OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Engines Questions On Briggs & Stratton Engines Rebuild: Masport 460 with Briggs 92908 Engine

Introduction

Here�s the Mower, Ready to be fixed up, and the workspace.



The engine was covered in a thick layer of muck, while underneath there was a build up of oily much around the engine base & crank, there was also no oil in the engine itself.



Once I got the engine off, I found it trickier to handle on the work bench than the Victa�s I�m used to. So I knocked up an engine stand using a milk crate, as so.



After giving the engine a bit of a clean back, I found the air filter to be filthy, and the carburetor needed an overhaul.



Inside the engine I found the head area severely carbonated, to the point where the carbon had started to bridge across the head itself. The valves, piston head, cylinder head, ports and valve guides were all encrusted heavily.





Inside the crank case there was confirmed to be no oil, however there was still a nice residue over all parts, and everything was clean, smooth and moved freely. The cylinder was smooth, and not scored, as were the skirts of the piston.


Carburettor Rebuild & De-Carb Results to come...

Carburettor Rebuild

The Rebulid of the carburettor was pretty straight forward, as, while it was in dire need of a good clean, it was complete, and all parts of it were sound. due to the cleaning needed, i opted for a complete, peice by peice clean & rebild, using clean fuel, rags and a toothbrush. as below.





Then once all the parts were washed, i flushed the tank, cleaned out the air filter holder (New filter on the way) and put it all together, I'm quite happy with the result on this one.

That is looking good. Did you check the flatness of the top of the tank, and the underside of the carburetor body? If they are not flat, the results will be dire. See
https://www.outdoorking-forum.com.au/forum/u...ds=Diagnostics+101&Search=true#Post22526

The project seems to be going well. I trust you followed the manual when you re-attached the carburetor to the tank? If you don't use the diaphragm preload process B&S specify, the automatic choke will misbehave.

Yep, its flat and pre-loaded, I'm fairly sire i have acces to a mower this will fit onto, that currently works, so i will be testing it soon.

I like to test the carburetor and fuel tank as an assembly, and only separate the two when actually necessary. It only takes a moment to swap the assembly from one engine to another, and nothing sensitive gets disturbed.

Thanks for the idea, that would also make sure i dont get muck into it from the other mowers tank!

Another thing I do, is take the opportunity to swish fuel around in both tanks (the one attached to the suspect carburetor, and the one attached to the "reference" (i.e. good) carburetor), then pour it through fine mesh back into the fuel can. That way I get two clean tanks for no effort.

Cheers for that idea, while i have the second tank off, I'll give it a rinse.

Ok, so the Head, Piston & Valves are done:

If you find a junked motor its a good thing to keep the carb and tank and do what youve done then have a good known setup for testing.
Ive got one here but i rarely use it. If it wont go and its got spark, fuel down the carb and if it fires and dies out the carbs got to come off the tank.

Another good thing is a snorkel attachment, then with the metal cover off and the snorkel on (either capped or with a tube on it off to the side) you can degrease and wash the motor and get right in around the top of the carb.
And some of the tanks (i think maybe horizontals) had a fuel cap with a single breather hole in the top of it. One of those with the hole blocked up, then you can tip the mower over and wash underneath without a bit fuel spill.

You said about a 10 series motor with no cover. Thats a later model 4hp. I think its the primer start ones. The older ones are 11ci.

The throttle control on the cover, they used that on those Masports i assume because of the handle and how it folds. Ive also seen the same type on utilitys.


How sloppy is your handle?? I have two here and the handle slops up and down heaps before the mower moves.
One has a white 4hp on it. The other a Tecumseh 2 stroke, id say not original, but it could be.

Do you have a catcher?? Ive got a couple or three here. They had either hard plastic or a metal frame bag type. Both mine came with bag type and i got the plastic catchers the other week. If you search masport on ebay theres a guy with a 2 stroke one on there, its green with a black motor and the brown hard plastic catcher.

I might have a spare front wheel cover here too. Will have to look.

Bob.

The Handle is Definatly sloppy, and i found it funny that the 2 mowers i got in one lot were this one, and the Jet-Fast jupiter, this one has the most coplicated catcher-on process i have ever seen (Relaes handle with pedal, Move handle to position 2, release catch flap pedal, lift flap, secure catcher into hooks, lock in with flap, release handle with pedal, lower handle to position 1) while the Jupiter had a simpler cathcer than a Modern Victa! my catcher is the hard plastic.

I have a couple of mowers set to be scrapped for parts, so i think i might just do that trick with there carbies, Thanks (engines are briggs with Vacujet, Briggs with Walbro, Techumseh, Suzuki)

I think i will rig up the snorkel next time, as this engine is a bugger to clean otherwise.

I'll put a photo up of the mower with no cowl, it looks newer, maybe mid to late 90's, its a rover easy start base, with some of a brigs engine (no cowl, no carby, no tank, no starter and no inner cowl)

Sorry to drag up such an old post Ty, but how did you get on with this? I have a very similar masport here that I will eventually get to. I dont know how I missed this thread but good work mate.

This one is actually still underway, After a few other projects came up, and i found this one might need some more extensive work (I'm suspicious of the crank) it was cleaned, coated in oil, and boxed till I have the time to look into it further.

Looking at the work that this engine may need, and considering I recently picked up a very nice black 92908, I may simply be replacing the engine, however if I can get past this crank issue, I wont, as I would like to see this one live.

What's wrong with the crankshaft, Ty? Not that I'm expecting to offer solutions, it's just that it's a 92908 - practically a sacred object - so I'm curious as to what might have afflicted it.

I'm under the impression it could have an ever so slightly bent crank.

Looking at some wear to the mounting holes on the base, and the condition of the mounts/mounting bolts, as well as some overall sloppyness and shaken out bolts, I am fairly sure this one had some ecxessive vibration issues, as it seems to have started to break away from the base.

Ty, bent crankshafts, if they happen in service, nearly always are bent on what B&S call the Power Take-Off (and I call the output shaft). So, if you can lay the main bearings in a pair of V-blocks, and put a flat metal object just under the far end of the PTO so it just barely clears it, you can measure the runout easily. Just rotate the crankshaft on the V blocks in small increments, measuring the clearance between the tip of the PTO and the flat block underneath it with ordinary feeler gauges. If that clearance varies by more than, say, 0.010" as you rotate the crankshaft a full revolution, you have a bent crankshaft. (Note that a total variation of 0.010" is what is known as a "Total Indicator Reading" or TIR measurement, implying that the center of the crankshaft is bent 0.005".)

The hardest part of all that is getting hold of a pair of V blocks. They are not easy to improvise, because the main bearings have to lay in them perfectly, not moving at all when you rotate it.

Those of us who are into machineshop stuff would use a magnetic-base stand with a dial indicator to measure the runout, but that isn't necessary, it's just a bit quicker than the feeler gauges.

When I have the box with that crank in it, I'll see if i can't have a look, I don't have V-blocks, But I think a friend nearby does, Hopefully it's not the crank, but even then, A similar masport yielded an identical crank a few months back.

It isn't all that difficult to get the crankshaft more or less straight Ty, though it would be quite a bit harder without a press than with one. My press came with a pair of hardened V blocks built into the base you press against, so it is all a bit quicker than if you are using blocks of this and that plus a rubber hammer, but I can say with confidence that a decent tradesman with experience would do it quicker and better using junk as a fixture, than I would using decent gear. Some people have got it, and some haven't - the tools aren't really what it is about.