Topic: What exactly do I have? 28n707

[turbo_bird]

So like the title says, I've got a Briggs and Stratton 28n707, and I've been eyeing up a few parts for it. I'd like to at least give it a bit of a refresh over winter, but don't know how to tell if it's an AVS, Intek, or whatever other acronyms they use. The other model number is 1166-E1, and the date code is 971204ZE, so from what I can find that means it was built Dec. 4, 1997. I don't really want to tear it open without knowing what parts might fit or if it's even worthwhile doing it. I'm thinking either oversize piston and rings if I can find one, or just fresh rings even. I should probably lap the valves and adjust them too, and maybe clean up the ports a bit. We're not supposed to use any performance parts, so I can't do too much to it. Is it worth making a stepped key to change the ignition advance on a relatively stock engine that isn't going to see much rpm? Also, is it worth getting rid of the stock intake and air filter to run a cone filter and velocity stack with the stock carb? I should probably keep it under 4000 rpm or so anyway with stock internals, and even then keep my eye open for another engine. The class I'm in only allows stock engines up to 17hp anyway, and I wasn't too far off the pace with it the way it sits, need more practice driving before worrying too much about power.
Kristian

[birdman_express]

If 17 HP is the max HP, I would try to find a 31CI motor.
They are out there, and that would be a better one to freshen as well.

[turbo_bird]

That is probably the most logical route to take, I should maybe go around to a couple local small engine shops and see what they've got for used stuff. I've been keeping an eye on marketplace for a bit too, but haven't found anything suitable yet.
Kristian

[The Tank]

As Birdman said, if you are allowed the 17hp then you might as well search for one of those which will be a 31ci engine. They are harder to find in the non AVS but are plentiful in AVS style. If they do allow air filter upgrades, change it over to the cone style would be my recommendation.

Where could we see your rules?

[turbo_bird]

Here's the rules they've posted. But tons of people build stuff to other sets of rules and race as well, so things like the 5" height and 36" width aren't really followed, and neither is the one about gokart spindles. They'll let basically anything run as long as it isn't too much of a death trap, but I was trying to follow what was posted to see how I could do.




There's also an outlaw class where you're supposed to follow the same rules for the chassis but engine and transmission are pretty much wide open. About the only stipulation is air cooled and maximum 750cc. That's where guys run bike and sled engines, but the guys with hopped up mower engines are still faster, probably because they have taken the time to build something that actually handles rather than just a straight line rocket.
Kristian

[Rrichard]

turbo_bird,

The "*Disconnecting the Governor*" in "External Modifications Allowed Section" is a MAJOR safety concern.

This has always been a huge No-No on here.

If rules were to stipulate a billet/aluminum flywheel  MUST be used if modifying engine to run  beyond stock RPM rating, that is one thing, however there is nothing to that effect in the "Rules" you show.
 
Please understand, no one wants to damper the fun you guys are having but, the last thing that we need on here is a potential Newcomer seeing the rules you guy's are going by and thinking that it's okay. It is NOT.

I would strongly suggest a conversation with your group about this and collectively address this oversight.

The reasons for not allowing one to spin a stock engine past it's factory governed RPM with the stock cast iron flywheel are well documented on here (Search Bar is your friend).

We want everyone involved in Lawnmower Racing to be as safe as humanly possible.

The easiest as well a lowest cost way to correct this would be to change the rules to disallow "disconnecting" the governor and enforce 3650 max RPM in post race check for say 1st thru 3rd finishers.

For your "Experimental" or anything past "Stock" classes make an aftermarket flywheel MANDATORY.  Yes it costs more to go fast.


 

[turbo_bird]

The local rules are definitely a bit bush league. They were talking about going to the ARMA rules a few years ago, but that never happened. I guess it's all fun and games until someone gets hurt, but they've been running the same rules and classes for about 8 or 9 years now, and I don't think anyone has blown up a flywheel yet. I think the original intent with not allowing modified engines was to keep costs as low as possible for people getting started and get enough people interested to get it off the ground, which they've definitely done. I wonder what they would say if someone showed up with either an aluminum or steel flywheel instead of cast iron? It wouldn't be all that hard to make my own even, I built a lightweight steel one for a car years ago that has probably seen 8000 rpm. It was enough to scatter the rods and pistons real good, but the flywheel was fine. I've even got a piece of titanium plate I could use, I'd probably be the only one with a titanium flywheel.
Kristian

[The Tank]

I've even got a piece of titanium plate I could use, I'd probably be the only one with a titanium flywheel.
Kristian

Thanks, I'm getting it Patent Pending right away since you gave me the idea


I've researched getting some billet flywheels made and everybody that I have talked to who has tried it, has given me the same answer. The magnets is where the nightmare come in they say. Most magnets are too weak from what I've been told.

If they call it a modified class, at the very least they should allow a billet flywheel since it is a safety factor. I know you said it has never happened but me personally I would show up with a billet wheel. All they can do at that point is let you race or turn you away. Me personally, I would take that chance before I risked turning one to take that chance of being hurt. We all have families we need to return home to.

[turbo_bird]

You're not wrong, I don't want to end up like Don Garlits, especially considering it isn't my foot that would catch it. I was actually more worried about breaking the rod or crank that the flywheel. I did that with an old gokart I had when I was a kid. I doubt they'd turn me away if I had a better than stock flywheel. I think I've got a seized engine I can rob the flywheel from to see about magnets even. Even a steel flywheel would be way better than cast iron.
Kristian

[birdman_express]

If you do not get an SFI rated flywheel made, you are flirting with disaster.
Do yall not realize, if you go with a national rules package, you can run
with insurance for your races? Innovation is the backbone of racing,
but which one of you will take financial responsibility for a failure?

[Rrichard]

Poke a Bear one to many times and he will more than likely awaken.

We as racers are willing to take chances, it's a personal choice, we ask ourselves is the risk worth the reward.

Consider the bystanders, track workers, spectators, are they willing to risk flywheel shrapnel, same as you?

You all may have been doing this for a good bit and never had a problem, while that's a very good thing, it don't mean it's all good, after all there never is a problem till there is, right?

There are areas that corners can be cut and improvised. If one thinks Basic Safety is one of those areas, frankly IMHO they are foolish.

Turbo_Bird  it seems like you are wanting to do things as best you can, even if you could come up with some kind of flywheel you feel is "Safer" for yourself, have you really solved the problem? Would you not still have cast iron spinning around you, on your competitors motors?

 Please heed Birdman's sage advice, Quote: "If you do not get an SFI rated flywheel made, you are flirting with disaster."

You stated the group has grown now, what better time to take things to the next level? Get on in there with the ones that make the rules, see if you can help them "see" things from a fresh perspective. Lord knows folks want to stay in their comfort zone and nobody wants to change things that appear to be working fine, however it's easy to miss things when all the trees are blocking the view of the forest.

I understand the line of thinking of trying to keep the costs down to attract newcomers, it is no doubt a valid thought.

But..... consider this,

We as racers will always be seeking "that little bit more". We will always be wanting to go "Faster". And lets just face it, left to our own devices we will find the breaking point of our machines.

So is it cheaper to twist a stock motor for all it's worth (with a proper billet flywheel) and then just replace it when it pops? Then salvage whatever parts you can, rinse and repeat?

Is it cheaper to go ahead and put the strongest parts you can find when you build it and (in the case of Briggs Singles) throw the balance system in the trash can where it belongs, and balance the crank?

Truth is any motor is a may-pop, it takes money to give them the best chance to live, as well as ongoing expense to maintain that level of may-pop prevention.


The known fact about Briggs Singles is if you want to spin it above stock governed RPM with all stock stuff in there, they are Will-Pops







 

[turbo_bird]

I get that racing is dangerous, but if we were all going for maximum safety all the time, we'd never leave the house. I'll talk to the guy that seems to be mostly in charge, but have my doubts that I'll change anyone's mind seeing as I'm the newcomer. I don't know if insurance would really figure into it with using a standardized rule set though, being in Canada instead of the USA.  Other places in the world also allow removing the governor and running the stock flywheel as long as the cam isn't altered or changed, so I wonder if an otherwise stock engine would be able to spin fast enough for the flywheel to be what lets go?
Kristian

[Rrichard]

I get that racing is dangerous, but if we were all going for maximum safety all the time, we'd never leave the house. I wonder if an otherwise stock engine would be able to spin fast enough for the flywheel to be what lets go?
Kristian

Sorry you feel that way, all you can really do is be a safe a possible.   Might fall on deaf ears but here are some numbers that may show the significance.

Flywheel is approx 9" round disc

At 3650 RPM Flywheel is traveling 8600 FPM (Feet per Minute)

8600 FPM = 97 MPH

So if flywheel were to fragment, the pieces would travel at the rate of 140 Feet per Second.

[turbo_bird]

Sorry you feel that way, all you can really do is be a safe a possible.   Might fall on deaf ears but here are some numbers that may show the significance.

Flywheel is approx 9" round disc

At 3650 RPM Flywheel is traveling 8600 FPM (Feet per Minute)

8600 FPM = 97 MPH

So if flywheel were to fragment, the pieces would travel at the rate of 140 Feet per Second.

Not falling on deaf ears, I'll definitely mention it to the guy that's running things, and I'll try to build mine as safely as possible, but I don't exactly have a say in how others build their machines. Realistically, my daily commute to work is probably more dangerous than disconnecting the governor with the stock flywheel, and that's something nobody gives a second thought to. I'll be keeping an eye out for a better flywheel for my own, or potentially building my own. It's not something I haven't done before, and that one has survived many years of double the rpm this mower engine will ever see. It's also got the added stress of a clutch disk and pressure plate on it. I'm not completely ignorant of the risks of engine failure and how violent it can be, just doubtful I will change any minds at the local races. And regardless of the risks, there are national organizations like in New Zealand that allow disconnecting the governor and running the stock flywheel as long as the camshaft remains stock. I've reached out to one of their members to ask how it's going, but haven't heard back yet.

In any case, this has gotten a fair ways off track, seeing as I was looking for ways to tell if an engine has the silly extra balance weight setup without opening it up. And I still don't know the difference between an Intek and any other OHV Briggs and Stratton. I'm just trying to figure out what parts I should be looking for that will fit my engine, and that includes a flywheel. Most Google results are completely useless, so I figured this would be a better place to ask.
Kristian