Horiizonatal shaft or GY6 Type Engine Better
 

Hi, I am new to all of this. I have my buggy about together and now I am doubting the motor setup that I have chosen. I have a Duromax 400cc 16hp with a polraris trailboss transmission, f,n,r, and running a comet 40 convertor. The downfall is only 3600 rpms unless I take out the governor. What do you suggest. Getting a higher rpm turning 250cc I am really confused. Please help. If so, where do you buy these engines. Thanks so much.. Robert

What kind of buggy do you have?

Custom Built
 

Here is a pic. I am a race car guy and fabricate. This is my buggy that is almost complete but now having doubts about motor. It will weigh about 300 lbs.

I think it's going to come down to what your riding style is. Do you want a lot of top end power for more flatlanding/rolling hilly terrain or bottom end grunt for steep hills, rough terrain, slower riding. The former is more suited for motorcycle engines with a higher rev range and the latter for lawnmower type (your duromax). Given that you have a drivetrain basically ready to go, I'd try it first before second guessing yourself. 16 hp is going to provide you with a good power to weight ratio. I'd bypass 250 and go right to around 400cc if you do change paths.

Agree with x-bird. When you started this buggy!! You wanted something the wife & son could drive and have reverse. Exactly what type terrain and driving style will give us the info. to provide a reasonable opinion. At one time I thought you were looking at a sled motor & driven set-up- has this idea caused you some second guessing too? I'm all about the ATV power plants, Find a known good running wrecked or damaged 4-wheeeler, that gives you all the electronics, wiring harness, gauges, ignition, lights,ect... and possibly many other useable parts.Gather your needs----Chain drive is the easiest- does it need to be an automatic? 2-stroke or 4 stroke? Do you want a rocket or a workhorse?
I hate to say this as you've done a superb job on the chassis- but the swingarm appears it will need to be more substantial (tubing) to ensure durability with a nice size power plant.

swing arm isnt done, i have a bunch of tubing cut and two more bearing hangers to add. It will be strong, just really sick, havent had a chance to do anything.