# 16.5 Briggs won't start



## Floridacruiser (Jun 4, 2005)

Go to start and it bumps but won't turn over. Keep bumping it and it eventually bumps and rotates back (counterclockwise) far enough and it will start right up.

If I try it and it bumps but won't start, I can take my hand and rotate it counterclockwise 180 degrees and it fires right up.

I put in a new starter, battery and start solenoid but still does it.

All help and suggestions appreciated. Ron


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## 30yearTech (Sep 14, 2006)

Most likely your valves need to be adjusted. Overtime wear increases the valve lash clearance and when it gets too much clearance, the compression release stops working. Without a properly operating compression release the engines compression is just too much for the starter to overcome. Remove the valve covers and check the valve clearances at 1/4" past TDC on the compression or power stroke.


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## Floridacruiser (Jun 4, 2005)

30yearTech said:


> Most likely your valves need to be adjusted. Overtime wear increases the valve lash clearance and when it gets too much clearance, the compression release stops working. Without a properly operating compression release the engines compression is just too much for the starter to overcome. Remove the valve covers and check the valve clearances at 1/4" past TDC on the compression or power stroke.


It is a newer Briggs (3 years old) 16.5 hp single cyl OHV. What are the valves supposed to be set at?

which valve is which....Top and Bottom?

Thank you


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## 30yearTech (Sep 14, 2006)

Post your model type and code numbers from the engine please.


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## Floridacruiser (Jun 4, 2005)

30yearTech said:


> Post your model type and code numbers from the engine please.


\
Model: 31A707...Type: 0335E1....Trim: 040903ZA


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## 30yearTech (Sep 14, 2006)

Floridacruiser said:


> Model: 31A707...Type: 0335E1....Trim: 040903ZA


Top Valve is Exhaust and Bottom is Intake

.003 - .005 - Intake
.005 - .007 - Exhaust


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## Floridacruiser (Jun 4, 2005)

30yearTech said:


> Top Valve is Exhaust and Bottom is Intake
> 
> .003 - .005 - Intake
> .005 - .007 - Exhaust


Thank you for the specs. I'll post back when I finish and let everyone know if the problem is fixed.:thumbsup:


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## Floridacruiser (Jun 4, 2005)

*Fixed It!!!*

Thank you to everyone. Fixed it and it runs and starts perfectly. Love this forum!!!


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## 30yearTech (Sep 14, 2006)

Glad we could help and glad to hear you got it going... :thumbsup:


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## flaco (Sep 5, 2014)

*Wow same issue different problem*

OK so here goes nothing, I had the same problem but here is where it gets super weird, I've adjusted the valves to factory specs, the tractor started right up, I allowed it to run for about ten minutes or so, shut it off, and..... it wouldn't start again. I am utterly perplexed!!!! Is it possible I didn't do it right or is there anything that could cause the valves to jump out of specs? I would really appreciate any help on this Momma is not happy about the grass not being cut!!!! Everyone knows when Momma's not happy no-one is happy.


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## Floridacruiser (Jun 4, 2005)

*Maybe!!!*



flaco said:


> OK so here goes nothing, I had the same problem but here is where it gets super weird, I've adjusted the valves to factory specs, the tractor started right up, I allowed it to run for about ten minutes or so, shut it off, and..... it wouldn't start again. I am utterly perplexed!!!! Is it possible I didn't do it right or is there anything that could cause the valves to jump out of specs? I would really appreciate any help on this Momma is not happy about the grass not being cut!!!! Everyone knows when Momma's not happy no-one is happy.


*There is no way the valves can get out of specs if adjusted properly. Over time they will need adjusted again. My manual says every 100 hours. Did you make sure the lock nuts on the valve stems were tight after you adjusted them? If they were not tightened, they would get out of adjustment quick which in turn would cause a no start problem.

I would pull the valve cover and check the specs again. If they are still set properly, you would have a fuel problem or spark problem.

I would suggest for you to start your own thread on the problem to get help from other people.*

*You say...It won't start again. What does it do when you try to start it?*

*Hope you figure it out soon.....Wanna keep mama happy!!!*:thumbsup:


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## OptsyEagle (Jul 17, 2007)

When it doesn't start again, are you getting the very same symptoms you had before you adjusted the valves. Those symptoms being that when you go to start the mower the engine stops on the compression stroke. That is the symptom of valves out of adjustment.

If the answer is yes, I would remove the valve cover and verify the valve lash clearances again to determine if they are out of spec. again. If they are in spec., I would turn the flywheel very, very slowly while observing the intake valve very carefully. What you should see is the intake valve open and then close and then fairly soon there after you should see a "very small bump" in that valve. That bump is your compression release working as designed. If you don't see it you may have a camshaft problem. If you do see the bump, you probably do not.


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## flaco (Sep 5, 2014)

*Losing my mind!!!!*

Alright so here's and update. 
I pulled the valve cover off again, checked everything again had to make a minor adjustment on the intake side. Put it all together, and the tractor started right up. I was running it for about an hour or so then shut it down for a break. When I came back out.... Nothing!!!! It lugged like it had too much compression again. Barely able to get one solid rotation. If I had any hair left on my head I would be pulling it out.






Floridacruiser said:


> *There is no way the valves can get out of specs if adjusted properly. Over time they will need adjusted again. My manual says every 100 hours. Did you make sure the lock nuts on the valve stems were tight after you adjusted them? If they were not tightened, they would get out of adjustment quick which in turn would cause a no start problem.
> 
> I would pull the valve cover and check the specs again. If they are still set properly, you would have a fuel problem or spark problem.
> 
> ...


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## Floridacruiser (Jun 4, 2005)

*We need to be informed!!!*



OptsyEagle said:


> When it doesn't start again, are you getting the very same symptoms you had before you adjusted the valves. Those symptoms being that when you go to start the mower the engine stops on the compression stroke. That is the symptom of valves out of adjustment.
> 
> If the answer is yes, I would remove the valve cover and verify the valve lash clearances again to determine if they are out of spec. again. If they are in spec., I would turn the flywheel very, very slowly while observing the intake valve very carefully. What you should see is the intake valve open and then close and then fairly soon there after you should see a "very small bump" in that valve. That bump is your compression release working as designed. If you don't see it you may have a camshaft problem. If you do see the bump, you probably do not.


Did you do as this poster suggested? If not do it and if you did what was the results? We need to know if it is a compression release and camshaft problem.

We can't help you if you don't post results after someone tries to help.


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## flaco (Sep 5, 2014)

I actually went back out to re-check the setting they were fine, so I rotated the engine 180 degrees and it started up immediately. I checked for the bump as suggested and noticed it was there. 





Floridacruiser said:


> Did you do as this poster suggested? If not do it and if you did what was the results? We need to know if it is a compression release and camshaft problem.
> 
> We can't help you if you don't post results after someone tries to help.


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## OptsyEagle (Jul 17, 2007)

OK good. Now you shouldn't need to rotate the motor manually just to get it to start so the next time you go to start it, if it doesn't start, let us know the symptoms. Does it crank an then stop? Does it crank and crank and crank and no start, etc.?


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## 30yearTech (Sep 14, 2006)

If the problem persists and you are sure that the valves are adjusted properly, then the issue could be with a bad battery, loose or dirty electrical connections or a bad starter.

Make sure that when you are setting/checking the valve lash you are doing this at 1/4" past TDC on the COMPRESSION OR POWER stroke.


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## flaco (Sep 5, 2014)

*Will update this weekend*

Thank you all for the help. I was able to cut the grass on Sunday, now I will again this weekend work on this issue. I intend to re-do my ground cable as well as install a new plug. As for the settings I absolutely ensured I was at 1/4" past TDC. I will take all advice into consideration when I attempt to tackle the yard again. 





30yearTech said:


> If the problem persists and you are sure that the valves are adjusted properly, then the issue could be with a bad battery, loose or dirty electrical connections or a bad starter.
> 
> Make sure that when you are setting/checking the valve lash you are doing this at 1/4" past TDC on the COMPRESSION OR POWER stroke.


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## 30yearTech (Sep 14, 2006)

flaco said:


> I absolutely ensured I was at 1/4" past TDC.


Just wanted to make sure it was on the Compression or Power Stroke, as TDC occurs twice during each run cycle of the engine. If you set the valves and your not on the power/compression stroke, the settings will be incorrect.


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## Floridacruiser (Jun 4, 2005)

*Please enlighten me*



30yearTech said:


> Just wanted to make sure it was on the Compression or Power Stroke, as TDC occurs twice during each run cycle of the engine. If you set the valves and your not on the power/compression stroke, the settings will be incorrect.


How do I determine if it is on the Power/Compression stroke??


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## OptsyEagle (Jul 17, 2007)

Remove the valve cover and observe the valves. What you are trying to do is determine the difference between the compression/power stroke and the exhaust/intake stroke, since both have a TDC. As you turn the flywheel by hand you will notice that there is a time where the exhaust valve opens and closes, and then, almost immediately the intake valve opens and closes. This is the exhaust/intake stroke and you do not want your 1/4 past TDC measurement at this point. At a 1/4 past TDC here, the intake valve will probably still be open.

As you continue to move the flywheel, after the intake valve has now fully closed, you will observe that the exhaust valve does NOT immediately open. This confirms that you are now on the compression stroke and you should be able to determine that the piston is on the way up. It is here, at TDC where you want to start measuring the 1/4" past TDC.


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## Floridacruiser (Jun 4, 2005)

*You are the Man!!!!*



OptsyEagle said:


> Remove the valve cover and observe the valves. What you are trying to do is determine the difference between the compression/power stroke and the exhaust/intake stroke, since both have a TDC. As you turn the flywheel by hand you will notice that there is a time where the exhaust valve opens and closes, and then, almost immediately the intake valve opens and closes. This is the exhaust/intake stroke and you do not want your 1/4 past TDC measurement at this point. At a 1/4 past TDC here, the intake valve will probably still be open.
> 
> As you continue to move the flywheel, after the intake valve has now fully closed, you will observe that the exhaust valve does NOT immediately open. This confirms that you are now on the compression stroke and you should be able to determine that the piston is on the way up. It is here, at TDC where you want to start measuring the 1/4" past TDC.


Nobody earlier told me how to determine if I was on the Compression Stroke or Exhaust Stroke so I never did get it right.

I printed out your instructions and followed them step by step. Fired right up and runs perfectly.

Thank you so much for your quick comeback and correctly detailed response.:thumbsup:

Ron~~~~~~~Mowing with a big smile!!!!


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## 30yearTech (Sep 14, 2006)

Floridacruiser said:


> Nobody earlier told me how to determine if I was on the Compression Stroke or Exhaust Stroke so I never did get it right.


Glad you got it going, but based on your post on 8/13 where you posted 

"Thank you to everyone. Fixed it and it runs and starts perfectly. Love this forum!!!"

didn't know you were still having any issues or needed any further help, but asking a question like you did will usually get you the help you need, so don't hesitate to ask if your not sure. You can also search the forums with your question and most likely find an answer, as I know I have explained this in the past.


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## Floridacruiser (Jun 4, 2005)

*Clarification*



30yearTech said:


> Glad you got it going, but based on your post on 8/13 where you posted
> 
> "Thank you to everyone. Fixed it and it runs and starts perfectly. Love this forum!!!"
> 
> didn't know you were still having any issues or needed any further help, but asking a question like you did will usually get you the help you need, so don't hesitate to ask if your not sure. You can also search the forums with your question and most likely find an answer, as I know I have explained this in the past.


Back in August it wouldn't kick over at all. So I adjusted the valves and it started right up. But....it smoked a lot and ran rough for a less than a minute. It cleared up and ran perfectly the rest of the day.

I got tired of it running rough and smoking at startup so I reread the thread and came across the post about Compression TDC and Exhaust TDC and asked how to determine the difference.

Everything appears to be working correctly now. No smoke or rough running on startup.

Thanks again for all the help you folks give on this forum.:thumbsup:

Ron


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## Floridacruiser (Jun 4, 2005)

*Torque*



30yearTech said:


> Top Valve is Exhaust and Bottom is Intake
> 
> .003 - .005 - Intake
> .005 - .007 - Exhaust


*F.Y.I. Don't forget to torque the little set screw inside the valve adjustment nut at 45 Inch Pounds. I didn't torque them enough the first time and they loosened up and I had to redo them after a few months of mowing.

Wouldn't start again so I redone them properly.*


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