CT 125/trail Suspension upgrades

[zigzagjoe]

These two pages are in the CT125 manual. There's the full service manual which has a lot more information in it, but it also says something like this is common suspension with a design not super specific to Honda, so you can probably find a generic suspension process.

RE: preload, someone suggested cutting a small section of piping and putting it under the fork cap nuts to increase the preload, rather than buying the Chimera bolts. There's also some heavier duty springs that someone linked to elsewhere on the forum, and someone (possibly outside of the CT125 forum) also tried mixing 10W and 15W oil in equal parts to get better results out of their front suspension. Lots of interesting things being done.

Thanks! My forks are filled with oil that appears to be ATF (dyed red). Apparently that's ~10W. I'm starting to think I might have made a mistake while measuring the fluid in the forks, though. I'll have to remeasure.

I was thinking that I'd check out the hardware store for either metal pipe or metal rod of appropriate diameter to act as preload spacers. Either that, or print a lump of ABS plastic - but I'd prefer metal.

 

[AZ7000']

Probably not atf, fork oil comes in many colors, the oil for my 450’s starts pretty clear.

 

[dmonkey]

People who ride dirt a lot and rebuild their forks often will sometimes run ATF because it's cheaper. I wouldn't, spend the dollar or two more and just buy the right product.

 

[SneakyDingo]

I was thinking that I'd check out the hardware store for either metal pipe or metal rod of appropriate diameter to act as preload spacers. Either that, or print a lump of ABS plastic - but I'd prefer metal.

Yeah, long term ABS or PETG would likely work just fine, although I would be a little worried about deformation over time due to continuous forces applied to them. Probably go higher on the wall count rather than the infill if you're going down that route, like use 5 walls and 15% over 2 walls and 40% Short term, if you're going to change the oil anyway, PLA would probably work if you have that loaded already since it won't matter if it dissolves a little for a quick spin around the block.

The Chimera bolts operate under the same idea, they're a fork cap bolt with a longer bit on the end. The Chimera bolts add about 15mm of additional length, not much, but definitely enough.

 

[m in sc]

PVC pipe is fine, ive run it for years in other bikes. fwiw, atf will lose lubricity faster than actual fork oil, have seen this 1st hand in fork applications more than once. Unless you are anal about changing fork oil regularly, i wouldn't recommend it.

 

[zigzagjoe]

Yeah, if 3D printing a lump I wouldn't do anything but 100% infill ABS. I ended up fabricating some spacers out of 5/8 grounding rod, adding a washer to bring it up to the right width. It was fun riding with an 8 foot piece of metal hanging off!

I left the factory fork oil alone. Performance wise, I'm happy with the spacers. Less dive under braking and overall feels more decisive. If pressing the front down, it springs back without bouncing which it didn't before.

So, critical dimensions:

Width: 17mm is minimum i'd suggest. 16mm does work, but it does not support the entire tube and that concerns me. Don't exceed 18.7mm.
Length: 15mm was about what I suspected the chimera spacers were. I ended up with about 21mm and I can tell you it was a pig to get the caps back on.

Substitutes: 11/16" (17.5mm) rod is probably perfect, but it's an uncommon size. 3/4" (19mm) is probably too thick unless you can turn it down a smidge. 5/8" is too small.

 

[m in sc]

I've just used pvc plumbing pipe. I'm serious. people have been doing that for literally decades. lol. the biggest improvement i have usually made was fork oil. also... the stock forks oil was uneven on mine when i checked it. just .02

 

[ducatirdr]

Somehow over the years I have a bunch of sockets that ended up in a toolbox of the misfits. These are retired sets from when didn't have any brains to take care of my tools. Well two of these matching sockets fit nicely into my fork tubes at just the right diameter. I had to press the cap to compress the spring almost to the point I didn't think it would work. But a little patience and I got it done. There you go! I saved myself $60 bucks in fancy caps.

FOR THE REAR SHOCK grab the lower shock collar and pull it up and compress the spring while you rotate it. This will get the post on the bottom of the shock to come out of that slot. Then rotate the collar 90 degrees so the slot and post are away from each other. Bingo! a notch of spring compression added for free. Yes it will stay there for a long time and not move.

 

[sieg]

Yeah, if 3D printing a lump I wouldn't do anything but 100% infill ABS. I ended up fabricating some spacers out of 5/8 grounding rod, adding a washer to bring it up to the right width. It was fun riding with an 8 foot piece of metal hanging off!

I left the factory fork oil alone. Performance wise, I'm happy with the spacers. Less dive under braking and overall feels more decisive. If pressing the front down, it springs back without bouncing which it didn't before.

So, critical dimensions:

Width: 17mm is minimum i'd suggest. 16mm does work, but it does not support the entire tube and that concerns me. Don't exceed 18.7mm.
Length: 15mm was about what I suspected the chimera spacers were. I ended up with about 21mm and I can tell you it was a pig to get the caps back on.

Substitutes: 11/16" (17.5mm) rod is probably perfect, but it's an uncommon size. 3/4" (19mm) is probably too thick unless you can turn it down a smidge. 5/8" is too small.

FWIW 1/2 inch water pipe is right at 17mm outside dia. or .665-inch. I cut two 15mm length off a 1/2 brass pipe nipple, works fine. $5 at ACE.

 

[CTExplorer]

Yes, I even drained it and refilled it to be sure. I used 15wt which seemed to help but I still get the clunking noise. Starting to wonder if it it's not coming from the headset.

Hey there, just seeing if you ever figured out the clunking noise you were explaining? I'm thinking I have a similar issue that on random abrupt bumps it makes a clunking like bottoming out but at times that don't really seem severe enough that it should he bottoming out. Has done it since new.

 

[zamdrang]

Hey there, just seeing if you ever figured out the clunking noise you were explaining? I'm thinking I have a similar issue that on random abrupt bumps it makes a clunking like bottoming out but at times that don't really seem severe enough that it should he bottoming out. Has done it since new.

Hi, no I never did. Adding a bit more oil was about as quiet as I ever got it. I ended up selling the bike, it even did it with the aftermarket springs so I never did figure out the source.

 

[TRF90]

What is involved? Just a set of vice grips and muscle?

Please keep the vice grips in the box. Put the bike on the centerstand and sit on the ground next to it. Using both hands, push-up and twist. If you have reasonable hand strength, it will come out of the slot pretty easily.

 

[cmb23trail125]

Not the same bike but basically the same fork. I just did my Yamaha TW200 with Racetech Gold Valve Emulators. Boy oh boy what a few $$ made a massive i mean MASSIVE difference in the front. I am 6'-1" 215lb ready to crash and i can carry 30-40mpg speed in the dirt no problem. The back is stock with just a spring and way better but i ride to aggressive so will change to a Cogent soon. My new to me 23' Trail 125 will get the same or better treatment.

 

[cmb23trail125]

Watched a few YT videos on the YSS fork upgrade system and crossed that off the list. Anyone use the below from Racing Bros. Looks very similar to a Cogent setup.

Racingbros Front Fork Anti-dive System

The back shocks i am still researching options.

 

[TRF90]

I posted the following elsewhere a couple months ago under Large Rider Fixes for the Front and Rear Suspension. It's the least expensive fix I can think of if you need a firmer spring rate than stock.

"So I found a pair of new Motion Pro 30% stiffer fork springs for the XR/XL 100s on eBay and got them home for $40 shipped. These are longer single rate springs with no softer progressive section. Now, finally, the forks sit up in their travel, and actually do something to absorb bumps. .....the preload pipes are no longer necessary, and I did not need to use the washers as pre-load shims."

Hope this helps!

 

[cmb23trail125]

I know mine did not say that but damn these components are small. Prepping for a trip and waiting for my shocks to come in so it will be a few before i throw these in.

Ordered 6/6/23 at 11:16am and just received 6/7/23 at 1:19pm. Steady garage is trying to compete with Amazon.

 

[cmb23trail125]

Treatland shocks came in today. Now i am off to find a spanner wrench for these as i forgot to look/order one.

 

[RustyRodder]

A heads up for anyone ordering treatland- They are awesome, but also run great sales around holidays.

 

[Sail38n]

Anyone else notice serious clunking from the front end on bumps of all sizes? What exactly is the cause? I initially thought it was just bottoming (and yes bottoming does make a clunking noise) but then I will also hear it very small bumps .... think of the curb pulling out of a gas station.

I've installed the YSS kit, without typing my soap opera i've put about 350 miles on it so far and still get the clunking noise, but strangely seems to be just the left fork. Preload adjustment doesn't seem to matter, stiff or soft I still get the noise.

Did you ever find the problem? Mine is doing the same thing.

 

[CTExplorer]

Did you ever find the problem? Mine is doing the same thing.

I asked him basically the same thing and he answered in post #51. From seeing a couple videos on the Chimera fork cap extensions I'm going to try a set or maybe the PVC spacers M in SC has mentioned to see if it makes a difference before spending the $$. Just haven't had a chance yet.