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Briggs engine won't fire after new piston rings on Craftsman mower---15.5HP

#1

T

theticket

OHV Engine # 28N707 Type 0173-01. Was smoking terribly, almost to the point of not running, so I replaced the piston rings, properly I think. I inspected all moving parts, OK. I put on new gaskets also. Now, when I put it back together, I get spark, but no firing in cylinder. I have gas on spark plug when pulled to inspect and it sparks, it will not continue firing. Starting fluid is of no help either. I'm pretty sure I got all wiring back correctly. I don't really know how to check if a kill switch is doing its job or not. I have a switch mounted on the bottom of the seat, but it looks normal. The mowing deck is not installed at this time. I set the coil gap at .12. This is the first time I have ever replaced piston rings. Do I have a bad gasket? Do I need to adjust valves? What should I look at next to resolve my problem?
Many thanks


#2

B

bertsmobile1

Ok lets get this correct.
You told us you have spark
You told us the plug gets wet
You told us
it will not continue firing.
Click to expand...
????
I am not quite sure what you mean by that statement? :confused2::confused2:

Does it fire, as in go bang at all ?
Does it go bang a couple of times & then stop ?
Do you mean you get a few sparks then no sparks ?


#3

M

motoman

Try running cold compression test. Did you measure the bore for oval and taper? Rings have side clearance and need end gap . If new rings were put in a worn cylinder the compression could be low?


#4

T

theticket

bertsmobile1 said:
Ok lets get this correct.
You told us you have spark
You told us the plug gets wet
You told us ????
I am not quite sure what you mean by that statement? :confused2::confused2:

Does it fire, as in go bang at all ?
Does it go bang a couple of times & then stop ?
Do you mean you get a few sparks then no sparks ?
Click to expand...

Sorry, I have spark when I ground the plug tip on the engine, so I assume it still sparks when it is screwed in, but it does nothing but turn over and over and does not start.


#5

T

theticket

motoman said:
Try running cold compression test. Did you measure the bore for oval and taper? Rings have side clearance and need end gap . If new rings were put in a worn cylinder the compression could be low?
Click to expand...


No, I did not measure anything. I am a novice. The lawnmower is 20 years old. I just ordered new rings and put them in.


#6

L

Luffydog

Do a compression check and set the valves in..003/.005 & ex. .005/.007 see if that helps out. Might start at the valves first just to check if you don't have a compression tester. Or if you pulled the flywheel make sure the key way is still in.


#7

I

ILENGINE

Also check the flywheel key. If not properly torqued when the flywheel was reinstalled could of sheared.


#8

Boobala

Boobala

theticket said:
OHV Engine # 28N707 Type 0173-01. Was smoking terribly, almost to the point of not running, so I replaced the piston rings, properly I think. I inspected all moving parts, OK. I put on new gaskets also. Now, when I put it back together, I get spark, but no firing in cylinder. I have gas on spark plug when pulled to inspect and it sparks, it will not continue firing. Starting fluid is of no help either. I'm pretty sure I got all wiring back correctly. I don't really know how to check if a kill switch is doing its job or not. I have a switch mounted on the bottom of the seat, but it looks normal. The mowing deck is not installed at this time. I set the coil gap at .12. This is the first time I have ever replaced piston rings. Do I have a bad gasket? Do I need to adjust valves? What should I look at next to resolve my problem?
Many thanks
Click to expand...

THIS , should be your engine O/H Manual, I think you will find this, AND a camera (digital preferred) very useful, BEFORE attempting repairs, ( camera helps you "see" things as they WERE , makes re-assembly much easier ! )

https://drive.google.com/file/d/0B6NaqjIxWV1ybEN0LWo3azl6OUU/view


#9

T

theticket

Luffydog said:
Do a compression check and set the valves in..003/.005 & ex. .005/.007 see if that helps out. Might start at the valves first just to check if you don't have a compression tester. Or if you pulled the flywheel make sure the key way is still in.
Click to expand...


I got a compression tester and it read 125. I have not adjusted valves yet. I read on B&S website that they don't publish compression PSI, that they prefer a leak down test. Does this 125psi sound correct? The flywheel is turning and I wouldn't think that it would turn if the key snapped off or fell out, would it?


#10

T

theticket

Boobala said:
THIS , should be your engine O/H Manual, I think you will find this, AND a camera (digital preferred) very useful, BEFORE attempting repairs, ( camera helps you "see" things as they WERE , makes re-assembly much easier ! )



Thanks for the information. Wish I had that before I started this adventure.
Click to expand...


#11

I

ILENGINE

theticket said:
I got a compression tester and it read 125. I have not adjusted valves yet. I read on B&S website that they don't publish compression PSI, that they prefer a leak down test. Does this 125psi sound correct? The flywheel is turning and I wouldn't think that it would turn if the key snapped off or fell out, would it?
Click to expand...


125 psi is high, so check the valve clearances to start with. The engine will crank with a sheared flywheel key but will not fire at the correct time.


#12

L

Luffydog

Possibly didn't put cam in correctly or the rings but thinking the valves is where u should start first before another tear down.


#13

Ronno6

Ronno6

Check that your muffler didn't get plugged by some critter during your rebuild.
If it can't exhaust, it won't run.
Ever pull the potato up the exhaust pipe trick?


#14

T

theticket

ILENGINE said:
125 psi is high, so check the valve clearances to start with. The engine will crank with a sheared flywheel key but will not fire at the correct time.
Click to expand...

I thought 125PSI was high also after reading other posts. I will check clearance on valves and check muffler for blockage before tearing back down. I will repost on results.
Thanks a bunch to all.


#15

T

theticket

Sure enough, the key sheared off. I will get another one. Any advice on how to prevent this from happening again. Is there a correct way to insert the key to make sure it won't shear off again??
thanks for all the help


#16

Boudreaux In Eunice La.

Boudreaux In Eunice La.

Make sure it's torqued down to the right specs.......... If the flywheel is a lil loose it will shear the key right away...........


#17

B

bertsmobile1

A taper needs to be clean & dry to lock in.
It also needs to be a close fit.
If a little lip has formed on the edge of the keyway on either the crank or the flywheel it will need to be removed or the taper will not lock no matter how tight you do up the nut.


#18

T

theticket

OK< thanks for the suggestions. I'll give it another go!!!


#19

T

theticket

OK, new key installed and flywheel torqued properly and everything is working like it should so far. Thanks to all!! I learned a lot....


#20

B

bertsmobile1

:cloud9: :banana: :drink:


#21

John R

John R

Luffydog said:
Possibly didn't put cam in correctly .
Click to expand...

Be my first guess too


#22

T

theticket

OK, so now it is not running very smooth and sometimes keeps running after I turn off the key and even backfired once. The only thing I did, as far as adjustments, is to adjust the valves to what I thought they should be. Could that be the problem?? I put everything back just like it was originally and only readjusted the valves(which probably didn't even need it. I used ..003/.005 & ex. .005/.007. Any suggestions before I start readjusting again? Seems to run hotter now than before also.
Thanks


#23

EngineMan

EngineMan

theticket said:
OK, so now it is not running very smooth and sometimes keeps running after I turn off the key and even backfired once. The only thing I did, as far as adjustments, is to adjust the valves to what I thought they should be. Could that be the problem?? I put everything back just like it was originally and only readjusted the valves(which probably didn't even need it. I used ..003/.005 & ex. .005/.007. Any suggestions before I start readjusting again? Seems to run hotter now than before also.
Thanks
Click to expand...

have you got a solenoid on the carb, if so check it out "sometimes keeps running after I turn off the key and even backfired once" on and stays on, off when you turn the key off.....



"Seems to run hotter now than before also" did you replace the rings with oversize ones..?, also check the carb, it maybe running lean a bit.


#24

T

theticket

The solenoid on the carburetor seems to be working properly although I don't know how to "check it out". I did not use oversized rings and the engine does not put out black smoke, which I assume it would do if it were running lean. Correct me if I'm wrong.
Thanks


#25

T

theticket

I think I'm wrong about the black smoke. My engine is not smoking at all, but it seems to be hard to start after I turn it off and it sits for a little while


#26

EngineMan

EngineMan

Un plug and take off the solenoid give it 12v on any of the two poles, does the pin pull in or out by doing so...? engine needs to be a little on the rich side so a little black smoke when starting and pulling is normal.

"but it seems to be hard to start after I turn it off and it sits for a little while"......RECHECK THE FUEL SOLENOID they're do go bad.


#27

T

theticket

Solenoid seems to be working properly. I'm going to try to readjust the valves. That is the only thing I messed with after putting it all back together again.
thanks for the suggestion.


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