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I used a bench grinder to shave off some width of the metal sleeve that goes through the linkage. Its hardened steel so it takes a lot to get through it but you don't have to take to much off. And as for the sleeves that go into the shock, I just used some aluminum tube. I drilled out the center to 10mm and then cut off a ~3 inch section. I put that into a drill and then used sand paper to sand down the outside. It took quite a while to get the right OD but I think it is a good method if you can't get anything else to fit.
Didn't think about shaving off some of the sleeve in the linkage. In that case, I might cut off some of the sleeve with my dremel and finish it off with a file for a nice fit. That's probably a lot easier with the tools I have. We'll see when I get there. For reducing the lower mount hole to 10mm, I got the sleeve from McMaster-Carr, and it's a really tight fit. Thanks for your input. This is a fun project for my bike.
 

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I may try this when the riding season is over, my girl rides the bike more than I do, but she does want to do a few track days with me in the future, this might be a good upgrade for relatively low cost.
 

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I finally did this 3 months ago, and it was worlds different on the track. Also added some RaceTech fork springs and some valve adjusters. Instead of changing out the top, I drilled out the frame to accommodate the R6 mount bolt diameter since I never plan on putting the stock one back on. If anyone is interested I can do a video on it, as I just bought a 2012 CBR250R and already have an R6 rear and a set of RaceTech (for my weight) springs ready when I go to pick the bike up. Also have adjustable rearsets and new clipons.
 
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Alright. I'm necroing this thread since I'll be doing this mod in the next 2 weeks.

Got a Yammie R6 shock on the way and picking it up next week.

I can't order from McMaster-Carr since they don't ship to Canada unless you already have a business account with them or you belong to a school. So I have to hit up Fastenal or another alternative shop for the sleeve bearings to reduce the lower shock mount eyelets from 12mm to 10mm.

As for the upper shock mount I'm thinking I might do what xbhobx did with enlarging the upper mount to 12mm since I don't forsee myself going back to stock but I'm not sure how to go about this. I've tapped things before but never something like this since I'm the fleshy meat popsicle wrapped around a metal frame not the other way around. (ie. for cars "eh duct tape will fix that" while for motorcycles it's like "if I don't put this plastic rivet in perfectly the engine will blow up and kill me").

Any other things I need? Any other caveats I should be aware of for people who have done this? Note that I'm trying to do the "no cut" method here.
 

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Any other things I need? Any other caveats I should be aware of for people who have done this? Note that I'm trying to do the "no cut" method here.
To extend the bolt for the upper mount I took the bracket off the CBR's shock and ground off the welds of the bolt head to remove it. Then I bought a longer hex head bolt and nut that I fed into the bracket. I then welded the bolt head to the bracket. To make clearance for the shock you will have to grind down the bolt head. That was a real pain because the bracket interferes so much. To space the bolt I just used some round stock I had lying around.

Make sure when buying a bolt that you get a high grade bolt like 5 or 8, 8 would be best. And get a locking nut to go on top. I would suggest either a distorted thread or nylock nut.

Goodluck with youre modding! Upgrading the suspension makes a huge difference on this bike! Do note though that this will end up raising the back end of the bike slightly and make the turning a bit quicker.
 

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Goodluck with youre modding! Upgrading the suspension makes a huge difference on this bike! Do note though that this will end up raising the back end of the bike slightly and make the turning a bit quicker.
Believe me, I know what a dialled in suspension feels like. Too many people I see think that the stiffer the suspension the better it is but I know that in reality you're trying to maintain as much contact as possible with the ground so that you can put power to the ground rather than having the tire "skip" on bumps and wasting that power. Originally I wanted to get a CRF450L and SuMo it so I could make use of the longer travel since I found myself bottoming out quite a bit on the stock weeBR suspension (I'm not even fat either, only ~155 lb but the fork preload is too far when I have a full tank of gas and am sitting on it, and when I brake it dives and I feel like it bottoms out).

What amount of sag/preload are people running on their bikes? Am I crazy in thinking that 30% sag on the street is a good setting?

Just to confirm though the upper bolt threading is M10x1.25 (fine threading) like I saw mentioned somewhere else and I want it to be about 40mm long?

Obviously I'm going to be looking for either grade 10.9 or 12.9 steel bolts because I don't want the bolt to yield and fail on me when I'm riding but if I beef this part up is there another part that's supposed to take any extraload and be the "sacrificial" part (or maybe this is me thinking too far into it and trying to be smarter than the engineers who designed the thing).
 

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Sorry to necro thread but this was the only info I could find on the net about a budget shock upgrade for my CB300F and CBR300R, and I just wanted to add some more info for any new interest.

After reading this thread a few dozen times I finally got my hands on an inexpensive R6 08-16 shock ($150AUD) and had a go at Installing it on my development/track/idiot CB (Front CBR300 forks and YSS fork kit) before throwing one at my partners CBR.

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I opted for the frame cut on mine as I've been combatting some stability issues which appeared to be caused by rake angle with the rear preload cranked to combat hitting bumpstop and the front sag set to match.

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I made up some shims for the lower 10mm bolt which I inserted into the R6 shock. I used a similar 12mm bolt and drilled a 10mm hole through it on a lathe and cut two 4mm slices.
OD 12mm, ID 10mm, Length 4mm.

I toyed with making my own bearing race but couldn't find someone to make one hard enough.
OD 17mm, ID12mm, Length 32mm.

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I was having some trouble with clearance on the triangular link that was binding the suspension, So a flapper disk on a grinder and it no longer binds.

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I then bent the ABS back as far as I could with a long bar for mechanical persuasion.

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Night and day difference in the handling of the bike, can't recommend it enough. I threw my partner on after riding their own CBR300 and they were astonished as how much lighter/agile the bike felt with the same level of stability. (Identical tyres, brakes, pressures etc etc).

Some numbers for those who care.
CB Shock: Extended 547mm, Static 540mm, Sag 520mm. (preload wound all but one click up trying to combat hitting bumpstop)
R6 Shock: Extended 535mm, Static 525mm, Sag 502mm.

I'm not too concerned about the cut to the frame as its a multi layered section of pressed steel, Although being that I love my partner, I will probably make a smaller and cleaner cut on their CBR300 and have a friend TIG up the edge to add back any lost strength.


As an addition I set the R6 shock to the factory settings and so far so good. I will be getting a friends help for rebound etc at the next track day.
Here are the relevant pages from the owners manual of a 2012 R6.
Font Material property Parallel Design Paper


To finalize, chicken strips are completely gone now, corner exit isn't so damned sketchy any more and my back loves me.
 

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Honda: INNOVA125i(2010); CBR250R(2013)
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Sorry to necro thread but this was the only info I could find on the net about a budget shock upgrade for my CB300F and CBR300R, and I just wanted to add some more info for any new interest.
Thank you very much(y) it's from those posts that even if I do not make such improvements I take a lot of inspiration from them ... Thank you very much for the detailed sharing and photos.
Maybe you have some tips for welding the motorcycle frame?
 

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Thank you very much(y) it's from those posts that even if I do not make such improvements I take a lot of inspiration from them ... Thank you very much for the detailed sharing and photos.
Maybe you have some tips for welding the motorcycle frame?
Only tip is its mild steel, mig or tig should work, just be sure to paint it to stop rust. (and disconnect your battery beforehand obviously)

Only reason I think it might be needed is I had to cut through a large seam weld that bonded the two sheets of steel, a good weld across the cut should prevent any movement or cracking.
As I said I wont bother on my CB (I will keep an eye on it and report back if there are any issues) but on my partners bike I figure its worth the effort.
 
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