trial bike Posted April 4, 2016 Report Share Posted April 4, 2016 Hi folks, What is the plastic fin directly in front of the rear sprocket for? And is it really necessary? I see some bikes with it and some without it. I don't think any twin shockers have them, do they? I have recently broken mine on rocks and haven't found or made a replacement yet. It is fairly flexible plastic and when it broke the sprocket and chain must have taken the impact with out any really visible damage. Am I risking damaging something if I choose to run without it? Or is it a requirement for modern trials? Any knowledge appreciated... Quote Link to comment Share on other sites More sharing options...
coop650 Posted April 4, 2016 Report Share Posted April 4, 2016 That is your chain guide. You don't see them on twin shockers because they have less suspension travel and the chain can have more tension. Your bike, if reasonably modern, needs a little chain slack for suspension travel so there is some potential for your chain derailing at the sprocket without running a guide. Quote Link to comment Share on other sites More sharing options...
trial bike Posted April 4, 2016 Author Report Share Posted April 4, 2016 Is it really? That surprises me, I thought that was taken care of by the chain tensioner / guide. The sprung runner a little nearer the engine. I assumed it was a protector of some sort, but was wondering how a flimsy piece of plastic was supposed to protect the hard chain and sprocket. I risk a derail then without it? Quote Link to comment Share on other sites More sharing options...
twinshocktosser Posted April 4, 2016 Report Share Posted April 4, 2016 (edited) It's to stop your fingers being cut off if you fall off the bike on to the rear wheel or someone tries to catch the bike. It is not for guiding the chain, they are fitted to mx & enduro bikes. Edited April 4, 2016 by twinshocktosser 2 Quote Link to comment Share on other sites More sharing options...
tshock250 Posted April 4, 2016 Report Share Posted April 4, 2016 What twinshocktosser said. It's not a chain guide. 2 Quote Link to comment Share on other sites More sharing options...
oz thumper Posted April 5, 2016 Report Share Posted April 5, 2016 It's to stop your fingers being cut off if you fall off the bike on to the rear wheel or someone tries to catch the bike. It is not for guiding the chain, they are fitted to mx and enduro bikes. Exactly, and over here ALL trials bikes are required to be fitted with them (and the gearbox sprocket under some circumstances. The Motorcycling Australia Rule book specifically lists them and checked every trial by the scrutineer. I am aware of two amputations from the rear sprocket, one at the SSDT a couple of years ago when the shark fin went missing during the trial. They are a really good investment. 1 Quote Link to comment Share on other sites More sharing options...
crazybond700 Posted April 5, 2016 Report Share Posted April 5, 2016 Everything that can help to save some fingers should be fitted imo. The new sprocket rules etc, I know already 3 people with fingers suverly hurt or missing! Quote Link to comment Share on other sites More sharing options...
trial bike Posted April 5, 2016 Author Report Share Posted April 5, 2016 Exactly, and over here ALL trials bikes are required to be fitted with them (and the gearbox sprocket under some circumstances. The Motorcycling Australia Rule book specifically lists them and checked every trial by the scrutineer. I am aware of two amputations from the rear sprocket, one at the SSDT a couple of years ago when the shark fin went missing during the trial. They are a really good investment. Everything that can help to save some fingers should be fitted imo. The new sprocket rules etc, I know already 3 people with fingers suverly hurt or missing! Yikes! I will "pull my finger out" (LOL) and get it sorted. Thanks chaps. Quote Link to comment Share on other sites More sharing options...
fourex Posted April 5, 2016 Report Share Posted April 5, 2016 (edited) Just wanted to show off my shark fin I fitted to my 1984 Fantic 300, as oz thumper stated this is mandatory here in Australia for competition use. It's a right sided modern Beta fin bolted to a 5mm alloy bracket I made which has been Tig welded to the existing alloy Fantic rear brake stay. It almost looks like it's meant to be there. This is what we have to do in Australia. Edited April 5, 2016 by fourex 1 Quote Link to comment Share on other sites More sharing options...
b40rt Posted April 5, 2016 Report Share Posted April 5, 2016 Without being pedantic, what's to stop a finger going in above the swingarm, still could do a lot of damage. Quote Link to comment Share on other sites More sharing options...
crazybond700 Posted April 5, 2016 Report Share Posted April 5, 2016 There are always places to hurt yourself, but more protection is better.. A finger underneath is instant gone... Quote Link to comment Share on other sites More sharing options...
brownie001 Posted April 5, 2016 Report Share Posted April 5, 2016 Keep it down b40rt, don't make it too obvious that any form of motorsport is dangerous. The next step will be 'Speedway' type fully enclosed wheels leading on eventually to fully enclosed 'Egg' bodywork and the sections being caged in with F1/NASCAR style debris protection fencing. Most of us learned as kids that things spinning fast should be left alone until they stop. The old addage of 'Common sense prevails' just get overruled sometimes by someone trying to help and that's the saddest part. 1 Quote Link to comment Share on other sites More sharing options...
tshock250 Posted April 5, 2016 Report Share Posted April 5, 2016 B40rt, usually the wheel rotates forward, you would have to be very unlucky to get your fingers in there whilst travelling backwards! 1 Quote Link to comment Share on other sites More sharing options...
fourex Posted April 5, 2016 Report Share Posted April 5, 2016 Here's a pic of the actual finished product on the Fantic with top guard on, but as others have said, this does not seem to be a problem due to the rotation. Even the modern day GG/Beta/Sherco have little to no guarding on top of the chain, but all have some form of protection on the bottom chain rung leading into the sprocket. Most of us here in Oz simply use something like that kitchen nylon cutting board stuff cable tied to the swingarm or brake stay and that seems to keep the scrutineers happy, we're simply doing what our rule book stipulates. 1 Quote Link to comment Share on other sites More sharing options...
b40rt Posted April 5, 2016 Report Share Posted April 5, 2016 (edited) B40rt, usually the wheel rotates forward, you would have to be very unlucky to get your fingers in there whilst travelling backwards! Unless it's a Bultaco, which seem happy to run in either direction ..... Edited April 5, 2016 by b40rt 2 Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.