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17 HP Briggs valve problems

#1

E

ekywildcat

Hello all. First time poster. I've worked on car engines all my life, rebuilt CAT, Cummins and Macks engines, but a 17 HP Briggs has kicked my rear end. The model # is 310707. It's on a LT1000 Craftsman mower. Replaced the head gasket and for some reason, I cannot get the valves adjusted to where it will run. Blows back through the carb, it was doing this before I replaced the head gasket also, but it would run some.

I'll get the piston .25" past TDC, set the valves, blows back and won't run. Turn it another turn, set the valves again, same. And when I turn back to TDC the valves are way wide around.125". I tried the method of getting the ex. open and adj the int. then adj the ex. with the int. open, wouldn't run. I've read about the comp. release device, could this be screwed up? The valves just don't seem to working like they should. I'm at my wits end, HELP! :confused2:


#2

Russ2251

Russ2251

Bent?


#3

EngineMan

EngineMan

Did you check when you had the head off that the valves was sealing (fully closed) lamp oil around the seat of the valves will tell you, also did you lap them, and are you sure the push rods are back in the right way ie Rod–Push (Intake) Rod–Push (Exhaust.


#4

E

ekywildcat

EngineMan said:
Did you check when you had the head off that the valves was sealing (fully closed) lamp oil around the seat of the valves will tell you, also did you lap them, and are you sure the push rods are back in the right way ie Rod–Push (Intake) Rod–Push (Exhaust.
Click to expand...

Yes I checked the valves. I filled the chamber with gasoline and it didn't leak. And I didn't lap them since they were sealing good. And I have the aluminum push rod on the bottom and steel on top. Thanks for the reply. I'm really stumped.


#5

EngineMan

EngineMan

If it "Blows back through the carb" the inlet valve is still open, have you check out the fly wheel key. (timing) and yes you could have a bad release device which is keeping the valve open.


#6

S

stretch5881

If the valves are loose after you set them, You may not be far enough past TDC. You state .25". Try 1/4 turn of the flywheel past TDC.
Backfiring through the carb is timing, flywheel key or the intake valve is not seating.


#7

E

ekywildcat

EngineMan said:
If it "Blows back through the carb" the inlet valve is still open, have you check out the fly wheel key. (timing) and yes you could have a bad release device which is keeping the valve open.
Click to expand...

Fly wheel key was fine. So the compression release does work on the intake valve? From my research I wasn't sure.


#8

E

ekywildcat

stretch5881 said:
If the valves are loose after you set them, You may not be far enough past TDC. You state .25". Try 1/4 turn of the flywheel past TDC.
Backfiring through the carb is timing, flywheel key or the intake valve is not seating.
Click to expand...

Ok thanks. I'll try the 1/4 turn tomorrow. I think it's in the valves. Key was fine and it doesn't really backfire, it just blows, I can stuff a paper towel in the carburetor, and it will blow it out. I'll try that quarter turn, may do it.


#9

EngineMan

EngineMan

ekywildcat said:
Ok thanks. I'll try the 1/4 turn tomorrow. I think it's in the valves. Key was fine and it doesn't really backfire, it just blows, I can stuff a paper towel in the carburetor, and it will blow it out. I'll try that quarter turn, may do it.
Click to expand...

"stuff a paper towel in the carburetor, and it will blow it out" it means that the inlet valve is still open, so recheck

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#10

T

Tinkerer200

"And I have the aluminum push rod on the bottom and steel on top"

As far as running this doesn't matter as they are both the same length also it is supposed to blow back SOME thru the carb as that is how they relieve some compression in order for the starter to turn the engine. Also, after checking the IPL, it appears that engine has a camshaft made in segments which have a fairly high rate of failure. I would remove the valve cover and make sure both valves open about the same amount. The exhaust valve cam lobe may be worn to where it is not letting enough air out.

I can send you detailed instructions on how to adjust the valves IF you like, address below.

Walt Conner
wconner5 at frontier dot com


#11

EngineMan

EngineMan

Tinkerer200 said:
"And I have the aluminum push rod on the bottom and steel on top"

As far as running this doesn't matter as they are both the same length also it is supposed to blow back SOME thru the carb as that is how they relieve some compression in order for the starter to turn the engine. Also, after checking the IPL, it appears that engine has a camshaft made in segments which have a fairly high rate of failure. I would remove the valve cover and make sure both valves open about the same amount. The exhaust valve cam lobe may be worn to where it is not letting enough air out.

I can send you detailed instructions on how to adjust the valves IF you like, address below.

Walt Conner
wconner5 at frontier dot com
Click to expand...

aluminum push rod in for the inlet, steel push rod in for the exhaust and it does matter when the engine is running...! do it right the first time.


#12

Boobala

Boobala

You did set the valves on the COMPRESSION stroke, and NOT the POWER stroke .. correct ( ie.) 180 * out ..??

MY BAD ... I meant to say compression stroke and NOT the exhaust stroke .. MY APOLOGIES !!


#13

E

ekywildcat

Boobala said:
You did set the valves on the COMPRESSION stroke, and NOT the POWER stroke .. correct ( ie.) 180 * out ..??
Click to expand...

I set them after the intake valve opens and the piston gets back to the top.


#14

E

ekywildcat

Tinkerer200 said:
"And I have the aluminum push rod on the bottom and steel on top"

As far as running this doesn't matter as they are both the same length also it is supposed to blow back SOME thru the carb as that is how they relieve some compression in order for the starter to turn the engine. Also, after checking the IPL, it appears that engine has a camshaft made in segments which have a fairly high rate of failure. I would remove the valve cover and make sure both valves open about the same amount. The exhaust valve cam lobe may be worn to where it is not letting enough air out.

I can send you detailed instructions on how to adjust the valves IF you like, address below.

Walt Conner
wconner5 at frontier dot com
Click to expand...

You mean the camshaft is made in independent sections that are put together? If that's the case, that may be the problem. I've eyeballed the valve openings, appear to be the same, but I'll check it better tomorrow. Won't have to remove the valve cover, it's not been on for two days. LOL. Unless you have your own special way to adjust valves, I've probably read a half dozen ways to do it and even made up a few ways of my own.


#15

B

bertsmobile1

Where most go wrong is not going the 1/4" back down after TDC on the firing stroke, it does make a difference.
The other biggie that traps people is the outside sleeve nut is the adjuster and the inner grub screw is the locking mechanism.


#16

T

Tinkerer200

bertsmobile1 said:
Where most go wrong is not going the 1/4" back down after TDC on the firing stroke, it does make a difference.
The other biggie that traps people is the outside sleeve nut is the adjuster and the inner grub screw is the locking mechanism.
Click to expand...

Agree, also from what OP has said about setting valves, he does need to know the correct way which in my case is simply giving more detail of the way B&S says to set them, but offer withdrawn.

"aluminum push rod in for the inlet, steel push rod in for the exhaust and it does matter when the engine is running...! do it right the first time."

Engineman, In case it was missed, OP is talking about getting the engine running not after it is running and which push rod is where does not matter in getting the engine to run as you seem to indicate. Actually many people are replacing the aluminum push rod with steel, running both steel.

Walt Conner


#17

E

ekywildcat

bertsmobile1 said:
Where most go wrong is not going the 1/4" back down after TDC on the firing stroke, it does make a difference.
The other biggie that traps people is the outside sleeve nut is the adjuster and the inner grub screw is the locking mechanism.
Click to expand...

Did the 1/4" down. When the head was off, I got the piston up, down 1/4" and made me a mark on the flywheel. One thing that seems strange is the engine turns clockwise, the instructions in the Briggs pdf manual says to turn it counter clockwise for the 1/4" down measurement. I assume this is correct? Of course I've tried it both ways.

In another thread I read that they had to set the valves on a Briggs at .0015 to compensate for a worn cam lobe. Think I'll try that too.


#18

E

ekywildcat

Tinkerer200 said:
Agree, also from what OP has said about setting valves, he does need to know the correct way which in my case is simply giving more detail of the way B&S says to set them, but offer withdrawn.



Walt Conner
Click to expand...

Meant no disrespect Tinkerer, didn't want to bother you, I've read the B&S manual on adjusting valves plus a number of you tube videos. If you can add more detail to the Briggs manual, I'd be grateful to read it.


#19

I

ILENGINE

ekywildcat said:
Did the 1/4" down. When the head was off, I got the piston up, down 1/4" and made me a mark on the flywheel. One thing that seems strange is the engine turns clockwise, the instructions in the Briggs pdf manual says to turn it counter clockwise for the 1/4" down measurement. I assume this is correct? Of course I've tried it both ways.

In another thread I read that they had to set the valves on a Briggs at .0015 to compensate for a worn cam lobe. Think I'll try that too.
Click to expand...

The flywheel turns clockwise as viewed, but most of the references are for the pto end which is counterclockwise as viewed. 1/4" past TDC on power stroke is the correct position.


#20

E

ekywildcat

ILENGINE said:
... 1/4" past TDC on power stroke is the correct position.
Click to expand...

Ok thanks, this clears up some confusion I had. :thumbsup:


#21

E

ekywildcat

I looked up the price of a new cam, around $70 on Amazon includes lifters too. Cheaper than I figured. What was interesting though, in the picture, when you browse over it and enlarge the picture, the lobes are installed on the shaft on splines! I guess that is what Tinkerer meant when he said it was made in segments. I'd say that's my problem, splines are worn throwing off the timing or lobes just wore out.

I found some used engines for $100-$150, may go that route if I can hear them run. Question, some of the engines had a different shaped blower housing, are any of the OHV Briggs in the 14-17 hp range better than another? TIA.


#22

I

ILENGINE

The blower housing are different shapes because they have used 3 different air filters. The oldest is the oval cartridge type filter, then they went to a oblong suitcase looking filter, and the newest is the round tube shaped cartridge filter.


#23

S

stretch5881

ekywildcat said:
I looked up the price of a new cam, around $70 on Amazon includes lifters too. Cheaper than I figured. What was interesting though, in the picture, when you browse over it and enlarge the picture, the lobes are installed on the shaft on splines! I guess that is what Tinkerer meant when he said it was made in segments. I'd say that's my problem, splines are worn throwing off the timing or lobes just wore out.

There are more parts to it than that. Just under the gear is the compression release. It is 3 parts. A pin, a spring and a flyweight. The flyweight often scatters.
I don't know if this is your issue though. If the compression release scattered, then the engine would act like a dead spot in the starter and be difficult to turn over.
Click to expand...


#24

E

ekywildcat

There are more parts to it than that. Just under the gear is the compression release. It is 3 parts. A pin, a spring and a flyweight. The flyweight often scatters.
I don't know if this is your issue though. If the compression release scattered, then the engine would act like a dead spot in the starter and be difficult to turn over.[/QUOTE]

Thanks, good info. I'd read about the compression release, just didn't know where and what parts were involved. And the engine is very hard to turn, when it hits the hard spot, the starter will barely get it past it.

I'm pretty certain the cam is junk, best I could check it yesterday, there's about .030 difference between the intake and exhaust lift. Thanks again, probably going the engine swap route. My brother has a 11 hp Briggs flatty that runs great, looks to be an easy swap, exhaust will take a little work, but it's free, and my grass needs mowed!!!


#25

E

ekywildcat

ILENGINE said:
The blower housing are different shapes because they have used 3 different air filters. The oldest is the oval cartridge type filter, then they went to a oblong suitcase looking filter, and the newest is the round tube shaped cartridge filter.
Click to expand...

OK. Appreciate the info.

:thumbsup:


#26

S

stretch5881

You could put the 11 horse on but it won't have the power of the 17. If you look up the part number of the cam, you could get a used one on Ebay for around 15.00. Add a new base gasket and crank seal and you are back in business.


#27

B

bertsmobile1

Unless you like to mow with the wind blowing through your hair or in the rain, then the difference in the Hp will not make much difference.
Hydros gobble up a silly amount of power but I can mow down 4' of rough growth on the side of the road quite happily with an old 8/24 or 10/32.

Lawn care professionals do not have a choice, but home owners do.
If you restrict your mowing to the 4 hours prior to sunset the 11 Hp will do you fine and it will be quicker than rebuilding the old engine so if your early spring it really good, the grass will not get away from you.
Then rebuild the old engine at your leisure.
Or if you are like me, pop it on the bench, cover it with a dust cloth then forget it till it is too late.


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