rearenginekarts.com

That's more like it! Thank you for the Tech Info. I will review those two links more thoroughly later this week.

Could someone enlighten me further on the "#4 Bearing" recommendation & what exactly it means?

Here is one of my previous posts that shows some of the options that I have for building an engine or two. I have refrained from tearing into any of them yet until I have gathered further information. http://rearenginekarts.com/phpBB30/view ... 494&hilit=

Scott,
Yes, June 1968 the MC49C was introduced, the MC49E came out in June 1972.



Jeff

Here is my Mc49C Runner. Finished her up today, ready for TBO!!!
Decided on a single late VanTech and an HL250 Tilly.
Its overbored as big as I could go and it has tons of compression, should run great. Now I will have to wait till spring to break her in. Thats the trouble with living in the great northeast. Now its down for a long winter's nap.

anyone have an ipl for the 49e?
thanks,Scott

Gee, I just realized that I do have the MCR revised MC49E IPL (it was never published on the Mac page here) .... here it is: ...OK, I checked for others, here are 3 more that were never published either. I have had these for many years, and was probably the only person that they were given to, better late then never.... Jeff

Scott Kneisel wrote:Here is my Mc49C Runner. Finished her up today, ready for TBO!!!
Decided on a single late VanTech and an HL250 Tilly. Its overbored as big as I could go and it has tons of compression....

That is a great looking resto! How much overbore is possible with these engines? Could you tell me more about the extra bearing housing you have on the output shaft. It looked familiar, so I dug through my box of old parts & found an old Kart Labs 3 bolt mount bearing housing that I had.

I could be wrong but I think the biggest bore for the Mc49 would be +.030" oversize or 2.155". The sleeve could be bored larger if you could find a piston that has the proper wrist pin position. The Mc49 uses the same type pistons the older kart engines used...... Mc5, Mc6, Mc10 & Mc20. When the Kart engines went to 6 cubic inch displacement (100cc) and the bore was opened up to 2.165" the wrist pin position was changed which allowed the piston to rise higher in the bore. This was done to accommodate the longer cylinder and change in port location due to the longer stroke of the 100cc engines.

That being said, If you were to use a 0.040" over piston (standard for the 6 cuin engines) in an Mc49 block, the piston would probably come too close to the head and maybe even hit the head. I can't be sure of this and I never bothered to measure so I don't really know. Maybe some others can help you out here. I know that 0.030" over is safe so that is all I'll bore a 49 block. The integral head is definitely a limiting factor in the Mc49. If it was a removable head, you could use a thicker head gasket to get proper clearance.

3rd bearing support....
Some believe that these are not needed because the stress on the crankshaft is out where the threads meet the taper. In these small engines with needle bearings on the PTO, I like to use them for extra support when using an outboard clutch. If you have an old 3rd bearing unit and want to use it, I would recommend replacing the bearing with a high quality bearing (ABEC3 or better). If you want a new 3rd bearing unit, Terry Ives sells nice reproductions.

I'll shut up now. Anybody chime in on maximum bore for the Mc49? I'm listening.
Scott

Scott Kneisel wrote:3rd bearing support....
Some believe that these are not needed because the stress on the crankshaft is out where the threads meet the taper. In these small engines with needle bearings on the PTO, I like to use them for extra support when using an outboard clutch. If you have an old 3rd bearing unit and want to use it, I would recommend replacing the bearing with a high quality bearing (ABEC3 or better). If you want a new 3rd bearing unit, Terry Ives sells nice reproductions.

I'll shut up now. Anybody chime in on maximum bore for the Mc49? I'm listening.
Scott

The 3rd bearing support that I have, is just the aluminum casting. The bearing is missing. I'm a real believer of always using new bearings, seals, fasteners, etc. It's not worth ruining a part to save a few bucks.

I have a few old NOS pistons & rods from other engine marquees. Is there a certain "Trick" piston that I should keep a watch out for?

The oversized pistons that will work best with your Mc49C are:

#53924 +0.010
#53925 +0.020
#53926 +0.030

The only +0.040 piston that I know of that has the proper wrist pin placement is the #61428 which has wide rings because it is a chainsaw piston. Maybe there is a thin ring piston in that size with the higher placed wrist pin but I don't know of one.

The #53924 and #53926 pistons come up a lot on eBay, I have bought them from Vintage Vixsin. If you get stuck I have one that I would sell you but I don't have the rings, you should be able to find them easily.
Good luck, make sure you check with your machine shop and be sure they can bore and hone a blind cylinder.
Happy New Year,
Scott