Engine Work

[WI_Chopper]

I am looking to build up a Briggs Flathead Engine, and want some bang for my buck. I am looking to either get a machined head, or bore out the block. If anyone has a bored out block or cylinder, pm me. I want to do a billet rod, cam, carb(not the traditional briggs, maybe a mikuni or tillotson), valves, valve springs, head/bored out cylinder/both? Want to be running about 9 to 10 hp by the end of this for my minichopper. Also looking to step up into a tav2 comet 30, was wondering how much comet underrates their engines. Need a tachometer for the engine, and remove the govenor. Also looking to nitrous the engine. Would like to continue to run pump gas, as this is only a fun bike and maybe run a few minibike drag races near us. thanks for any answers. being that i live in a residential neighborhood, i cannot do a straight pipe, as i need to muffle the engine.

 

[freakboy]

you dont wana mill the head out at all cause that will KILL FLOW

do a port polish a arc billet connecting rod a billet flywheel a highlift cam shave eyebrows get stainless steel valves polished to hell.... not sure bout carb... advanced flywheel key and maby a fire slot.

 

[WI_Chopper]

maybe i should hae said this is my first engine, and a billet flywheel is out of my price range, would a 3.5 hp flywheel do the same job?

 

[WI_Chopper]

and can i do a high lift cam with a standard head? i was looking at a 345 lift cam, but am afraid of putting a valve into the head, it would seem that you would need a milled head for higher lift

 

[freakboy]

you would have to put the cam in then put playdough ontop of the valves put the head on tighten it down turn it over and then if it just stops... back off the flywheel then take the head off... it it dont go clunk.. just measure how much is between it...

and i wouldnt add a flywheel from anyother engine...

 

[Rotore]

for that just buy a clone and modd it get like 20hp out of it, or a bike engine or a twin like me mod it and get 50hp plus out of it

 

[WI_Chopper]

i cant fit a clone in my frame, my 5hp briggs barely fits as it is, i have no air cleaner cuz it wont fit

 

[Rotore]

post a pik of your frame

 

[WI_Chopper]

its here

http://www.diygokarts.com/vb/showthread.php?t=4647

 

[Rotore]

it'll fit if you move the motor mount forward

 

[WI_Chopper]

cant, its welded as far forward as it can be

 

[WI_Chopper]

after thinking this through further, i have decided to sell the bike. I will be placing a post in the for sale section for those who may be interested.

 

[modelengineer]

i have no air cleaner cuz it wont fit

Not really much point modding an engine which will trash itself...

 

[WI_Chopper]

thats the point of changing the carb, so i can run one off to the side instead of up, where it will hit the frame

 

[JHen]

You can run a tube, like a car coolant hose, out from the intake on the carb and to where ever you can fit the filter.

 

[solomon]

I was gonna say the same thing, but to use pvc fittings, and some sealant.

 

[Kenny_McCormic]

Billet rod and flywheel are a must if you like your testicles. To get that kind of power on gas it will be revving pretty high, higher than a a stock flywheel is safe at. The billet flywheel is actually cheaper than the OEM iron when you could still buy them new.

http://www.arcracing.com/servlet/the-126/5-HP-Raptor-flathead/Detail

You will probably want to go to head studs with NOS. I haven't read up on flatheads lately but IIRC there is an area in the valvetrain portion of the block that will need to be reinforced with a weld.

I would go here and start asking questions if I were you.
http://karting.4cycle.com/forumdisplay.php?f=1

 

[solomon]

I believe the lifter bore must be reinforced with that weld.

 

[oscaryu1]

you dont wana mill the head out at all cause that will KILL FLOW

do a port polish a arc billet connecting rod a billet flywheel a highlift cam shave eyebrows get stainless steel valves polished to hell.... not sure bout carb... advanced flywheel key and maby a fire slot.

Don't over do it... up to .005 IIRC.

maybe i should hae said this is my first engine, and a billet flywheel is out of my price range, would a 3.5 hp flywheel do the same job?

Yes... somewhat.

and can i do a high lift cam with a standard head? i was looking at a 345 lift cam, but am afraid of putting a valve into the head, it would seem that you would need a milled head for higher lift

It'll hit the head.

i cant fit a clone in my frame, my 5hp briggs barely fits as it is, i have no air cleaner cuz it wont fit

Don't be an idiot, put it on. Or find a way to.

thats the point of changing the carb, so i can run one off to the side instead of up, where it will hit the frame

Yeh, a Tillotson or something should be a good alternative.

I believe the lifter bore must be reinforced with that weld.

Yup, especially with high lift cams. Place junk/spare lifters inside it to keep the lifter bore from collapsing though.