Custom Exhaust Build Part 1

Discussion in 'Video Gallery' started by 66cc, Oct 31, 2015.

  1. 66cc

    66cc New Member

    Check out our Custom Exhaust Build This is Part 1. "What were Working with"
    Like, Comment, Subscribe. Stay tuned

    Last edited by a moderator: Dec 15, 2015

  2. mikedabomb

    mikedabomb Member

    I would highly suggest moving the clip on the carburetor's needle down a notch or two. It is running lean without a doubt. Those rpms shot up and stayed there for a while, and a properly tuned 2t motor will drop rpms faster and have a snappy/crackling idle with a very pronounced combustion that makes a "ting ting ting tating ting" sound. Right now, it's a mumble wine because it's lean. Sometimes the restrictive exhaust gets rid of the popping sound but there's no visible oil and those rpms stayed higher than where they should be. Look at how this kx does not pop, it has a very soft hitting sound/wine. It also revs to the moon and stays there. No visible oil coming out the exhaust either. That will eventually be a blown up bike, seized at best. Here's what a proper mixture sounds and looks like - hear how it makes a popping noise and emits a little oil? I had a kx100 and it made the same poping sound when properly tuned, the engine displacement is not a factor here as any lean 2t engine will sound vastly different from a rich 2t. If you are running a rich oil mix and still don't see oil out of your exhaust, the air/fuel mix is very lean. I'd get the mixture right before doing anything else as adding a pipe might make the problem worse and you'll wonder why the pipe made it do (xyz) when it was really the lean air/fuel ratio screwing things up.
  3. 66cc

    66cc New Member

    Excellent insight, quite a broad array of 2stroke knowledge you bring here. So glad to see this, I myself prefer 2strokes for their higher power per cc and simplicity, not gonna lie, also love those oil gas laden exhaust fumes!

    Ive noticed how messing with the exhaust has a big impact on the engine as a whole, idling, reving power, top end low end etc.

    Also Ive never gotten too much success with needle positions; they end up either running lean or rich etc.

    Stay tuned when I change the different Exhaust and you see how the bike likes and dislikes different setups.

    Good day brother.
  4. Rolling2High

    Rolling2High Member

    He has anybody but the tuned port exuast? Demon something. We'll anyway it's has low torque but took my top en off. I'm thinking of putting a hole or 3 in the end if the exaust mini pinoe it can get air out. I can tell a 5 m p.h. loss from the old factory. The top weld has broke on it .
  5. KCvale

    KCvale Motorized Bicycle Vendor

    If you want to make a custom exhaust for your 2-stroke you have to understand how they work, and how big a part exhaust can play.

    Watch this for awhile and follow the green gas/air mix flow.

    It has no values like a 4-stoke...


    The way 2-cycle motors work is to try and do the exhaust and intake in the same up/down/up cycle of the motor with nothing in the way so it can fire on each top visit, and because of that a lot of unburned (green) fuel goes out the tailpipe.
    An Expansion Chamber (on the right of that animation), named for its peculiar looking fat section, is tuned to push that unburned fuel back into the cylinder, thus giving each cycle an extra Boost of fuel.
    ~$60 to ~$80.

    PROS: In most every case the performance of a motor is drastically increased with a properly tuned Xchamber, and the #1 pure performance booster in my book.
    CONS: For the 'shock wave' of the exhaust cycle to be perfectly timed with the motor to do its job the pipe needs to be tuned. Many pipes are one piece so they need to be for the right sized motors, other types can be tuned to you needs and power band desire.

    I hope that helps.
  6. Arty

    Arty Active Member

    Is that illustration you provided above ever useful!!
    Thanks for sharing it. Although I already had a basic understanding of the concept, the illustration really helps.
  7. KCvale

    KCvale Motorized Bicycle Vendor

    You're welcome Arty.
    Here is another I find useful, just turn the volume down if you are not a Rocky movie fan.

    Last edited by a moderator: Dec 15, 2015