My Build, need input on parts.

[2quick]

I have a Boonie with a 5hp Briggs on it. I will be going with a billet rod and flywheel so I can crank it to the moon and come back in one piece.

I took the motor apart today and it had some issues going on that I noticed and this is my first go around with a briggs. First thing was the cyl bore had lots of scratches and a few gouges in it. Second thing was the valves had what seems like excessive movement in the guides. Third thing was the exhaust valve retainer was not fully seated on the valve. Fourth there was lots of carbon build up around the valves guides, valves, and the head.

I got everything cleaned up and now I am ready to build this on "paper" before I build it. There seems to be tons of parts for these little motors and I have looked all day at different rods, cams, pistons etc... I never did see a full kit deal. Thats what I am used to in the performance car world.

My goals are to still be easy to start with the pull rope, be able to ride for long periods of time with no heating issues. Plus to make plenty of power.


So what piston, rod, cam would be best to meet my goals? Should I keep the stock head and have it milled? Deck the block? Bigger valves?

 

[pat.n23]

i would get a billet rod i have used ARC alot i like there rods i am running a stock length rod right with a raptor 3 piston. i would get a 3 hp billet fly wheel with the adjustable drop coil bracket. idk about the cam alot of ppl like the 94ss cam i am using a 04-3 cam its seems to be ok havent really tested yet. run a thin head gasket. last mayb some heaver valve spring and billet lifters for the high rpm

hope this help alittle

 

[5 Horse Fan]

If you haven't already, you should look through this:
http://www.oldminibikes.com/forum/b...some-guide-modding-briggs-5-hp-flatheads.html

To make as much power out of your engine as possible, you would want to bore the cylinder over-sized and use a brand new piston & ring set. Looks like you might have access to that type of machinery. If not it could be expensive and finding a new cylinder or a good used one would be best especially if you think the valve guides are worn.

 

[2quick]

I have been tossing around the idea to ship the block off to a machine shop who specialize in kart racing. I would have them bore/hone and install new valve guides. I will port the intake and exhaust ports myself.

I was talking to my uncle lastnight and he told me he has the original 5 horse motor that came off the bike. Should I build that one, or just put it on a shelf and not "build" it?

I have looked over the link you posted several times and I have had no luck finding the head they recomeded. The blueprinted raptor 3.

Thanks for the help guys.

 

[pat.n23]

i cant find ne blocks ne where i might get into the honda or the clones not too sure yet tho i am a flathead nut :smile:

 

[AKAxAUTO]

I have been tossing around the idea to ship the block off to a machine shop who specialize in kart racing. I would have them bore/hone and install new valve guides. I will port the intake and exhaust ports myself.

I was talking to my uncle lastnight and he told me he has the original 5 horse motor that came off the bike. Should I build that one, or just put it on a shelf and not "build" it?

I have looked over the link you posted several times and I have had no luck finding the head they recomeded. The blueprinted raptor 3.

Thanks for the help guys.

You should look into sleeving the engine as well. The aluminum bore isn't terrible but rebuilds will be more frequent especially when revving as high as you want. I've also heard good things about the 94-ss cam and it isn't real expensive. As for which engine you should build, take a look at the condition of each engine and decide which one will be better suited. :thumbsup: