how fast can i spin it?

[Russ2251]

No. Not even a little bit.
Briggs 2 and 4 cycles both run at same speed.

 

[oscaryu1]

Stock cast iron, maybe a used billet. Didnt know a cast 3 existed.

3HP's came with cast iron flywheels.

 

[sayre315]

well what can a 5hp cast iron flywheel spin at?

 

[Kenny_McCormic]

6k rpm

 

[oscaryu1]

Rumor says that Briggs and Stratton tested their flywheels to 9000RPM.

IMO, if that rumor was true, then people wouldn't have their 5HP flywheels exploding at 6500 or so.

I've heard 3.5HP flywheels spun 8500+ no problems though. I doubt you'll be doing that with a stock carburetor.

 

[Russ2251]

then people wouldn't have their 5HP flywheels exploding at 6500 or so.

Load or no load?
This is a question that must be answered as there is a major difference between these 2 conditions.
An engine with a load will never reach it's max rpm, Plus (as stated many times before) different things are happening in an engine with a load as compared to one with no load.
Inertia is a big part of the equation.

 

[oscaryu1]

Seeing as this I got it from a kart racer, I'm guessing on the track. He also mentioned that when they switched to 3HP flywheels, the explosions decreased.

Russ, care to explain? Never heard that side of the story before.

 

[sayre315]

im gonna ask a kart racer
if i cant find the right flywheel then im probebly gonna make a1/4" shield on the inside of my shroud with a 3hp cast flywheel

 

[sayre315]

just recieved on of those square mikuni fuel pumps
i was wandering how to hook it up
what i was thinking is that the in nipple go to the gas tank, the out goes to the carb and the part sticking straight out goes to the crank case cover

 

[Russ2251]

Explain which?

 

[sayre315]

heres a pic
http://cgi.ebay.com/ebaymotors/Miku...m14QQhashZitem330274369894QQitemZ330274369894
its an "arctic cat fuel pump" but its the same as this one

 

[Jerryburger]

Explain which?

-Russ

I think he was referring to the loaded vs noload rpm max capabilties.

Please correct me on this if I'm wrong. From what I understand (I love this stuff) is that an engine is going to develop harmonic vibrations no matter how well its balanced. A flywheel helps (by its mass and inertia) to smooth or reduce these vibrations. Most engine/flywheel combos are designed with flywheel mass (weight) and a load in mind. (A load also acts like a flywheel by damping vibration and harmonics.) When an engine is ran no load, you've lost "x" amount of damping/inertia that the designers were counting on.
So you think to yourself, "Oh, big deal- my engine will vibrate more...", but harmonics can twist/shatter and weaken solid objects if they are strong enough. (The Memerex commercial with the champagne glass, for instance.) Usually the harmonics are much higher frequency than the primary vibrations and I guess they're a force to be reckoned with.

Now I'm by NO way saying that all engines must have load to run at their rated rpm, but when a load is ran on the motor, it's safer.

Part 2 of this is that a motor that's designed to spin at "x" rpm with "x" load will obviously spin much faster with no load applied. The you run the risk of failure due to explanation #1 above, and that the motor is spinning/vibrating at a higher rate than intended.

I'm sure that most of these motors can spin quite a bit faster under load than the default "3600 rpm", but I'm also sure the manufacturers won't support it at all for legal reasons, and sometimes I wonder if some of these motors are designed for 3600 rpm with little leeway for excess. (Cheapness.) So we all have to rely on personal experience (Russian Roulette Experimentation) or the "I heard/read blah blah blah..."

Kinda frustrating, huh?

Sorry to babble on.

 

[Russ2251]

Jerry, what can I say. You've nailed it once again.
This fear of disintegrating flywheels is WAY OVERBLOWN.
It's exceedingly rare that it happens at all.
Some folks get it stuck in their heads that explosions are inevitable. You really have to go out of your way to accomplish it.
I have blown a flywheel (anybody else?) and it was because I did something to it that should not have been done. I knew the risk but did it anyway.

 

[crazycart]

Yes the only way i can see a flywheel detonating is if there is a flaw from the manufacturer or its modified to the point where its weak. I think its funny how half the people on here go DON'T RUN IT OVER 3600, IT WILL EXPLODE! if someone asks how high it can rev or withstand.

 

[sayre315]

well i know (usally) on briggs that it will throw a rod wayy before the flywheel explodes

 

[sayre315]

ok well i put my horstman rod in and its OBVIOUSLY NOT the correct size
the head of the bolt will NOT clear into the cylnder
wich makes me REALY mad

 

[jr dragster T]

About that fuel pump you asked about. The top brass nipple is for your pulse Via intake or block. The other two are fuel in and out.

 

[sayre315]

ok, thanks

 

[oscaryu1]

ok well i put my horstman rod in and its OBVIOUSLY NOT the correct size
the head of the bolt will NOT clear into the cylnder
wich makes me REALY mad

What do you mean? Pics!

 

[sayre315]

well right before the cylnder there is a lip
it hits that
but i talked to the guy and he said it was normal and all horestman H beam stock length rods have to have te block die grinded
what is die grinding?