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FantasticMrFo... |
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FantasticMrFo... Nova Slayer
Joined: 10 Jun 2012 Karma :
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Posted: 19:00 - 10 Jun 2012 Post subject: Hello! How better to introduce myself than with a question? |
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Hello All!
I've just registered on this forum and have to say it's really well laid out and run
I thought I'd start my introduction with a question, It's one you may have been asked many times before so please be a little patient with me.
I own a Honda CBF 125, which I got from brand new. Around London it's the business, but since I moved out of the city into a more rural setting where the roads are faster, it's clear that it needs a bit more top end.
I commute to London quite frequently, and have to go through about 40 miles of 70mph zone, which my bike can manage at a push but it really doesn't like it, if I drive that stretch at a speed my bike feels comfortable with, its usually about 60mph.
So I've been thinking of changing the final drive ratio, to take a bit of the acceleration from low speeds (Which will make 1st and 2nd a bit nicer to use, I have to change into 3rd rather fast) and stick a little on the top end, hopefully making it so the comfortable speed for my bike to take the 70mph limit section is 70mph.
My question is this, Is it going to be possible to achieve that from changing the cog's? If so which way do I need to go about it, smaller front and larger rear or the other way around?
Could anybody talk me through the maths involved in working out which tooth combination would be best (on paper at least).
Being a mechanic, I understand a little about gear ratio's, but not enough to be able to work out the best gearing combination for getting 70mph in 5th gear at low rev's (The CBF doesn't really rev highly in 5th gear, which is whats making me thing that it has the torque to be able to pull me along at 70 fairly easily if given the right gear combination.)
Sorry for the first long thread, and for asking such a tedious question.
Thank you for having the patience to read this without falling asleep lol! |
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..... Quote Me Happy
Joined: 15 Jan 2005 Karma :
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Posted: 19:04 - 10 Jun 2012 Post subject: |
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You can look on www.gearingcommander.com for an idea.
Bear in mind though, gearing for a higher top speed can make the bike slower as it might not have the power to rev out at the different ratio. |
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neil. |
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neil. World Chat Champion
Joined: 24 Feb 2008 Karma :
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FantasticMrFo... |
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FantasticMrFo... Nova Slayer
Joined: 10 Jun 2012 Karma :
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Marmalade |
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Marmalade World Chat Champion
Joined: 28 Apr 2009 Karma :
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Posted: 20:55 - 10 Jun 2012 Post subject: |
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Usually changing the rear gives finer adjustment.
If you changed to 1 tooth larger on the front it would be like changing to 2 or 3 teeth smaller on the back.
What one of the posters above means by not having the power, if you dropped the rear sprocket size by a quarter you may well get 20mph out of 1st instead of 12 mpg but by the time you get to 4th or 5th it won't have enough engine power to maintain any speed meaning you'll have to constantly rag the life out of it in 3rd to go anywhere
You need to find a happy medium that keeps the bike happy in top at the best sensible speed you can get ____________________ Nobby the Bastard: How yo tell the difference between the actual japanese and her just screaming because she's had live fish stuck up her arse? [url=https://www.nicks-shop.co.uk/bcf-goodies-15-c.aspGet BCF stickers and things here[/url] Reflective helmet stickers - Legal requirement in france - Clicky |
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FantasticMrFo... |
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FantasticMrFo... Nova Slayer
Joined: 10 Jun 2012 Karma :
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U_W v2.0 |
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U_W v2.0 World Chat Champion
Joined: 07 May 2012 Karma :
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Posted: 21:21 - 10 Jun 2012 Post subject: |
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what year is yours?
https://www.gingerparts.com/parts/chains-sprockets?cat=126
thats a really good place to order from. if anything goes wrong they'll see you right. they also have all the dimensions of the sprockets so you can simply measure your existing one (the hole in the middle) and get one with the same hole size in the teeth you need.
or drop them an email and ask which one. ____________________ BCF's biggest cunt list: Cansa, Pits, Rob |
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FantasticMrFo... |
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FantasticMrFo... Nova Slayer
Joined: 10 Jun 2012 Karma :
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U_W v2.0 |
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U_W v2.0 World Chat Champion
Joined: 07 May 2012 Karma :
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Posted: 21:38 - 10 Jun 2012 Post subject: |
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well i cant find a specific sprocket for you but im sure you can go through the link i sent and you'll find the right one ____________________ BCF's biggest cunt list: Cansa, Pits, Rob |
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FantasticMrFo... |
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FantasticMrFo... Nova Slayer
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J.M. |
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J.M. World Chat Champion
Joined: 27 Mar 2011 Karma :
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karthead |
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karthead Trackday Trickster
Joined: 01 Apr 2012 Karma :
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Posted: 01:14 - 11 Jun 2012 Post subject: |
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Hi there,
I know that you only want to change gear ratios, but it may do you good if you upgrade the engine (bore out, bigger carb, tuned exhaust ect if possible) to give you're engine a bit more oooooouumph if you do that, combined with a small change in gear ratios (possibly 2-3 teeth smaller on front sprocket), then you will gain speed, but likely not lose any acceleration because the upgraded engine will give you more power.
I understand its a new bike, so if you dont want to risk tinkering with it thats fine, just another idea for you to consider |
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FantasticMrFo... |
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FantasticMrFo... Nova Slayer
Joined: 10 Jun 2012 Karma :
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Posted: 03:41 - 11 Jun 2012 Post subject: |
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andresoccer10 wrote: | Hi there,
I know that you only want to change gear ratios, but it may do you good if you upgrade the engine (bore out, bigger carb, tuned exhaust ect if possible) to give you're engine a bit more oooooouumph if you do that, combined with a small change in gear ratios (possibly 2-3 teeth smaller on front sprocket), then you will gain speed, but likely not lose any acceleration because the upgraded engine will give you more power.
I understand its a new bike, so if you dont want to risk tinkering with it thats fine, just another idea for you to consider |
I had considered that, tinkering with the bike isn't a problem, new or not, as I'm a mechanic by trade albeit with cars, stripping an engine is no problem, the issue I'd face with that is the legalities of it all, that and cost, for the price of a bore kit etc I'd be able to afford to do my full licence.
I had been considering putting a CG250 lump in it as I've been told (all though not checked myself so could be wrong) That the engine mounts etc are the same so an engine swap wouldn't be impossible, but I intend on giving the bike to my missus when I've got a bigger one, so I don't particularly want to do too much to it.
I'm not trying to make it something that it isn't, just hoping to squeeze a little more top end out of it to make cruising at 70 easier rather than having to thrash it silly to keep it there.
Thanks though, all of those are valid points, and ones I'll be more inclined to consider when she turns round and says "how the hell did you put up with this for 2 years, its too bloody slow, make it quicker!" lol |
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bodger |
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bodger Nova Slayer
Joined: 18 Apr 2012 Karma :
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Old Thread Alert!
The last post was made 11 years, 294 days ago. Instead of replying here, would creating a new thread be more useful? |
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