Well that is a little disconcerting...

Sorry for the delayed post. I try to get these out on Fridays so I can work on the bikes over the weekend and write up the next one. This past weekend was a long weekend and my house was being tented for termites so not much happened in the shop. Have no fear, I have a double featured week this week and you can expect another post later on. Enjoy!

Another box from a back-and-forth Internet forum deal arrived a couple of weeks ago. This time I worked a trade. Technically the trade isn't over with yet as I have to finish my end of the deal. By the time you, the adoring My Motorbike Obsessions reader, read this I should have completed the deal. This is a follow up to an earlier post where I swapped my countershaft sprocket only to find a surprise waiting for me within the confines of my sprocket cover. This time something a bit more scary awaited me when I pulled the sprocket cover off for a look. See what happened below. 

I didn't take a picture of the box this time around. I figure that delivery box pictures may be getting a bit old. I mean who wants to look at a box. Here is my small Harbor Freight Ultrasonic Cleaner in action going to town on the contents of the un-pictured box. Inside the soothing bath of degreaser and hot water is an OEM Ninja 250, 14 tooth countershaft sprocket. If you clicked the link above to my earlier sprocket escapade you would have learned that I found that a previous owner had put in a +2 16 tooth sprocket for better highway cruising rpm. Right now I'm running a -1 13 tooth sprocket for better get up and go out of the corners. After two runs at Chuckwalla I wanted to experiment with gear ratios by getting a 14 tooth stock ratio sprocket for more options. 

Here are the three sprockets. For Chuckwalla, a track is more open and flowing, I think the 14 tooth is the way to go. For a tighter track like The Streets of Willow, the 13 tooth might be better since that track has more low gear slow corners. The smaller front sprockets will let the engine rev a bit higher for a given speed. Since the Ninja doesn't make much torque in general and virtually none in the lower rpm band, dropping the tooth count on the countershaft sprocket is the way to go. You can do the same thing by putting on a bigger drive sprocket on the rear wheel. That takes much more effort to do. I'd have to remove the rear wheel along with 6 bolts and lock washers every time I wanted to change ratios. The countershaft sprockets can be removed by loosening the drive chain, removing the sprocket cover and removing two bolts and a sprocket washer. It is so easy do that I could do it at the track with minimal tools between sessions if I so desired.

Here is the bike on the paddock stand. An 8mm socket gets all three of the cover bolts off as well as the shift lever pinch bolt enabling access to the countershaft sprocket. After loosening the drive chain adjusters and the rear axle nut I easily moved the rear wheel forward which lets me pop the chain off the drive sprocket. 10 minutes is being generous with how much time this took. While the new 14 tooth sprocket was enjoying its spa day, I did all of the wrenching needed to make the change. I cleaned off some chain lube gunk from the sprocket cover and went back to remove the 13 tooth sprocket from the bike.

The first thing I noticed was that one of the bolts holding on the sprocket washer was missing. Then I noticed that most of the sprocket washer was also missing. In one of the two track days since I installed the 13 tooth sprocket all of this damage occurred. The inner shape of the die cast sprocket cover makes a bearing type surface for the transmission shaft. When the cover is bolted to the engine case, there is nowhere for the sprocket to go if these parts were to break. I dodged a bullet here since the missing piece of the sprocket washer could have possibly jammed up the drive chain causing the rear wheel to lock up. Maybe I need to create a better post track maintenance checklist to catch things like this before the next track day.

In this picture you can see the inside of the sprocket cover. There is some scarring and a bit of gouging on the outside, front face of the countershaft sprocket and chain would be spinning. I don't have a picture from the first time I removed the cover to add in the other sprocket. I would imagine that this kind of damage might make a little noise. I'd also imagine that loosing a bolt and shredding my sprocket retainer would also make noise, but I don't remember hearing anything from that either.

Hear is the new retainer next to the shredded remains of the old one. I installed the new retainer and bolts with a dab of blue thread locker to ensure that this doesn't happen again. I bolted everything up and cleaned and adjusted the chain making sure I had plenty of slack for the track. While I was at it, I went over my pre-track day checklist to eliminate any other surprises. I'm am going to try the 14 tooth countershaft sprocket at my next track day at Chuckwalla in two weeks. The bigger sprocket will mix well with the open sweeping curves of the counter clockwise rotation. It should help me keep my momentum up and beat the bigger bikes through the corners. They will get me on the straights, but I should be able to dance with them in the curves.

Stay tuned for more posts coming up. I should have one done this Friday and another ready for next week as well. I have a track day with a good buddy coming up over the Thanksgiving weekend and maybe some other events in December. It should be a fun filled winter for My Motorbike Obsessions!

Blue