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Discussion Starter · #1 ·
The two biggest things I noticed on my daily commute is the ease the stock fork bottoms out and the lack of power when braking.
I am 180lb on a bad day, so the fork problem may be more of my weight than the spring, but I can easily bottom out my fork by pushing on it with a bit of weight.
As for the brakes I feel like the front brake is just lacking. They will unload the rear if pulled to heavy, but at speed it feels like they don't give enough bite. I know some people see that as good so they don't endorsed, but, to me, if it can't lock the front out it's not powerful enough.
Considering these are lower end bikes I expected to see some entry level components, but with my weight and style of riding I think it would be nice to have those two things upgraded a bit.
 

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You can change your fork springs for heavier ones, common mod for racers. The racetech ones seem most popular, member @DaBinChe has done this conversion and lots of info on cbr250.net as its the same forks on both models. They are available in three different strengths. See link below. You have to click CBR250 in the check box.

Race Tech Fork Springs - Motorcycle Superstore

Best place to start with the brakes would be higher spec pads, again something guys tracking their bikes do.
A braided line from the master cylinder on the handle bar to the caliper would help too.

http://www.cbr300forum.com/forum/wheels-tires-suspension/6641-ss-braided-line.html
 

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I swapped to ebc sintered double-h brake pads, motul 600 fluid and a gaffer steel line as part of track prep and the lever is much stiffer and the bite much harder (I used to use all four fingers now just 2 is fine for normal stops). I did them all at the same time as part of track prep so i can't tell which was the best but it made a huge difference such that I kept lifting the rear till i got used to it lol.

I am pretty close to your weight and find the fronts pretty soft but when on the street I like it so don't see myself changing them (same with the rearsets).
 
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Seems odd that the forks bottom out. I wonder if there is the proper amount of fluid in them?


I've searched online for a larger front brake rotor but never found one. There are braided stainless brake lines available from
Galfer. I would try that first. The easiest mod is race type brake pads but they wear out the rotor quickly.
 

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Well?? yes/no or maybe.......
 

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The theory seems sounds as it would preload the springs just like the adjustable rear we have, but would reduce your effective travel along the shock so stiffer springs with less preload are probably more desirable assuming $ isn't a factor. <- Extrapolating from my car knowledge
 

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You shouldn't be able to bottom out by pushing on it. As mentioned by another poster you might have a problem with the fluid leaking out and could check your fork seals for signs of leakage.

You don't have to replace the springs right away as that could be expensive. Try a heavier viscosity fluid first. I did this on a CBR 150 and it made a world of difference by just going with a heavier fluid.
 

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The theory seems sounds as it would preload the springs just like the adjustable rear we have, but would reduce your effective travel along the shock so stiffer springs with less preload are probably more desirable assuming $ isn't a factor. <- Extrapolating from my car knowledge
I would concur with this thinking but I'm no suspension guru. They would be easier to install than changing your springs tho.
I'm just lucky with my light body weight that the soft springs aren't too much of an issue for me. Lightening the bike up a bit has probably helped too
 

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That's a good point, unless you are doing proper wheel to wheel racing it probably makes sense to start with the easiest/cheapest way and see if that meets your needs before going down the rabbit hole further. The tech guys usually have a good laugh (at the softness) when testing my forks at each track day lol!
 

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As i mentionned in another thread : http://www.cbr300forum.com/forum/wheels-tires-suspension/3449-fork-springs-2.html

(So i did last week, i took a 1 inch longer steel pipe and put it instead of the originals. The difference is awesome, the front is now not pointing to the ground and react well on highway. Much more confident in that way.)

I'm still happy with it and still braking to stop in traffic when going down a hill without bottoming like it was before.

I will agree with others that say: Nothing like real heavier springs, they are right, but at what price ?


Take care
 

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(So i did last week, i took a 1 inch longer steel pipe and put it instead of the originals. The difference is awesome, the front is now not pointing to the ground and react well on highway. Much more confident in that way.)

I'm still happy with it and still braking to stop in traffic when going down a hill without bottoming like it was before.
1" is equivalent to a lot of washers! :D

Hey sounds like a sweet mod, good on ya. Does it still give a comfortable ride on less than perfect roads where there's small bumps etc?
 

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Discussion Starter · #14 ·
Go to the RaceTech website, and look under cbr250r, punch in your weight and figure out which spring you want for type of riding
It says the stock is .49 kg/mm while I should be using .81 kg/mm... Seems like a big difference.

I am 6 foot and weigh 175lb-ish, so the 300f is a little small under me, but nothing crazy/

edit: and the preload adjusters are only $30 cheaper than new springs from race tech
 

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If the preload adjusters are that much I would just buy the springs from race tech.

a very low cost way to firm up the stock springs is to replace the preload spacer. Don't remember what the stock length was but I would go 5mm more each time. Use 3/4" pvc pipe, only cost a few bucks at homedepot for a 24" lenth. Just make sure you have a washer on each end of the spacer. I had to do this with the RaceTech springs even with getting them for my weight and riding style. In fact RaceTech comes with the pvc pipe for you to cut down to adjust for preload. The proper amount of sag is 20-30% of total travel. With the front wheel of the ground measure the length of fork from the seal to the triple clamp, now sit on the bike fully geared up then do the same measurement, the difference is the sag.
 

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I would imagine that Honda didn't spend very much time thinking about the suspension on the little CB - which was probably 'designed' by a spreadsheet, more or less, with cost being the most important factor.

Having said that, they will have got the spring/damping more or less matched, so it is likely that swapping the standard springs for 'heavier' alternatives would require a proportionate adjustment to the damping. With very basic forks however, I suspect the only easy tweak you could effect is to go to heavier oil.

It would take a more sensitive rider than me to determine the best combination, but you guys who love to fiddle should have a go. it would make for an interesting project.
 

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1" is equivalent to a lot of washers! :D

Hey sounds like a sweet mod, good on ya. Does it still give a comfortable ride on less than perfect roads where there's small bumps etc?
As i'm 6 foot tall and 215lbs the bike do not likes me, but now small bumps are managed with springs instead of bottom !

Winter is long but not a lot of snow ! Will it melt down soon ? I hope
 

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if they did a progressive rate spring, i could be tempted. but i ride on too many bumpy roads for a spring that stiff.
 

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