Sunday, May 1, 2011

CB650 Top End Overhaul

Our cafe racer is one of those bikes that runs like a champ and then when you decide to fix one issue numerous others start to appear and have to be done immediately. We have only been left on the side of the road once due to our diligent maintenance but this fix hopefully curbed a much larger issue about to appear.

After one afternoon of riding I noticed a breathing or weezing sound coming from the left side of the engine. I shrugged it off thinking the carbs might be a bit clogged and needing some cleaning. As it turned out, they needed cleaning again but the bigger issue was that a top bolt securing the valve covers on the cases had stripped loose and shredded the threads. Initially a helicoil was going to be the first option but doing it right required a top end tear down to avoid any possible drill shavings in the engine compartment or over drilling into the rocker arms.

We pulled the spare engine out from the under the fab table and tore down that top end as well to trade out for parts. After polishing up the cylinder head and cleaning it up completely the switch over was complete without having to redo any threads via helicoil or going to a larger bolt size. Having a spare engine for parts has been absolutely necessary for this bike as its so hard to find parts for these engine years as they were only around from '79 to '82. Once we get our new carb kits in we can pop in the new gaskets and get the vacuum pressure checked and be back on the road. Hopefully we can finally hit the fastest speed on this yet, pushing for 85 - 90 mph. Next upgrade will be a taller sprocket which should get us there.