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Discussion Starter · #1 ·
Guys,

I installed my aluminum swingarm & YSS shock this weekend. Fairly uneventful except for two issues:

The stock shock is 245mm, bolt CL to CL. The YSS is 250mm, in the closed position, it's adustable. I purchased one of the fully adjustable shocks, just like the other three sets of YSS shocks that I have on other bikes. On the other shocks, 250mm means, in the mid point of the adjustment. So it will go from 245mm to 255mm. These go from 250mm to 260mm, so it puts the swingarm on an extreme angle, hard to adjust the chain. I emails Targa & YSS, I'll see what the say. All the other YSS shock were purchased from the US distributor, not Thailand.

The second issue, is probably more interesting to the forum. Both the stock steel swingarm & the new aluminum arm use the same Honda rubber bushings. Unlike almost all motorcycles, that have bronze bushings or needle bearings, these are more like the rubber bonded bushing in your Ford or GM pick-up. But the truck bushings have a lot of rubber, so they can twist. These bushings have very little rubber between the steel tubes. I found out the "non movement" issue by accident. I didn't completely tighten the swingarm axle bolt. When I sat on the bike, I had normal sag, and a new YSS shock that worked like a real shock. When I torqued up the axle nut & bolt ,it all bound up. The bushing is acting like a rubber torsion spring. I backed off the nut, everything works fine. So the bottom line is, until I make bronze bushings & spacers, it makes no sense to change out the shock. It's a total waste of money. I'll try to take some photo's tomorrow to help explain what I mean here. It's this simple, if you disconnect the shock from the swingarm, it does not drop, or fall away. It's held in place by the bushings. Very odd, very cheap?
Brian S
 

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so needle bearing upgrades are on the list now? you can get the bearings custom made if you can get the measurements.
 

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Thanks for the heads up.

The news is disappointing, but good to know.

Looking forward to hearing about better bushing replacement and replacement swingarms that come with decent sealed bearings.

Thanks all!
 

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Discussion Starter · #7 ·
Bushings

The Japanese swingarm has the same rubber bushings, so it will be the same. It will not be any better than the steel swingarm, until the pivot bushings are change.I have been looking the past couple of days. I can find 25mmx18mm bronze bushings that will work. I have found 25mm seals to keep out the dirt, I can make the 18mmx12mm inner shaft. I have not found a good way to deal with the end play issue. I'll work it out, but it may take time. The main issue with needle roller or ball bearings is the 25mm diameter. All the bearings that I have found are either 24mm or 26mm, that have the right ID.
Brian S
 

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The Japanese swingarm has the same rubber bushings, so it will be the same. It will not be any better than the steel swingarm, until the pivot bushings are change.I have been looking the past couple of days. I can find 25mmx18mm bronze bushings that will work. I have found 25mm seals to keep out the dirt, I can make the 18mmx12mm inner shaft. I have not found a good way to deal with the end play issue. I'll work it out, but it may take time. The main issue with needle roller or ball bearings is the 25mm diameter. All the bearings that I have found are either 24mm or 26mm, that have the right ID.
Brian S
Is this the size?

 

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Discussion Starter · #9 ·
Swingarm bushing/bearing update

Hi Guys,
I attached 4 photo's of my progress on the bushing / bearing change-out on the Grom swingarm. I made the tooling to remove the bushings. Not too bad, but it did take 2 tons to press them out. I honed the bores, just to clean them up, before I press in the needle bearings. I'm going to leave out the seals until the last minute, because I want to fit it up, sliding the parts in & out. I'm not going to use the steel swingarm after I'm done. I'll redo the aluminum swingarm next. The tool steel spacers weren't too hard to make, but I had to purchase about a $100.00 in tooling to make them. I need to harden them to 50C Rockwell, so that will get done on Saturday. I did figure out the endplay issue.I also figured out that when you tighten up the stock bushings, they distort inward to take up the endplay, so they are really bound up. I'm not sure how the any of these aftermarket shocks could possibly work correctly with the extra spring rate of the rubber spacers. I hate to say it, but I think people are kidding themselves, thinking they made a big change, they just spent money. That includes me.
I'll keep moving forward.
Brian S



 

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Discussion Starter · #10 ·
Just About Ready To Install The Swingarm

I finished machining the tool steel swingarm bearing spacers this weekend. I know it's a little hard to tell what this photo is, but it's the first set of hardened swingarm axle spacers ever installed on a Honda Grom frame. What I'm doing is verifying the spacer width, so that the foot peg side plates mount up corrrectly. I should have the steel swingarm mounted this week, and the aluminum one remounted in a few weeks.
Brian S
 

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I just read everything again and i have a question

I removed the swing arm bolt when i installed my pegs, but i just tightened the bolt as firm as we could but i didnt have any movement issue after. Are the european groms different?
 
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