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Blow back through the carb on 314


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#46 shantzonpoint OFFLINE  

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Posted June 11, 2016 - 06:23 PM

Ok I looked at my service manual about how to do a timing test. Here is the description of how to do a static timing test.
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Being an electrician by trade, I went wth the ohm check. As I rotated the flywheel, I was reading .02 resistance. As I got to this point, the circuit opened. It's not to far from what the manual says but I'm not sure if it's acceptable?
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I then decided to pull the head off to see how close the TDC was compared to the mark on the flywheel. It's pretty much dead on. Both valves are open as well at TDC.

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You can see how much carbon has built up already. I had it really clean when I put it back together. Where should I go from here?

Edited by shantzonpoint, June 11, 2016 - 06:52 PM.


#47 DH1 ONLINE  

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Posted June 11, 2016 - 06:49 PM

I think you need to check the CAMSHAFT timing. Cam and crank timing.

The points plunger is camshaft driven.

For sure it's off.


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#48 shantzonpoint OFFLINE  

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Posted June 11, 2016 - 06:54 PM

I think you need to check the CAMSHAFT timing. Cam and crank timing.
The points plunger is camshaft driven.
For sure it's off.

I edited my above post. I made a rookie mistake. I was looking at the wrong spot on the flywheel. Two spots are posited white and I was looking at the wrong one.....

#49 DH1 ONLINE  

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Posted June 11, 2016 - 06:58 PM

I think you need to check the CAMSHAFT timing. Cam and crank timing.

The points plunger is camshaft driven.

For sure it's off.

 

 

I edited my above post. I made a rookie mistake. I was looking at the wrong spot on the flywheel. Two spots are posited white and I was looking at the wrong one.....

 

Then what I said is also wrong.

IMO from what I see in your latest picture cam timing looks OK.


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#50 shantzonpoint OFFLINE  

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Posted June 11, 2016 - 07:12 PM

Then what I said is also wrong.
IMO from what I see in your latest picture cam timing looks OK.

You have to set the valve gaps on TDC of the compression stroke don't you?

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#51 DH1 ONLINE  

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Posted June 11, 2016 - 07:53 PM

Yes



#52 shantzonpoint OFFLINE  

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Posted June 12, 2016 - 08:32 AM

Ok please correct me if I'm reading this wrong.  

 

aa58465e38122899680ae5cf787a87be.jpg

 

The part that says "Rotate engine normally until points are just starting to OPEN.  Where I'm confused is on my ohm meter, when the "S" on the flywheel hits the mark (which I adjusted so it lines up perfect), the contacts on the points have just CLOSED.  As an electrician, contacts opening means they are separating, and closed means they are coming together.  Is it opposite when they are talking about points?  I'm seeing it as doing the exact opposite of what it's supposed to.  Please correct me if I'm wrong.....



#53 DH1 ONLINE  

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Posted June 12, 2016 - 08:42 AM

I think you need to check the camshaft timing, the points are cam driven, if the cam timing is not right the points will not open/close when they are suppose to.

Sounds to me like the cam timing could be off 1 tooth.


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#54 Sawdust OFFLINE  

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Posted June 12, 2016 - 09:27 AM

Have you tried to pull your points push rod out to see if it's bent or damaged. This can also damage the lobe on the cam.
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#55 shantzonpoint OFFLINE  

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Posted June 12, 2016 - 10:36 AM

Have you tried to pull your points push rod out to see if it's bent or damaged. This can also damage the lobe on the cam.

Everything seems fine with the plunger except the fact that I think it's closing the points when I think it's supposed to be opening them. Would the engine even run if what I'm thinking is true?

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#56 WNYTractorTinkerer OFFLINE  

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Posted June 12, 2016 - 05:52 PM

Have you pulled the crankcase cover off the engine yet?  

 

FYI another way to know if the engine is on the compression stroke is that it is the only stroke that the points open as they are Cam driven..  (crankshaft turns twice for every cam rotation..)  Both valves should be fully closed near TDC on the compression stroke also. If the valve on either side does not close you have a gap or other problem..  

 

My $$$ is still on the cam timing off a tooth or broken ACR..  



#57 shantzonpoint OFFLINE  

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Posted June 12, 2016 - 06:19 PM

The points closing when they should've been opening was a big clue for me. I have a great understanding how electricity works. However, my inexperience in the mechainical side of engines has really came to light. I'm all but positive the timing is off exactly 180°.

I started thinking about how the piston should work. Correct me if in wrong but on the intake stroke, the intake valve should be opening when the piston is in its downward travel to suck air in correct? It should spring close when it's at the bottom?

Then on the exhaust stroke, the piston should be traveling up as the exhaust valve opens to push everything out?

What is happening is the complete opposite of that. The intake valve opens as the piston is coming up. When the piston is at TDC, the intake valve slams shut. It should be shutting at the bottom of the stroke and then compressing the air/fuel on the way up right?

Then on the exhaust stroke, the piston is going down as the exhaust valve opens.

I have no clue how this thing runs as good as it does.

Edited by shantzonpoint, June 12, 2016 - 06:23 PM.


#58 WNYTractorTinkerer OFFLINE  

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Posted June 14, 2016 - 06:35 AM

It isn't 180° off..  you are on the wrong cycle..  the piston goes up and down twice.  One crank rotation per cycle..  If the valves are closed and as the piston rises, the intake valve will stay open a bit on the compression stroke (a puff out the carb is normal) and shortly before the piston gets up to the top (~.015") the points should open/ break contact which causes the spark.  

 

**If this is not the case the cam is fubar somehow..  Pull the cover and check the ACR spring..


Edited by WNYTractorTinkerer, June 14, 2016 - 06:37 AM.


#59 shantzonpoint OFFLINE  

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Posted June 14, 2016 - 06:53 AM

It isn't 180° off.. you are on the wrong cycle.. the piston goes up and down twice. One crank rotation per cycle.. If the valves are closed and as the piston rises, the intake valve will stay open a bit on the compression stroke (a puff out the carb is normal) and shortly before the piston gets up to the top (~.015") the points should open/ break contact which causes the spark.

**If this is not the case the cam is fubar somehow.. Pull the cover and check the ACR spring..

I'm embarrassed to admit but I was spinning the motor the wrong way. ....lol. That's why it was off 180°.....ugh.

I brought the engine into work and had a coworker that's rebuilt hundreds of engines look at it. He spun it the wrong way at first too. He caught that much, much quicker than I did tho. ....

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

I have my doubts anything will be different. I'm putting it back together tonight and trying it.


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Edited by shantzonpoint, June 14, 2016 - 07:25 AM.


#60 shantzonpoint OFFLINE  

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Posted June 14, 2016 - 09:11 AM

If you clean the valves up and re-gap and it still dies it, The cam has ACR.. Sometimes the spring takes a hiatus and it won't stay in the correct position @ WOT.. It would definitely have the same symptoms as the ACR keeps the valves open a bit on the compression stroke releasing compression for cranking purposes,,

Once the engine gets going weights on the cam extend and return the cam lobes to the full compression position.. Missing or busted springs are a cause of symptoms you are seeing. LOOK at the cam in the picture to show what I'm talking about..

Ignition timing could also cause the issue due to firing too early.. The rotation of the ACR also affects that too since the whole cam lobe spins independently of the inner shaft..

Just saying..

Is there any way to test to see if the ACR is working properly without tearing it all apart?

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