I have had this impact wrench for about 20 years. It never has been all that good. It had gotten so bad the 3/8" air ratchet was stronger.
Today I needed it to remove the nut from the tillers flywheel. So I pulled it apart and washed the guts in the ultrasonic cleaner. The parts did not show any discernable wear. I reassembled it using ATF. It works at least as good as it did when it was new.
The images here were taken to help in reassembly.
I also opened up the air chisel/hammer and coated the barrel with ATF. Worked better too but I doubt it will continue to do so when it we get warmer temperatures.
Finally found a procedure for honing kool bore blocks. By RED-85-Z51
myTractorForum
I've punched out a number of 11hp engines, among dozens more kool-bore engines. I used a 2 stone rigid hone, and some ATF as lube...I ran the coarse stones on it until I could slip the oversized piston down the bore..(but not the rings). Then I swapped on the fine stones and started honing for...10 second intervals until I had set my ring gaps to spec, as checked at the top, middle, and bottom of the cylinder. Ill reiterate, make sure a piston is available in the oversize you need, a bare piston will not work (aluminum piston on aluminum cylinder = instant gall). The piston will need to have the factory chrome coating on it.
Also the briggs manual section 9 is the best boreing info I found so far.
Still been wondering about the grit used for Kool Bore cylinders. Briggs sells a hone set .
I ordered a set of 320 stones for the Lisle hone when I was researching this a while back.
It is cold out but I wanted to get a handle on what shape this tiller's engine was in.
The cylinder does not seem to have any major scoring. Just light lines from the carbon that should hone out. Need to check these.
We need to see how the cylinder compares to the 2.5625 aka 2 9/16 inch. The standard bore.
Built up 2.6520 inches with blocks and locked the gold digital caliper there. It does not matter what the caliper reads.
Put the bore gauge in the caliper and set it to zero.
.
Measuring the cylinder. Contrary to the caption in the video the tool was zeroed using the gauge blocks.
A set of chrome rings alone could do the job. I think I read anything to .005 over can be fixed with just chrome rings. Briggs 298982
Ordered NOS briggs chrome rings off ebay. Unfortunately Briggs never made chrome rings so don't follow my example here.
There is a popping noise when you turn the engine over without the head. Could be a reluctant breather. Need to check it when warmer.
The intake valve is loose. Turns even on the power stroke where it should be shut. This engine still may be useable without a rebuild.
Wednesday, February 25, 2015
Took the engine off and then took it and the tiller to the car wash.
Striped the carb and gas tank off the engine. This is one of the newest engines I have worked on and it used torx and maybe other strange fasteners.
The valves are out. Note that spring retainer 40B goes on the exhaust valve.
The intake valve tappet seems odd. Check that out.
Cleaned the valves and breather in the ultrasonic cleaner.
Next I need to take the air wrench after the nuts on the crankshaft. There is one holding the drive pulley on.
Friday, February 27, 2015
I started on this yesterday but could not get the nut off the flywheel. I filled the starter drive cup with PB blaster and let it soak overnight. This afternoon I tore down and cleaned the 1/2" impact wrench. With the cleaned wrench it came right off as did the flywheel.
The rod cap bolts are 5/16" hex heads. I was fearing they might be torx drive like the 18HP. I don't care for them.
No surprises but the governor has not come loose from the cover.
The oil remaining in the engine seemed to have a lot of aluminum in it. Well I guess that is where it goes when it leaves the cylinder bore.
The outside face of the gear is flat and of course it will have the timing mark on it.
The pan gasket is in good shape but stuck to the block. I will see if it comes loose when I soak the block. It is too cold to clean the parts outside and the kitchen is busy so I may make a pattern for a new gasket.
The crank has a bit of end play need to watch that when I assemble it. My gasket material is the same thickness as the standard gasket .015" but I ended up reusing the original gasket. If the engine works I may fix the end play by using a thin layer or RTV.
Monday, March 2, 2015
I spent much of yesterday reassembling the engine. The assembly was done with vasilene and a couple of tablespoons of motor oil when installing the piston. Had I done this in the shop instead of my office I would have used much more oil. It should be ok.
Today I ground down the intake valve stem to get .005" clearance.
The chrome plating has worn off the piston. Looks to be the rings are too weak to hold it steady in the bore or the bore is just too large.
Anyway I just want to get it back together and see how it runs cleaned up ad adjusted.
The rings I ordered are a total flop. They do not fit this new style piston and they are not chrome. So much for trusting a single document even if it is B&S!
Maybe just maybe one of the pistons from a mower can use these rings. No real plans at this point just want to see what it does.
Original
Raster Export MTC
Cleaned the carb. It may have been OK as is but as long as I had it off the motor I did not want to take the chance. Still have to cut a new gasket. Actually 4 to get past the .05 thickness of the original. It took way to long to cut a gasket from this image. I had to trace over it and ended up with just a few nodes which cuts quite fast. Still need to adjust the size of the bolt holes.
The linkages are on the complex side. Took lots of pictures but I do have a similar tiller in the garage that maybe identical motor wise. That would be very helpful.
So about all I need now is to clean the gas tank, put the head one, and put it all back together. Maybe bring some oil in the house to warm up install the motor before it gets too cold.
This is kind of neat. I have taken a shine to zip lock bags of all sizes. Up to the point a motor is all buttoned up keeping it clean is essential. These may even be a good idea for storing smaller unused engines. Might cut down on condensation.
The 5.5HP tiller motor is on the left and the 1st 18.5 on the right.
Wednesday, March 4, 2015
Cleaned the head bolts. Gasket looks reuseable. The last of the parts are in the tub soaking.
I am dreading getting the linkages right.
Installed and torqued the head. It has a lot more compression than prior to cleaning. Will have to run a compression test once I get it running. Note the optimism!
Sorted out where most of the bolt nuts and screws came from.
I am missing the muffler and its bolts. The special washer that goes under the flywheel nut and the entire shroud. Me thinks they are hiding out together.
Thursday, March 5, 2015
Cut the carb gasket today. Three layers combined it .05 thick uncompressed. Cut a 4th but did not use it. Had to redo node work as it was lost or misplaced.
Found the muffler and shroud. I am thinking briggs may have done away with the washer. Still looking for it but I am getting doubtful.
Need to drag the engine over to the shop and connect the carb to the gas tank then that unit to the engine etc.
This picture was taken during disassembly. It is fairly conclusive evidence that there was no conical washer on the crank nut.
The engine is now in the shop for reassembly. As I imagined the linkages are somewhat of a challenge. Esp the stuff between the carb and governor.
Friday, March 6, 2015
Finished putting the engine back together.
Found a youtube vid to explain the bits of the linkages.
Ran the engine on the picnic table. Smoked.
Aired up the tires using some bead sealer. I think the problem is/was dirt on the beads.
Installed the motor on the tiller and did some tilling. No problem with power but it still smoked. Ordered some new standard rings. Think the oil control ring is bad as it has good compression and power.
The new rings did the trick. Did not hone the cylinder. Put a few hours on the tiller over 2 years and sold it.
After twisting off the long air cleaner bolt I wised up and started treating this carb with more care. I heated the bowl nut with the propane torch and it came loose.
But wow what a mess of rust! I makes me wonder why more of the carb is not missing.
After knocking out the loose rust it was subjected to the ultrasonic cleaner. First tide then dawn plus ammonia.
The float was still stuck so I tried CLR for about an hour. I did not trust to use it for longer than that. It was still frozen.
We cut the top off a plastic peanut jar and filled the bottom with Pb Blaster. My guess is that it would not pay to check it for at least a week but who can wait that long? Not me.
Just for the record I want to mention that I also have this carb salvaged from a 11HP snapper RER on its way to the dump. It too is a rust bucket. I may subject it to the same treatment as the Murray's carb. This carbs throttle shaft is on the loose side.
Friday, February 20, 2015
Looks like I only need to change the choke and I have that out of the Murray's carb just need to slide it into the one from the MTD. But this thread will continue on the subject of saving the carb.
Saturday, March 7, 2015
The float hinge is still soaking in PB Blaster. I don't know if additional soak time will help but what can it hurt.
Tried to swap the transaxles but the distance between the mounting holes is different. The correct transaxle has bad tires.
The input pulley is rotted away and will have to be exchanged, The better one could stand a bit of electrolysis.
It is amazing how much simpler this tractor is compared to the Gilson Super 8.
The carb is off but it is junk. Notice the rust on the end of the large welch plug in the center of this image.
The larger air cleaner bolt twisted off. The bowl nut will not turn. Same story as on the carb from the snapper riding mower I junked out a year ago.
A member of myTractorForum said Ford Toreador Red is a close match for the original color.
I am slipping. The first thing I have always done is to get the number off the engine. I don't see where I did that for this tractor.
Wednesday, February 18, 2015
Model 252707
25 ci
series 2
7 vertical crankshaft
0 plain bearing non flange
7 electric starter with alternator
Code
8109211 = Sept 9th, 1981
The tractor data plate is hard to read.
Maybe 7 357 8X92 3016
Asked on MOT and got this reply
In 1987 there was 36506, 36508, 36557 and a 36560. Although I agree that the second number looks like a 5, I believe it is actually a 6. My guess is a 36508
I have had this impact wrench for about 20 years. It never has been all that good. It had gotten so bad the 3/8" air ratchet was stronger. 
Today I needed it to remove the nut from the tillers flywheel. So I pulled it apart and washed the guts in the ultrasonic cleaner. The parts did not show any discernable wear. I reassembled it using ATF. It works at least as good as it did when it was new.
