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Now that my Mc 45 is all together and broken in, it's ready for the course. I've been reading on these posts, though, that you guys who know Macs much better than me, say those needles up top come out more often than they should. I'm itching to run, but would this rare motor be at risk? The piston bearings are new, as are the mains, crank, rod and rod needles (all made in USA), and seals. You can see there's a lot in this motor, and no spares to back me up if the unthinkable happens! I used to sniker at those who would leave a rare bird on the shelf, but am beginning to wonder if they know something we don't. I'll get over my phobia eventually, and probably let her rip. It's been said that a 45 will keep up with a 91, all else being equal. True?
bill

Bill - the main concern is usually the bearings moving out of of the piston or the wrist pin walking out of the rod. The only time such things happen is when the press fit isn't adequate. This is one reason why its a good idea to install new piston bearings and new wrist pins if the old ones are removed. Also its a very good idea to heat the piston prior to removing-installing a bearing, and to also heat the rod prior to pressing in a wrist pin. Also, if possible, its a good idea to simply replace the piston, instead of replacing the bearings in it. If you did all these things, and you are sure your rod hasn't had a lot of wrist pins pushed in and out of it ... you really should have nothing to worry about. I follow these precautions, and have never had a piston bearing or wrist pin walk out. Also, keep in mind you probably will not run a zillion hours on that motor anyway. Most of my vintage motors see the track maybe twice a year.

Jeff

Bill,

The original Mc 45 piston used a closed end bearing on the exhaust side of the piston. Beginning with the Mc91 and all models thereafter the piston was redesigned to use bearings that were open on both ends on both sides of the rod. The design change allows the exhaust side bearing to receive better lubrication and run cooler than the earlier models. It is true that wrist pins or bearings occasionally move and cause problems but the vast majority of the problems with the piston bearings is bearing failure caused by inadequate lubrication or poor maintenance. If you plan to use your Mc 45 for a lot of running there are two recomendations I would offer. First, fit the motor with a late model piston with the improved bearing arrangement.. you can get new pistons from Terry Ives. Second, regardless of which piston you use, always inspect the piston bearings before each event to assure that they are in good shape and move freely as the rod is swung from side to side. While the piston is out for inspection, lubricate the bearings thoroughly with a good quality oil at full strength... not a gas oil mix like you will run in the motor. If you run castor and let the motor sit for several months between use the castor can dry up and become a very sticky substance that needs to be disolved and flushed out and replaced with fresh oil. Other oils may have similar results so the safe bet is remove and inspect before each race weekend. When inspecting pay careful attention to the color of the bearing casings and the end of the wrist pin. If the parts show a color change to dark amber or blue you have a heat problem and the wrist pin should be removed and inspected and the bearings should be cleaned and inspected as well.
Your Mc 45 is a rare and valuable collector motor so it is worth the trouble to assure that it is protected from preventable bearing failures. For motors that I plan to run I never reuse rod bolts. If they have been run get a new set to install when you reassemble the motor after inspecting the piston bearings. Use the splined "101" version... they are stronger.
Also, while the piston is out, inspect the ring lands and ring pins. Your Mc 45 has a single wide exhaust port and if you lose a ring pin and the ring rotates around to let the ends fall into the exhaust the ring will hook in the wide port and tear things up. Make sure the ring pins are not rubbing on the bore and are tight in the piston. Last but not least... use a new head gasket each time you reassemble the motor and always pressure check to make sure you have everything sealed up after she is back together.
Regards,
Steve O'Hara

Jeff-
Thank you for the great advice! I'm using your tips as a check list as each step comes back to me from the recent assembly of the 45. My heat source is an upside down hi-hat with a 100 watt bulb and a heavy screen across the "top". I used a step pin to guide the bearing, and another to press it home. A piston cradle was used throughout. A spacer was inside the piston when the top bearing went in. I watched how far in the wrist pin was when it touched the closed bearing before the rod went in. Care was the order of the day, as it's my only Mac. Before your post, i thought the design of the bearing itself was the cause of needle loss. These motors really don't belong on the shelf, after all. I'll feel better now when the 45 spools up!
bill

Steve-
I didn't see your post before. Between you and Jeff, there's info. here that's huge, some of which doesn't appear in even the best manuals. The racers really do have the most know-how, and most importantly, are willing to share it on the Forum as well as the track. Thank you much!
bill

Bill..
Simply said, I have only lost a piston bearing if the bore is so crooked, the wrist pin worked the bearing out or the rod was bent. Or, if the engine got to hot and the wrist pin backed out and allowed the bearings to fall out.
Run her rich and cool and you will eliminate most of the possible reasons for the bearing working out.
If I have no idea how much time the rod has on it or a standard wrist pushes in to easy,
I always replace the standard wrist with a wrist pin Terry Ives sells that is +.001 over in the center.
And I always grind about .060" off the length and then chamfer both edges.
This allows more oil to lubricate the bearings no matter if it is a closed bearing or open bearing.
Everone has their ideas, these are mine.
Run it and have some fun with it..
Rick

Bill - I think the older motors (pre MC91 & MC101) are something to be treated differently, I like to run mine, but I don't put even an hour of run time per year on most of them. The great thing about vintage karting is that you can collect many motors of various condition and eras ...some to be enjoyed for the motor they are and the others for enjoying the ride they give. You will worry less about your MC45 once you start building an MC91 for driving enjoyment!

Jeff

I'm ready to switch over to the 91 piston. Will need new bearings, 101 screws, wrist pin also. I still have a few new std. ring sets. Luckily, the 45 already has a new rod in it. It,s easy to see now how difficult it was for oil to reach the early closed bearing, the only route a tiny gap between the rod and the boss. Now, how can Terry Ives be contacted?
bill

Parts & Resourses
topics (back one)at top of colume ron

Just a little add.

Certainly the Mc91 piston is a good idea but the old style pistons utilized the 3rd port intake as a source for lubrication of the closed end bearing. The fuel traveled into the 3rd ports, thru the hollow wrist pin and out to the closed bearing. Even though the Mc45 does not have 3rd port induction, fuel will still take that path because the boost port arrangement for that engine gets its fuel source from the old 3rd port intake with the isolation wall removed.

Karters in the old days got in trouble with this outer bearing failing when they blocked off the 3rd port intake. Then the only lubrication path to that bearing was thru that small gap between the rod and piston boss.

Be careful when you install the piston you get from Terry, the needle rollers are not captivated well in the race and will fall out if you try to wash out the grease before installing the piston. (personal experience) Terry will ship the piston with a piece of plastic tubing inserted in the bearings to hold them in place. Just remove the tubing and install the rod carefully and you will be OK.

Good luck,
Scott