Green Tractor Talk banner

1 - 20 of 39 Posts

·
Premium Member
Joined
·
12,157 Posts
Discussion Starter #1
I have an Ariens with a 17.5HP B&S engine. All of a sudden when I try to start it the starter just clunks and the flywheel jumps a bit but it will not turn over.

The battery is being sucked down to 9V when I try to crank so I tried a new battery and it too is sucked down to 9V. I checked the starter solenoid for continuity and everything checks out. The odd thing is, if I remove the spark plug the engine will turn over fine. Reinstall the spark plug and it's back to starter clunking and flywheel jumping. Could the starter be defective and drawing too many amps?

To eliminate the entire starting circuit I tried touching a positive jumper lead directly to the starter terminal and I was greeted by a shower of sparks and no starter rotation.

Things seem to be pointing to a bad starter. It almost seems like it is drawing too much current.

Anyone ever encounter anything similar. I'm not sure what else I can try before plunking down $90 for a new starter.

Thanks!
 

·
Registered
Joined
·
5,437 Posts
New starter

I had something similar on a 17 hp Briggs on a White lawmower. Messed around with it and finally bought an aftermarket starter for about half the Briggs price. It worked fine.

Treefarmer
 

·
Premium Member
Joined
·
12,157 Posts
Discussion Starter #3
Thanks Treefarmer. I want to do one more test tomorrow and then I guess it will be time to shop. I'll probably pull the old one off first so I can be sure I get the correct one. The B&S parts manual that came with the tractor is listing an invalid part number compared to what I'm seeing in on-line searches.
 

·
Registered
Joined
·
3,228 Posts
I have an Ariens with a 17.5HP B&S engine. All of a sudden when I try to start it the starter just clunks and the flywheel jumps a bit but it will not turn over.

The battery is being sucked down to 9V when I try to crank so I tried a new battery and it too is sucked down to 9V. I checked the starter solenoid for continuity and everything checks out. The odd thing is, if I remove the spark plug the engine will turn over fine. Reinstall the spark plug and it's back to starter clunking and flywheel jumping. Could the starter be defective and drawing too many amps?

To eliminate the entire starting circuit I tried touching a positive jumper lead directly to the starter terminal and I was greeted by a shower of sparks and no starter rotation.

Things seem to be pointing to a bad starter. It almost seems like it is drawing too much current.

Anyone ever encounter anything similar. I'm not sure what else I can try before plunking down $90 for a new starter.

Thanks!
Before you buy a starter try this. Do a valve adjustment on the rocker arms. Then see if it will turn over. Also look for any damaged parts while you have the valve cover off. Like a jumped push rod.
These engines have a compression release built into them. It opens the exhaust valve slightly to let the engine turn over more easily. If the adjustment is out of whack it won't open stalling the starter. This is why it will crank over no problem with the spark plug removed. Put the plug back in and the compression won't let it turn over.

Good luck
 

·
Premium Member
Joined
·
12,157 Posts
Discussion Starter #5
Before you buy a starter try this. Do a valve adjustment on the rocker arms. Then see if it will turn over. Also look for any damaged parts while you have the valve cover off. Like a jumped push rod.
These engines have a compression release built into them. It opens the exhaust valve slightly to let the engine turn over more easily. If the adjustment is out of whack it won't open stalling the starter. This is why it will crank over no problem with the spark plug removed. Put the plug back in and the compression won't let it turn over.

Good luck
That's a good idea. Could this just happen out of nowhere? I mean, I ran the tractor Sunday and it worked fine. I shut it off and then Monday morning it wouldn't turn over.

The bad part is it looks like B&S does not have their manuals available on-line like Kawasaki does so I do not have the procedure for adjusting the valves. I really need to get this thing back running quickly.

Do you know any place on-line where the information is available?
 

·
Registered
Joined
·
4,433 Posts
One thing you can try is to give it a few smacks with a hammer. oh yeah and pick up a service manual. you never know...:flag_of_truce:
 

·
Premium Member
Joined
·
12,157 Posts
Discussion Starter #7
Before you buy a starter try this. Do a valve adjustment on the rocker arms. Then see if it will turn over. Also look for any damaged parts while you have the valve cover off. Like a jumped push rod.
These engines have a compression release built into them. It opens the exhaust valve slightly to let the engine turn over more easily. If the adjustment is out of whack it won't open stalling the starter. This is why it will crank over no problem with the spark plug removed. Put the plug back in and the compression won't let it turn over.

Good luck
Now that I think about it... isn't the compression release a spring loaded cam driven by a gear off the crank? I don't think there is an adjustment for that. You can adjust the valve clearance but I believe the compression release is fixed.

If I knew what to look for and when I assume you could see the little bump to the exhaust valve during the compression stroke.
 

·
Registered
Joined
·
390 Posts
Follow H-D's advice before investing money in anything except maybe a service manual. There is a very good chance excess valve lash is the problem. The typical compression release on the small engines does have a spring tensioned apparatice on the side of the camshaft gear that sticks up just slightly from the nearest cam lobe. This interferes with complete closing of that valve until it is revolving fast enough to be disengaged by centrifugal force, allowing only the cam lobe to raise and lower the valve lifter. The system in modern Briggs engines with overhead valves is very sensitive to proper valve lash (valve to rocker clearance). Too much clearance and the compression release won't work. Checking valve lash is part of routine maintenance for these engines, so you won't be wasting any time even if this is not the problem. You might need a new rocker cover gasket if it uses one.

If you can post some numbers from the I.D. tag for your engine maybe we can help find the valve lash setting for you. Besides normal wear and tear adding clearance, look for any rocker stud having backed out or loose. Or a lock nut that doesn't hold well. I have not worked on one of these for some time, but think the rockers fit on a stud and are adjusted with a self locking nut, very much like the old small block Chevys. The Kawasakis I am familiar with use a tiny adjustment screw and lock nut at the end of the rocker, but I haven't seen a Briggs like that. But I haven't seen them all!

Let us know how it goes.

tommyhawk
 

·
Registered
Joined
·
3,228 Posts
One thing you can try is to give it a few smacks with a hammer. oh yeah and pick up a service manual. you never know...:flag_of_truce:

This trick only works if the starter doesn't engage. His is engaging but not turning the engine.

I seen quite a few videos on YouTube showing how to adjust the valves on a B&S single cylinder engine.
 

·
Registered
Joined
·
3,228 Posts
Follow H-D's advice before investing money in anything except maybe a service manual. There is a very good chance excess valve lash is the problem. The typical compression release on the small engines does have a spring tensioned apparatice on the side of the camshaft gear that sticks up just slightly from the nearest cam lobe. This interferes with complete closing of that valve until it is revolving fast enough to be disengaged by centrifugal force, allowing only the cam lobe to raise and lower the valve lifter. The system in modern Briggs engines with overhead valves is very sensitive to proper valve lash (valve to rocker clearance). Too much clearance and the compression release won't work. Checking valve lash is part of routine maintenance for these engines, so you won't be wasting any time even if this is not the problem. You might need a new rocker cover gasket if it uses one.

If you can post some numbers from the I.D. tag for your engine maybe we can help find the valve lash setting for you. Besides normal wear and tear adding clearance, look for any rocker stud having backed out or loose. Or a lock nut that doesn't hold well. I have not worked on one of these for some time, but think the rockers fit on a stud and are adjusted with a self locking nut, very much like the old small block Chevys. The Kawasakis I am familiar with use a tiny adjustment screw and lock nut at the end of the rocker, but I haven't seen a Briggs like that. But I haven't seen them all!

Let us know how it goes.

tommyhawk
What he said. lol

This starting problem will usually get worse over time but can happen all of a sudden. This is why I suggested looking for other damage/problems while the valve cover is off. If something besides the adjustment is wrong it should be pretty apparent. However just to much lash/gap is enough to cause your problem.

Sorry I don't have the specifications. You can give your local dealer a call and ask them.
 

·
Premium Member
Joined
·
12,157 Posts
Discussion Starter #11
I found the valve specs. I reconfirmed that the engine will turn over at full speed with the spark plug removed but when the spark plug is reinstalled the flywheel just gives a jump.

So I removed the valve cover and checked the valves. They were off maybe 0.001 but I went ahead and adjusted them. Put the valve cover back on, hit the ignition and VAROOM it starts right up. I let it run a couple minutes and then shut it off. I waited 5 mins and tried to start it again... nothing... the flywheel just jumps like before.

I have a voltmeter on the battery and it is still getting sucked down to 7-8 volts when the starter wont move. I even tried attaching my big 200 amp charger/booster. Same thing, the flywheel just jumps.

I've put the battery on a load tester which tested good and I've tested it with an electronic batter analyzer and everything says the battery is good. If it is the battery it seems weird that not the battery, my 600 amp jump box or the 200 amp booster can start this thing.

I just can't seem to isolate any faulty component. I hate to just start throwing parts at it.
 

·
Registered
Joined
·
3,228 Posts
I found the valve specs. I reconfirmed that the engine will turn over at full speed with the spark plug removed but when the spark plug is reinstalled the flywheel just gives a jump.

So I removed the valve cover and checked the valves. They were off maybe 0.001 but I went ahead and adjusted them. Put the valve cover back on, hit the ignition and VAROOM it starts right up. I let it run a couple minutes and then shut it off. I waited 5 mins and tried to start it again... nothing... the flywheel just jumps like before.

I have a voltmeter on the battery and it is still getting sucked down to 7-8 volts when the starter wont move. I even tried attaching my big 200 amp charger/booster. Same thing, the flywheel just jumps.

I've put the battery on a load tester which tested good and I've tested it with an electronic batter analyzer and everything says the battery is good. If it is the battery it seems weird that not the battery, my 600 amp jump box or the 200 amp booster can start this thing.

I just can't seem to isolate any faulty component. I hate to just start throwing parts at it.
Sounds like you had success until it ran for a little bit.
I'd pull the valve cover back off and recheck the adjustment. Make sure that you set up the valves on the tighter side of the specks. One of them rocker adjustments could have moved since it was running. From what I remember doing it on the B&S in my old L108 they can be a little tricky to adjust.
I think that you loosen the center screws then use the nut to adjust it. Then lock the nut adjustment down with the center screws. Also make sure that you have the engine at TDC on the compression stroke. This can also throw the adjustment off.
 

·
Premium Member
Joined
·
12,157 Posts
Discussion Starter #13
Well... after spending a few hours fiddling with the engine and adjusting the valves to the minimum clearances I've come to the conclusion that the problem has to be the compression release mechanism on the cam shaft. I've turned the engine over by hand multiple times while watching the intake valve VERY carefully and I cannot detect any "bump" near the top of the compression stroke. From everything I've been reading on-line that pretty much means the compression release mechanism isn't working.

Also, when the starter just clicks and the flywheel jumps, I can get the engine to start by taking my hand and rotating the cooling screen on the top of the engine backwards to get the engine off the compression stroke. When I do this it turns over, gives a quiet little backfire, starts up and runs normally - every time. This tells me the starter isn't able to turn the engine over due to the compression.

There are several videos on YouTube showing the process of changing the cam shaft. I've ordered the service manual so I will have all the torque specs and the only other thing left to do is order the parts. A new cam shaft is around $80.

Of course the engine has to be removed and turned upside down for the repair. Fun.
 

·
Registered
Joined
·
4,433 Posts
Not to discourage you but...

Of course the engine has to be removed and turned upside down for the repair. Fun.
I think the governor has to be put back together, too. :painkiller:
 

·
Registered
Joined
·
3,228 Posts
Well... after spending a few hours fiddling with the engine and adjusting the valves to the minimum clearances I've come to the conclusion that the problem has to be the compression release mechanism on the cam shaft. I've turned the engine over by hand multiple times while watching the intake valve VERY carefully and I cannot detect any "bump" near the top of the compression stroke. From everything I've been reading on-line that pretty much means the compression release mechanism isn't working.

Also, when the starter just clicks and the flywheel jumps, I can get the engine to start by taking my hand and rotating the cooling screen on the top of the engine backwards to get the engine off the compression stroke. When I do this it turns over, gives a quiet little backfire, starts up and runs normally - every time. This tells me the starter isn't able to turn the engine over due to the compression.

There are several videos on YouTube showing the process of changing the cam shaft. I've ordered the service manual so I will have all the torque specs and the only other thing left to do is order the parts. A new cam shaft is around $80.

Of course the engine has to be removed and turned upside down for the repair. Fun.
The compression release opens the exhaust valve to relieve the excess pressure. Not the intake valve.
 

·
Premium Member
Joined
·
12,157 Posts
Discussion Starter #16
The compression release opens the exhaust valve to relieve the excess pressure. Not the intake valve.
It's somewhat confusing as I've heard both valves mentioned. Is it possible the valve used varies by engine model?

Looking at the mechanism the compression release lever is attached to the cam lobe closest to the cam gear. The cam gear is on the bottom end of the cam shaft towards the bottom of the engine. The intake valve is the lower valve. So on this engine it appears to be connected to the intake valve.

I also found this on the B&S website:
[h=5]Compression Release System[/h]Some small engines incorporate a compression release system to decrease operator effort when pulling a rewind starter. A compression release system is a system that relieves excess pressure during the compression event by allowing a small amount of compressed gas to be released through the muffler or carburetor.


The compression release system lifts either the exhaust or the intake valve slightly off its seat during the compression event (this is why the piston is positioned past top dead center to about 1/4" down from the top of the cylinder when adjusting valve clearances). This releases pressure and reduces the force required to pull the starter rope or load on the starter motor. A compression release is used on most Briggs & Stratton engines and does not affect engine performance above engine starting rpm.
 

·
Registered
Joined
·
3,228 Posts
It's somewhat confusing as I've heard both valves mentioned. Is it possible the valve used varies by engine model?

Looking at the mechanism the compression release lever is attached to the cam lobe closest to the cam gear. The cam gear is on the bottom end of the cam shaft towards the bottom of the engine. The intake valve is the lower valve. So on this engine it appears to be connected to the intake valve.

I also found this on the B&S website:
[h=5]Compression Release System[/h]Some small engines incorporate a compression release system to decrease operator effort when pulling a rewind starter. A compression release system is a system that relieves excess pressure during the compression event by allowing a small amount of compressed gas to be released through the muffler or carburetor.


The compression release system lifts either the exhaust or the intake valve slightly off its seat during the compression event (this is why the piston is positioned past top dead center to about 1/4" down from the top of the cylinder when adjusting valve clearances). This releases pressure and reduces the force required to pull the starter rope or load on the starter motor. A compression release is used on most Briggs & Stratton engines and does not affect engine performance above engine starting rpm.
Never ever seen an engine use the intake valve for a compression release.
I have seen plenty of manual releases. It's an extra valve (very small) installed into the cylinder head. You push it down (open) before trying to start the engine. Then the first power stroke closes it. They are fairly common in motorcycle engines. On air cooled V twins it's usually right next to the the spark plug. Never seen one installed in a lawn mower engine before. However it would solve the problem.

Did you try adjusting the valves with the piston a 1/4 way down like stated?

It's entirely possible that your problem with the release is at the cam shaft end.
 

·
Premium Member
Joined
·
12,157 Posts
Discussion Starter #18
Never ever seen an engine use the intake valve for a compression release.
I have seen plenty of manual releases. It's an extra valve (very small) installed into the cylinder head. You push it down (open) before trying to start the engine. Then the first power stroke closes it. They are fairly common in motorcycle engines. On air cooled V twins it's usually right next to the the spark plug. Never seen one installed in a lawn mower engine before. However it would solve the problem.
I am familiar with those motorcycle manual releases also. This B&S automatic thing is totally new to me. I've watched several YouTube videos and it looks like these single cylinder Intek engines use the intake valve whereas some other models use the exhaust valve. With the mechanism sandwiched next to the cam gear it has to use the lobe closest to the gear which is the intake lobe. No one ever said this B&S stuff made sense. :)

Did you try adjusting the valves with the piston a 1/4 way down like stated?
No, but I will give that one last try when my manual arrives on Sat. I have adjusted the valves with both at TDC and yesterday I adjusted them the way a lot of B&S repair shops do... and that is by adjusting the intake when the exhaust valve is fully open and adjusting the exhaust with the intake fully open. Both methods resulted in the same adjustment.

It's entirely possible that your problem with the release is at the cam shaft end.
Unfortunately that is where everything is pointing. All information indicates that you should clearly see the compression release valve "bump" just before TDC, which I do not. I know the valve adjustment is critical for the compression release to work but I don't believe it is quite this picky.

I went out and started the engine again this morning using the same method of rotating it backwards to get it off the compression stroke and then turning the key. It turns over, gives a quiet backfire and then starts right up and runs normally.
 

·
Old Pa-pa
Joined
·
11,740 Posts
Just to add one small point, I have a 14.5 Briggs OHV engine and the manual says to be absolutely certain to be 1/4"
below TDC when adjusting the valves.
The valve settings have to be right on also, meaning not even .001" off.

These newer OHV engines can develop 125 - 135 PSI compression, right up there with outboard motors.

Whenever it starts to balk at spinning with the starter, I know it's time to readjust the valves.
Was having the same trouble as you are last time where I could move the crankshaft a little from the top screen and the
starter would spin it with no trouble to start.

Readjusting the valves took care of that problem.

Hope you don't have to pull it down for compression release failure.
 

·
Registered
Joined
·
3,228 Posts
I am familiar with those motorcycle manual releases also. This B&S automatic thing is totally new to me. I've watched several YouTube videos and it looks like these single cylinder Intek engines use the intake valve whereas some other models use the exhaust valve. With the mechanism sandwiched next to the cam gear it has to use the lobe closest to the gear which is the intake lobe. No one ever said this B&S stuff made sense. :)



No, but I will give that one last try when my manual arrives on Sat. I have adjusted the valves with both at TDC and yesterday I adjusted them the way a lot of B&S repair shops do... and that is by adjusting the intake when the exhaust valve is fully open and adjusting the exhaust with the intake fully open. Both methods resulted in the same adjustment.



Unfortunately that is where everything is pointing. All information indicates that you should clearly see the compression release valve "bump" just before TDC, which I do not. I know the valve adjustment is critical for the compression release to work but I don't believe it is quite this picky.

I went out and started the engine again this morning using the same method of rotating it backwards to get it off the compression stroke and then turning the key. It turns over, gives a quiet backfire and then starts right up and runs normally.
Did some poking around on YouTube. Searched B&S compression release and all kinds of stuff came up about your tractor's problem. Apparently this is a fairly common failure with this single cylinder engine. The release parts brake off of the camshaft and end up in the bottom of the engine. You were right about it opening the intake valve vs the exhaust.
One video suggested setting the valves to zero lash/gap. This should allow the engine to crank over with the broken release. However you can't leave it this way. Might be something to try before gutting that sucker.
 
1 - 20 of 39 Posts
Top