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Bottoming out

djbiker90
djbiker90
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Bottoming out Empty Bottoming out

Post by djbiker90 on Mon 04 Mar 2019, 10:04 pm

Hoping this is the right place. I have a 2006 CBF500 ABS model that I just picked up. Whilst I know odd bits (brakes, general servicing, electrics) and am not afraid of a challenge I am a complete novice when it comes to suspension.

It has had new fork stanchions in the last year or two after a slow speed ding. The previous owner mentioned to me that it could do with heavier fork oil. I've noticed that when i test the suspension if i'm pressing very hard it will just about bottom out. The bike is on 65k miles and otherwise runs fine. I'm around 105kg when in full kit. 

Can anyone recommend whether I should just change the oil or go for something like hyperpro progressive springs?

I have a K1200R that I use for any motorway work and only intend to use the CB for commuting and pottering around town in so i'm not looking for razor sharp handling - just safety and comfort.
liverpool_f_
liverpool_f_
the 900
the 900

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Post by liverpool_f_ on Mon 04 Mar 2019, 10:54 pm

You may get some help as there are a few owners on new cb500's on here, but we are mostly owners of the 90's cb500's.

That said, you should not be able to bottom out forks by just pushing on them, no matter how heavy you are. If the forks have been rebuilt previously, it sounds likely that something didn't go right during that process. Wrong oil, missing spacers etc.
skyerae
skyerae
the 800
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Post by skyerae on Tue 05 Mar 2019, 7:58 am

I seem to remember from when I rebuilt the front forks that the springs are progressive, thanks to Mr Honda. I also have to agree with liverpool_f_ , there is an issue with your front suspension. I am a little heavier than you and I have never bottomed out my front suspension on any of the bikes I have owned. I bottomed out the back suspension on the CB500 (1994) but the springs were shot, but somehow always passed the MOT.
kungfupoodle
kungfupoodle
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Post by kungfupoodle on Tue 05 Mar 2019, 2:52 pm

It's possible the CBF is softer than the CB.

I found a reference to the progressive spring rate(s) of the CBR500. It's only 0.6KG/mm for the first 70mm of travel which means it takes a mere 36KG to use up nearly 2/3rds of the travel. It gets stiffer after that - maybe another 36KG to take it to 100mm which is nearly all the travel.

If the CBF uses this spring rate then it sounds like it's working as it should.
Jameshambleton
Jameshambleton
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Location : Bedale, North Yorkshire

Bottoming out Empty Re: Bottoming out

Post by Jameshambleton on Sat 09 Mar 2019, 8:39 pm

Fork oil level will be too low (air gap is too big) that'll be your issue, who ever built your forks didn't get the air gap amount right.

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