5hp briggs build

[karl]

Im building a 5hp Briggs for my next project. The motor I got with it and im gonna build it up. I also have a parts motor pictured below. Ill get the pic of the motor soon. What Im doing to it in list form.

1. Shave eyebrows
2. Port
3. Fireslot?
4. Welded cam, little more lift, mostly duration
5. Straight header
6. Dirt bike round slide carb
7. Lap Valves
8. Hone lightly with glaze breaker+ new piston rings
9. Governor delete
10. Shim valve springs

I am going to make the carb adapter at school metal shop. My friend can give me some old ones from smaller dirt bikes. Also I will weld, grind, and file the cam there. This motor is not going to rev to high, it will be paired with a 30 series comet TC. Also, I haft to buy a hf $8 dremel tool.

Any questions, comments, or tips would be greatly appreciated.

 

[Doc Sprocket]

Are you having a machine shop cut the new cam profile?

 

[karl]

Are you having a machine shop cut the new cam profile?

Nope. Hand filed and ground. Ill go a neat job and use clay to measure max lift I can go.

 

[Doc Sprocket]

You pull this off, I'll be suitably impressed.

 

[karl]

You pull this off, I'll be suitably impressed.

And if I dont, I got another cam from the parts motor.

 

[DustinWolfe]

i did it without incident although its hard to say what max lift is. my suggestion is stay away from the base circle and concentrate on adding duration and not neccesarily max lift. i will say though that this is the wrong way to change cam profiles but that it can be done. actually i just cleaned the carb and rode it today and it is definetly stronger and pulls smoothly. I used a stick welder with kt hardface rod and ground with various tools. bench grinder at first with a flat file to square it off (not perfect but it works) then polished it smooth with a dremel and flap wheel then super fine grit sandpaper on a block then finally some polishing compund to finish it up. i might add mine is a clone so ymmv and that i reread your post and you clearly say that your going for duration not max lift.

Edit: bump. also any updates? i decided to do basically the same thing the other week when the mosled thread came up and started the engine yesterday

 

[FlatFootRacing]

What carb are you running? What duration are you looking for? There are alot of variables in grinding a cam! Are you going with a billet rod? In racing the stocker class runs a max of .232" lift....in the Limited mod class we run up to .400" lift cams. Let me know what you are planning to do and I can get you some specs on a good profile for your cam! You can get more lift on a stock cam by grinding/filing the base circle of the cam down some and adjusting your valve lash with some longer lifter tappets!