Hi guys, I'm a long term reader here and I'm looking for some advice is possible in regards to my 2017 765RS Long story short I was replacing the friction plates of the clutch due to slippage beginning to occur at 26,000 miles on the bike particularly noticeable at a recent track day at KnockHill in Scotland. Unfortunately while doing this I managed to snap a bolt where the lower clutch cable adjuster attaches to the engine. This means I cannot tension the clutch cable correctly. At this point I managed to get some help removing the bolt from a local mechanic who drilled the bolt out with a view to inserting a Helicoil. Unfortunately this proved difficult as the aluminum in this area is so soft that he struggled to drill a straight hole which resulted in the Helicoil not taking once the hole was taped. Although he has a very good reputation he has since not returned and is not responding to me leaving me completely stuck, which leads me to believe there is no easy fix. I've attached some photos and was hoping you would be kind enough to provide ay advice on where I go from here. The repair does not need to be pretty just safe to use. Thank you all.
That should have helicoilled ok. I have done this on quite a few bikes from different manufacturers with success but it does need care. Here's a 675 camchain tensioner top bolt resolved with the engine in the frame, awkward yes but with care and a few tools easily solved. By the sound of it your assistant was gung ho and has made a bigger problem hence why he's disappeared. The first issue and question is, what is the current hole size now? You need to measure it and the easiest way, assuming limited tooling is available, is to use drills. If you haven't the right size then pick the next one down, then add one wrap of insulation tape at a time until a nice snug fit. With a caliper or micrometer then measure and post the size here? Alternatively, if you do have some bore gauges, like I do, then measure directly. As seen above, the wall thickness is very thin and critical to a successful outcome. Can you also measure the available wall thickness around your problem?
Thank you so much for taking the time to get back to me, yes I suspect that's why he has ran away and is now avoiding the problem. I have a caliper which I will use to measure when I am home from work and report back.
I have measured as follows Thickest section of wall 5.13mm Thinest section of wall 3.18mm Diamater at entrance 6.5-7mm (difficuly to get a precise figure with the tool i have.) Thanks again
I'd need to check but the 6mm helicoil drill is something like 6.3mm so you are already far beyond that which is an issue. M8 tapping drill is 6.8mm but your pushing the case wall thickness there.
That's my worry, not a lot of material lot to work with, would you know of any other solution rather than a helicoil/threadcert? or is it time to strip it down and sell for parts haha Thanks again for your help.
Hi I have had problems with helicoils personaly have found them to unwind if fixing is unscrewed a few times if fitted and left alone are fine there are better options out there if a fixing is to be removed on a permanent maintanance schedule
Better options being? If the clearance drill is held true and a new hole created with care, likewise with the helicoil tap, then a sound repair should be the result. I have helicoiled undamaged holes, yes holes as good as new, especially in magnesium or aluminium off road motorbike components to make them harder wearing, including items that are frequently removed, and not experienced your issue @philip ham The emphasises here is on " with care". A sloppy hole is no good to anyone
Welcome to the family. spot of bother there. I my self prefer inserts to helicoils alought nothing wrong with them done properly. But like someone said have found they are great for fixed but removing every new and then does weaken them. I have also mended things like this by taping with a 7/16 if the hole is not to over. But do let us know how you get on Joe
Hi yes if holes are in good condition but helicoils don’t always utilise the full depth of hole available not a being critical but just saying
I think a stud rather than a bolt would be a good solution for you. With care and accurate measuring to ensure the issue doesn't escalate to scrap crankcases, I'd be tempted to thread M8 and bond with red threadlock ( strong bond) an M8 stud and drill the clutch bracket to suit. This would avoid any future removal issues and should give adequate strength. Are you aware that helicoils do come in different lengths? The basic sets available don't show this but they are available and I'd guess in my collection, I have x3 different lengths of say M6 for example.
Like Eldon says it is fixable, have a look at bikers toolbox website, they do a great range of Helicoil inserts etc.
Thanks for all the responses guys, I was considering attempting to use one of these as to not remove anymore material prior to having a go with a drill to increase size to M8 https://www.accu.co.uk/self-tapping-inserts/410832-HSTI-M5-A2 An M5 is roughly similar in diameter to the hole and I could use an appropriate washer on the bracket to size down from M6 to M5. Does anyone have any experience with these? I believe Wurth produce similar.
I wouldn't do that It basically forces its way in, so if wall thickness wasn't an issue then no problem. If, as in your case, the surrounding metal is thin then it could, quite possibly, just split the casing wide open. An accurate size of the current hole including it's depth and shape i.e. round or oval as in off the original center? I was thinking last night about this and I'd be tempted to helicoil to M7 to retain the maximum casing. I have a lathe, so I'd then machine a stud with M7 one end and M6 the other ( I already have M7 taps/dies but they are easily available). The original bracket would then fit as before and other than it now showing a nut instead of a bolt head, the repair would be sound and invisible. If you want a ride to Yorkshire, and pay me for my time, I'll sort it for you?
I don't know if this is possible on a 765, but my Speed Triple has the clutch cable bracket attached to the clutch cover using 2 of the cover bolts. Is it feasible to abandon the original damaged mounting point and fabricate a bracket to attach to 1 or 2 suitably positioned existing fasteners? Probably not but just a thought.
