Flathead in motovox?

#1
Has anyone here put a 5hp Briggs in a mbx10? I have a nice 5hp I/C that I'd like to put in rolling chassis. If it doesn't work than I figure I can go with the predator but I would prefer the flathead. Any info would be helpful.

Thanks
 
#3
I wish I had the answer for you...but i'm truly more interested in this being your first post and you have been a registered member for almost 5 years!! How does this happen? I am truely intrigued as i've seen this happen a couple of times since I myself have been a member!! :shrug: Good luck in your flat head quest and I do like the Motovox rollers!! :thumbsup:
 
#5
To answer jdogg. I have just been lurking for years (obviously). I always enjoyed mini bikes and tote gotes when I was a kid and had a fantasy to make another as an adult. Well one income and two small kids delayed that for a few years. Time warp to present and I've bought 2 motovox mbx10's for my 8 and 9 year old boys and I have a rolling chassis on the way to throw in something more appropriate for an adult (we'll have a biker gang:). The stock ones are great for my boys and I figured since I was going to have a fleet of bikes I'd try and keep them similar. For ease of maintenance and upgrades.
I was planning on picking up the engine mount, clutch, and chain from hotrodminibikes if I think I can get the briggs to fit. If not I'll buy the stage 2 kit and call it good. I'm interested in finding out if anyone else has made it work so that I can have all of the parts here when the chassis arrives but my best bet is to slide the flathead in when the chassis arrives. Then decide if I can make it work or head down to HF and pick up the predator.
 
#6
To answer jdogg. I have just been lurking for years (obviously). I always enjoyed mini bikes and tote gotes when I was a kid and had a fantasy to make another as an adult. Well one income and two small kids delayed that for a few years. Time warp to present and I've bought 2 motovox mbx10's for my 8 and 9 year old boys and I have a rolling chassis on the way to throw in something more appropriate for an adult (we'll have a biker gang:). The stock ones are great for my boys and I figured since I was going to have a fleet of bikes I'd try and keep them similar. For ease of maintenance and upgrades.
I was planning on picking up the engine mount, clutch, and chain from hotrodminibikes if I think I can get the briggs to fit. If not I'll buy the stage 2 kit and call it good. I'm interested in finding out if anyone else has made it work so that I can have all of the parts here when the chassis arrives but my best bet is to slide the flathead in when the chassis arrives. Then decide if I can make it work or head down to HF and pick up the predator.
Thanks for the reply rentonhighlander!! Seriously I had began to wonder if its a glitch!! :laugh: Maybe I just like to gab? LOL!! But please keep us posted on your powerplant cunundrum because I dont recall a Briggs being dropped into that frame.......yet!! :thumbsup: Not that it cant be done.........:scooter: And welcome to the site!!!!
 

GustoGuy

Well-Known Member
#7
Thanks for the reply rentonhighlander!! Seriously I had began to wonder if its a glitch!! :laugh: Maybe I just like to gab? LOL!! But please keep us posted on your powerplant cunundrum because I dont recall a Briggs being dropped into that frame.......yet!! :thumbsup: Not that it cant be done.........:scooter: And welcome to the site!!!!
I have seen many Tecumseh powered DB30 but not a Briggs. The Briggs 5 hp would be a nice power match with the DB30 frame since the Predator 212cc can make them into a wheelie machine that is not user friendly with children under 12 years of age. With the Predator engine in mine I decided to enlarge the opening in the air box to nearly twice its size and drilled an additional large hole in the other side of the air box bottom piece to increase airflow to the engine. I then needed to jet it richer since it had huge a lean bog after doing this. After enlarging the main jet a bit to richen it up so it would no longer bog. I tested it and it had a noticble increase in grunt of the bottom end that you could actually feel in the seat of your pants. However the resulting 1 extra hp or so from my air box mod turned it into a wheelie machine for novices and I needed to add 12lbs of steel weight to the front of my bike to help keep the front wheel down. The Briggs 5hp will not over power this bike and it would be a great bike for novices to ride.
 
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MKW

Active Member
#10
OK, a Briggs 5hp won't fit unless you change the carb set-up. The airbox hits the frame tube and you would need, at least, an inch or two more clearance. This is on my Motovox that I have cut the engine plate out and moved it all the way down to the lower frame rails, so a stock frame would have even less clearance. My 3.5hp Briggs slid right in.

Mike
 
#11
MKW,

Thanks for checking. I thought the airbox or muffler might not fit although I could change the muffler style I just wanted to keep the original on as a spark arrester. My briggs has the gas can mounted below the carb does yours?

For the record two of the bikes are staying stock for my boys at this time, they are plenty sufficient, I'm just building the chassis for me. Also, I don't have the skills/confidence to modify the frame so I'm sticking with options that are simply bolt on. I plan to leave the governor on and would not modify the 212 filter and exhaust except that I have to to make it fit.

These bikes will be used for trail riding and I don't need a drag bike. Will the 212 with a 12T clutch be sufficient for climbing hills or will I need a jack shaft? At this point I was going to just hook up the clutch and make the call later but any input would be helpful.
 
#12
Anything is possible. I tried to fit a raptor in a DB30 frame. It was a bit too tall, and the gas tank did bump the rear fender bar. However, I removed (on accident) the rear fender stay, and I think it would fit now. Yes, the carb is a problem. I've been told that an old tecumseh carb, would fit on there, and a gravity feed tank could be used. I'm sure it can be done. It might not be cheap or easy, but it can be done. I say go for it.

I have two sons. One is 6 and the other is 3. I now have two minis, and I'm looking for a third. We too will have a mini biker gang to terrorize the neighborhood. I can't wait!
 
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