2 stroke stealth mods?

Discussion in 'General Questions' started by sactownie, Jul 12, 2013.

  1. sactownie

    sactownie Member

    Hi, I am currently acquiring the parts for my MB. I have the engine kit on the way to me but I am not going to install it until I get the SBP shifter kit. I want to build mine as stealth as possible which to me means quiet exhaust, fuel tank mounted any place other then the top bar and possibly a side cover formed out of sheet aluminum to cover both sides of the engine.
    Its all going on a 99 marin muirwoods mountain bike so I just want it to look like a mountain bike.
    Anyone here done any stealth mods to give me any more ideas for my build?
     
    Last edited: Jul 12, 2013

  2. professor

    professor Active Member

    As you will find, the intake roar needs a silencing box along with a better muffler (I don't have a 2 stroke but I read the "Poo po " muffler is quiet.

    Quieting the gears in the engine - some guys glue cardboard or a mouse pad onto the inside of the gear cover.

    I have my gastank behind the seat on a rack ,and works fine until about a quarter tank. Higher would be better. Having no motorcycle style tank on the bar goes a long way to keeping it looking like a bicycle. I used the tank off the HF engine I am using, but any tank will do.

    Pedaling, good helmet, safety vest, gloves, glasses and sane riding all equate not attracting undue attention and thus, are stealth.
     
  3. MotorBicycleRacing

    MotorBicycleRacing Well-Known Member

    Why do you want to be stealthy?
    Do you have a drivers license?

    Motorized bicycles are legal in California.
     
  4. sactownie

    sactownie Member

    I prefer to be able to ride without people gawking at me and my neighbors not being able to hear me every time I leave.
     
  5. grinningremlin

    grinningremlin Active Member

    First part of stealth, rack-mount, if I don't point out my engine nobody seems to notice (when not running).Since you're going with frame-mount, that ship has sailed.The little cigar silencers can be used in line, two hooked up with the hi-temp silicone tubing would take care of most of the exhaust.Next is your intake, if you can figure out a way to make the airflow do a right angle it really cuts the noise.I put a ADA juice-box on my Tanaka pf-4000 and it cut intake noise 20%.So a velocity stack on your intake, then a radiator hose for your right angle, then something to hook the air-filter to.There's a pic on the forum, that shows a velocity stack hooked to a hose then a plastic electrical (4S??) box with a hole cut at a right angle, and the air-filter was rigged to that.
    I'm more worried about my ears, and not having to wear plugs than making people mad.
    Good luck, GG
     
  6. sactownie

    sactownie Member

    where do you get the silencers from or is there a brand I can search for? sounds kind of like the nitro r/c cars I used to have, the exhaust pipes connected with silicon tubing.
     
  7. jaguar

    jaguar Well-Known Member

    I have an "Torque Pipe" expansion chamber with a "belly stinger" and my Stealth Silencer. It is amazing how quiet it is.
     
  8. grinningremlin

    grinningremlin Active Member

    Here's one supplier,http://www.davesmotors.com/s.nl/it.A/id.4389/.f
    I've searched trying to find the company I bought mine from, as it came with 2ft. of tubing (no luck).Make sure it this type tubing (reinforced-braided), the high temp stuff without likes to kink on any bending.If you're good with your hands (metalwork, sheetmetal manipulation-cutting) I'd just buy a few feet of tubing and make my own silencer, simple concept and VERY effective.Ebay has a few on occasion.
    Goped suppliers always have some neat crossover stuff for us.
    GG
     
    Fabian and sublunacy like this.
  9. sactownie

    sactownie Member

    Well heres what i have experienced incase anyone else wants to know the same question I had , I built my bike and used all the tricks to quiet it down including using a shifter kit and mounted the fuel tank in a bag in the rear rack but the only way to make the bike completely stealth that I have found is to cut the motor and start peddling. It works everytime!
     
  10. Fabian

    Fabian Well-Known Member

    Exhaust noise (from a standard exhaust system) can be significantly reduced by adding two and a half feet of (13mm internal diameter) high temperature, chemical resistant, clear silicone tubing.

    The tubing on my bike is 6 months old and it's still holding up well to the 400+ degrees Celsius (752 Fahrenheit) exhaust temperatures, with EGT spikes up to 480 degrees Celsius (896 Fahrenheit), even though the silicone hose has since discoloured to a light brown shade from the time that this photo was taken.

    2012-142.jpg
     
  11. Fabian

    Fabian Well-Known Member

    A Rock Solid Engines reed valve intake system will also noticeably reduce intake noise, not to mention boosting low and midrange torque - a win, win situation.
     
  12. FurryOnTheInside

    FurryOnTheInside Active Member

    Please can you tell me what temperature should the hose be rated to? None that I'm finding for sale are rated to anywhere near 400 Celcius so I really don't know which hoses are suitable. Is a rating of 200 Celcius sufficient?
     
  13. Fabian

    Fabian Well-Known Member

    The hose i purchased was rated to 260 degrees Celsius, which was the maximum i could find. That said, the hose installed on my bike has lasted over a year and it's still soft and flexible, although it has discoloured from clear to a light brown.
     
  14. FurryOnTheInside

    FurryOnTheInside Active Member

    Thanks Fabian. I might as well get the 200C (black, fibre reinforced) hose I found if I don't find some 260C rated hose, can't hurt to try as it's only a few $ per metre so could even be replaced every few months if need be. :)
     
  15. battery

    battery Member

    Look into straight through silencers. you can make one yourself for the intake and the exauhst. I made one quite simply by taking a tall boy cutting a hole in the bottom and sliding in a tube of chicken wire wrapped with 0000 steel wool. you can fit this to your stock pipe with a flexi hose and will not mess with the resistance of your stock pipe.
     
  16. FurryOnTheInside

    FurryOnTheInside Active Member

    Thanks battery that's a good tip. I think I may have too many dimensional/clearance issues to be able to use a silencer like that, but it's certainly something to consider. :)
     
  17. Fabian

    Fabian Well-Known Member

  18. FurryOnTheInside

    FurryOnTheInside Active Member

    Thanks, this gives me a better idea of the type of tubing I would need to find, if I need such high temperature rating. So far this type of tubing I've only seen for sale here in much longer lengths which has been quite frustrating.
    I will probably just try the cheap stuff and see how well it holds up, then try this if/when I find it's neccesary. :)
     
  19. battery

    battery Member

    you could possibly try a short lenth of bx cable insulation. it is the old style spiral metal wire insulation. would have to be thick at least 3/4" or 19mm so you dont have restriction. also the direction of the tube would matter. it wont get too hot and has its own baffling. ;)
     
  20. butre

    butre Well-Known Member

    As far as exhaust goes, adding length and extra baffles is the best way to quiet an engine down. The biggest head turner about these things seems to be the way they look rather than they way they go though, so I would suggest making or having made a good vented frame fairing, say it's in the interest of aerodynamic efficiency and just about anyone will believe you.

    Cutting gear chatter noise down is probably not necessary, a lot of regular push bikes make some chatter of their own anyway. Intake noise is probably a bigger issue, and a reed valve should cut that down sufficiently. Other than that the biggest head turner will be if you're going 30 miles an hour without touching the pedals, so don't do that if stealth is your aim.
     
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