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Blow back through the carb on 314


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#61 WNYTractorTinkerer ONLINE  

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Posted June 14, 2016 - 09:47 AM

If you still get the symptoms you were before after the timing change..  CCW ls the K-series rotation..  I almost mentioned it..  (It did occur to me..)  Oh well..


Edited by WNYTractorTinkerer, June 14, 2016 - 09:47 AM.

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#62 shantzonpoint OFFLINE  

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Posted June 14, 2016 - 05:38 PM

If you still get the symptoms you were before after the timing change.. CCW ls the K-series rotation.. I almost mentioned it.. (It did occur to me..) Oh well..


I got it all back together. I started and it ran perfect for about 20-30 seconds. Then it started fluctuating RPM just a bit and started blowing out the carb again. It was running a little higher RPM than normal so I slowed it down and the popping went away for about 10-20 seconds. Then it started popping once again and it did it continued through all RPM ranges.

When I took apart after installing new valves and running it for about 2-3 minutes, there was already a build up of soot on the intake valve. You can see it here.
39900b4b8b10c0e6d5d64c0c91fd3b4a.jpg

Is there any chance the carb is messed up (wrong size main jet for example) and feeding it to much fuel? Another thing I should add. There is steam coming out of the carb after I shut it off.

https://youtu.be/_MC5ocoI7qw

#63 DH1 OFFLINE  

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Posted June 14, 2016 - 05:41 PM

Have you tried to adjust the carburetor fuel mixture?

Your carb has high speed and low speed adjustments on it from what I see in the video.


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#64 shantzonpoint OFFLINE  

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Posted June 14, 2016 - 05:46 PM

Have you tried to adjust the carburetor fuel mixture?
Your carb has high speed and low speed adjustments on it from what I see in the video.

Yes I have. I adjusted to the manuals starting specs and leaned it out as much as I could before it starts sputtering.

I would think if it's a timing problem it would run bad the entire time. I can't figure out why I'm getting so much carbon build up.

Edited by shantzonpoint, June 14, 2016 - 05:52 PM.


#65 Trav1s ONLINE  

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Posted June 14, 2016 - 06:00 PM

How does the bottom side of the head look?  

 

Thinking outloud right now...

Weak spark will run but will cause incomplete burn... Got another coil to try? Condenser? 



#66 shantzonpoint OFFLINE  

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Posted June 14, 2016 - 06:03 PM

How does the bottom side of the head look?

Thinking outloud right now...

Weak spark will run but will cause incomplete burn... Got another coil to try? Condenser?

No I don't have a spare of either. :-/

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#67 shantzonpoint OFFLINE  

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Posted June 14, 2016 - 06:16 PM

Whats making me think it's a fuel problem is both times I've taken the carb off (drained all fuel out) it's started and ran beautifully for 20-30 seconds. I thought maybe it was just by chance the first time but now it's done it twice. It will spit every time I start it from now on. Add that to the excessive carbon build up......

Is there any chance my fuel pressure is to high? I just rebuilt the carb and put in new seat and needle valve so I don't think that's an issue. But if pressure is to high it might overcome the weight of the float? I'm just tossing if out there.

I've proven time and again I don't know what the hell I'm doing throughout this thread. ...lol. I really appreciate all of the help you guys have been giving me.

 


Edited by shantzonpoint, June 14, 2016 - 06:33 PM.


#68 DH1 OFFLINE  

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Posted June 14, 2016 - 07:06 PM

You could rig up a temporary fuel supply, tank, hose, filter, up high and gravity feed the carb.


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#69 shantzonpoint OFFLINE  

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Posted June 14, 2016 - 07:12 PM

Here is another video of what is doing. Sorry for the poor lighting. I was pulling the choke in/out to see how much that effected it.

https://youtu.be/vug4sv_89uk

Edited by shantzonpoint, June 14, 2016 - 07:13 PM.


#70 DH1 OFFLINE  

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Posted June 14, 2016 - 07:30 PM

Looking at the colour of the exhaust  valve I don't think it's running rich otherwise it would be black.

 

Looking at this picture it almost looks like the head gasket is leaking to the left of the exhaust valve. ???

 

Looking at the last video, if it was me I'd double check the intake valve to make sure it's sealing, re lap and re gap. 

 

The ACR or decompressor only works the exhaust valve has nothing to do with the intake valve.

 

 

39900b4b8b10c0e6d5d64c0c91fd3b4a.jpg

 

 



#71 shantzonpoint OFFLINE  

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Posted June 14, 2016 - 08:03 PM



Looking at the colour of the exhaust valve I don't think it's running rich otherwise it would be black.

Looking at this picture it almost looks like the head gasket is leaking to the left of the exhaust valve. ???

Looking at the last video, if it was me I'd double check the intake valve to make sure it's sealing, re lap and re gap.


I installed new valves last week. I lapped them to make sure they were seating good.

b38061a24734426ec713d2c08d4f4f31.jpg

0addad9d6bf42c20876b56fc5a82c688.jpg

I made sure the tappet gaps were spot on. I even did a bench test by sticking my compressor hose in the spark plug hole to see if I could feel air blowing through the intake. I didn't feel or hear a whisper.

I'm going to try the gravity feed tomorrow. I don't have any hose small enough. I have every size under the sun bigger than what I need of course. .....

#72 propane1 ONLINE  

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Posted June 14, 2016 - 08:24 PM

I've only read from page four. In post 46 with the picture of the piston at TDC, the picture shows the valves open. If this is the end of the compression stroke, then both valves should be closed. If this is the end of the exhaust stroke, then the exhaust valve should be closed and the intake ready to open, for intake stroke. Seems to me your cam timing is off. Please correct me if this not the case.
The area where the intake valve is, is the coolest part of the explosion. It burns incomplete at the start, until it gets hot. Just my guess on the soot part on the intake valve. I wouldn't worry about it thou.

Noel

#73 shantzonpoint OFFLINE  

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Posted June 14, 2016 - 08:29 PM

I've only read from page four. In post 46 with the picture of the piston at TDC, the picture shows the valves open. If this is the end of the compression stroke, then both valves should be closed. If this is the end of the exhaust stroke, then the exhaust valve should be closed and the intake ready to open, for intake stroke. Seems to me your cam timing is off. Please correct me if this not the case.
The area where the intake valve is, is the coolest part of the explosion. It burns incomplete at the start, until it gets hot. Just my guess on the soot part on the intake valve. I wouldn't worry about it thou.

Noel

What you're seeing possibly isn't accurate because I was spinning motor in the wrong direction. I'm a noob learning as I go. .. lol.
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#74 schweitz OFFLINE  

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Posted June 28, 2016 - 12:51 AM

I just came across this forum subject after being off for a time, so you may well have solved the problem of spitting carb. Thought I'd share my recent experience with a spitting JD312 carb. Engine started losing power and ran very hot resulting in blowing head gasket and ruining cyl head. Had repair man install new head gasket and replacement used head. Took home and blew gasket and ruined head within 2 hrs of mowing.

 

I knew the carb was spitting due to worn throttle shaft allowing air sucked thru worn throttle shaft causing serious lean burning, so I solved that with inserting bushing on top end of throttle shaft. Repair man checked timing and found it was a little off, so he adjusted that. After another new head gasket and replacement head the 312 has been running better than it ever did before.

 

Your video shows carb spitting much like mine was and throttle vibrating similarly, so I'd recommend looking at those closely.


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#75 shantzonpoint OFFLINE  

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Posted June 28, 2016 - 06:13 AM

I just came across this forum subject after being off for a time, so you may well have solved the problem of spitting carb. Thought I'd share my recent experience with a spitting JD312 carb. Engine started losing power and ran very hot resulting in blowing head gasket and ruining cyl head. Had repair man install new head gasket and replacement used head. Took home and blew gasket and ruined head within 2 hrs of mowing.

I knew the carb was spitting due to worn throttle shaft allowing air sucked thru worn throttle shaft causing serious lean burning, so I solved that with inserting bushing on top end of throttle shaft. Repair man checked timing and found it was a little off, so he adjusted that. After another new head gasket and replacement head the 312 has been running better than it ever did before.

Your video shows carb spitting much like mine was and throttle vibrating similarly, so I'd recommend looking at those closely.

I'm still having an issue with the spitting. I installed a brand new carb a couple weeks ago but it is still doing the same thing.

I cannot figure out for the life of me what is causing it. I went through and triple checked everything I can think of. I replaced anything I thought could be the issue.

Now I'm thinking maybe the air wasn't coming from the cylinder but rather air being forced back from the intake valve closing. Like it's being fed to much air through the carb.

The engine was pulled at some point before I bought it (butt spices on wires is the giveaway).

I'm wondering if I have wrong carb size. Is there any way to tell the difference between a K321 and let's say a K301? Are the engines physically the same size? Same engine mounting holes? Etc.? Maybe the original K321 died and they popped in different engine and they used the carb of the K321? It's a long shot but I'm to that point. ....lol.

Upon thinking of this theory I put the air cleaner and side covers back on (to restrict air flow as much as possible.) I wanted to see if the mower deck that came with it worked as well. So I started it and it ran perfect. I pulled out of the garage. ....running perfect, lowered deck and kicked on the PTO. Everything was perfect. I cut about 100' strip and shut off the PTO. I then took it for a spin around my pond and not once did it spit. Now I'm starting to fist pump. I idled it down and pop........pop........pop. I idled it up pop..pop..pop. Gah! I pulled it into the garage, threw up my arms, and said f*** it!!!

This was by far the longest is ran without the popping issue tho. It ran prolly 4-5 minutes total before it started. Normally it's around 10 seconds.

The only thing I haven't done anything with was what a reply earlier said. It's possible the timing could be off by a tooth. I checked TDC with the flywheel and it seemed spot on (after a minor point adjustment) but it's still a possibility I guess.

Edited by shantzonpoint, June 28, 2016 - 06:20 AM.





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