Old Masport chipper/mulcher needs tlc

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.

 

.



Set screws or grub screws are not the best way to resist high torque on a driven shaft.

And it will be difficult to set them "into" the shaft that is most likely hardened steel.

At only 5 hp.....the keys probably sheared when the machine was pushed beyond it's limit.

Normal wear & tear, a large branch, or slow rpm can put tremendous force onto the keys.

Also.....the repaired blade assembly should be balanced prior to re-installing to minimize vibration.


.

 

I'd just weld them, but more than what they were from the factory, then try to balance the blade as mentioned. Make sure the crankshaft doesn't have side play, it may have worn out the crank bearing from the unbalanced load. Also, keep in mind that this sin't a chipper, just a leaf shredder. Trying to use it as a chipper is probably what got it to this point.

 

Many thanks to you both for your sound advice. I see the sense in not using grub screws, rather relying on the keys to do their job. I wonder, cheese, is the check for sideplay in the shaft just a hand test? It doesn't make much sense to go ahead with the blades if the motor is too far gone, so I'd like to be sure I could repair it economically. Is the bearing readily replaceable? Something I might include in the job of replacing oil seal/s? I also wonder where would I go to balance the blade assembly. I guess some kind of engineering works.

 

You can check it by hand if you are able to detect very slight movements. Push it side to side and up and down and see if you see it move at all while watching very very closely at the seal lip to see it it wiggles at all. If you see it moving, it needs to be measured with a dial indicator. If it moves a decent bit, it's worn out. If it's worn out, that means you probably have no replaceable bearing and it will require replacement of the side cover at least. If you have a replaceable bearing, it probably isn't bad, since they are pretty tough and don't wear out.

You can balance the blade well enough by putting it on a shaft that can freely turn and see if there are any overly heavy spots that cause the heavy part of the wheel to fall to the bottom quickly. If so, either weld a little on the opposite side, or grind a little off the heavy side.

 

I've done as you advise, and can't feel the slightest movement in any direction, so that's good news. I have blamed the crankshaft oil seal for the amount of oil around the motor, and on the machine generally, but I notice quite a bit of oil around the crankcase gasket, and wondered about the governor shaft as well. I'm assuming that I split the crankcase and replace all relevant seals, which would cover all leakage options. Is that correct? In these pics the underside of the engine has been wiped clean.

 

Yep, might as well replace the seal and gasket, because you don't want to have to take it down this far again in the near future. The governor seals rarely leak to speak of, so it's probably okay. You generally don't want to mess with the governor settings unless you have to.

 

cheese, I'm about to order parts, and have one question please. Would the bearing be pressed onto the shaft, and into the housing as well? If so, is there a technique for separating the housing? It seems that the bearing would make it quite tight.

 

Looking at the picture, I can see that your model doesn't have the replaceable bearing. Just take the bolts out and pop the cover off.

 

Even better, thanks. I'll just do gaskets and oil seal then, when I can get parts.

 

After the holiday break, and a mixup with the supplier, I've finally got the parts I need. I hadn't wanted to dismantle the crankcase until I had the parts in my hand, and now that I have, I find the bushing a little rough when I run my finger inside it. It had no play that I could detect, so should I take a chance and reassemble, or would you replace the crankcase cover/sump?

 

If it has no play, it should be fine. If it has too much play, you will ruin the new seal and it will leak again.

 

OK cheese, thanks for that. Happily, it's what I hoped you'd say, as I've since checked prices on the crankcase, and I'd rather chance the oil seal!

 

I've finally got everything back together, having re welded the blade assembly with new edges, crankcase gaskets. I started it today, first time since I got her. Hard to start initially, would only run on part choke for a while; eventually runs on fairly high throttle setting, with some surging. I would like to adjust mixtures; do you have any advice on that? The engine no's are 130902 1260 01. Vertical shaft, carb. mounted on fuel tank.

 

The only setting on that carb is the idle mixture screw which should be set about 1 1/2 to 2 turns out from lightly seated.