Cub 126 K301a Rebuild Questions

[Bum454ss]

Hi all...
Wealth of information here and I thank you all for the extremely informative posts. However, the more I read the more questions I have. I am going to do some clutch work next week on my old 126 and figured I would rebuild the motor while Im in there. This was my grandfathers tractor that he bought new so I know it hasn't been rebuilt yet. My question is.. I'm going to order one of the Master rebuild kits off Ebay http://www.ebay.com/itm/MASTER-REBUI...item20cfac3275

... and wondered should I pull the balance gears out of it while torn down?

... should I precision balance the crank/rod/piston assembly while it's at the machine shop?

... should I go ahead and order everything at .10 (piston/rod) or assume its
good to stay standard sizes?

... do i need crank bearings also or should they be okay to reuse?

I believe there is a ton of carbon build up on the valves now and my flame in the muffler problem will be solved with the new valve job.

Am I missing anything here?

Thanks so much in advance for any info you can add. I want to do the job right the first time so I don't tear anything up. This tractor means the world to me and I'd like it to run at least another 40 years. Maybe my grandson will think it's as cool as I do.

[cmatthew]

the machine shop should check the crank, piston, and cylinder for proper specs before ordering new parts. wouldnt hurt to replace the governer also.
if it has the balance gears then pull them.

[samiam44]

No need to balance @ 3600 rpm, it's not a racing engine. Some ppl add a weight to the crankshaft to change the balance factor.

Getting the proper size piston/rod are important and the quality of valve work will pay for itself. I think some places the quality can be poor b/c "this is only an old lawn mower engine" mentality.
It's not uncommon to have to turn the crankshaft and then buy a 0.010 undersize rod.

Besides the govenor, make sure you have the steel pin for the points(upgraded part).

Crank bearings you'll have to clean and oil. If they are smooth and no spalling in the races, you can re-use or replace them. If your grandfather did reasonable oil changes, it won't take much. Rebuild the carb is a must and add throttle shaft bushings if needed.

Michael

[cubs-n-bxrs]

I just had all that work done at my local machine shop. I did all the measuring myself. I went with a .020 over piston just because it was bought for a past project and never used, went with a .010 under rod and a valve job. The block was cleaned and boiled looks like brand new. The final price was $175 which I did not think was all that bad. Good luck with your build. There is nothing in the world that smells better than a fresh motor build breaking in.

[Sam Mac]

Originally Posted by cubs-n-bxrs

I just had all that work done at my local machine shop. I did all the measuring myself. I went with a .020 over piston just because it was bought for a past project and never used, went with a .010 under rod and a valve job. The block was cleaned and boiled looks like brand new. The final price was $175 which I did not think was all that bad. Good luck with your build. There is nothing in the world that smells better than a fresh motor build breaking in.

Kelly

If you want a sweet smell try Sunoco Standard race gas.

[cubs-n-bxrs]

Originally Posted by Sam Mac

Kelly

If you want a sweet smell try Sunoco Standard race gas.

Sam Sunoco race fuel is pretty awesome but the smell of a fresh motor being broke in is still just a touch better.

[IH Cub Cadet]

Originally Posted by cmatthew

the machine shop should check the crank, piston, and cylinder for proper specs before ordering new parts. wouldnt hurt to replace the governer also.
if it has the balance gears then pull them.

+1

You might be able to get away with a cylinder hone and new rings. I wouldn't spend a dime on parts until you have the engine measured for wear.

BTW - I've got a 126 that I bought recently and am looking forward to your posts as you get the tractor going again.

Good luck,
Bill