Chain drive "case saver" warning.

earthmover

opinionated, me?
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Some of you may already know about this, but those that don't may remember this and save themselves some grief in the future. The bike in question is a Honda CRF250x, though it may apply to any bike that has a "case-saver" fitted. Those of you who don't know what this is, it's a c-shaped piece of metal which curves around the gearbox sprocket in line with the run of the chain. Should the chain break, it directs it downwards away from expensive and difficult to fix items like the timing cover and clutch actuating arm. If you don't know what a gearbox sprocket is, then stop reading now.:augie
So, here's the scenario:
After an enjoyable day trail riding, I loaded the bike into the trailer. It had been a fairly wet ride (It often is in Wales) and the bike was caked in mud. As is usual for me, I took the trailer to work the next day to use the wash bay in my lunch break, so as not to deposit large amounts of liquid scenery on my driveway. When I undid the straps and tried to roll the bike backwards out of the trailer, there was some resistance, as though it was still in gear. I ensured it was in neutral (again) and tried again. Still, a reluctance to roll backwards. "Perhaps the brakes have stuck on with all the crap", I though, and gave a fairly substantial tug rearwards on the bars. That worked a treat, as with a jerk the bike shot out of the trailer with me struggling to keep up.
Washed off, usual quick checks, chain, air filter, brake pads, wheel bearings, nothing hanging off, back in the garage till the next ride. (It is a Honda after all. In a previous life, I would have done a virtual strip down after every ride, but then I only had one bike, and I had a wife. Now I have three bikes.:D)
Fast forward to my next ride, and as I drop the bike off the step-stand to load it into the trailer the night before, I find oil on the platform. "Must have overdone the air filter oil", I thought to myself, touching it to check for stickyness. Not sticky. Runny, and greenish, very much like gearbox oil. Not good.:eek
Peering up behind the gearbox sprocket, I can see it looks wet and oily, giving the indication of a leaking shaft seal. Undo the top sprocket guard bolt, to find that the guard then falls off in my hand. The bottom bolt has sheared off at the crankcase, leaving behind a small hole from which vital fluids can escape. Much speculating with friends over a glass or two of falling down water led us to the conclusion that a small stone must have fallen onto the chain whilst travelling in the trailer, and my attempts to move the bike backwards has jammed it into the case-saver, and my ham-fisted snatch on the bars was enough to break off the mounting (the bottom lug has broken, not the top as would have if the chain had been travelling in it's usual direction.)
The immediate solution was to clean the area and apply a small blob of metal repair putty, pressing in just enough to get a grip on the hole without filling the crankcase. This has since done a 90 mile trail ride without leaking, so I will consider it fixed.
So remember, if your bike won't freewheel backwards, it may be for a good reason.:thumb
Mark
 
that was a useful read. :thumb2
Thank You.

i had a honda 400/4 that locked its rear wheel.
though in my case the layshaft in the gearbox had snapped in two, rotated and ruined the crankcases.
which i kinda suspected when i drained the oil and it looked like.... metal flake paint! :eek:

its the little warning signs that if you know in advance can save Sooooo much grief later.
 
Particularly useful info, Mark. Thanks.

I've got a CRM & just fitted a casesaver to it after getting a chain wrapped in between the front sprocket & the swingarm. I only prevented the chain snapping by having a quick clutch hand... Then we had to strip the chain/sprocket/rear wheel down on a snowy hillside in the York Dales. It could have been so much worse, so I got the casesaver.
 
Chaps, can I take it that you have all removed the front sprocket cover casing and not refitted it, leaving the front sprocket including a case-saver visible?
Two reasons, one being the front sprocket including case-saver are visible :P, and two it that it helps to prevent the build up of mud/stone/grass, etc, carried around the chain during riding.

Timpo.
 


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