Briggs 5HP Modifications?

[oscaryu1]

Wanted in for all those modifications available. So... since I couldn't find a good used engine, I decided to start from scratch:

Out of the box from eBay:

Eww

Eww even more

 

[oscaryu1]

Took me 20 minutes to completely strip it apart (13 power! )

A few hours of washing and scrubbing later:

I'll get more pictures tomorrow.

EDIT - Notice the 2 missing bolts, new head gasket, exhaust header, and quick ported intake + exhaust.

 

[Kenny_McCormic]

Get new exhaust bolts, powerwashers clean these up quickly.

 

[oscaryu1]

The ones from the lawnmower are fine... I prefer dremel wire brushes.

 

[oscaryu1]

 

[newrider3]

While you're there, cut the eyebrows. It removes a small amount of compression, but the huge gain in flow is worth it. It could be offset with a milled head too.
It looks like this when you're done:

 

[oscaryu1]

Could I do this with a dremel?

 

[Kenny_McCormic]

Could I do this with a dremel?

Thats how its usually done. My bad, was thinking about port claenup.

 

[newrider3]

Yeah, I used a dremel with those sanding bands. Used the same thing to port it too.

 

[Kenny_McCormic]

Be sure to clean up the casting defects in the ports so they flow better too.

 

[oscaryu1]

Hehe, defects? You should've seen the 3.5's "defect". It was literally a jagged edge right in the middle of the port haha.

 

[enel1221]

dual valve springs

another thing you could do is put dual valve springs (this will only help if you are taking the govner off, this helps with valve float and allows the engine to rev higher). I just bought some springs from local hardware store, and cut them to fit.

 

[Kenny_McCormic]

another thing you could do is put dual valve springs (this will only help if you are taking the govner off, this helps with valve float and allows the engine to rev higher). I just bought some springs from local hardware store, and cut them to fit.

Yea, but running ungoved with stock parts 4k is the limit for the rod and flywheel and thats where springs float to slow it down.

 

[oscaryu1]

5k is the max for the rod... Dipper goes at around 4,200. Flywheel? Probably 5,000 too.

 

[oscaryu1]

 

[newrider3]

Nah, the steel flywheel will last pretty high, but you need billet once you get to the 9,000+ rpm range.

 

[oscaryu1]

Steel? The stock ones are cast iron. Never spin a cast iron one above 6,500. 9,000? Impossible.

Just because it's heavy or takes a good beating once in a while does not guarantee that is will not blow. The Clone flywheel is greatly prone to splitting... Never over 6,500.

The Clones spread word about ignored warnings. Improper torquing of the side cover, thus warping it... Flywheels blowing and killing (yes...)... Not using girdles, thus blowing them apart, or warping the block, ect...

 

[newrider3]

Sorry, I meant Iron. People racing them turn between 7,000 and 8,000 regularly, but if they are over that range it is all billet. They can definitely handle 6,500, stockers run higher than that and are required to run a stock flywheel. In terms of quality you can't even compare a clone flywheel to a Briggs flywheel, providing it hasn't ever been dropped, hammered, modified, etc. If you can afford billet, by all means go for it, but it might be overkill unless you are building something in the range of a Limited Mod or Open.

 

[ironman]

you know you here about the flywheel braking and rods snapping and parts flying every where.but i don't no not one person that has shattered a flywheel. i know it can happen.but these guys race everyday here in ky and never no story like like .and alot of these guys are on some stock parts.i mean im running the hell out of mine.im just saying if you keep the oil good and use good oil you should be safe.thats just my 2 cents.and i do have a few karts.

 

[oscaryu1]

Most of the people here run non-Clones, and they're better quality I admit. I run the hell out of every motor I have, but it isn't all about oil. Oil can't save a flywheel, or prevent rod breakage, or stop valves from floating.

Regular automotive oil doesn't cut it. For regular use and gasoline engines with light modifications, Mobil1 is fine. More expensive modifications and motors require "better" oils. Oil made for splash type lubrication... Red-E, CoolPower, ect.

I'm not planning on spinning a NOS (hopefully) no more than 7,000, as the rod I'm planning on getting goes.