briggs vs clone

[the-cyborg]

How does it keep it from floating valves? And sorry for the dumb question, but what exactly is that?

unless you replace the cam leave the valves and springs alone.

 

[CaptCanadia]

Alright.

 

[the-cyborg]

And unless your willing to take the chance of possibly blowing your clone don't mess with the cam

 

[kendelrk]

its when your exaughst and intake valve are open at the same time because of how fast the cam is turning, i dont know much about valve springs. but i think when they get compressed all the way it makes the valves float, but when you get stiffer springs its harder to compress them stopping valve float, making it not float valves and itll go boom, if you upgrade valves, get billet con rod and arc billet rod and flywheel

 

[CaptCanadia]

Ya I think that's a project for the future Thanks.

 

[kendelrk]

and if you go that far with it, make sure to have a good carb, somthing like mikuni, a nice big header and a good filter, because if your spending that much money, why not upgrade all the way? and then just show them how its done when you blow past them

 

[CaptCanadia]

Yeah, that would cost me about 600 bucks and like 250 for a crank alone. I'm good.

 

[kendelrk]

projects of the future for when we become rich

 

[CaptCanadia]

Exactly.

 

[kendelrk]

id rather myself upgrade a briggs flathead more than my honda gx

 

[CaptCanadia]

I'd rather just buy a used racing cart for 600.

 

[the-cyborg]

If you know what your getting into on the front end, knowing there is a high probability of crateing an engine, and willing to pay the cost for it, then leave it stock and enjoy.

 

[South Kart3377]

The truth yes I want a clone on my Other toy thing, but on the Streaker I am Happy with the 8 hp Briggs flathead, it sat outside for 15 years, I got it poured gas in and it started.The clone will not do that I promise. The Briggs kicks @$$!! Plus The stock muffler flows better than the RLV B-91 mini thing, all it does is go around a round thing and to the out put holes. The stock air filter is pretty good too. Bottom line, clone has its pupose but my Streaker Model 8 is NOT IT!!!!

 

[95badbird]

There absolutely nothing wrong with Subaru, I have a souped up EH41 13.5 hp on my dirt kart, for an OHV engine they are extremely well built, smooth running as h3ll, little to no vibration, and will take a beating like nobodies business.

I had it bored .20 over, custom modded cam, shaved and ported, 36mm intake, 31mm exhaust valves, roller rockers for gx390, 34mm mikuni flat slide carb , and one of those make your own exhaust kits for gx390 that NR racing has, of course no governor.

Considering how heavy the kart is + my 185lb, I've had it up to 62mph at a local puddle jumper air strip near my house, let me tell you on a dirt kart running speeds like that, it's a white knuckle ride, but I didn't build it really for speed, but more for raw power and torque for riding in various terrines, I also use it for hunting combined with a home made deer hauler trailer. instead of a 4 wheeler just to be different, and can go just about anywhere my buddies can. I've even use it for hog hunting to out run and herd the hogs where ever we want them.

I need to get with you and pick your brain some......I would like to do some mild upgrades to my OHC Subaru, but like other's have stated, not much aftermarket.
You seem to know a great deal about them!

 

[karl]

How does it keep it from floating valves? And sorry for the dumb question, but what exactly is that?

When the engine reaches a certain rpm, the springs are not strong enough to bring the vavle all the way down, thus limiting rpm.

 

[Doc Sprocket]

When the engine reaches a certain rpm, the springs are not strong enough to bring the vavle all the way down, thus limiting rpm.

Yup- Karl gets the prize. But I'm going to expand the explanation a little.

It works like this- the cam lobe (via the lifter, pushrod and rocker) opens the valve. The valve spring closes it with some force. It causes the components to follow the downslope of the cam lobe, and hopefully close hard enough and seal well enough to seal the combustion chamber.

As engine RPM increases, (naturally), the speed at which those valves open and close is increased. Eventually, the speed gets to be great enough that the valves are whipping open and closed fast enough that they are only in a given position for a fraction of a second. If the springs are not particularly firm, eventually the valve won't even make it into a fully closed position before the cam lobe asks it to open again. This is called valve flutter or valve float. Since the valve does not reach a point of being fully closed, the cylinder does not seal, and compression is lost. The engine can therefore not continue to make power. This acts as a natural rev limiter.

So why build an engine with weak springs, forcing us to upgrade them? Well, there's a couple of good reasons. 1) See rev limiter comment. Our stationary (industrial) engines are designed to run implements at 3600RPM all day long, and the stock provided springs are not only sufficient for the task, but help guard against a runaway engine. 2) Cost is a factor in everything, isn't it? 3) Wear- Having valve springs that are overly stiff has the potential to cause accelerated wear in the valvetrain, as the tension (and therefore friction coefficient) is increased. The lifters ride harder on the cam lobes, and the valves slam shut harder.

So when and why should you upgrade your valvesprings? For quite some time now, I have been telling all askers the same thing. Your valvesprings should be one of the last parts for you to upgrade. With so many RPM-increasing possibilities, there is always a potential for something to go wrong. Without getting into the myths again, I will say that things have to be handled responsibly, and there really is only so much you can ask of factory stock flywheels, rods, pistons, etc.

So- go ahead and mess with the exhaust. Slap on a high-flow filter. Maybe swap out the carb and adjust or even ditch the governor. But leave those stock springs in there to help keep the RPM reasonable until you're ready to go high-dollar on the big ticket internals.

One little disclaimer I feel inclined to add-

Do not rely on valve float on a consistent basis to keep your RPM in check. It will ultimately beat the crap out of your valvetrain. Picture an air chisel doing it's thing. If you float, you float. But it's much better to use engine tuning and correct gearing to keep RPM and roadspeeds in check.

 

[CaptCanadia]

Thanks for the detailed explanation that puts a lot of questions to rest.

 

[Doc Sprocket]

S'allright!

As far as the original question goes, I really do see it as a personal preference thing. They both have ups and downs.

Somebody commented about there not being a lot of aftermarket support for the GX's and clones as compared to the Briggs. I'm not sure if that's entirely true- I've seen a lot out there.

If it's just Briggs or Clone, no ifs, ands, or buts- I'd probably go with the Briggs, based on out of the box quality. However, when you start swapping parts and modifying, you're really at the mercy of the individual parts suppliers, and that's where the lines start getting blurry. Sooner or later, you're down do just a factory original block (maybe), and like it or lump it, there's a ton o' good clone blocks out there.

Now- Somebody else (kendelrk, maybe) suggested he'd rather do up a Briggs rather than a genuine GX. I think I would take the other side of that. I prefer the OHV design, even though the L-head is simpler. I have heaped abuse by the shovelload onto my GX, and it truly was the most solid, dead-nuts reliable engine I have ever owned. Japanese or not. I would use a GX for anything, anytime.

I think there are two exceptions to that sentiment from where I stand. I would prefer the Briggs
1) On a minibike or similar application where OHV engine may not physically fit due to dimensional constraints, or
2) On a vintage kart or 'bike where an OHV kills the vintage look.

 

[kendelrk]

my first engine was a flathead, i learned on that engine, before ending its life, my next was a clone, which i didnt get until a year later, i like flatheads design, and it really does provide a nice look to my older bike. i find my flatheads have more oomph, and toystory, im talking about a clone, yours was a genuine honda, which is alot diffrent,i like how my briggs looks and i like how it sounds, and there is a big aftermarket parts market because of the famous raptor, theres alot, you could get blueprinted carbs, heads, all of it, on a clone or gx, theres still a big parts market, but its modern junk, briggs back then was built to last

 

[Doc Sprocket]

and toystory, im talking about a clone, yours was a genuine honda, which is alot diffrent,

I understand you are referring to clones, which is why I was very specific in my statements.

on a clone or gx, theres still a big parts market, but its modern junk,

Based on my own personal experiences, I would never refer to a Honda as "junk", modern or otherwise. There is some very good factory and aftermarket support for the GX series.