Need some info on vintage Briggs motors.

[Twinjetguy]

Hey guys,

I need your help. You may have recently seen the Cat roller I recently bought. I would like to find a period correct Briggs motor for it. Pretty sure these originally came with a 3hp?

I was told to go with the 5hp because there are more parts available for them and the 3hp will leave me wanting more power immediately lol.

Here is where I need help. Is the 5hp taller than the 3hp? From the top of the motor plate to the bottom of the top frame tubes it is 13 inches. I was considering a 79cc Predator but the gas cap is on the top and I don't think it will work. Plus I would like to try and stick with the era.

Any advice/info is MUCH appreciated!

 

[Havasu Dave]

Only if your bike was an original (pre 1970) Cat 300X. There is nothing on your bike that says it was one of those. That is why in your original post, I said you didn't need to stick with a "period correct" engine. If you want a 3HP engine, that is another thing.

The neck spring for example is a 400X or 400 series, as they based several designs off of that frame. In 1969, that would have been a Briggs 4HP, and there were not a lot of those made. I can't see what kind of foot pegs you used to have. What is on there has been greatly modified. Also, I cant tell what the original brake was on your bike, or if it had shock mounts and they were cut off or not. Your brake was added on.

I could be that originally, you had a 400-series bike with a 4HP Tecumseh engine on it. Just because there were so many of them. There should be a serial number stamped in the frame on the engine plate, forward left side. First two digits will give you a year.

Yes, a 5HP engine is taller than a 3HP. It WILL fit a 400 series frame, barely. Not a 300 series frame which is what you are saying you have.

Here is a 400X with a hot rod 5 HP Briggs on it. One of my first restorations. Note the tank is in front, and not in the rear with a pulsa jet carb. That affair puts it up at the frame, tight. You are going to need MORE than 13.2" to mount a Briggs 5 HP in a bike.

 

[Havasu Dave]

By the way, a vintage Briggs 5HP is going to be a 130200 series. A lot of mini bikes had the gold colored 130202 engines. The gold color was what Briggs painted their "replacement" engines. They were sold in hardware shops to repower tillers, etc, and as such, we also supplied to mini bike MFGR's.

These engines were modified by Briggs in an endeavor to run a kart program, which they did. They eventually built the Raptor series, with hotter cams, beefier internals, and valves canted slightly towards the piston. Most of the flat head 5HP parts interchange, and a lot of after market support still exists, with billet rods and flywheels available, and a large selection of cams. A great modification is to use a Mikuni carburetor on it with an external tank. With the right internals, it will really wake that engine up, easily tripling the horsepower.

You really need to figure out which Cat you have. I've been looking at these bikes for a long time, and I guess you have a 400X, but so much work has been done to yours, I can't tell. Maybe CatMan @derekbmn can tell from your initial thread.