420 predator

[redflash]

sounds like a bunch of compression....should pull, but the more compression ....the harder to pull is pretty much a standard story.

 

[Dfish1247]

That’s what I figured, it still has the stock cam, so no help there. I’ll pop the stock key back in and see if that helps any, if not, I’ll hook up the electric start and try that. If that don’t work, I’ll put a stock height gasket back in. Thank you

 

[Denny]

Yup.

 

[Functional Artist]

Classic "hot rodder" move
Beef 'er up till the starter (in this case you) can't crank 'er over

 

[Dfish1247]

Well duh, ain’t a hot rod if it ain’t a pain,lol.

Done a little rooting around, I may have the exhaust valve lashed too loose and the comp release won’t work. It’s at .006”, I’m going to try .004” and see if that’s easier to pull.

 

[Denny]

Try .003

 

[Dfish1247]

Will do.

 

[madprofessor]

Electric start, the hallelujah answer. Wouldn't put any more unnecessary grinding on my joints by yanking on a pullrope at all if I had that option. After all, it's a 420cc gokart, not a little weedwhacker.

 

[Dfish1247]

Well, finally checked valves, exhaust was too loose, watched it skip right over the compression release, tightened It down to a tight .004”. Three pulls and it was running. I treated it like a brand new engine, run around 2500rpms for 20 minutes. I’ll drain the oil in the morning and put the converter on, then see how it runs. It sure revs quick and acts like it’s strong.

One thing I do need is a valve cover breather, would auto zone or somewhere have something I could use?

 

[Dfish1247]

Something else, is there any kind of muffler that flows good and isn’t horrid loud? The straight pipe is deafening,lol. My neighbors are ok with my engine shenanigans, but I like to be somewhat decent on the racket.

 

[Armilite]

If you turn any of these Industrial Engines over 5000rpm the Cast Iron Flywheel can Explode! The Stock Rod is designed for 3600rpm, so if turning it a higher 4000+rpm, use the Billet Rod. If turning it higher than 3800rpm the Valve Springs need to be upgraded.

A 460 Single (92mm x 69mm) 458.8cc using a 34mm Carb, 11.0cr, 307 CAM, 40mm/32mm Valves, K&N Air Filter, Tuned Header Exhaust, Dynoed 37.37hp@5000rpm. A 440 built to the same Specs should be -2hp about 35.37hp@5000rpm, a 420 built to the same Specs should be -2hp about 33.37hp@5000rpm.

 

[madprofessor]

is there any kind of muffler that flows good and isn’t horrid loud?

Yeah, there is. Round cylinder or flat rectangular box. I've had/have both. Thing is that I had to design/build both, so would you if you want the disputed "quiet but unrestricted" result. An online troll kept calling me a liar about that, to the point that I made and posted a youtube video of the minibike running and revving to prove myself. Is now deleted by time limitations of youtube.
They're both based on the same principle as noise-cancelling headphones, using matching sound waves going out as the waves coming in, cancelling each other out without reducing flow that would cost ponies. Just have to build oversized, with huge passages.
The 90-degree bulkheads provide the sound reflection back the way it came, 4 of those 180-degree switchbacks in both.
Pics of the first one (round) on a 12+hp. Predator 212 below...............My performance guy in N.C. (Jerry Dover) told me that it would be a trade-off of hp/noise even if I bought the best RLV muffler/silencer. Only a unit without restrictive packing could have free-flow, and therefore wouldn't have any way to quiet the exhaust on what would be basically a straight-thru resonator.
EDIT: 3rd stage "muffler" section with baffle and steel wool packing on the designing drawing was never built, and silencer was still completely effective enough, like a lawnmower.

 

[panchothedog]

Hey Dfish
For mufflers I like the RLV brand sold by Go Power Sports and OMB warehouse
I am sure that they are sold by many other shops as well. I 've done a ton of business with those two places, so that's why I mentioned them. I don't know how much they lower the decibel level, probably not a lot, but they really help with tonning down that piercing STING that comes out of a straight pipe.
Performance wise I don't think they hurt at all. I have 5 of them, 2 on 196 cc
2 on predator 212 cc engines and 1 on a predator 301 that I am just now building . I know that my neighbors appreciate them and I am very satisfied with the results.

 

[Armilite]

Something else, is there any kind of muffler that flows good and isn’t horrid loud? The straight pipe is deafening,lol. My neighbors are ok with my engine shenanigans, but I like to be somewhat decent on the racket.

A Muffler is like a Gun Suppressor! It's the Hot Gases hitting the Cold Atmosphere that makes the Sound. The Tuned Header is to make Power, the Muffler is designed to absorb some of the Heat and Slow Down the Hot Gases allowing them Time to Cool before exiting the Exhaust. Using to Restrictive a Muffler creates too much Back Pressure which Restricts hp made.

Download a Free Sound Meter App for your Smart Phone.

Sound Meter - Apps on Google Play

Measure the environmental noise by tidy sound meter

play.google.com

The direction you Point your Tuned Header makes a difference in what you Hear! There are probably 100's of different Mufflers out there you can use.

I suggest you Time yourself over a Distance like Stopped to 60ft, there are Free Apps for that also.

db at Idle.
db at Max rpm open Header.
db at Max rpm with Muffler #1
db at Max rpm with Muffler #2
db at Max rpm with Muffler #3
db at Max rpm with Muffler #4

If other People have the same Engine with a Muffler you can Record their db also.

The Bigger the Longer, the more Efficient it will be, but also Weigh more.

Muffler, Open Modified 1 5/16" $45.95​

Muffler, Open Modified 1 5/16"

OMB Warehouse - Go Kart Parts and Mini Bike Parts. OEM and Aftermarket supplier of Outdoor Power Equipment Parts, Arborist and Landscape Supplies.

www.ombwarehouse.com

Mud Boat Header & Muffler GX390 Predator 420 13-15HP Clone. $54.99​

Mud Boat Header GX390 Predator 420 13-15HP Clone

OMB Warehouse - Go Kart Parts and Mini Bike Parts. OEM and Aftermarket supplier of Outdoor Power Equipment Parts, Arborist and Landscape Supplies.

www.ombwarehouse.com

Low Noise Super Silent Muffler Honda GX340 / GX390 Exhaust.​

Low Noise Super Silent Muffler Honda GX340 GX390 18310ZB8SIL | Honda Engines and Generators | Gear GB

Low Noise Super Silent Muffler Honda GX340 GX390 18310ZB8SIL |Honda Engines and Generators | Gear GB

www.geargb.co.uk

Hmf performance**420 Rancher​

 

[Dfish1247]

I’d just like to tone it down some, doesn’t need to be Cadillac quiet, but the Ramcharger loud can’t stay. I was thinking something like a motorcycle muffler.

I don’t think I’d notice a minor performance drop, went for the first ride yesterday, this thing is a rocket now. It spun the tires on dry pavement, well, they spun maybe 6” or so, didn’t do that before, and it does have more top speed.

 

[Denny]

I’m pretty sure the noise comes from the explosions and has nothing to do with hot air mixing with cold air. Be it gun or engine. You could just go to the hardware store and get the biggest screw on muffler and make a header and then screw it on to the end.

 

[panchothedog]

Yeah, I also always thought that the noise created by an internal combustion engine was created by the explosion in the combustion chamber.
I guess when it gets really hot this summer and I have my air conditioning
running real hard I better make sure my porch muffler is working before I open up my front door.

 

[Denny]

Better put one on your refrigerator door also. Or you could loose your hearing making a ham sammich!

 

[madprofessor]

A silencer (illegal) on a gun works by delaying and stretching out an explosion of expanding gases' exit from the end, and it has to work on every stroke of your trigger finger. A silencer on a 4-stroke engine only has an explosion of expanding gases 25% of the time, so the larger the internal volume of a silencer is, the more space and time it has to expand further before gradually pressuring out through the tailpipe. It has 75% of the time to do the expanding inside/pressuring out before the next explosion. That's basically the same delay/stretching action that a gun silencer (illegal) does, so picture an empty big metal coffee can (or two welded together) with opposing in/out connections. That huge area for expansion actually does a surprisingly fair job of silencing a 4-stroke with no internal restriction whatsoever. Baseball-sized stainless steel wool scrubbing balls can then be stuffed into the can(s) through the tailpipe one at a time to gradually quiet it down further and further if desired.
I've actually heard this work on Jerry Rinkel's Kawasaki, and even appropriately burned the hide off my leg on the coffee cans wearing shorts while riding on the back as we did wheelies through the pumps at a gas station. BTW: I can wheelie way better than him with Jette Craft on the back of my Kawasaki.
Jeez, excuse the life history, guess I was just enjoying old memories.

 

[Dfish1247]

A muffler showed up today, it’s a motorcycle muffler with a bolt in restrictor. 1.5” inlet.

I just stuck it on the pipe and it tones it down wonderfully. Noise is down to hot rod level, not top fuel ear death. I don’t notice much sound difference with the restrictor removed vs installed.

If I just weld on to what I have, the muffler will stick out the back about two feet. The pipe is just a straight back pipe. Any harm in shortening it so the muffler is tucked in more?