OutdoorKing Repair Forum Forums Repairs and Maintenance Questions On Chippers, Mulchers, Shredders & Stump Grinders Petrol Chippers, Mulchers & Shredders masport 5hp belt drive chipper shredder rebuild

Hi
I have inherited a 15year old Masport belt drive chipper shredder fitted with a 5HP BS engine.

A standard engine service, ie carby rebuild, spark plug , air filter and oil change has the old engine running fine.

Now the fun bit the rusty, bent and badly worn mess of flails, shafts and spacers in the shredder wheel.
I am having trouble getting it apart and am tempted to cut it out as i will have to replace the spacer and flails anyway.

OK finally to the question...

Are these spacer and shafts just mild steel? That I can get from the local steel supply and cut to size? Or do I need to find something harder or try and order genuine parts?

The local Mower shops only stock the chipper blade and flail blades.

Also are these flails interchangeable with any of the similar shredders on the market as the masport ones seem expensive @ $6-7 each for a flat blade with a hole ate on end (especially when you need a set of 9 flails)

Thanks in advance

mutt,

The steel is hardened for the shaft, spacers and blades because if they were just mild steel you would have to replace about every third time you used the unit.

Thanks Bruce,

I expected that would be the case.
I'll have to try and get it all apart without destroying the shafts.
Maybe I can cut the spacers off somehow as they need replacing anyway.
Anyone know a masport dealer or aftermarket that keep stock of these? The local guy (Adelaide) trying to get anything other than blades from masport can take ages ATM.

Cheers

G'day Mutt. I can't help, but I'm tagging along with a similar problem. I've bought a well used Masport chipper/mulcher, I believe 1994 model, with a 5hp B&S. The blade assembly is in need of repair (see photos), and the crankshaft oil seals need replacing, probably due to the blade condition. I'm wondering whether anyone has one, or is familiar with them. The three blades have been welded to two bosses, which in turn are keyed to the shaft with what I believe are standard B&S keys, half round in shape. These had long since failed, as had most of the welds. It's hard to believe these welds were OE, as they are so poor, yet I can't see any other means of attaching them to the bosses. I'm considering re welding the blade assembly, then using grub screws through the bosses, set into the shaft, perhaps two to each boss, and wondered what anyone's thoughts were. I'd be grateful to hear back.

I suggest you should not increase the drive torque capacity beyond what those two Woodruff keys can transmit, or you will break the crankshaft. The keys are supposed to shear when the machine is overloaded, that is an essential protective measure Briggs and Stratton have provided for their engine.

It does not look badly made to me, and I note that the keys failed, as they were supposed to, without much damage to the blades. Remember that the blades will wear (the machine looks as if it has been used very little or very lightly, in your pictures) and it looks as if when that happens the next step would be to break or grind away those tack-welds so you can replace them with new pieces of spring steel with three small holes in each. You would re-use the original spacers.

OK, thank you. I think I would have trouble replacing those blades, wouldn't I, given that they have the key way punched in them? I was guessing that the amount of slack in the keys and the welds, would have overloaded the system via vibration.

It looked to me as if the two collars with the keyways in them are positioned to coincide with the keys. The blades have to have big enough slots in them to allow the whole assembly to slide over the crankshaft, but they do not need to be fitted keyways - they can be filed roughly, since they are not driven by the keys.

The Woodruff keys should be a decent fit in the crankshaft and the collars. Those are all properly machined keyways, so good fits should be achievable. As you said, if there was a great deal of slack in the keyways, there could be a form of chattering that would hammer the parts, deforming them and causing premature failure. Keys and keyways must always be well-fitted, to work properly.

I do not know what you mean by slack in the welds.

Oh, by that I meant the slack created by loose keyways and failed welds. Half of the welds were just surface metal, with no penetration at all, so I expect would have failed early. If I re weld the blade assembly, and all else is OK, any thoughts on having the blade assembly balanced? And should I expect a damaged crankshaft bearing, given the leaking seal?

If it works the way I think it does, the keyed collars are driven by the keys in the crankshaft, and the blades are driven by the small welds joining the keyed collars to the blades. Those welds should be stronger than the crankshaft keys, but easy to break each time you need to replace the blades. An alternative would be to omit the welds and drive the blades only with friction from the sides of the keyed collars, in the same way as Victa lawnmower blade plates are driven. I think I'd use the small welds, since I'd dislike opening up the cutter housing every five minutes to remove some slightly oversize piece of sapling that had become wound around everything.

With only a 5 hp engine, I see this as just a thin sapling shredder, not something you feed tree branches into.

Masport tell me that parts are unavailable, so given that I didn't pay too much for it, I just hope to get it running OK, while planning never to replace the blades again.

If it works properly, by the time it wears out its blades you'll be having so much fun with it you'll happily make up a new set of blades from spring-steel strip. It looks like it should be just a few minutes work to cut the pieces of strip to length and drill three holes in each.

Drill? How would I drill them? They appear to be leaf spring material. If I can get the material, and can drill it, I'll go down that path now!

ronn, the method I was taught for drilling spring steel is to use an ordinary carbide-tipped masonry drill bit with plenty of speed, pressure and cutting oil. If you let the cutting point dry up, the brazed joint between the carbide tip and the steel body of the drill bit immediately melts. You'll have to resharpen the carbide tip fairly often - I use an ordinary bench grinding wheel with light pressure, and of course the wheel finishes up blunt for a while. To give you an estimate of how far you can drill before the bit gets blunt, I've drilled a 3 mm hole through a 5/8" spring steel bar without resharpening during the process, but I then had to resharpen for the next hole. I suggest drilling a pilot hole of about 3-5 mm if you are drilling bigger holes than that.

OH, OK. I'm quite happy to have a go at that. I guess the material is just salvaged car springs from the wreckers? I've also been thinking that I can just turn the blades over for new edges. My biggest question may be the key ways in the spacers. If they are OK, and they do look OK, then it's new keys, better welding and replace or turn over the blades. I'll need to have the keys in my hand to check the keyways, so soon after Christmas I should be at that stage.

Ronn,

The blades, sleeve and spacers are available and note that the unit is the same as a Rover chipper. Also note that the blade boss is not welded.

Hi Bruce.
That is interesting. The main difference seems to be in item 5, which appears to be the means of transferring torque to the blades. The relevant holes aren't shown in the blades, but the spacers and bolts are. It seems a much more definite means of driving the blades than the Masport's; maybe a later modification. Maybe I could modify the Masport?

Ronn,

I am pretty sure that the Rover is the same unit just badged different but will have to check with Masport or Rover when they return in the new year. The engine would be the same I am sure. Check the measurements HERE and if they are ok you should be able to make the change.

Note that I don't think the one you have is original because the welding on the spacer could cause issues like grumpy said about the crankshaft being damaged. The bolts are there for a purpose and that is that they should shear off and not damage the crankshaft and the key should shear as well.

Anyway I will try to confirm with Masport when they return from the break.

Bruce, is there a specific name for the crankshaft on this engine since it has the step on it? I am looking for an engine for a speciific application that has this step but forgot to take a pic of the old motor before it landed in the scrap bin....

ronn, could you post the information stamped on the cooling air cowl of your Briggs engine (Model, Type and Code) please? I don't recall seeing a stepped crankshaft PTO like that, and hopefully the model and type will lead us to a parts list, which may tell us more.

Hi Guys,

Below is a drawing of crankshaft combinations for Briggs 8 and 9 Series.

Thanks all, for your help. The stepped crankshaft is a definite difference from the Masport to the Rover, but that crankshaft drawing certainly looks like mine, although my model no. isn't listed. Mine has a definite shoulder, shown in my earlier photos. I've attached a photo with that detail highlighted from the drawing. Is that the shoulder, or a bearing? Engine details are: Model 130902 Type 1260 01 Code 9109042. I have looked into these numbers online, and see that puts the engine manufacture as 1991.
Another point is that I took the blades to my son yesterday, who is well qualified and experienced in working with steel, and he said the blade material is definitely not spring steel, or even hard. It seems to be mild steel or close to it. That was a surprise,as it looked like spring steel.

I attempted to reply to your post Bruce, and I don't know where it went. It's on the site somewhere, so if you stumble across this somewhere, you'll know why:
Novice Registered: 24/12/12
Posts: 10
Loc: Macclesfield, Victoria, Austra...
Thanks all, for your help. The stepped crankshaft is a definite difference from the Masport to the Rover, but that crankshaft drawing certainly looks like mine, although my model no. isn't listed. Mine has a definite shoulder, shown in my earlier photos. I've attached a photo with that detail highlighted from the drawing. Is that the shoulder, or a bearing? Engine details are: Model 130902 Type 1260 01 Code 9109042. I have looked into these numbers online, and see that puts the engine manufacture as 1991.
Another point is that I took the blades to my son yesterday, who is well qualified and experienced in working with steel, and he said the blade material is definitely not spring steel, or even hard. It seems to be mild steel or close to it. That was a surprise,as it looked like spring steel.

Ronn,

Does the top part of the blade holder boss only go up to the step in the crankshaft or go over it?

Also it appears that the cutter system might have been made up if you are saying that it is not hardened steel and I would assume that you would have some vibration when running.

The uppermost blade rests under that shoulder, which I've just found is actually a loose ring giving clearance between the top of the blade and the four engine mounting bolts. That suggests that it would be a machine part rather than an engine part, doesn't it?

Ronn,

It suggest to me that the cutter system does not appear to be original and a made up one especially the welding to the blades.

I have got the machine back together, having rebuilt the blades. I started it today, for the first time; it was a bit hard to start, and would initially only run on part choke. Eventually it would run on throttle only, but at pretty well full revs only. It all suggested the need for a carby tune up to me. Can you help please Bruce, either with instructions, or a link. The engine again is B&S 130902 1260 01, vertical shaft with tank mounted carb.Many thanks.

(When I say tune up, I'm meaning mixtures)