Vertical to horizontal conversion

I have a freebie motor that I'd like to test the vertical to horizontal shaft conversion on. If it doesn't work, I'm only out a few bucks in gaskets and time. The motor is an 11hp (25 ci) flathead briggs with an aluminum cylinder, no cast iron sleeve. All the more reason for this being the sacrificial tester. I have a lot of the details figured out, in theory anyway.

Carb/intake: This would be easiest, I'm just going to make a 90 degree adapter to turn the carb in the proper direction and then support it with a bracket to the engine.

Oiling: This is more difficult and if anyone has pics of the insides of a horizontal briggs and it's oiling it would help me a lot. Buying or making a dipper for the connecting rod is simple. Some of the oil passages on the crank and cam will need to be filled and new ones cut. I can't think of anything more that would be needed for the oiling.

Counterbalance weights: This is the parts I'm stumped on. I've looked at both manuals for the vertical and horizontal motors and each uses a different design on the crank counterbalance. Would I need to get the horizontal counterbalance and use that, or would the vertical counterbalance work running on its side? I really don't know about this one.

Governor: I don't think I'll be able to reuse the stock governor, but I could safely run without it. This motor wouldn't be going on a go kart or anything I'd be revving high anyway.

Anyway, that's my plan. I'll take pics as I go and if I'm successful it might help people in the future.

Ok, got the motor completely tore down and ready for cleanup. However this is what the piston and cylinder looked like when I got it apart. I plan on buying a cylinder hone soon. My question is, does this cylinder need machined or will the hone clean it up? And what about the marks in the piston, new piston or really fine sandpaper? I'm willing to toss $20-$30 of parts into this attempt to turn a vert, into a hor. but if the price keeps going up I don't see that it's worth it.

Personally, I'd hone it, clean up the piston and run 15w40. If it goes well, then use a better motor for version 2.

That's what I was leaning towards. I've seen a couple videos on youtube where guys say that if your fingernail doesn't hit the scratches then you're fine. Some of these are deep enough to catch a nail though. I'm getting the hone tomorrow and will need it for other engines, so I guess I have nothing to loose to see how honing turns out on it.

I'm still stumped on the counterbalance situation. It's part of the crankshaft, so I can't exactly do away with it, yet I doubt it works properly when turned 90 degrees.

Its possible to make a verticle shaft motor horizontal - this kid on YT made a 10HP verticle flathead a horizontal shaft motor - basically remounting the carb and other things, specially proper oil level.

Im not sure if the governer needs to be pulled out, the breather will need to be modifed and depending which way its mounted, the oil fill also needs to be relocated.

Ive seen OHV verticle motors also used horizontal on racing tractors- he mounted the motor at an angle , altho in the one build the guy kept breaking cranks- the flattys would be easier, since the oil doesnt have to go to the rockers .


Someday itd be a neat test to try - for me id use my oil puking 12HP OHV teccy - since its a POS motor - then i wouldnt self destruct a decent motor- maybe when i get my wizard done ill try it on that.

Might be easier to find a cheap cart or tiller motor and just rebuild it. I dont see a problem experimenting with a ragged out motor, but if you are looking for some thing reliable, I would go with one that is already set up to run horizontal and rebuild that one.

Just from past experience, I have not had much luck with a cylinder hone on anything more than a just scuffing the cylinder. Big gouges should be sent to a machine shop. Unless you are a regular or want to pay extra, this may take a few weeks to get done.

If the cylinder is egged out, this wont fix it and if it isnt , it could make it that way.

this is one of those projects where the finished product will equal the $ invested. No cheap way to do it right

Get a ten thou over piston, and hone your cylinder to fit the piston, then fit your rings, and check their gap. The cylinder should be a lil smaller at the bottom. I find about a 10 thou difference in the ring gap from top to bottom. On my engines, with 3.5" bore I do a .014 gap for the top compression ring, .017 on the second compression ring, and same for the oil rings. Thats measured at the tightest point. The gap ends up being around .024 - .027 at the top of the cylinder.

Cheap hones don't do a great job of over sizing cylinders, but I use a cheap hone, it works. It takes a surprisingly long time to get 10 thou over in an aluminum cylinder.

Good info and suggestions, I may do that on this 11hp eventually. However I am going to convert a different vert. or hor. engine, a 14hp opposed twin. The main concern I had with the 11hp was the counterweight, the opposed doesn't have this problem. So when I get around to it, I'll just post the work on the twin here.

I get my block work done at the local kart shop. I dont have the equipment to measure and machine them right. I have used a bead hone to clean a few up but if you have an egg shaped cylinder, the DIY stuff wont fix it.
The machine work is cheaper than buying parts for a junk motor only to find out later it still burns oil and has crappy compression

That's what I was leaning towards. I've seen a couple videos on youtube where guys say that if your fingernail doesn't hit the scratches then you're fine. Some of these are deep enough to catch a nail though. I'm getting the hone tomorrow and will need it for other engines, so I guess I have nothing to loose to see how honing turns out on it.