joostio Posted November 4, 2010 Report Share Posted November 4, 2010 update: I ignored my cracked frame (cracked above rad) and I discovered more cracks on the down tubes. ignoring it was not a good idea. I tore the bike apart and took it too a buddy to have it welded. He came up with a theory as to the cause of the cracking. The bolt (none threaded portion) that goes through the motor case and the swing arm is about 1.5 mm too short. It was not long enough to go between the ears on the frame. The wide part of the bolt is the same size as the ears but on the threaded end it is stepped down for the threads, this side was not supported by the ears on the frame. This caused the swing arm to move and caused the motor to flex the frame further causing the cracks. my friend machined my bolt down a bit on the allen end so it sits farther in the hole and now the wide part of this bolt is supported by the ears on the frame. Check your swing arm bolts on the nut side to see if it is seated all the way in the frame ears and let us know what you find. its a theory, what do you guys think? Quote Link to comment Share on other sites More sharing options...
neo Posted November 4, 2010 Author Report Share Posted November 4, 2010 Hi joostio, Thanks for sharing this with us. Yes I think it could be a contributing factor if the bolt was even slightly lose. But not sure it would have a big effect if the bolt's done up tight. In that case the ears would get good support from the engine casing at those points. It's this kind of brainstorming stuff that will get us the solution in the end... Or maybe some at Sherco could kindly tell us what's happening?? Best of balance. Neo Quote Link to comment Share on other sites More sharing options...
neo Posted November 4, 2010 Author Report Share Posted November 4, 2010 Also, thought I'd put up my finished job ... yet to be tested on the rocks The brace plate is made of 2mm stainless steel. Hard but not brittle...Drilled and tapped out. With HS bolts and nylock nuts doubling things up. Best of balance. Neo Quote Link to comment Share on other sites More sharing options...
joostio Posted November 4, 2010 Report Share Posted November 4, 2010 on my 06 even if the swing arm bolt is tight it is not seated properly. the bolt came too short from the factory. on the end that is threaded it is stepped down in diameter, when tightened up the threaded part is in the frame ear as opposed to the shoulder of the bolt. I had my bolt machined so that the shoulder portion is 1.5 mm longer than original. I hope this is the fix I am looking for. Quote Link to comment Share on other sites More sharing options...
neo Posted November 4, 2010 Author Report Share Posted November 4, 2010 Sorry joostio, Any chance of a photo or a sketch to illustrate this? Best of balance. Neo Quote Link to comment Share on other sites More sharing options...
copemech Posted November 7, 2010 Report Share Posted November 7, 2010 Also, thought I'd put up my finished job ... yet to be tested on the rocks The brace plate is made of 2mm stainless steel. Hard but not brittle...Drilled and tapped out. With HS bolts and nylock nuts doubling things up. Best of balance. Neo Well, for what you did there, it looks good enough. Time will tell! Quote Link to comment Share on other sites More sharing options...
joostio Posted November 16, 2010 Report Share Posted November 16, 2010 (edited) here are some pics to try and exdplain what I meant by the swing arm bolt being too short and not being properly supported by the frame. I had and issue apart from all this cracked frame bussiness which resulted in me stripping the threads off of my swing arm bolt. I over tightened it trying to eliminate a noise. My swing arm bolt is now modified, the threaded section has been cut off and it has been drilled out and tapped. My swing arm bolt is held in place with a bolt as opposed to the original nut. This modified bolt aside I still think the factory messed up in my swing arm bolt very possibly causing my crack. here are some pics to show what I mean.I guess I have no clue as to how to post pics here, help anyone?trying again Edited November 18, 2010 by joostio Quote Link to comment Share on other sites More sharing options...
neo Posted November 16, 2010 Author Report Share Posted November 16, 2010 I guess I have no clue as to how to post pics here, help anyone? Yes Upload your pics onto Photobucket and paste the link in as an "Add Image" Best of balance. Neo Quote Link to comment Share on other sites More sharing options...
joostio Posted November 18, 2010 Report Share Posted November 18, 2010 (edited) my swing arm bolt that has been modified swing arm bolt too short, not supported by the frame, not all the way in the hole, look closely the fit after the head of the bolt was machined down, fits in all the way now. Edited November 18, 2010 by joostio Quote Link to comment Share on other sites More sharing options...
neo Posted November 18, 2010 Author Report Share Posted November 18, 2010 Thanks joostio, I see what you mean now. Those bolts are always a bit short but the ones I've worked of have always stayed secure. Did the thread your one strip or get damaged some how? Cope knows more about these things than I Best of balance. Neo Quote Link to comment Share on other sites More sharing options...
joostio Posted November 18, 2010 Report Share Posted November 18, 2010 stripping of the swing arm bolt was a few weeks ago, I was tightening everything up to eliminjate a noise. If the swing arm bolt is not properly seated in the frame there is a chance that the cracked frames are caused but it. If the swing arm and motor flex enough it could cause the cracking, that bolt should be supported properly by the frame. its only a theory but it sounds pretty solid to me. Quote Link to comment Share on other sites More sharing options...
neo Posted November 18, 2010 Author Report Share Posted November 18, 2010 (edited) I'd agree that your theory sounds solid but I haven't ever found that bolt lose on my bikes after seeing a crack. So there must be more to it I think.....Cope you've been too quite on this subject And what happen to Sherco's Customer Reassurance Department?? ... I mean it's not as if we're asking for our money back or anything. Best of balance. Neo Edited November 18, 2010 by Neo Quote Link to comment Share on other sites More sharing options...
joostio Posted November 18, 2010 Report Share Posted November 18, 2010 I am not suggesting that the swing arm bolt loosens up due to the poor fit, just that it is poorly supported by the frame on the nutted side. With this poor support, every time the swing arm moves it could cause unessasary frame flex therefore causing the cracks. My welder/riding buddy came up with this theory, not to dumb for a Gas Gas guy. Quote Link to comment Share on other sites More sharing options...
copemech Posted November 19, 2010 Report Share Posted November 19, 2010 (edited) Uh, I had to think about this a bit and look at the diagrams again. I do not have one apart in front of me. Someone correct me if I am wrong, but I think they are made that way on purpose. The nut and head of the bolt must put the frame, swingarm bushings and motor into compression sandwich for rigidity. If the bolt was longer, the nut could bottom out on the threads before achieving proper tension, allowing things to move which would not be desireable and could cause wear on the component contact areas, even under micro movement. If the shank of the bolt did come too close, this would not allow for any manufacturing variences and short of adding washers, would not insure proper tension to keep things tight. After trimming your bolt by 1.5 mm, your situ may be marginal, and with the current arrangement with she smaller diameter bolt into the shaft, I kinda doubt if the ali threads will hold the torque required to keep things without pulling the threads out of the modified shaft. It may hold, but if me, I would get a new shaft and nut, start over, and inspect lube the bearings up in the process. The swingarm just rotates on the bearings. Edited November 19, 2010 by copemech Quote Link to comment Share on other sites More sharing options...
trialsnutterman Posted November 20, 2010 Report Share Posted November 20, 2010 I don't really like pointing this out but do you realise you've missed a small crack in the top right when looking from the back. Quote Link to comment Share on other sites More sharing options...
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