briggs 3hp rebuild

#21
i plan on the port and polish, and i plan on putting a mikuni carb on it(i'd like to that is but have to get the right size).wat size of jr dragster should i get? and how much will it run me? i'd be happy at 6000-6500 rpms. my clone does 6500 rpms and i'm satisfied with that for now. basically i need a list of parts and sizes of the parts i will need to get to acheive this rpms. like is aid i am new to rebuilding and i have to be taught like i'm a 6 yr old!!! i am trying and very eager to learn and willing to take all the help and wisdom i can get.
 
#22
so i just found a jr dragster flywheel, new, for a 3hp on ebay for $136, not wat i'm looking to spend on a flywheel unless i have to. also do i need to replace the rod and piston?
 
#23
They dont make billet rods for 3hp so the rod you have is fine. But that casing you have on each side in the middle of the rod remove that with some kind of sander. This will help keep that rod together. I figured a flywheel would be over 100 bucks its your call. Just be careful with your revs 6500 sounds kinda scary on the stock fl. As for piston if yours doesent have to bad of scoring it should be fine. If you have anyother ?s just ask :thumbsup:
 
#27
I'm gonna make an intake to put this 13mm mikuni off a mitsibishi 5hp ohv on a 3.5 i've heard you can use a 5hp raptor type if your carb will mount to it. I'll try making one first, I have enough stuff to get started I think. Here's my 13mm mikuni made in japan! $15 shipped on Ebay and it's new.



I think it'll compliment a 3.5 well and allow the use of a remote tank of which I have many! Good luck on your quest!:thumbsup:
 

125ccCrazy

Well-Known Member
#28
I'm gonna make an intake to put this 13mm mikuni off a mitsibishi 5hp ohv on a 3.5 i've heard you can use a 5hp raptor type if your carb will mount to it. I'll try making one first, I have enough stuff to get started I think. Here's my 13mm mikuni made in japan! $15 shipped on Ebay and it's new.

I think it'll compliment a 3.5 well and allow the use of a remote tank of which I have many! Good luck on your quest!:thumbsup:
13mm? thats tiny...the little 49cc weedwacker pocketbikes come with 15mm carbs.....you can run at least an 18mm....
 
#29
well i havent got much done to it due to the fact most people say the 3 horse isntt worth beefing up, but i am still planning on doing it. been really busy getting my bikes ready for the last chance mini bike show. but it is over now so i can focus my time on the 3 horse, and a couple 5 horse flattys that i'm gonna rebuild as well. thanks to everybody that has given me alot of info, espeacially minibikefreak, also 125ccCrazy i'm gonna try that 18mm carb, thanks! also 125cc were you at the last chance show? i will keep everybody updated as i go
 
#30
well i havent got much done to it due to the fact most people say the 3 horse isntt worth beefing up, but i am still planning on doing it. been really busy getting my bikes ready for the last chance mini bike show. but it is over now so i can focus my time on the 3 horse, and a couple 5 horse flattys that i'm gonna rebuild as well. thanks to everybody that has given me alot of info, espeacially minibikefreak, also 125ccCrazy i'm gonna try that 18mm carb, thanks! also 125cc were you at the last chance show? i will keep everybody updated as i go
:doah: Thats what I've been telling you since the start... :lol: Just bring it with you when ya come get this bike... we'll do what can be done to it for ZERO dollars... Hell if ya want a lightweight flywheel those are like a dollar at the junkyard, as many as you want.. :doah: I have Mikunis and Tilly's and Tecumseh carbs that will bolt right on it... The Flowjet that you have is just as good as anything you're gonna put on it though really... :shrug: It will easily feed AND EASILY ADJUST to anything that 3 horse is going to do... :shrug:

I GUESS if you REALLY WANTED to spend $64,000 dollars trying to make 5 horse power.... I'll just sell ya a 5 horse for 75... :shrug:
 
#31
ya i will probably bring ya a freashly tore down 5hp flatty and a 3hp to play around with for me. one of those tillys or mikunis i would be interested in for sur. do you have a 22mm or 24mm mikuni by any chance? i think i would like to put one on my clone, its better than stock. also do you know how to port and polish? i never have so i wouldnt want to screw nothing up.
 
#32
Yeah.. I have router bits that make that a friggin breeze.. I do all my motors.. I have Mikunis but not sure what all I have for main jets.. :shrug: I have one jetted for one cylinder of a 300 Honda bike engine.. About 150CC OHV Honda.. :shrug:
 
#33
well i havent got much done to it due to the fact most people say the 3 horse isntt worth beefing up, but i am still planning on doing it. been really busy getting my bikes ready for the last chance mini bike show. but it is over now so i can focus my time on the 3 horse, and a couple 5 horse flattys that i'm gonna rebuild as well. thanks to everybody that has given me alot of info, espeacially minibikefreak, also 125ccCrazy i'm gonna try that 18mm carb, thanks! also 125cc were you at the last chance show? i will keep everybody updated as i go
Well in the near future im gonna try fully building up a 3hp ive been taking machining classes in my high school and learned a lot maybe make a billet rod crank and who knows what else ?!?!?!?! But good luck on urs and im always here to help :thumbsup:
 
#34
if ya make a billet rod crank let me know i would defintely buy one off you. you are in high school? damn i feel really old and out classed now!!! i tell ya wat i would love to see a 3hp beat the :censure: out of a 5hp!!!
 
#36
if ya make a billet rod crank let me know i would defintely buy one off you. you are in high school? damn i feel really old and out classed now!!! i tell ya wat i would love to see a 3hp beat the :censure: out of a 5hp!!!
Okay i will let you know but will probally be in the future im a sophmore so im really focusing on getting good grades so my insurance for my truck is cheaper. But i will let u know if i try to make one.
 
#37
sounds good i keep you posted on the build! i found a post on shoving a bunch of 5 hp parts in a 3hp block, i may steal some ideas off that. search for 3horse and you should find it
 

125ccCrazy

Well-Known Member
#38
well i havent got much done to it due to the fact most people say the 3 horse isntt worth beefing up, but i am still planning on doing it. been really busy getting my bikes ready for the last chance mini bike show. but it is over now so i can focus my time on the 3 horse, and a couple 5 horse flattys that i'm gonna rebuild as well. thanks to everybody that has given me alot of info, espeacially minibikefreak, also 125ccCrazy i'm gonna try that 18mm carb, thanks! also 125cc were you at the last chance show? i will keep everybody updated as i go
NO I didn't make it to the show, I got my weekends mixed up and missed it..:doah:

Yeah I wouldn't fool with that 13mm....I am putting a 3hp together now with some light mods, milled head with fireslot, advanced ign timing, 5hp valve springs, ported, mikuni fuel pump, header and a pz20 carb.....This will be going on my Wilder Goose instead of the 5hp due to better fitment......I did the mods to the 3hp because everyone says don't waste the time and to just get a bigger engine...I like the looks of the little engines and wanted to give it a tad more umphh for a cool rider..I wouldn't build one to race with but for a rider they are nice lil engines and run pretty strong...
 
#40
3horse

NO I didn't make it to the show, I got my weekends mixed up and missed it..:doah:

Yeah I wouldn't fool with that 13mm....I am putting a 3hp together now with some light mods, milled head with fireslot, advanced ign timing, 5hp valve springs, ported, mikuni fuel pump, header and a pz20 carb.....This will be going on my Wilder Goose instead of the 5hp due to better fitment......I did the mods to the 3hp because everyone says don't waste the time and to just get a bigger engine...I like the looks of the little engines and wanted to give it a tad more umphh for a cool rider..I wouldn't build one to race with but for a rider they are nice lil engines and run pretty strong...

a pz20 carb huh? i will have to check into that. ya, i don't want to race mine either but i would like to pull up to a 5 horse and they look at my 3 horse and i blow them away on the road!!! i to like the looks of the smaller blocks, i have two bikes right now that have 3 horses on them. the one scoots pretty good but the other is lacking badly in the hp department.i will keep ya updated as i go as i hope you do as well. i like some of you're ideas i may have to borrow a few for my build!!
 
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