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Discussion in 'Motorized Bicycle General Discussion' started by xlite, Sep 17, 2009.
Pablo that is without the extra muffler.
Hey Charged, this might help you with the neighbors
One of the things I really like about the SBP system is it's "tunability" - not just performance, but for fit and even customization. The silencer is indeed a glasspack, which is wonderful for flow... but you do need to periodically replace the fiberglass packing as it gets saturated with oil and carbon, particularly with a 2 stroke. Not to worry, it's not something that needs to be done frequently and it's a simple matter of drilling out four rivets and repacking it. Standard household fiberglass insulation works fine.
When I got mine my first thought was that the silencer was a touch on the small side and indeed, it didn't silence much. I actually wondered if there was any packing in it at all. The addition of a high temp rubber hose served well enough to reduce the "bang" and I kinda forgot about it. I noticed we had a pile of 2" OD aluminum conduit at work so I grabbed a chunk and brought it home... and promptly forgot about that too lol
I got bored last week so I drilled out the rivets and pulled the silencer apart, cut and "polished" the 2" conduit, made a tube extension out of heavy mesh screen, wrapped it in fiberglass and reassembled it - replacing the stock 3 1/2" silencer with a 6" one.
It worked so well I'm going to build another as long as I can without hitting my kickstand. Noise levels are hard to describe ofc - but now when I pull my clutch in at speed and the engine drops to idle I cant hear it at all anymore over the road noise and chains, the first time I did that I thought it had stalled lol
Thanks for that info BA. I wasn't aware the silencer had glass pack. Maybe my 50:1 has saved me from clogging so far. I wonder how one of those lawnmower silencers on the end compares with your 6" aluminum deal.
Well it's prolly jus' semantics and ya know this - but the "clogging" is limited to the batting loading up w/oil and not silencing as well as before. I wanted to clarify this just in case someone was worried about a loss of performance, which is not effected ofc.
I have no idea how well the lawnmower silencers work insofar as noise, but I suspect they're a baffle design and I'd bet the interruption of flow increases back pressure and effects performance. A glasspack absorbing the concussion wave a bit but allowing a straight pass through of the exhaust wouldn't effect backpressure to any significant degree regardless of length... within reason ofc.
Still, I wonder... mebbe the lawnmower style would be quieter *shrug* I suppose someone could try both for the uber-stealth approach, but I for one am a lil too performance greedy to try it lol
Barleyawake, I will have to try that out. Right now I am breaking in
a 69cc slant head plug style with the new style carburetor at 25:1
break in mixture. I have about 1 gallon run through it so far. What
amazed me was the plug, it is choclate brown with no 4-stroking.
I tried to put the SBP tuned pipe on the big oversized tubing on the
Micargi 7-speed and the 2.5" copper pipe is to long to let it match up with
the engine to bolt on. I already have 1/4 inch cut off the copper tubing from
trying it out on another bike. I would have to take quite a bit off the tubing
to make it work on this bicycle. Not sure how that would effect performance
or even cutting the copper tube down that short.
I wouldn't worry about it too much - I chopped mine right down to get it to fit my bike as snugly as possible and there was still quite the performance gain. While I'm sure different header lengths does effect where you get the most gain, it does increase performance across the entire powerband, quite significantly in comparison to stock.
So while it would be nice to "tune" it to where you wanted the most gain, it's not like you lose gain if you hafta chop it down. I prolly cut out a total of 2" from various sections (about 1/4" at a time with test runs in between) with no perceivable loss.
You have another new motor? lol - how many does that make now? Color me jealous
I picked up some copper tubing at Home Depot to experiment with and found the length of the copper tube had little effect on the power band. Doubling the length and eliminating it completely made no big difference in acceleration or top speed. My theory is you would have to make significant changes in length of the header pipe to do anything. The copper tube does not play a big part in this.
I realize this goes against everything Pablo and Ghost say here and on their site but it is what I experienced with my Zoom 80cc slant.
It really doesn't go against what we say it is simply that the changes are very minor and you would need to do extensive testing with either a dyno or timed acceleration and top speed runs to tell the difference. So yes changing the length plus or minus 2 inches from stock will be hard to tell much of a difference unless you measure it accurately. But if you change directly from 2 inches shorter to 2 inches longer than stock there should be a perceivable difference. 4 inches is a lot on a tuned pipe.
A note on the additional muffler, it does not have a baffle in it but is just an additional "glass pack" style muffler so it really does not effect performance but does quite it down a fair bit. Most customers say that the pipe run stock is slightly louder than stock, and with the additional muffler is slightly quieter than stock.
If you still have it i will buy it,lol