Help needed GP460 muffler

Discussion in '2-Stroke Engines' started by demolition_dave1, Jan 15, 2012.

  1. I just put on a new gp460 on my catrike Road and took it for it's inagural ride this afternoon. It is VERY fast and flies up hills.
    But it is extremely loud, which I expected. I tried the stock muffler and then put on an aftermarket muffler but neither really help much.

    Has anyone found a good muffler that really dampens the sound? Ive heard a motorized bike ride by that sound like it was underwater.....just a gentle gurgling sort of sound. Granted it wasnt a 2 cycle HO engine but there has to be something better than what I am hearing right now. With earplugs it isnt unbearbale but I would really like to muffle a LOT.

  2. 5-7HEAVEN

    5-7HEAVEN Member

    My 460 engines were loud too with stock muffler. I tried the 460 Dominator, still loud. I also tried ADA S1 pipe, much quieter.

    Then I bolted on an SBP Happy Time expansion pipe.

    The engine became so quiet, I swear I could hear the piston ring scraping the cylinder @ idle! :tt1:

    I thought I'd LOSE power, because the pipe's exhaust flange was GROSSLY mismatched with the 460 exhaust port. Surprisingly, it made a goodly amount of power. Maybe not as much as the Dom, especially @ high rpm, but there was power to spare.

    My friend reworked a 460 Dominator pipe to work on his rear-engined bike. With it, his top speed was 53mph on flat ground.
  3. I assume the pipe is larger than the exhaust port? not smaller? But the bolts are spaced the same?
    Can you give me a link to the Happy TIme pipe youre talking about?
  4. BTW, Im only getting about 40mph with mine but after riding a Honda35 it feels like a rocket. Man it is FUN! I wish Id gotten an earlier start today so I could have ridden for hours. Also I glanced somewhere you had a 4 liter gas tank for yours? Can you link me to one of those too? Also what kind of mpg do you get from yours?
  5. 5-7HEAVEN

    5-7HEAVEN Member

    Actually, the SBP exhaust pipe flange is smaller than the 460 port. Not only that, but the 460 port is rectangular and the SBP pipe is round!

    I also installed the pipe on my Tanaka 47R racing engine. Its port was MUCH larger than that same SBP pipe. However, it also quieted the 47R and made more power than a stock 47R muffler.
    Last edited: Jan 15, 2012
  6. 5-7HEAVEN

    5-7HEAVEN Member

    My friend Rick also used a Honda 35, then upgraded to a CY460 engine. He's running 53mph on the flats.

    What's your gear ratio or spindle size?

    I got about 65mpg on the 460 with friction drive. I got about that same mpg with the 460 ANNND the Tanaka 47R engine with Scooterguy drive and shift kit. However, I shelved the 460 and stuck with the 47R. Now after a series of improvements, the Tanaka is getting about 125mpg.

    FWIW, the 460 is more powerful and has greater potential than a stock 47R. I sidelined it because of its unreliable clutch. When I find a dependable clutch, I'll use the 460.

    Here's the 4-liter tank. It
    Last edited: Jan 15, 2012
  7. Ok, so I am clear.
    The pipe does completely cover the port exhaust right?
    or is some exhaust still coming out at the port?
    And the flange bolts are spaced the same as the exhaust port holes so it matches up nicely? A
    nd do you have a photo of your setup? I
    would like to know where it will be positioned.
    I would really appreciate it.

    Im getting ready to go all the way down to the Keys and dont want to be deaf when I get there. And I would also just as soon not draw un-necessary attention to the trike by the noise as well. I hear the cops are tight down there.
  8. Not sure. I dont know the gear ratio of the gear box so I can't calculate it. Im running 72/20 on the other gears though but whatever it is, I like it. I have 20 inch wheels and it is geared right where I want it.
    My only concern at this point is noise.
  9. Id guess it was 5 to 1 and with the 72t and 20t gears that would be 18 to 1 right?
  10. 5-7HEAVEN

    5-7HEAVEN Member

    Yes, 18:1 would be correct with 26" wheels @ 9300rpm. If it was that simple, there'd be more power/rpms to go faster.

    However, with your 20" wheels, your effective gear ratio is 23.4:1 @ 12,500rpm. That's why you can't go any faster. You're way past your redline @ 40mph.

    Swap your sprocket from 72t to 63t for more speed. At that same 12,500rpm, speed of 47.2mph is theoretically possible.

    With 26" wheels, it'd be 15.75:1. However, with 20" wheels, your effective gear ratio is 20.5:1.
    Last edited: Jan 15, 2012
  11. NM< I just bought it, Itll make sense when I have it my hand....all that matters is it is quiet . But about the gas tank, do the fuel lines match the 460 or do I need adapters?
  12. Right . Im good with the speed. I need the torque and hauling ability so I will just stick with the ratio I have for now. If I change anything I will probably go the other way...when I get to the Rockies next Spring.
    But for now I am only concerned with the muffler and the gas tank.

    But I just bought this muffle you mentioned so I will just see how it goes I guess.
    Now about the gas tank you mentioned. Do the fuel lines match the gp460 intake and return lines or do I need an adapter?
  13. 5-7HEAVEN

    5-7HEAVEN Member

    To align the exhaust flange, the bolt holes are slotted so everything lines up. There will be no exhaust leaks.

    The gas line from the tank's petcock is larger than the 460's fuel line. In fact, the 460 line slips deeply and tightly into the petcock's rubber fuel line and clamped.

    I forgot to mention that it would be wise to replace this tank's petcock with the one from SBP. The HT petcock plugged up on me. Its valve severely restricts flow. The SBP's valve's inside diameter SEEMS almost as large as the petcock itself! There is absolutely no restriction flow.
    Last edited: Jan 16, 2012
  14. Thanks, I have everything on the way now. Im still riding it with all the noise though. It is just so darned fun after riding the Honda engine for so long.

    One more you know what size bolts fit the 460s exhaust port? I have 5mm and either it is too small or I stripped the interior threads/ they seemed to fit tightly for a day but the came out and now one doesnt want to grip....Im hoping theyre just too small and the threads are still good to try again.
  15. 5-7HEAVEN

    5-7HEAVEN Member

    I believe they're M6 bolts.
  16. 5-7HEAVEN

    5-7HEAVEN Member

    I can't wait to see and hear your 460 run!

    You'll be amazed how quiet your 460 will be, but it might hinder the top end.

    What you could do is fab a port-matching head pipe for better performance.:idea:
  17. lowracer

    lowracer Member

    Any place you know of selling the scooter guy mount?
    I got another project in mind involving a Chung Yang 460 & I would like to find that mount or will need to make my own.