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Need to get the tractor going for this summer, I did a leak down on the eng and air is coming out the exhaust muffler (both valves closed) so i guess the first thing to do is pull the head and take a look at the valve seats. I have a piston and a ring set for this engine also, My question is do i have to remove the eng from the tractor to gain access to install the piston?

You will have to remove the belts, engine pulley, and the four mounting bolts alongs with the fuel line, control cables, and electric wires so you can remove the engine from the frame to get to the sump mounting bolts on the bottom of the engine. I wouldn't worry about removing the piston until I had the head off and could inspect the cylinder walls and find out why the exhaust valve is leaking. Maybe the exhaust valve seat came out, or something is holding the valve open.

ILENGINE said:

You will have to remove the belts, engine pulley, and the four mounting bolts alongs with the fuel line, control cables, and electric wires so you can remove the engine from the frame to get to the sump mounting bolts on the bottom of the engine. I wouldn't worry about removing the piston until I had the head off and could inspect the cylinder walls and find out why the exhaust valve is leaking. Maybe the exhaust valve seat came out, or something is holding the valve open.

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Will make that todays project while its still warm out, let ya know what i see. Thanks for letting me know there is no access to the rod without removing from tractor.

I got the head off today, the gasket did not appear blown but close to it, i could see some black carbon under part of the gasket, also see some scratch marks in the head where son in law removed removed a gasket a few years ago, the ex valve was not stuck, but from the looks might not have been seating correctly. I got the eng out and it up on the work bench. The cyc walls are smooth can not hang a nail anywhere.

The head gasket will blow between the cylinder walls and the recess area for the push rod cavity. Any carbon trail in that area is a blown head gasket, in your case hadn't burnt through yet. Also it looks like the crosshatching pattern is gone from the cylinder walls, If the picture is accurate than you have a far amount of cylinder wear.

ILENGINE said:

The head gasket will blow between the cylinder walls and the recess area for the push rod cavity. Any carbon trail in that area is a blown head gasket, in your case hadn't burnt through yet. Also it looks like the crosshatching pattern is gone from the cylinder walls, If the picture is accurate than you have a far amount of cylinder wear.

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This is where i become lost, what do i need to do about this condition? Do I remove the piston, then the rings, and measure the ring gap by inserting them in the existing bore? Son in law gave me a piston and ring set B&S #797009, the existing piston has a number on it 215624 STD an another number at the top 0.39.

Did some checking around this morning to find someone to clean the bore up or bore it. Two machine shops wont do it, now what?

At a minimum you will need to remove the piston and break the glaze on the cylinder walls with a ball hone or another type of hone to reseat the new rings. Being able to tell how much wear you have requires special measuring tools. Finding shops to bore cylinders are getting hard to find.

ILENGINE said:

At a minimum you will need to remove the piston and break the glaze on the cylinder walls with a ball hone or another type of hone to reseat the new rings. Being able to tell how much wear you have requires special measuring tools. Finding shops to bore cylinders are getting hard to find.

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I do have a measuring tool, i think im using it right, I placed it at the center of piston sitting level, only at 1 location in the bore. I don't know what the original bore size is are where to look.
I do have access to the ball hone you mentioned.

I guess my next step is to remove the bottom of the case to gain access to the rod and remove it. Thanks for your input.

What the son in law told me was the complaint was that oil was coming out of the breather hose going to the air filter after about 10 minutes of running.

I can look up the bore size if you give me the model, type and code from the engine.

ILENGINE said:

I can look up the bore size if you give me the model, type and code from the engine.

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model 21B707 type 0453 E1 code 06031ZA

update: I got piston out the 2 top rings are broke and came out in pieces. The cyc wall still looks ok.

I can also move the piston back and forth on the piston pin, I don't think that's suppose to happen.

Briggs says the bore is 3.437 I think you will be fine just breaking the glaze on the cylinder walls and installing new rings.

ILENGINE said:

Briggs says the bore is 3.437 I think you will be fine just breaking the glaze on the cylinder walls and installing new rings.

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Have been cleaning the old gasket off the bottom part of the engine.
I took the existing piston off the rod and about to install the new one, what is the arrow on top the piston for?

The arrow on the piston must face the MAG markings on the rod when the two are assembled together, then the arrow faces the flywheel when the piston is installed in the bore.

ILENGINE said:

The arrow on the piston must face the MAG markings on the rod when the two are assembled together, then the arrow faces the flywheel when the piston is installed in the bore.

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I see there is a arrow on the bottom and the top of the piston. I'm not familiar with "MAG markings" , bbut there is a mark in the rod shown in picture at the top, is that it?

The arrow on top of the piston is the one shown in the service manual, and briggs says the MAG should be in the recessed area of the rod. If you remember the orientation of the rod to the old piston, it should be installed the same way.

ILENGINE said:

The arrow on top of the piston is the one shown in the service manual, and briggs says the MAG should be in the recessed area of the rod. If you remember the orientation of the rod to the old piston, it should be installed the same way.

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Yes, I made some scratch marks on the piston and the rod before taking it apart. I got the hone but dont know if it is ok to use it, it lacks about a 1/4" of filling the bore, can i use this and work my way around the bore?, or look for something else to use.

You need the hone to fit the bore to keep it round, More metal removed in one area will negate any improvement you will get with the new rings.

I got the cyc honed and cleaned up. Order gaskets today. I hope I did this right. Still have to lap the valves into the seats. Is there a place I can get the torq spec for the engine ?

Hopefully this will post, be aware there may be cases where a paper flyer insert in the gasket part may override what I just posted


ENGINE SPECIFICATIONS
Armature Air Gap .010 - .014 in. (.25 - .36 mm)
Crankshaft End Play .002 - .034 in. (.05 - .86 mm)
Spark Plug Gap .030 in. (.76 mm)
Valve Clearance – Intake .003 - .005 in. (.08 - .13 mm)
Valve Clearance – Exhaust .005 - .007 in. (.13 - .18 mm)
FASTENER TORQUE SPECIFICATIONS TORQUE
Air Cleaner Base 50 lb-in. (6 Nm)
Alternator 20 lb-in. (2 Nm)
Armature 30 lb-in. (3 Nm)
Blower Housing 90 lb-in. (10 Nm)
Breather 60 lb-in. (7 Nm)
Breather Reed 40 lb-in. (5 Nm)
Carburetor to Intake Manifold 70 lb-in. (8 Nm)
Carburetor Solenoid 40 lb-in. (5 Nm)
Connecting Rod 175 lb-in. (20 Nm)
Control Bracket 45 lb-in. (5 Nm)
Crankcase Sump 175 lb-in. (20 Nm)
Cylinder Head 240 lb-in. (27 Nm)
Cylinder Shield 30 lb-in. (3 Nm)
Exhaust Manifold / Adapter 45 lb-in. (5 Nm)
Flywheel Nut 100 lb-ft. (135 Nm)
Flywheel Fan 140 lb-in. (16 Nm)
Fuel Pump 90 lb-in. (10 Nm)
Fuel Tank 180 lb-in. (20 Nm)
Fuel Tank Bracket 180 lb-in. (20 Nm)
Governor Lever Nut 40 lb-in. (5 Nm)
Intake Manifold to Cylinder Head 90 lb-in. (10 Nm)
Muffler 140 lb-in. (16 Nm)
Oil Drain Plug – Side 100 lb-in. (11 Nm)
Oil Fill Tube 140 lb-in. (16 Nm)
Oil Pump Cover 90 lb-in. (10 Nm)
Regulator / Rectifier 40 lb-in. (5 Nm)
Rewind Starter 30 lb-in. (3 Nm)
Rocker Ball Set Screw or Nut 45 lb-in. (5 Nm)
Spark Plug 180 lb-in. (20 Nm)
Starter Motor 140 lb-in. (16 Nm)
Rocker Cover 70 lb-in. (8

The 2 top rings being broken isn't very common. Why do you suppose they broke?

SeniorCitizen said:

The 2 top rings being broken isn't very common. Why do you suppose they broke?

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I have no idea, but I will say this I could move the piston on the pin , the pin in the rod was a good fit.

I have to put things on hold for a few day until gaskets get here on Monday, got the valves lapped in and head cleaned up.

I have a question: The piston i got came with a piston pin and a package containing 2 pin clips. The piston pin only pass's through the piston from 1 direction, My question is do both clips have to be installed? There is a note in the box that says" Piston pin installation, all parts in this kit must be installed as a set. Do not re-use existing parts"

I have never seen a briggs engine piston that the wrist pin could only be inserted from one direction. Is it possible that one of the clips may be already installed.

ILENGINE said:

I have never seen a briggs engine piston that the wrist pin could only be inserted from one direction. Is it possible that one of the clips may be already installed.

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No clip existing, if I look closely I can only see 1 side that has a set for the clip. The original piston and pin pass's through either side and has seats for the clips, like you were saying.

Dryan said:

I have a question: The piston i got came with a piston pin and a package containing 2 pin clips. The piston pin only pass's through the piston from 1 direction, My question is do both clips have to be installed? There is a note in the box that says" Piston pin installation, all parts in this kit must be installed as a set. Do not re-use existing parts"

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there might be 2 different piston types requiring 2 clips for one type
i am curious about broken rings and no damage to the cylinder wall, did you reinstall the rings and check the piston land to ring gap

snorky1 said:

there might be 2 different piston types requiring 2 clips for one type
i am curious about broken rings and no damage to the cylinder wall, did you reinstall the rings and check the piston land to ring gap

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Not quite sure what you mean, I did install 1 of the new rings and squared it up in the bore using a piston, measured the the gap, it was .010, thought that was good.


I have the piston and rod together now using 1 clip, there is no way it could go together using 2.

The rod cap has 2 torq #40 bolts the same size, a #40 bit not not fit like it should, hope this does not become a problem when tightening up. To test the condition of the fit I stuck the bit into the fan to flywheel bolts that were also T-40 and it was excellent fit.

Could be a running change in part design or manufactured by different company. Maybe they had issues with the clip coming out, so redesigned the piston to eliminate the circlip. I am assuming the side without the circlip faces the bottom of the cylinder when assembled correct.

ILENGINE said:

Could be a running change in part design or manufactured by different company. Maybe they had issues with the clip coming out, so redesigned the piston to eliminate the circlip. I am assuming the side without the circlip faces the bottom of the cylinder when assembled correct.

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yes, the clip is on flywheel side . I got the rings on tonight. tommoro will install.
















i will get back to

put the old rings on the old piston and with a feeler gauge measure the gap between the ring and the piston land, there are min and max allowances for this and if the are too great the ring can snap and if too thin hang on the cylinder wall.

Dryan said:

No clip existing, if I look closely I can only see 1 side that has a set for the clip. The original piston and pin pass's through either side and has seats for the clips, like you were saying.View attachment 31270

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Did that piston come from an authorised B & S dealer of from a online retailer on evilbay / amazon etc.

While there is some logic in that shoulder it would make accurate machining of the pin hole almost impossible as you can not hone all the way to a shoulder.
I have a sneaky feeling that piston have have it's origins elsewhere.
It is the sort of thing I would expect to see in a counterfit engine.
If it is genyine then one side of the piston pin should be square on the end to do against the clip while the other end would need a substantial chamfer at the end to compensate for the zone where you can not hone.

snorky1 said:

put the old rings on the old piston and with a feeler gauge measure the gap between the ring and the piston land, there are min and max allowances for this and if the are too great the ring can snap and if too thin hang on the cylinder wall.

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Thanks some learning going on here.

top ring= .043
2ed ring=.022

bertsmobile1 said:

Did that piston come from an authorised B & S dealer of from a online retailer on evilbay / amazon etc.

While there is some logic in that shoulder it would make accurate machining of the pin hole almost impossible as you can not hone all the way to a shoulder.
I have a sneaky feeling that piston have have it's origins elsewhere.
It is the sort of thing I would expect to see in a counterfit engine.
If it is genyine then one side of the piston pin should be square on the end to do against the clip while the other end would need a substantial chamfer at the end to compensate for the zone where you can not hone.

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I bought the mower from home depo in 2006, used it about 6-7 years to cut my moms field (its not grass) mower sat for a few years , son in law got a piston and rings for it but did not install, thats how I got it, the piston is in a B&S box that he got from dealer PISTON ASSEMBLY 797009 Date Code 1441,DD025.

The light colored piston in the picture is what came in it when I bought it, the piston is a little different than the replacement I was given to replace.

The new replacement piston ring measurement:
top ring .002
2ed ring .002

Dryan said:

I bought the mower from home depo in 2006, used it about 6-7 years to cut my moms field (its not grass) mower sat for a few years , son in law got a piston and rings for it but did not install, thats how I got it, the piston is in a B&S box that he got from dealer PISTON ASSEMBLY 797009 Date Code 1441,DD025.

The light colored piston in the picture is what came in it when I bought it, the piston is a little different than the replacement I was given to replace.

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You just need to be careful.
there are a lot of fakes out there and just being in a box with B &S printed on the outside is no guarantee it is genuine.
God fearing, church going , pillars of the community will happily go to China & buy 10,000 fake pistons in fake boxes then come home , set up an amazon -ebay shop and sell these defective products to their fellow countrymen.
Close that shop when they re all sold .
Then go back to China and do it all over again with another product.

oem b&s parts are made in china!! and wowzers on those used piston/rings gap

tried installing piston today, bent bottom oil ring,not doing something right.

Is it possable to over tighten a ring compressor? Video's on utube sure make it look easy, ordered ring.

yes it is very easy to over tighten a ring compressor esp with the ones that use a 3/8 ratchet to tighten like a lisle brand
u need to inspect the piston carefully for damage now and never fully collapse rings as you can damage the rings and not even see it or damage the piston and not see it