Model 81

[kclark]

i found a free model 81. i think it might need rings. do they make a .10 over kit. it has no compression when turned slow but if you turn it fast it has good compression. is this a sign if needing new rings.

 

[mbounds]

Kevin C: Does it smoke when running?? If yes, then new rings are in order b-u-t if not, then an automatic compression release system may be what you are experiencing. You get low compression to start but once running the ACR returns compression to normal. Kohler used one and I think B&S did also. To test compression on an ACR equipped Kohler engine, you must rotate the engine backwards and check at TDC just before the ACR gets involved. Not sure about the B&S system. Someone with more experience on B&S engines than I can chime in here.

Myron B
CCSupplyRoom

 

[kclark]

i never tryed to start it yet. can anyone tell me if it is a 12 volt system or a 6 volt system. i am picking up a paycheck tomarrow and will go get a battery and some gas and we'll see what happens. thanks for the input Myron!

 

[kmcconaughey]

12 volt.

 

[kmoe]

The copmression spec as per my BS...um B&S manual is. " Place your thumb over the sparkplug hole and rotate the flywheel counterclockwise. If your thumb is pushed away from the spark plug hole than the engine is considered to have suficient compression."
There are .10 over kits avalable but you may just need to re-ring. I'd get the engine running first though and check for excessive blowby / oil usage. Unless someone swapped engines yours should have an aluminum bore and sometimes putting in a set of chrome rings will correct a compression/ blowby issue so long as the bore is still in spec.

 

[kclark]

i tryed it yesterday and it did a lot of poping through the carb but would not fire. i called the local cub dealer and crome rings are like 40 something dollars. thats nuts for a set of rings. i am going to take it apart within the next couple of days anything i should look out for>

 

[mbounds]

Kevin....Ya got spark, so get a new head gasket, remove the head and free up the stuck valves. That's most likely why it's spitting back out the carb. Careful, the valve seats can come out on this engine in my experience. I tend to use MMO to lube the valve stems to free up the carbon. While you are at it, clean the head, block surface and the piston head of all carbon. DO NOT use a metal scraper. Wood or hard plastic...anything softer than the aluminum parts. Also, you are likely gonna have to clean up that carb. I hope you have a bucket of Carb/parts cleaner and a B&S "L" Head single Cylinder repair manual....It'll help tremendously...I think I bought mine at Books-A-Million or Barnes & Noble....

After checking my manual, B&S did use a Compression Release system for easier starting. but I don't think that is your problem...It's the valves and the Carb....

Just one note of caution. These old B&S engines are terribly prone to shearing the flywheel key and thus putting them out of time (another reason they can spit back out of the carb). Just another thing to check and even more reason the have that repair manual at hand...The fins on the Cast flywheel will break off and ruin the balance if you don't do it correctly....

Myron B
CCSupplyRoom

 

[kclark]

i was thinking it was a stuck intake valve cause when it pops fire through the carb. i did clean the carb think that was the problem. what kind of flywheel key is it? does it look like a half circle?

 

[mbounds]

Hi Kevin...

The flywheel key is square and about 3/4 - 1 inch long. It is tapped into the slot after the flywheel is placed on the crankshaft. If you use an impact wrench and remove the flywheel nut, it can be obvious if the slot in the crankshaft and the matching slot in the flywheel do not line up exactly. Look close because sometimes the key is only partially sheared or just beginning to shear...basically just replace it and be sure....Be safe and not sorry, remove the flywheel only following the instructions in the repair manual!!

Myron B
CCSupplyRoom

 

[kmoe]

Do what Myron said. Broken fins are no fun. It is also possable that the points are out of adjustment. If the flywheel key checks out then go ahead and pull the flywheel to check the points. It's probably just as well to replace them while the flywheel is off. Points are inexpensive but a pain to service on that engine.

 

[kclark]

it has good spark and the valves god in and out fine so i am going to order new rings and see if that helps. i dont think this engine have points is looks like a solide state ignition

 

[mbounds]

Kevin: Hmmm... If it was mine, I'd look under the flywheel and take a peek under that li'l ole aluminum cover you are likely to find under there. Being they aren't liquid, I, too, would say that those points you are also likely to find under there are about as solid as you can get.....I've said about all that I can say, so I won't mention this again... but the service manual is critical when working on equipment which you are not thoroughly familiar with....

Myron B
CCSupplyRoom

 

[kclark]

there is a cover that goes over the starter and when you take it off you can see the fly wheel. it lookes like there are magnets on the outside of the fly wheel. that why i thought it was a solid state ignition

 

[kmoe]

You are either seeing the stator for the charging system or the magnet that activates the coil. Go here and you can download a parts diagram for that engine and order a repair manual.
http://www.briggsandstratton.com/display/router.asp?docid=78484

You'll need the model number and engine type code. They are located on the flywheel cover just above the sparkplug.

 

[kclark]

ok i finally got pictures of it.and Kyle Moe you were right it does have points, sorry

 

[kmoe]

Kevin,

"Kyle Moe you were right"

Will you write that down and send it to my wife?

 

[kclark]

lol, sure!

 

[kclark]

what is a good replacement motor for this tractor. i want something that will bolt right in

 

[mriffe]

My experience with changing motors on an 81.
I had over hauled the 8 hp once, but it began to give trouble 2-3 years ago just when I needed it the most. Went to a local small equiptment place and bought a 12 hp. It did bolt "right in", but the cowling would not fit. Not wanting to alter the cowling I used two pieces of angle iron bolted to the frame. (only had to drill a hole on each side of frame) This let me set the cowling ahead about 1". Hold it closed with a bungy strap, tacky, but it works.

 

[digger]

Melvin,
Welcome to the forum!
And it's great to see a new guy jump right in and help out with his first post.