reducing the compression and making it easier to rotate the engine.  If that fails, and stays on, then the corresponding valve will bump open of the compression stroke, possibly causing the engine to fire out the carb or exhaust.

 

All of that means you have to open the engine to see what is not where it belongs.  Hope that helps.  

Attached Thumbnails

  • DSCN3140.JPG
  • crankcase 2.jpg

Edited by New.Canadian.DB.Owner, June 28, 2016 - 09:00 PM.

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#82 DH1 OFFLINE  

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Posted June 28, 2016 - 09:09 PM


Wouldn't the problem be evident from the time it starts if the timing was off? It usually took like 10 seconds when I had the air cleaner off. With the air cleaner on, it takes minutes for it to start.

 

 

You probably already done this but have you adjusted the fuel mixture, high and low speeds?

 

With the air cleaner on the engine would get a richer mixture, makes me think that maybe the mixture is a little lean. ???

 

I'd try opening the adjustments up a bit richer, see what happens, better to run a little rich than lean.

 

When you adjust the mixture you should allow the engine some time, few seconds, to react to the new setting.


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#83 New.Canadian.DB.Owner OFFLINE  

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Posted June 28, 2016 - 09:12 PM

...

He said everything looks good from what he can tell (without tearing into it) He said the small adjustment I made to the timing might be all it needed. It wasn't off much, maybe 1.5 - 2" on the flywheel. You think that could be all it was? Here's the pic again.
313c6aacb70fc51118eed5c9d7a5d40f.jpg

 

 

 1.5 to 2" on the flywheel is about 34 degrees on a 10 inch flywheel.  (1/2 x 10 x pi / 360 x 34) = 1.5 inches


Edited by New.Canadian.DB.Owner, June 28, 2016 - 09:14 PM.





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