Intek engine hard to turn over after new rings

[Tinkerer200]

You are absolutely right, FOOT LBS.

Walt Conner

 

[Captn Cliffy]

Thanks for all the posts, sorry I haven't had time to respond. The friend I got the engine from has been a machinist, mechanic, and millwright, so he knows about engines. He's also old enough where hearing protection wasn't a big deal in his younger days. He thinks the engine seized up due to low oil. It was on a riding mower - he said that he used the mower, shut it off, then when he tried to use it the next time, the engine was seized. If it threw a rod when he was using it, he said he probably wouldn't hear it (see hearing protection earlier).

Bertsmobile1, I did pull the head off with the engine still mounted on the mower. It turner over easily with the head off.

After pulling the engine apart, here's what I noticed: Pulling the piston out, there was slight scoring the length of the cylinder wall. If you look at the cylinder with the magneto at the top, the scoring would be on each side, more pronounced on the side farthest from the camshaft. Ring end gap is 018 for middle ring; 010 for middle ring and oil ring - all within specs per factory manual. What the manual refers to as "ring land clearance" should be 002-005, but on this cylinder, it is less than 0015" for both compression rings (the thinnest feeler gauge I have wouldn't fit in the groove with the ring). I have a second piston from another engine (but same part number, same piston) where the rings are just as tight in the groove. When taking the engine apart originally, the old top ring was so tight, it would not come out in one piece, even using piston ring tool. Is it okay for the compression rings to be this tight?

 

[Tinkerer200]

"When taking the engine apart originally, the old top ring was so tight, it would not come out in one piece, even using piston ring tool. Is it okay for the compression rings to be this tight?"

No, the piston ring land is carboned up. They make a tool for cleaning them but I use a broken ring making multiple passes in both directions until the land is clean in all lands.

Walt Conner

 

[mhavanti]

As Walt says: clean the lands. Don't take any aluminum from the lands.

Remove the piston, remove the rings from the piston, put the rings in a padded vise, use a smooth file and file away one thousandth of material. Everything expands with heat and a mower engine is usually air / fuel cooled. This type of engine's rings expand more than a liquid cooled engine. An air / fuel cooled engine does carbon more so than fuel cooled meaning tolerance too close and you may experience ring abutment which will score the cylinder(s).

File your rings. Check them for gap tolerance inside the cylinder at the top of their travel. Use an old piston with a ring on it, turn the piston upside down to press the ring down into the cylinder until the ring on the piston hits the deck. The ring you're using will be sitting at the exact spot it will live at (TDC) Top Dead Center. This is where you want to check your ring gap. Piston isn't in your feeler gauge territory and you can see if the ring ends are straight and true.

Good luck.

Max

 

[Captn Cliffy]

Walt, the teacher for the small engine classes I took also used an old ring to clean out the land. I did this, and removed the carbon build-up (a friend who's a mechanic also looked at the piston and the lands looked clean to him. He has a ring groove cleaner, but the smallest blade was too large for this piston). My question is, when you install new rings in an existing piston where the lands have been cleaned out, is it normal to have basically no land clearance, or should there be the .002-.005 clearance per the Briggs service manual?

 

[Tinkerer200]

I never check them other than make sure the rings move freely in the piston ring groove. The engines I worked on (I am mostly retired now) were bound to be out of spec somewhere but fortunately B&S engines are very forgiving. For example, I hardly ever used standard rings when doing a ring job. After inspecting and measuring the cylinder to my satisfaction, I used +.010 rings and hand fitted them to the end gap I wanted. Now I don't want to hear a bunch of - - - - about this from people here as I have been thru that multiple times over many years and I have the service experience to back up what I do. I am also equipped to and do resize the cylinder bore if I feel it is needed.

Walt Conner

 

[mhavanti]

As a machine shop owner, I recommend always checking ring end clearance as I described above. If there isn't enough clearance after starting the engine, the rings will grow in length and "may" experience abutment. If this takes place and tightens to the point of seizure, you'll have more problems that you do at this point. Always and I mean always check ring gap.

Always check to see if a ring compressor can collapse the ring entirely into the ring land. If the ring can't fit all the way into a new piston, either the ring land is too shallow, which very seldom is ever experienced, or the ring is the incorrect ring for the piston.

A replacement ring may have too much ring gap in mid stroke and at the bottom of the bore, however at the top dead center, it may look perfect. Check the ring gap at the bottom dead center, mid bore and top. If there the ring has cut into the cylinder, remove the material at the top of the bore until it is the same size bore diameter as the worn area of the cylinder bore. Then hone very lightly. You do NOT need a rough bore.

The reason you hone a cylinder is to hold the oil on the side of the bore for lubrication during break in.

Good luck.

 

[Tinkerer200]

As a machine shop owner, I recommend always checking ring end clearance as I described above. If there isn't enough clearance after starting the engine, the rings will grow in length and "may" experience abutment. If this takes place and tightens to the point of seizure, you'll have more problems that you do at this point. Always and I mean always check ring gap.

Always check to see if a ring compressor can collapse the ring entirely into the ring land. If the ring can't fit all the way into a new piston, either the ring land is too shallow, which very seldom is ever experienced, or the ring is the incorrect ring for the piston.

A replacement ring may have too much ring gap in mid stroke and at the bottom of the bore, however at the top dead center, it may look perfect. Check the ring gap at the bottom dead center, mid bore and top. If there the ring has cut into the cylinder, remove the material at the top of the bore until it is the same size bore diameter as the worn area of the cylinder bore. Then hone very lightly. You do NOT need a rough bore.

The reason you hone a cylinder is to hold the oil on the side of the bore for lubrication during break in.

Good luck.

Well I partly agree. Actually the maximum end gap clearance will be at top of the stroke and minimum will be at the bottom. You want to be sure you have at least the min. end gap clearance at the bottom of the stroke, learned the hard way. Of course the ridge at the top of the cylinder will be smallest and should be removed first and the taper of the bore reasonably close to spec. min.

Walt Conner

 

[mhavanti]

Yes Sir Walt, that's what I said. lol

Except for the gap changing in the bore. If the bore is smaller at the bottom than the top, somebody going to need some training on setting up their boring bars and or honing machines. The bore should ideally be the same thru the entire length.

The ridge does need to be removed before a new ring is deployed. Otherwise, the radius made by the old ring as the cylinder wore in will not match the minute radius of the new ring. Therefore, major problems can come about and nobody going to like it. lol

Thanks for bringing to my attention I was unclear. Certainly not my intention.

Hope between Walt, Bert, Tinker, Tom and so many others we've helped this gentleman out.

 

[bertsmobile1]

All good stuff but re-reading I am not all that sure his tightness is in the bore as with out the head on the engine spins freely.
He specifically mentioned it was hard on compression and he has reasonable end gaps at the top of the bore.
Insufficient side clearence usually causes a lack of compression as the charge can not force the ring to seal against the bore.
It would have been good to see what it spun like head on & plug out .
I am leaning towards a bent cam or damage to the cam bush ( hole actually )
Possible spring bind although that should not happen at tdc as we all know.