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Old 12-21-2011, 02:57 PM
5-7HEAVEN 5-7HEAVEN is offline
Motorized Bicycle Elite Member
Join Date: Aug 2008
Posts: 1,912
Default Re: what did you do to your motor bike today?

I'm doing major preventive maintenance while on vacation.

New chains haven't arrived yet, so I scrounged up some 8mm pieces and assembled one. This will be my spare for now.

Gearbox is leakproof with no runout or wobbles. Seal is good. It's not as noisy as it was earlier this year. Clutch drum shows normal wear.

The 11t sprocket is showing normal wear; backlash between splines is increasing a smidge. They cost $8, so I'll order two more for spares.

The circlip that secures the 11t sprocket to the gearbox spline wore out and looks like a fishook! This is an engineering design defect; the sprocket diameter is too small. The 8mm chain passes so close to the snapring that it rubs against it at times, wearing one of the circlip's "eyes" to a sharp hook.. This is the SECOND time I'm replacing it in two years. A 14t sprocket would prolly have enough clearance between the snapring and the 8mm chain. However, if I did not install a larger engine chainring sprocket, it would drastically reduce my gear ratios from 46.36:1 to an ineffective 36.43:1. With a 14t, replacing the 72t with an expensive, hard-to-get 92t sprocket would change first gear back to 46.55:1. Their diameters would increase from 7.2" to 9.2", which MIGHT present clearance issues at the chainstay frame.

The expansion pipe's belly positions itself very close to the gearbox sprocket. If the snapring were to fail, the pipe would keep this sprocket and chain from falling off.

It's not worth paying $100 or more, replacing the 11t/72t sprockets to 14t/92t ones to cure this factory miscue. Besides the expansion pipe, a simple gear retainer could be fabbed to keep the sprocket from slipping off the gearshaft. A broken 9/16" circlip is only 40 cents, and is so easy to replace.

The Tanaka 3-piece expansion pipe needs to be better sealed at the slip-fit flanges. This is the reason why this exhaust is considered a loud pipe. With the correctly-sized sections of silicon hose, this engine-specific exhaust system should become more quiet. The pipe's belly is chafing on the 8mm chain 4" below the gearbox sprocket at times, so I'll need to correct that. The air cleaner is also chafing against the chrome resonator, so it'll need clearancing. This engine and pipe were engineered to fit on a gokart and a scooter, not a bicycle. Fitment is needed.

When I ran over an object on the wet road, it also damaged the chainring sprocket's freewheel. That caused even more sprocket wobble than normal. A used Chinese freewheel has been temporarily installed, while an SBP HD freewheel is having its 5-bolt pattern drilled to match the pocket bike sprocket's 4-bolt pattern.

Parts needed are three short pieces of exhaust hose, An 11t sprocket, one circlip and lube for the cables. I should also service my K&N air cleaner.

Preventive maintenance needs to be done on a regular basis, especially for a daily commuter.

Last edited by 5-7HEAVEN; 12-21-2011 at 09:02 PM.
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