Hi all. I picked up a '94 CBR1000F project bike and the side stand bracket (the kickstand and gear shifter are attached to it) nuts that were tack welded inside the enclosed frame are broken off and wondering what the fix action options are?


Side Stand Bracket and Frame


Tack Welded Nuts Loose Inside Enclosed Frame


'94 CBR1000F

The right repair may be to take it to a shop and have them cut a hole in the frame, weld the nuts, and weld the removed metal (patch) back on? Just looking for any alternatives, options, and recommendations because I am assuming this has had to someone before. Hate to have an un-fixable bike because of 2 nuts.

 

Welcome to the forum, ohh that is a tricky one!
What is on the other side of the frame? Could you drill through and fix with longer bolts and nuts?
I believe that you can also get rivet nuts, just not sure they would be strong enough but this site suggests that they are. e.g. https://www.fastenright.com/products/general-fixings/rivet-nuts
https://www.fastenright.com/general-fixings/rivet-nut-flanged-smooth-open-end/rn09

 

Thanks for the welcome and yes this is an interesting issue and introduction to the CBR.
I am comfortable doing a lot of mechanical things but this one is outside my knowledge base and comfort zone.
There is 2-3 inches of free space on the other side so I could drill straight through a put a nut on the back side use a longer bolt. The chain does run through that area but I think the nuts would be low enough not to interfere. I would be concerned about compressing the frame so I could also use a spacer/sleeve to minimize that? Or maybe just weld in a thread sleeve by itself?

 

I would certainly look into the rivet nuts as they look ideal for this type of application as it replicates the original intent of the welded nuts, not sure if M12 is big enough

 

Riv-nuts are way to go. Don’t have to chop hole in other side of frame, possibly weakening it. Faster too.

And riv-nuts would go on outside layer of frame, so no worries about compressing layers of frame. Side-stand doesn’t have high-load demands.

You can actually braze riv-nuts in place once installed for permanent fix.

 

Thanks for the additional vote. I've actually started looking into them. The current bolts are a M10s with 1.25 thread pitch but those riv-nut don't appear to be made. I can get 1.5 course thread pitch and checking to see it that would make a difference and the corresponding load/sheer values.Also looks like there is a small lip but I can fabricate a spacer so the mount sits flush against the frame to minimize torquing.

 

Use whatever 10mm threading riv-nuts come with. Then get new bolts with matching threads. Again, 10mm bolts are way, way stronger than loads placed on them by kickstand. Only if you crash at high-speed with kickstand down, would you ever come close to damaging those bolts.

To deal with lip from riv-nut, can mill backside of mount with end-mill to clear. So mount only press on frame. Not that tiny offset from riv-nut would matter to kickstand.

 

Thanks for the recommendations. After doing some research with Dr. Google, I will try rivnuts (or plusnuts - there does seem to be debate which is better). The existing frame hole is ~11mm so I would have to drill out the frame holes to 13mm to accept an M10 rivnut but I could use M8 rivnuts and bolts without any frame modifications/hole expansion. The M8s do have the benefit of 1.25 thread pitch whereas the M10s have 1.5 thread pitch. I like the idea not modifying the frame (not that drilling out 2mm is a big deal) but at the same time I obviously don't want to have a failure while riding. Fundamentally I feel the rivnut is the weakest link and would fail first regardless if I use an M8 or M10 so I think I am going to try M8s first. I can always drill out and replace them with M10s if the M8 won't suffice. I am a bit concerned about the sheer forces so I will end mill the bracket or fabricate a metal spacer to have the bracket sit flush against the frame to minimize them when using the footpegs and/or kickstand. I'll also have to add a spacer around the bolts to take up the 2mm difference between the M8 and M10 diameters. The other concern is rivnut spin so can only torque them down to ~20ft-lbs (averaging across a couple rivnet manufacture specs) but I think it'll work when everything it's bolted together. Now for the threadlock question ... yes I over analyze things...

Appreciate the help and does this sound like a good route to go? Depending on what I do with the bike, probably the better long term fix is to get thread sleeves welded in but I would like to get a couple riding seasons out of it first to decide.

 

Measure OD of M8 rivnut. It must fit snuggly into hole, otherwise it’ll spin when you try to tighten and expand it.


No shear forces when bolts are tightened. This generates tonne of friction between sidestand bracket and frame. Since sidestand load is significantly lower than friction, all loads are transmitted across as if it’s bolted to one piece.

Only if you apply large enough force on stand, such as crashing at 100mph with stand down, would you be able to generate large enough load to overcome friction and bracket would move relative to frame. Only then would bolts be loaded in shear.

https://boltscience.com

 

Thanks again for all the advice with this. I going to go with M8 rivnuts. I actually have to drill out the frame holes slightly larger (<1mm) for the M8 rivnut to fit so they will be snug. I am getting ready to order parts figured I go with stainless steel rivnuts and wanted to make sure that was good material to use? I also need to order the rivnut tool and wondering if there are any recommendations? There plenty of hand and pneumatic ones available from the major web retailers but prices very greatly. McMaster-Carr has a lever-style one with a visual stroke indicator to ensure the rivnut installs correctly. I also like the idea of a pneumatic tool so I can more easily set them square but they either are "cheap" or seriously expensive. Definitely willing to spend more on a quality tool to make sure its done right (cheap insurance) but there are limits.