Skeptics Review of SBP Tuned Pipe
Well... I finally went for it. The famous tuned pipe kit. I promised I'd never spend more for a hop-up than for a new motor. But it was highly recommended by a couple individuals here whose opinions I respect and only $1 over my limit sooooo..... turned out to be well worth the investment.
The install took less than a half hour with a Zoom 67cc slant on one of my Magna Glacier Point bikes even encountering a couple small issues.
The first was holes on the flange were too small for standard HT exhaust studs. Only took a minute with a hand drill to fix that. Might suggest doing that a service to customers or at least mentioning in the manual. At that point I noticed a defect in the flange surface that might cause leakage (see pic). SBP promptly responded to email with suggestion to machine the surface (yeah right!) or send it back for replacement (yeah right!). I decided to simply plow ahead and see if and how bad it might leak.
After a few minutes of fitting and twisting it became apparent the stock mounting hanger was not going to allow use of my regular kickstand. The manual mentions switching to a different type kickstand. Not an option for me. So out with the kit hanger and in with some galvanized baling wire(see pic).
Positioning the pipe is a little tricky due to clearance issues between front tire, left and right pedals, and rear tire. It also initially wanted to direct exhaust onto the rear rim. A few minutes of twisting and re-aiming came up with a reasonable compromise. Cutting an inch or so off the copper tube solved front tire clearance. Bending the pipes original pocket bike mounting bracket out of the way helped with right pedal contact. It still hits occasionally so I'll probably cut it off completely at some point.
Next problem was the hose clamps are too small. They were both the same size and barely fit over the small end of the silicone tube and not even close to fitting over the fat part. Fortunately I had one of those Harbor Freight assortments and the biggest ones fit. Now we're ready to go!
It was immediately apparent more low end power was available. However the motor ran out of poop and made that "too lean" sound at WOT. And I noticed full choke don't stop the motor any more which is the only way I ever shut down. Needle clip down one notch fixed the choke. Replacing my "wide open filter" (see pic) with the stock air filter cover (see pic) took care of the WOT problem. I may investigate opening up the jet from it's current .028" and taking the stock filter off again later.
Once more with feeling! Even before getting to "dynamometer hill" the increase in low end torque was obvious. Even with the 36t sprocket ($12 BGF) it was now possible to get rolling w/o pedalling and took much less time to get up to speed. Evident beyond the realm of placebo effect. Prior to the install I did a test run up dyno-hill at the expected 23mph. Now it zipped up at 27-28mph. The GPS don't lie.
Noise was significantly louder than stock. Part of this may be due to leakage caused by the flange defect but I suspect SBP sells that lawn mower muffler option for a reason. After the test runs I put on the smaller silicone tubes but no real change in sound. Like mentioned by others it now has that "dirt bike" sound specially when throttling down. No room to stick a muffler on the end because of kickstand clearance but not as bad as a stock exhaust w/holes.
IMO only room for kit improvement might be bigger hose clamps and mentioning undersized flange holes or even drilling them out. Maybe remove the original pocket bike mount too. Easy for a machine shop. Maybe others don't have problems here.
I'm not sure how much of the power increase is due to the leak and how much due to the tuned pipe. In any case well worth the $78 in terms of engineering and materials. I bought the same exhaust w/o fititngs from another vendor last year for about half that but, after assessing effort needed to adapt to a HT, put it on the shelf. A wise move considering how easy it was to intall the SBP kit. Definitely a keeper.