This weekend I had a chance to change my 2008 Triumph Bonneville front sprocket from the stock OEM 18 tooth one, to a 19 tooth version purchased at British Customs (Part: BC704-001-19).
I had to purchase a motorcycle jack in order to complete this upgrade, but that was something I needed to do anyway. I ended up getting one (and ratchet action safety straps) from Harbor Freight Tools on sale, and it worked great!
Once I had the motorcycle up safely and securely on the jack (with the help of the safety strap), I removed the front chain sprocket cover, then the rear foot pegs and mufflers, and chain guard.
Although not required, I also removed the seat, side covers and gas tank just to do some other small maintenance tasks and cleaning.
At this point, I realized I did not have the correct 36mm socket to remove the front sprocket retaining nut, so I went to my local Sears and purchased a 1/2″ drive Craftsman socket. I flattened the washer that was holding the nut in place using a hammer and chisel.
The manual says to have a partner stomp on the rear brake while applying pressure to loosen the nut. I did not have this option, so I inserted a 2×2 wood bar between the spokes on top of the swing arm to keep the rear when from turning. This enabled me to loosed the retaining nut.
Once this was removed, I then loosened the rear wheel axle nuts which allowed the wheel to slide forward. loosening the chain tension. This allowed me to remove the front sprocket, then spend some time cleaning and lubricating the chain. I then turned the rear wheel alignment adjuster bolts forward 5 complete turns. This allowed me the extra room to installed the new sprocket on the shaft, using the original nut and locking washer.
I then backed out the rear adjuster bolts until the chain was the correct tension, and tightened the rear wheel axle bolts.
After some other maintenance (adjust spark plug gap) and cleaning I put everything back on the bike: gas tank, seat, side covers and sprocket cover. I left the chain guard off. I carefully lowered the bike and removed the jack. After visually inspecting everything again, I took it for a short test run to make sure everything was working properly.
This morning I had a chance to ride it 10 miles to work on side street and the highway. I did not notice any lack of power to start in 1st gear, but did notice the changes in shifting at different RPM’s. Most noticeable is the change at higher speeds. It have more power at higher speeds as the engine is turning slightly less at those speeds. I’ll be interested to see if this affects my gas mileage.
Hope this helps you if you ever try this change. Let me know if you have any questions, or a different experience or outcome.