Briggs and Stratton 18hp v-twin ohv valve adjustment

[AlanHolt]

New member from Australia , have a question about valve clearance adjustment . My Briggs model no. 350777 . Not very mechanical so bear with me . Manual tells me to set no.1 cylinder at 1/4" past TDC , then set clearance .005" for both intake and inlet valve . Does this mean I set clearance for both valves while piston is at 1/4" past TDC ? Then do I go to no.2 cylinder and turn that to 1/4" past TDC and do the same ? Also on the photos of no. 1 cylinder why is the adjusting screw on the exhaust valve sticking out when all the others are nearly flush ? Hope you can understand me . We live on 40 acres of eucalyptus forest and I have a B414 International tractor and a Kingcat ride-on with the briggs in it , thanks Alan.

 

[bertsmobile1]

:welcome:

The No 1 cylinder is the one on the left hand side when you are in front of the carb
It does not matter which cylinder you do first, just so long as you do the adjustment with the piston 1/4" past TDC ON THE COMPRESSION STROKE .

TDC Compression stroke is when the piston get to the top of the cylinder ( nearest the head is top ) after the inlet valve ( the on on the top ) has closed.
The inlet will open just near top dead center on the exhaust stroke then stay open while the piston goes down.
Usually it will reopen , or stay just open till the piston gets near the top again.
This is normal as it is the low speed decompression but can get a little confusing which is why you go 1/4 past top.
Depending upon the actual spec of your engine ( code number ) both side might do this or only one side.

The pushrod has a ball at both ends which should fit into a cup in the cam follower and the rocker.
Some times the pushrod gets stuck and sits on the rim of the cam follower and not in the cup.
So pull that one out and push it back in feeling for the rod end to slip into the cup.

If the middle pivot nut has been done up too tight that will also make the valve adjuster stick out more

 

[AlanHolt]

New member from Australia , have a question about valve clearance adjustment . My Briggs model no. 350777 . Not very mechanical so bear with me . Manual tells me to set no.1 cylinder at 1/4" past TDC , then set clearance .005" for both intake and inlet valve . Does this mean I set clearance for both valves while piston is at 1/4" past TDC ? Then do I go to no.2 cylinder and turn that to 1/4" past TDC and do the same ? Also on the photos of no. 1 cylinder why is the adjusting screw on the exhaust valve sticking out when all the others are nearly flush ? Hope you can understand me . We live on 40 acres of eucalyptus forest and I have a B414 International tractor and a Kingcat ride-on with the briggs View attachment 35496View attachment 35495in it , thanks Alan.

Thanks for that info mate , I don,t think the pushrod is pushed in , just sitting there . I,ll have a go pushing it in early in the morning and let you know how I get on . Really appreciate the reply mate , thanks again Alan

 

[AlanHolt]

Thanks bertsmobile1 , got the mower going and back into the barn . The push rods where seated into the cam followers but while I was trying to adjust clearances one of the valve springs popped out a bit . Does that mean the valve was stuck ? Anyway all the adjusting screws / lock nuts were level then and mower started . Thanks a million for the great advice !

 

[hrdman2luv]

Thanks bertsmobile1 , got the mower going and back into the barn . The push rods where seated into the cam followers but while I was trying to adjust clearances one of the valve springs popped out a bit . Does that mean the valve was stuck ? Anyway all the adjusting screws / lock nuts were level then and mower started . Thanks a million for the great advice !

When you rotate the engine, the valves should move. You'll be able to see if one is stuck or not. Check that spring to make sure it's not cracked or broken. You should be able to wiggle or pry it back into position.

 

[motoman]

The cup depth Bert talks about is important as I measured it at .080" on my Intek. This means that if the pushrod is hung up on the rim of the cup and you miss it, but it "seats," that pushrod will probably jump out of contact with the rocker arm and (hopefully) wait for you to find it after one cyl stops, or (horrors) it wanders into the oil sump and causes major problems.

For the newbie a couple more tips that may help. When tightening you should always check AGAIN after setting the gap (clearance). What typically happens (to me) is that the clearance you want has changed during the last bit of locking torque to the adjuster nut. Leaving the feeler in place has not helped me, it typically results in clamping action which is clearance below the one I want. ( I may be no good at this). I typically have to do each valve a couple times before satisfied.

Another skill for the newbie is judging when that feeler gauge strip gives off the "proper" feel so that you really have .005", for instance. Trying to describe this "feeling " is like trying to describe the feeling when you first remain upright when learning to ride a bicycle . I can't.

But be aware that you can easily use a thicker feeler gauge strip and push it past the intended clearance due to the lightweight valve springs used . When you do this you cannot necessarily feel that action without some practice. But if you go too thick you should feel the unwanted "clamping" action. Try using feelers below and above the clearance you want, and hopefully this will help. The sensation that may describe a proper "feel" is perhaps coating index and thumb and feeler strip with oil and pinching the feeler with moderate pressure while withdrawing it.

Pros should chime in here and improve/correct this discussion. ....give me hydraulic lifters any time.

 

[AlanHolt]

When you rotate the engine, the valves should move. You'll be able to see if one is stuck or not. Check that spring to make sure it's not cracked or broken. You should be able to wiggle or pry it back into position.

Thanks for that information mate , just come back from holidays so will check for cracked or broken Spring in the morning , thanks again hrdman2luv

 

[AlanHolt]

The cup depth Bert talks about is important as I measured it at .080" on my Intek. This means that if the pushrod is hung up on the rim of the cup and you miss it, but it "seats," that pushrod will probably jump out of contact with the rocker arm and (hopefully) wait for you to find it after one cyl stops, or (horrors) it wanders into the oil sump and causes major problems.

For the newbie a couple more tips that may help. When tightening you should always check AGAIN after setting the gap (clearance). What typically happens (to me) is that the clearance you want has changed during the last bit of locking torque to the adjuster nut. Leaving the feeler in place has not helped me, it typically results in clamping action which is clearance below the one I want. ( I may be no good at this). I typically have to do each valve a couple times before satisfied.

Another skill for the newbie is judging when that feeler gauge strip gives off the "proper" feel so that you really have .005", for instance. Trying to describe this "feeling " is like trying to describe the feeling when you first remain upright when learning to ride a bicycle .
But be aware that you can easily use a thicker feeler gauge strip and push it past the intended clearance due to the lightweight valve springs used . When you do this you cannot necessarily feel that action without some practice. But if you go too thick you should feel the unwanted "clamping" action. Try using feelers below and above the clearance you want, and hopefully this will help. The sensation that may describe a proper "feel" is perhaps coating index and thumb and feeler strip with oil and pinching the feeler with moderate pressure while withdrawing it.

Pros should chime in here and improve/correct this discussion. ....give me hydraulic lifters any time.

Thanks motoman , I will go and re check clearances based on what you,ve just told me . Very valuable information