Bonneville America Forums Forums Technical Forums General Tech Chain gaurd came off at 60 mph....

While riding home from work tonight (65 miles through Los Angeles traffic) I hit my offramp at 60 mph and heard a brief odd noise, then a tug in the seat/back tire area, then no power. Shut the bike down, grabbed the clutch and coasted to a stop. I lifted my visor (full face Shoei) and heard a metal clank clank behind me. Get off the bike and see my chain is off the rear sprocket, drive side of tire is
a little melted from something rubbing it (chain guard). I got the twisted hunk of chain guard out of the traffic and kept it for display purposes. I got the chain back on the sprocket and checked out the tire for cut marks. (Will buy a new one anyway). Fired up the bike and very easily slipped it into gear. So far so good. So I take off down the road for the last 20 miles ride home. No problems, thankfully. Bike rides good so far. Will look into it tomorrow under sun light.
Considering what could have happened, cut tire at 80 mph, wedged chain, broken pieces and very possibly broken ME, I'm very fortunate. Odd thing was I just check over the bike pretty good and didn't feel, or see anything the two days before. Seems like the chain guard went from secure to loose to flying off at speed during my ride home. Some much for the "smoothness" of I-5.
Check the guards and ride safe!
Steve

With as much as I have heard about this happening lately, it should be a warranty thing.

Soren

Like Soren says, this has been reported before. Any way to tell if yours broke or if one of the screws came loose?

Glad you came through this o.k. - I have a spare black guard if you need it. I'd question the dealer about this one. I'm going to ask mine next time I get over there...

Look at the rear attachment point. Seems that this is the faliure point.

Chain guard failure & customer service response

Could this be caused by chain being too loose and slapping against the chain guard during acceleration/decelration?

From the thread I linked to above, a metallurgical issue seems to be more pertinent. Not with stock chain guards, but with chromed replacements. The rear attachment point seems to crack. Now about your question of the chain being too loose and slapping against the chain guard during acceleration/deceleration. Time for a new chain! Or at least an adjustment. One inch of play should not allow the chain to slap the chain guard.

To answer the question about a loose chain. The bike has 4700 miles on it. The chain wasn't slapping and feels just fine. I just cleaned and lubed it the week before. Matter of fact the dealer just had the bike on Friday for my "bogus oil pressure light" indication.
Thanks for the tread by the way.
Steve

I had this happen on my way to Idaho. The chain gaurd did not come all the way off but the back screw fell out. I noticed it when we stoped at a parts place and the lady was very nice and GAVE me 3 of them just in case. It made it all the way home and then I put locktite on it just to be safe.

Back when all I could afford was parts from a (thankfully) now defunct place called Jammers, I had chainguards and pipe clamps breaking apart all the time because theirs were all cold formed to overly tight radii. I finally gave up on chain guards and started using heavy duty hose clamps on the pipes.

I read somewhere,that after you chrome your wheel spokes you need to anneal them slightly,because the plating process hardens/stresses/changes the metal.Wonder if that is what is happening with the chrome chain guard? Al

Thats scary, but thank for posting because it's an important heads up. Maybe it's only with the chrome ones, i don't know. But this will surely make me check mine. It also reminds me i'd better start checking all important screws regualrly !

In a similar incident about a week after i got my bike i was riding home from work when i heard a clunking sound. Sounded like something was loose like the battery and bouncing when i'd hit bumpy areas in the road. i wrote it off as being something normal that i hadn't noticed before with the bike being new and all. Got home and as i was pushing the bike into the cramped area i park it i noticed the front brake disc badly grinding against the pad. Looked down and the left caliper was hanging there by one bolt, the other having vibrated out and was gone ! The dealer had swapped front fenders with another bike before i took delievery because my bike's fender had a scratch in it. So apparently they hadn't tightened them, or at least not enough. Had the other bolt came out the caliper probably would have caught in the wheel and i'd have done a swan dive over the handlbars.

There's a ultra important lesson in all this....check bolts on a regular basis and torque as necassary !!! Thanks for the reminder.

The chain guard wasn't chrome. Stock factory Black, the way Speedmasters should be.

"Colors, I don't need no stinking colors"

Vagas is right, any sort of plating or especially galvanizing will effect the strength of the metal, except for maybe paint and powder coating, altho the powder coating is baked on right? So that might anneal the metal slightly... More than likely it is metal fatigue. If that vertical piece isn't wide enough, it won't support the weight of the chain guard as it bounces with each bump you hit, and bends slightly. Think of it like gently bending a paperclip over and over till it cracks.

Time for 3rd party heavy duty chain guard. I wonder what type of design would make it unbreakable...

On the other hand would it make sense to make it out of composite material instead of metal?

Composite would be big bucks!! I think just a slightly thicker gauge metal, or even just making the shape a little different to reduce stress points like real tight curves. You know, the reason airplane windows are rounded, so the stresses down't compound to make cracks. Same theory... Then again, mine's an '02 and it's still in tact.