Exhaust How Do I Seal An Exhaust Slip-Fit Connection?

Discussion in '2-Stroke Engines' started by 5-7HEAVEN, May 21, 2011.

  1. 5-7HEAVEN

    5-7HEAVEN Guest

    I have a Tanaka 47R 2.8 hp racing engine on my Diamondback bike. After recently installing a Tanaka three-piece expansion pipe, I am plagued with leaks at three separate slip-fit connections. The head pipe bolts nicely onto the cylinder, so that's not a problem with its flange gasket. This 29mm pipe then slip-connects to the neck of the fat chamber. This leak is 24" below my chin. Exhaust gas leaks there and burns my eyes, so I bought a VERSACHEM high temperature exhaust bandage wrap kit(for cars). It's an epoxy/fiberglas mesh/aluminum tape combination I used to wrap and seal the large slip-fit pipe below my chin. At the pipe's exit, there's a 15mm slip-fit which I also wrapped and sealed.

    The last slip-fit is from the silencer's tip to the OEM muffler. There is a slip-fit adaptor w/retaining spring, but it's designed to "bottom out" onto the silencer. This leaves no overlap to seal. I just know it'll be a waste of time and materials to use the fiberglas/aluminum tape wrap. I also bought a CAR-GO high temperature exhaust repair kit. It looks like liquid in a bottle that turns hard like epoxy. This MIGHT work, but not sure.

    Does anyone have any suggestions how to seal this connection? The outside diameter of the flange adaptor is mm. Maybe a high-temperature oil seal like something from an old VW pushrod tube would fit and work.

    Any suggestions?

    Here's the Tanaka engine and the three-piece pipe:
    http://wikiscootia.wikidot.com/tanaka-47r
     
    Last edited by a moderator: May 21, 2011

  2. Bugsy

    Bugsy New Member

    Take it to a welding shop and have it brazed.
     
  3. Oddzball

    Oddzball Member

    Or you could braze it yourself. Get a torch, a block of metal, and some solder. takes 5 minutes.
     
  4. 5-7HEAVEN

    5-7HEAVEN Guest

    Thanks for the suggestions, guys.
     
  5. motorpsycho

    motorpsycho Active Member

    well, you would need an acetylene torch (not a propane torch because it will not get hot enough),and some brazing rod with a flux outer core.
    not sure why you would need a block of metal tho???
    heat the 2 peices of pipe at the joint until the brazing rod will melt when you touc it to the surface. it's just like soldering, except you are using brass and much higher heat.

    normally tho, slip fit pipes are held together with springs and the 2 pipes are usually a pretty tight fit. each peice of pipe should have a couple of hooks on them, you stretch the springs and hook them onto the hools on the pipes.
    but, these springs are usually very stiff and hard to stretch without a special tool.
    brazing would be the fastest, easiest and best way to make the joint leak proof.
     
  6. 5-7HEAVEN

    5-7HEAVEN Guest

    Slip-fit connections are tight fit, but not air tight. This is good enough for rear-mounted gopeds, but not for center-mounted engine mounts where exhaust leaks are nauseous to the rider. Besides, since this pipe was made for gopeds, the mounting and fitment is a compromise. Pipe fittings are maybe 45* off, so the springs' hooks don't line up. They hook up, though and do their job for a rear-mounted engine, but not for front-mounted drive setup..

    Brazing is the best way, but not fastest or easiest or cheapest. Labor charges are outrageous for machine shops. I'll need to find a competent welder at good rate. I'm going to wait until the other slip-fit repairs fail. Hindsight is always 20/20, or I would have had it welded to begin with. The exhaust repair kit was cheaper than the high cost of welding, so I had to try the kit first.
     
  7. Most large towns have a muffler shop of some sort, They have much experience brazing and welding thin wall pipe and probably will charge a lot less than a specialized welder. You can rent a torch and tanks to braze it yourself, but for such a small job the muffler shop will be cheaper. An independant shop, rather than a large chain like Midas or Monroe will probably be more open to small jobs.
     
  8. rustycase

    rustycase Banned

    Would RTV red accomplish the leak fix effectively?
    It would provide any strength, but should seal it.
    Good luck
    rc
     
  9. 5-7HEAVEN

    5-7HEAVEN Guest

    TRV red? Okay, might try that.

    SBP uses short pieces of silicon exhaust tubing to seal their expansion pipe's slip-fit connection. Since the Tanaka engine's head pipe is much larger than HT engine pipe, I'll need to search for larger-diameter silicon pieces. A piece of 1/2" silicon exhaust from davesmotors might be good for the endbleed's connection.:idea:
     
  10. Oddzball

    Oddzball Member

    Just how i do it. I used to seal holes in gas tanks. I had a metal block/bar i would heat up, then use regular old solder touch the heated block near the hole, and melt it in to close the holes. Did it with radiators too.

    Not sure about exhaust as i would just use a welder normally, but you could technically just use a soldering iron and some solder. But I am not sure about if the exhuast owuld get hot enough to remelt the solder.
     
  11. DuctTapedGoat

    DuctTapedGoat Member

    Solder would melt under pressure with the heat from an exhaust.

    It wouldn't take a full on welder, I have an Oxy-Mapp rig, cost me just a few bucks. It's just hoses with valves and a tip, but for the simple stuff I do, it's really enough.
     
  12. motorpsycho

    motorpsycho Active Member

    the way you are describing your method doesn't sound like it would work very well to me.
    you want to heat the actual area(hole) that you are trying to solder.
    by heating the metal block that you are talking about, and not the area, the solder won't stick to the hole for very long. it may cool down, stick and become solid, but that's a cold solder joint. a cold solder joint will usually fall off after awhile. in order to solder correctly you have to heat the area that needs to be soldered, and the heat will draw the solder into the hole. the heat around the hole will assure that the solder and the metal will cool together and become more solid. (just watch a plumber "sweat" copper pipes.)
    brazing is like soldering but with a higher heat. to get good strong solder joints you have to use a propane torch, silver solder and acid flux. resin core solder is not as strong and won't stick to some metals.
    brazing rod has an outer shell made of flux, that melts when it gets hot enough and this makes the brazing rod (brass) stick to whatever you're brazing.
     
  13. motorpsycho

    motorpsycho Active Member

    on the other hand, correctly applied silver solder will not melt under the heat of exhaust. I silver soldered these 3 rings to my pipe to cover up a weld, and that was last summer and 150 miles ago. the 3 rings are right at the hottest point on the exhaust. I have no idea if silver solder would hold up on a slip loint tho because you would be trying to seal the pipes. IN this case, these rings are just cosmetic and the 2 peices of pipe are welded together, which is what's doing the actual sealing of the joint.
    [​IMG]
     
  14. DuctTapedGoat

    DuctTapedGoat Member

    I should have clarified - standard electrical rosin core solder won't hold up - especially if you tried to do it with a standard soldering iron, no matter what you did, the joint would be cold. With the heat and vibration the exhaust receives, a cold joint wouldn't last a hundred miles.
     
  15. retromike3

    retromike3 Member

    silver works

    I used silver to replace the copper pipe I had in my SBP tuned pipe. I was melting the copper so I replaced the tube with a steel pipe of the same diameter. Put it on and have had it going for about 15 hours (according to my new tack) I still have one place that I did not weld(the other joints have brass) on my pipe in case I needed to "tune it" a bit more.

    I went to the hardware store and got some heat resistant tubing that is good for four hundred degrees. Its been holing together for the same time. It was a bit of a pain to slip on and I do have two clamps on the tubing, just in case.


    mike
     
  16. rustycase

    rustycase Banned

    I like your setup, Motorpsycho... will look for other pics of your bike...
    rc
    sry, that's an off-topic!
     
  17. skrew37

    skrew37 Member

    what diameter of the high temp silicone hose is needed for exhausts in general? and if using copper, what size are those couplings?
     
  18. DuctTapedGoat

    DuctTapedGoat Member

    7/8" - 1" Id
     
    Last edited: May 24, 2011
  19. skrew37

    skrew37 Member

    Thanks. Did anyone ever hear of GatorBITE couplings sold at lowes? They're compression fit (just push the copper pieces into them and they "bite" on also creating an airtight seal. I looked up the o-rings that are inside and they're rated to 250 degrees. I found the same type of o rings (red silicone) that are rated to over 450 degrees. I wonder if your could just pop out the stock ones and replace with the higher rated ones. Could these could work for sealing up an exhaust? The look would be very clean, especially with their copper-mirror finish...hmm...
     

    Attached Files:

  20. motorpsycho

    motorpsycho Active Member

    I have never seen those (and i got to Lowes quite often).
    i would guess that the original o-rings wouldn't hold up because the exhaust can get hotter than 250, especially right where it exits the engine.
    if you could replace those with the 450 degree silicone ones, they might work.
    this might be an easy wat to make a custom exhaust, but it may end up looking like a plumber made the exhaust for you.
    on a certain style bike with a certain look, they might be right at home (think rat rod).
     
Loading...