Tuesday, 6 December 2016

CBF Clutch Fix - Part #1 - Taking it Apart

Earlier this year I took my Honda CBF250 off the road for its annual "spring clean". The little bike is my daily transport and runs through the winter so is affected by exposure to rain & salt etc. I didn't post about this since it was just the repeat of things I've done in previous years.

The bike, though, has a niggling problem. There is a whine from the engine. In the past I've put in earplugs and ignored it. But riding it again after a couple of months off I realised that this was bad enough to require attention. The whine was becoming a shriek. After a careful listen I was sure the noise is emanating from the clutch. It sounded like something metallic rubbing together. The bike has done 56,000 miles. That's a lot for a 250 but the bike is otherwise in good condition. I've didn't miss it over the summer - I've got my FJ1200 and new SV650 - but for winter I need the little bike on the road.

I'm comfortable enough taking engines apart. But, thinking about it, it's a while since I've had to do any engine work except for routine maintenance. In fact it would be in 1988 when I stripped another Honda 250 single, a CB250RS, to replace a broken gearbox selector fork. (Except for MZs, but they are something different) 

Like most bikes access to the clutch is simple. Drain the oil, remove the oil pipes, undo the screws and off it comes. 

There is a coarse oil filter inside

You need a special tool to hold the clutch body while removing the centre bolt. This is available but because this is (hopefully) a one-off job I made one.

Removing the clutch centre bolt

Examining the internals everything seemed ok except for the teeth on the clutch body. These had severe wear, to the point of having little flakes of steel scuffed off. This is a bit strange. There doesn't seem to be anything causing the damage. The bike has always been run on fully synthetic oil. The 250 is worked hard but there's only 22 bhp going through the gears. 

The crankshaft gear had slight scuffing
The clutch basket had some wear but it wasn't affecting its operation

The clutch plates were at the top end of the thickness range, ie there has been zero wear in 56,000 miles!

While it was off I took the opportunity to paint the engine casing.

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