1996 B&S 15.5HP engine issue

[Auto Doc's]

Thank you Doc. Makes perfect sense on the shim and I can see it did have a little wear on it. McMaster Carr may have one similar.

I did see that repair on YT by Teryl and have seen a lot of his videos over the years. It seems as if others have also copied his idea as they are using the same procedure and 10-24 set screw, I may go to a 10/32 set screw. It is not a problem for me to do as I am setup with small machine shop for the vette diff's I build, so I should have everything here. I haven't put a straight edge on the head yet but I will, just to make sure it's not warped. I can set it up in the Bridgeport if needed but I think it may be ok. The head gasket was still good and one I replaced several years ago.

Hello G.,

A correct size roll pin punch or a shoulder punch with a shop press works nicely for getting the guide out of the head pushing towards the top and then when you place the guide back in position (A hammer will work also but be careful). There will be an age line from the old oil resin on the top portion of the valve guide that will indicate where it should be in relation to the head. Both guides set about even otherwise.

The careful part is the drill stop depth, threading the hole and setscrew placement.

A flat section of tempered glass and 600 grit paper is what I have been using to relevel aluminum head for years. A Ron Popell rotisserie door to be exact, but I have used the glass kitchen table top a couple of times (Don't tell the wife)

Don't reuse a modern graphite coated head gasket once it has been run for any amount of time. These are not like the old "flat head" engine foil side gaskets from years ago.

I've never had to have a head milled and hope I never have to.

 

[gtr1999]

Hello G.,

A correct size roll pin punch or a shoulder punch with a shop press works nicely for getting the guide out of the head pushing towards the top and then when you place the guide back in position (A hammer will work also but be careful). There will be an age line from the old oil resin on the top portion of the valve guide that will indicate where it should be in relation to the head. Both guides set about even otherwise.

The careful part is the drill stop depth, threading the hole and setscrew placement.

A flat section of tempered glass and 600 grit paper is what I have been using to relevel aluminum head for years. A Ron Popell rotisserie door to be exact, but I have used the glass kitchen table top a couple of times (Don't tell the wife)

Don't reuse a modern graphite coated head gasket once it has been run for any amount of time. These are not like the old "flat head" engine foil side gaskets from years ago.

I've never had to have a head milled and hope I never have to.

Thanks for the info.
The last head gasket I used was the foil gasket and it was still good when I pulled the head. Are they still available?
A side note I was going to lap the valves but my handle is 25 years old and the suction cups lost the grip. I went to 3 parts stores to buy one and they had no clue what I was talking about.

 

[Auto Doc's]

Hello G.,

eBay for the lapping tool or simply use a variable drill with a hand chuck on the tip of the valve stem at very slow speed while moving the valve open and closed. (I quit hand lapping because I kept wearing out the suction cups as they got cheaper over the years)

Hand lapping tools are hard to find in any part stores now because most are only interest in fast moving stock items.

Aside from that, many people don't do any kind of serious DIY small engine work anymore. Only older "die hard" folks prior to the 90's have any ambition to actually work and make things work again. (There are a few younger exceptions sprinkled in, but it is rare.)

 

[slomo]

A side note I was going to lap the valves but my handle is 25 years old and the suction cups lost the grip. I went to 3 parts stores to buy one and they had no clue what I was talking about.

O' Real'ies and NAPA have valve lapping cup sticks in stock. Online as well.

 

[smallenginerepairs]

31R907-0007 might be a possible replacement. Your original engine is supposed to supercede to the 31A607-3026, but that engine isn't showing in the briggs distribution system. and Briggs shows the replacement engine is the same as the original 31A607-3026 engine.

If you go to Amazon for an aftermarket carb, Hipa carbs are a trustworthy company to buy from. Good quality carbs and many times there is little or no adjustment needed.Other carb manufacturers are a crap shoot. Some you can't adjust to run properly.

 

[Auto Doc's]

Thanks for the info.
The last head gasket I used was the foil gasket and it was still good when I pulled the head. Are they still available?
A side note I was going to lap the valves but my handle is 25 years old and the suction cups lost the grip. I went to 3 parts stores to buy one and they had no clue what I was talking about.

Hello G.,

If they are the foil layer gaskets and not damaged, they will still work fine. Many new replacement head gaskets are now designed that way. Of course, they now use the term "improved". The engineers made a mistake years ago when they switched to the cheaper graphite coated "one time use" head gaskets.

 

[Sockmonkey]

Hi,
I am a new member here and have a Craftsman 42" tractor with the original B&S 15.5 hp engine.
Model #28N707-0173-01
Code # 95121348
I have kept this old machine running since new. We bought it for a small business and once they stopped doing lawn maintenance, I bought the tractor to use at home. All in all it's been a great machine but the other day I fired it up, took it out, there was slight glitch turning over the engine, but it fired up and I used it for a few minutes until it shut down. Dead in the water, spins all day long not binding, nothing. I checked the initial parts and found the coil wire must have had a break in it as the spark was good at the coil but not at the terminal end using a spark tester and spark test pen. I replaced the coil with a new B&S coil and set the gap, checked it for spark and it was complete then. However, it was still dead.

I checked compression using two different testers, both the Shrader vale in place in the tip, and both were about 45 psi. Wet test brought it up to 50 PSI. I didn't have a leak down tester handy to check it.

I jacked it up, pulled the valve cover and found the aluminum intake push rod broken. The plastic rectangular guide was broken as well. The head gasket didn't appear to be blown out in the typical location. The head gasket I replaced several years ago, this was the second one in 30 years.

My questions are
1- It spins free, so is the compression release still good?
2- I pulled the head and didn't get to it yet. I was thinking possibly the seat was damaged possibly being the cause of the lower compression. I don't see any cylinder grooves at all. Smooth. Does this sound reasonable?
3- Is there a direct replacement engine for this tractor and if so doesn't anyone have a model number?
4- I am debating pulling the engine to check the cam or just putting in a new intake push rod and probably a new exhaust rod, hew head gasket, and seeing if it fires up. Why were the intake rods not steel, sacrificial ?

Thank you

Hit smallenginewarehouse.com for re-power options. I've had great experiences with these guys.

 

[first pull]

Hi,
I am a new member here and have a Craftsman 42" tractor with the original B&S 15.5 hp engine.
Model #28N707-0173-01
Code # 95121348
I have kept this old machine running since new. We bought it for a small business and once they stopped doing lawn maintenance, I bought the tractor to use at home. All in all it's been a great machine but the other day I fired it up, took it out, there was slight glitch turning over the engine, but it fired up and I used it for a few minutes until it shut down. Dead in the water, spins all day long not binding, nothing. I checked the initial parts and found the coil wire must have had a break in it as the spark was good at the coil but not at the terminal end using a spark tester and spark test pen. I replaced the coil with a new B&S coil and set the gap, checked it for spark and it was complete then. However, it was still dead.

I checked compression using two different testers, both the Shrader vale in place in the tip, and both were about 45 psi. Wet test brought it up to 50 PSI. I didn't have a leak down tester handy to check it.

I jacked it up, pulled the valve cover and found the aluminum intake push rod broken. The plastic rectangular guide was broken as well. The head gasket didn't appear to be blown out in the typical location. The head gasket I replaced several years ago, this was the second one in 30 years.

My questions are
1- It spins free, so is the compression release still good?
2- I pulled the head and didn't get to it yet. I was thinking possibly the seat was damaged possibly being the cause of the lower compression. I don't see any cylinder grooves at all. Smooth. Does this sound reasonable?
3- Is there a direct replacement engine for this tractor and if so doesn't anyone have a model number?
4- I am debating pulling the engine to check the cam or just putting in a new intake push rod and probably a new exhaust rod, hew head gasket, and seeing if it fires up. Why were the intake rods not steel, sacrificial ?

Thank you

I think that there is too much damage! You have done a great job cleaning everything up,but the wear exceeds limits. I agree that it was over heated. It's done It's job, you can get a new block from craftsman.

 

[Auto Doc's]

I've gotten a couple of good engines through eBay in recent years. You have to make sure the seller gives some history and details of how it has run. If they cannot give any details leave them alone. Facebook marketplace (local) is also pretty good.