CT 125/trail Suspension upgrades

[m in sc]

incorrect. there's deflection at the pivot point (rubber bushing) that's multiplied by the length of the arm. it allows movement left to right at the axle, and binds in every rotational movement. the weak link is the bushing for rigidity. the 10mm bolt is a double shear mount around the swingarm, it's not flexing around in the 1.25" or so it spans thru the arm. sorry, just isn't. I've done this mod to both my grom (that has over 40 hp) and the trail and it was absolutely a huge improvement on street riding. the tire sidewall is now the weak point as far as flex, and i plan on getting different ones soon as these are getting worn out (not the originals) .

 

[dmonkey]

I have the bronze bushing on mine and will echo what @m in sc said. I installed Ohlins suspension on mine first, and after replacing the swingarm bushings it was clear how much the rubber ones were binding. On a stock bike I wouldn't bother with them, but if you are going to upgrade the suspension replacing them is not a diminishing return but instead the other half of what is necessary to get the full result of your rear shocks upgrade.

Suspension Upgrade - Öhlins fork springs and shocks

With about 2 months on my Ohlins suspension setup I figured I'd share my thoughts for anyone else interested. My motivation for upgrading was that I was frequently bottoming out the stock suspension off-road, and the bike would easily go into a bounce on-road which didn't inspire confidence at...

hondatrail125.com

MNNTHBX Bronze Swingarm Bushing Kit

From MNNTHBX (MAN IN THE BOX)'s product page for the bushing kit: About MNNTHBX Bronze Swingarm Bushing Kit for Honda Grom / Monkey Fits any year Honda Grom or Monkey. BY FAR the single largest improvement you can do to your Grom/Monkey suspension. Our exclusive swingarm bushing...

hondatrail125.com

 

[kevvyd]

hope you guys changed out the shitty rubber swingarm bushings to bronze or bearings.

I ordered the AVAIL ones but I messed up and bought the CRF110 version instead of the Grom/Monkey version!.... (CRF version is ~37mm overall VS ~45mm overall for the Monkey/Grom/Trail125)
When the correct ones arrive they will compliment a brand new pair of KitacoXGEARS shocks I bought last week from Webike on "Summer Sale"
I'll probably use the drill press, tap, and install OEM pillion pegs I've had on hand for "a while now" on the swinger I am waiting for the correct AVAIL bearing kit to arrive.

(OEM rubber bushing can be removed without destruction...it is a very, very, tight press fit!)

 

[dmonkey]

Drill and tapping the swingarm for passenger pegs will be easier with it off the bike, but for the passenger's comfort I would recommend going with passenger pegs that are not fixed to the swingarm.

 

[DeadguyAle]

Based on the input from @dmonkey and @m n sc I moved forward with upgrading to the MNNTHBX swingarm bushings.
Just finished installing, couple things noted on the original setup.
Did not see any "binding" as in one spot in the movement catching or being stiffer than other parts of the swingarm movement when going through the range by hand.
Ends of the inner bushing sleeve are the only point of contact with the frame mounting points. Very small surface area and easy to see how it could bind under a load.
Swingarm bolt and bushings had zero lubricant applied from the factory when assembled. Resistance/ease of swingarm movement is reliant on swingarm bolt nut torque.

Installation is not overly difficult but requires a fair amount of disassembly reassembly.

New bushings address the limitations of the stock design providing a much larger bronze bearing face that mates to the frame and can rotate within the SS carrier, ease of movement is still dependent on swingarm bolt nut torque but should be much improved over stock given the same torque value.


Got things back together and did a 40 mile test ride on a mix of pavement and gravel.
Improvement in ride quality is noticeable but not dramatic, backend feels more connected and there is enough of a change that the shock spring preload feels like it could be backed down a bit as well as the rebound damping.
It does compliment the shock upgrade nicely and is undoubtedly an improvement over the stock configuration.
I would guess you could get 50 percent of the improvement noted simply by greasing the ends of the bushings, the Swingarm bolt and maybe backing off a couple ft pounds on nut tightness.
From a long term perspective, coupled with a quality shock upgrade I do feel it's worth the time and money to do.

 

[m in sc]

actually, no, movement does NOT rely on swingarm bolt torque, at all. that's the whole point. see how the inner bushing is longer than the sleeve? thats what the bolt toques against, it lets the arm move independently of it.

torque the bold down to the factory spec. it will settle in and be fine.

TBH, the stock rubber bushings don't rely on swingarm bolt torque to control rotation either. the center of any setup is fixed and the arm rotates around it. the problem w the stock one is its reliant on rubber, in rotational bind. the bronze bushings are in NO bind.

 

[Dia1Up]

Still very new to bikes and mods in general, so take what I have to say with a grain of salt.


1: But regarding front end "clunk". Mine absolutely does it. I ride the same off-road trail once a day, so far every single day.

It just simply seems to be the front fork hitting the end of it's stroke in either direction. As far as I can tell online, there's no "bump stops", so the fork internals just slam metal on metal both in compression and rebound. I have absolutely bottomed out the front fork. I'm only 165lbs, but down hill braking and hitting a particular large bump on the trail can easily find the limits. (It's a fairly deep rut from water runoff that I cross at a 90-degree angle) That is a serious clunk and shock through the wrists if I hit it too fast. We of course know how soft the stock fork is, and how much the front dives under braking, not a good combo for some slightly heavier trails I've found

As for the clunk and the long end of the stroke, we all complain about the rebound damping on both the front and rear. I don't think it's a surprise even with the droop the bike can buck enough to allow full outwards travel of the front fork. This is one I get much more commonly for sure. Especially going up hill

2: Rear, I have the stock coilovers sitting at the stock preloads with no cargo. I don't have and issue with the spring rate or compression damping, but that lack of rebound damping is the killer I think. I've almost been bucked OTB with how much the rear pogos sometimes. Not even bottoming out the rear, just the rebound being inline with the end of the bump at the right time.

I might go full YSS (Rear Ohlins are the dream of course, but I don't have that kind of money heh). I think the front emulators would be helpful with the dive on the front, and something with adjustable rebound on the rear would be key, as long as it is more than stock anyways

 

[Kuro Neko]

... with my low impact use, my front suspension seems to do an OK job.
At least compared to my only benchmark of 25 years of pavement commuting across Tokyo.

I do however notice a heavy CLUNK on full droop traversing deep depressions.
Not sure I've ever had it bottom out, or any other rebound or compression issues.

However:




These adjustable kits are available locally, and I assume replaces part numbers 19 and 4 (and 23)?
What is not clear to me though, is if they adjust height, firmness, or something else.

Looking at the basic construction, I assume by tightening down the adjustment I may get some extra ground clearance and a firmer ride (with perhaps less likelihood of a full droop KLUNK)?

Comments to assist, gratefully accepted...

 

[TRF90]

I know the clunk is a common problem on some of the CT 125s. For that, you might check the oil level in each leg and make sure it's within specification. As far as a firm a ride and higher ride height goes, the kit you show seems to only affect preload. A spring that is too soft will not become firmer if it is preloaded. It will just ride a little rougher at low speeds and still bottom out just as quickly. I weigh over 100 kg so this led me to go to stiffer fork springs. However, even if you are a much lighter rider, you might find those springs to be helpful with both ground clearance and the clunking. Someone who's had more experience with fixing the clunking problem may offer better advice here.

 

[DeadguyAle]

... with my low impact use, my front suspension seems to do an OK job.
At least compared to my only benchmark of 25 years of pavement commuting across Tokyo.

I do however notice a heavy CLUNK on full droop traversing deep depressions.
Not sure I've ever had it bottom out, or any other rebound or compression issues.

However:

View attachment 13799
View attachment 13800

These adjustable kits are available locally, and I assume replaces part numbers 19 and 4 (and 23)?
What is not clear to me though, is if they adjust height, firmness, or something else.

Looking at the basic construction, I assume by tightening down the adjustment I may get some extra ground clearance and a firmer ride (with perhaps less likelihood of a full droop KLUNK)?

Comments to assist, gratefully accepted...

@Kuro Neko The replacement tube and caps simply let you add additional preload to the springs firming up the front suspension.
Problem with this approach is that the stock springs are progressively wound springs.
Top 60% of the spring is wound looser and probably accounts for 3.5" of the 4" travel. By preloading the stock spring you give up some of the initial softness and engage the lower much stiffer part of the spring sooner. Not sure how much of a real world difference this makes in the overall ride but it does make a case for straight wound stiffer springs to address the overly soft stock ones.
Not sure what would cause the KLUNK, part #7 is the spring of last resort that keeps the fork tube from a hard impact with the the bottom of the outside fork tube but it is possible that it gets fully compressed resulting in a KLUNKING sound.

 

[Kuro Neko]

Thanks both, as it seems I am better to leave it with the stock set-up, and just tolerate the occasional klunk on full droop.
I like the softness of the current set up regardless... I would guess because the roads here are really smooth, and it does most of its work in first gear on forest trails.

 

[Harley rider]

... with my low impact use, my front suspension seems to do an OK job.
At least compared to my only benchmark of 25 years of pavement commuting across Tokyo.

I do however notice a heavy CLUNK on full droop traversing deep depressions.
Not sure I've ever had it bottom out, or any other rebound or compression issues.

However:

View attachment 13799
View attachment 13800

These adjustable kits are available locally, and I assume replaces part numbers 19 and 4 (and 23)?
What is not clear to me though, is if they adjust height, firmness, or something else.

Looking at the basic construction, I assume by tightening down the adjustment I may get some extra ground clearance and a firmer ride (with perhaps less likelihood of a full droop KLUNK)?

Comments to assist, gratefully accepted...

i installed one of theese adjustable type mine and it did stiffen suspension, which i needed since i am heavy, made my ride perfect and no more clunks