My lil' 5HP guide...

[Russ2251]

...I replaced the head gasket with some gasket maker silicone stuff and drilled four holes in the flywheel, to make it lighter. Both the drilling and removing the gasket mods I have already tested on another engine, and I have noticed some power increase. Also, the flywheel didn't explode after tons of extreme revving. Still waiting for the silicone to cure...

What 'silicone stuff' did you use?
Drilling holes in flywheel is really dangerous stuff. Would be much safer getting the lighter flywheel off of an equivalent rotary mower.
If you insist on using your modified flywheel, make absolutely sure (at the very least) it is dynamically balanced.

 

[jr dragster T]

I would NEVER trust that drilled flywheel!

 

[Russ2251]

Just a few grams out of balance translates to many pounds at high rpm.
I'm glad you chimed in Mr. Tyler.

 

[GoAlterBridge]

Yeah, I know. All I drilled was four 3/16" holes, AFTER I Carefully measured the hole exactly opposite each other, the correct distance away from the outer edge of the flywheel.

http://img.alibaba.com/photo/10349852/Lion_Silicone_Gasket_Maker.jpg

Same stuff I used, but mine is black.

I wouldn't have done this, but I've tryed it on a few other engines, and never had any problems whatsoever.

 

[jr dragster T]

Personally 4 3/16 holes is NOT going to show any improvements whatsoever. And now matter how precise you where even a few thousand's off and it could explode and kill somone. If anyone has cut glass in there life they wil know what all the cutter does is scratch the surface then apply some force and the glass cuts across the scratch line. Same thing applies here. A small hole greatly decreases strength.

 

[Russ2251]

RTV you're using not designed for your application.
Quote from website:

HI-TEMPERATURE RTV SILICONE GASKET MAKER
• Designed To Replace Most Traditional Cork, Felt And Rubber Gaskets
• Provides Superior Leak Control, Torque Retention & Flexibility & Resistance To Oils &
Fluids
Applications: Valve Covers, Oil Pans, Water Pumps, Thermostats, Axle Covers, Intake Manifolds, Transmission Pans, Oil Pump Flanges, Etc.

Everything listed in applications are low or no pressure. If it holds, good. Keep a sharp eye on it as eventually it will blow through.
I've done a lot of research and testing on these products and found that the 2 best bets are http://www.permatex.com/products/au.../Permatex_Super_300_Form-A-Gasket_Sealant.htm (best) and http://www.permatex.com/products/Au...ng_Formula_Gasket_Dressing_Flange_Sealant.htm (next best).
Every else I used eventually blew out. I also discovered that factory machining did not make the best seal (hence the need for gaskets). Mr. Kibble can back me up on this. I ended up lapping both surfaces using Clover grinding compound (320 grit). About 40 minutes work.

 

[GoAlterBridge]

Ok, I'll keep an eye on it.
I guess all this constructive criticism is good;
It means you are all looking out for my safety. Thanks, guys.

Update:
I tried the engine: Has a bit more power and RPMs now, left it running for 10 minutes at various speeds after I got it tuned. So far no metal fragments in my head.
I don't think.
Lol

Dang, I love these Briggs.

 

[Russ2251]

Check out flywheels from tossed rotary mowers. You may get lucky and find one that fits.
This flywheel will be far lighter and far safer than the one modified.

About a year ago I sold a 2hp Briggs (horizontal) from early '60's.
It originally had points/magneto.
I removed flywheel and cdi from a seized 1998 3.5hp Briggs rotary mower and bolted it up to the 2hp. It fit like it was made for it and ran like champ with the added bonus of disposing of points ignition.

 

[GoAlterBridge]

I've been trying to find one of those flywheels, but our dump has stopped me from picking stuff now. They make money on the junk. I'll probably end up getting a rotary mowers flywheel.

 

[oscaryu1]

Aren't aluminum Briggs flywheels dangerous for spinning over their designated RPMs?

 

[Russ2251]

Haven't had a problem. First did it in ...a long time ago.

 

[newrider3]

Aren't aluminum Briggs flywheels dangerous for spinning over their designated RPMs?

Yes. Highly dangerous.

 

[Russ2251]

I've proven otherwise as I am still here.
You have documentation?

 

[crazycart]

Yeah i have seen no proof of this ever happening.

The worst ive had is a bolt came undone under the recoil and shot through the housing and hit me in the a$$. Stung a bit lol...

 

[newrider3]

Yes. There is a webpage with proof of cast aluminum flywheel explosion. Unfortunately I can't seem to find it, it was linked in ARC's page but it is down.

 

[Russ2251]

When you find it let me know, please.

 

[jr dragster T]

Yes. There is a webpage with proof of cast aluminum flywheel explosion. Unfortunately I can't seem to find it, it was linked in ARC's page but it is down.

Yeah I've have red that article of the lawnmower flywheel exploding!

 

[Russ2251]

Let's see it!!!

 

[oscaryu1]

Oh yeah that! Heh, website down

 

[Russ2251]

Of coarse!