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1983 V45 Sabre Cafe Racer

This is a discussion on 1983 V45 Sabre Cafe Racer within the Project Builds forums, part of the Caferacer.net Forums category; shortening the actual usable travel always requires a firmer spring rate,which cannot be achieved with preload if the main spring is a straight constant rate ...

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Thread: 1983 V45 Sabre Cafe Racer

  1. #61
    Senior Member XB33BSA's Avatar
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    shortening the actual usable travel always requires a firmer spring rate,which cannot be achieved with preload
    if the main spring is a straight constant rate then cutting to remove active coils will firm up its rate

  2. #62
    Senior Member Cyorg's Avatar
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    Here's a gift for you (includes Sabre). Aftermarket manuals aren't always up to snuff. Read it from cover to cover. Take an iPad to the shitter with you to expedite the process. Just tape off the cameras so your junk doesn't show up on a web site somewhere in the Balkans.

    Ps. quit dicking around spending money and figure out what you are going to do with those cases and "dented" frame.

    VF750C Shop Manual
    "Non urinat in ventum"

  3. #63
    Member BalkanMoto's Avatar
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    Thanks for the indexed service manual. I had a copy of it already but this helps with finding things quicker.

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  5. #64
    Senior Member XB33BSA's Avatar
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    and i might add that taking 2'' of travel out of a 5-6'' travel fork,will give you a terribly bad mannered motorcycle
    why are you lowering it in the first place ? you do realize that besides completely ruining the comp[liance of the forks that you are moving the steering geometry closer to that of spontanious instability
    and if you lower the rear 2''
    to match the front and spring it stiff as fuck as well to keep it off the bottom bumpers
    then the only roads you will be able to play on are the very smooth ones because i defy you to miss all the bumps and holes
    you know those litle used roads that are narrow and twisty and curvy
    the best riding roads also used by log trucks.... the smooth chuckhole free logging roads lol
    back to the main question why are you fucking up the handling and suspensioon ?
    because you have the oportunity here to listen to us and learn what will work to improve the machine
    if you are lowering it for a look well then dont waste my time tell me now
    woodsman likes this.

  6. #65
    Member BalkanMoto's Avatar
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    I understand that any sort of modification of the internals of a fork, deviate from the engineered specs and 9/10 ruin performance. And i understand that by definition (on this forum, and any other forum where people care about performance) doing so is completely wrong and pointless. I am not arguing the correctness of that, in fact i do agree. Unless you are an engineer or have enough experience to know exactly what a different component or one modified will achieve, its more or less just an educated guess at best.

    So moving past the impacts of that on the performance of the fork, the affects on the handling and stability, and the aesthetics. Also lets remove the bike as a factor completely. You have a pair of forks and want to shorten them by 2 inches. Now in that context what in my approach of cutting things the way i described above is incorrect? I am trying to learn here if there is indeed something about that process and the math of my measurements that is completely wrong. I guess it would help if someone that understands them would be able to explain what the effect on the fork would be if left like this, or modified further.

  7. #66
    Senior Member woodsman's Avatar
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    Completely agree with XB, the best riding is always the secondary and tertiary roads. In Ontario, Quebec and the northern US those roads are going to have heaves from frost, cracks from baking in the sun and broken/missing pavement. Some of it will be on the line you're travelling when leaned into a corner, it won't be fun with a poorly thought out bike.

  8. #67
    Senior Member woodsman's Avatar
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    Quote Originally Posted by BalkanMoto View Post
    I guess it would help if someone that understands them would be able to explain what the effect on the fork would be if left like this, or modified further.
    "Why are you lowering it in the first place?".

  9. #68
    Senior Member brad black's Avatar
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    this is a piece on top out springs, as fitted to the newer varieties for forks. don't mistake any of this for what you have done, which is put a very stiff spring in to reduce to fully extended length. a spring that short will have a very high rate and won't do a lot in terms of moving.

    https://www.sportrider.com/how-do-to...ngs-affect-sag

    how much travel do the forks have? some long forks don't have that much travel, they're just long for the purpose of the motorcycle - ie, look like a chopper.

    as i posted, cutting a spring is one way to make a spring harder, but you've not done any of the maths with regard to initial spring loads and modified spring loads.

  10. #69
    Member BalkanMoto's Avatar
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    Ok so here are the specs and facts:

    Stock fork travel is quoted by honda at 5.5", that is for the full 21" spring. We can all agree that the travel(compression) amount is proportionate to the length of the spring. Also these springs are constant rate springs not progressive ones (aka there isn't more coils on one end). So cutting 3" off the spring would constitute a 14.28% change. So the argument then can be made that the new travel of the fork, given that its mounted in the same location as stock (which it is) would change by roughly the same amount. In other words the travel on the modified fork should be ~4.71". This is obviously very rough math, and we can agree that what honda quoted as the stock travel is actually probably slightly less. In any case the modified fork should have anywhere from 4" - 4.5" of travel. Now i agree spring constants do change when you cut the forks, and those are proportional as well. Which should result in a 14.28% easier to compress spring (if i am not mixing things up). So those 4"-4.5" inches should be quite a bit softer to compress. Yes of course that will result in a slightly softer ride, but its not like i cut the spring in half and made things a crazy amount more softer and less travel.

    Another thing to put to rest is i just measured the uncompressed trail. It is roughly ~6.5". Which is plenty for stability and agility. Given that the stock fork was 2" longer that would have resulted at a longer trail that would have made the bike less nimble but more stable and high speeds.

    So in conclusion to answer the question everyone is dying the hear the answer they already knew. I shortened the forks because aesthetically it is more pleasing. Now before you all start loosing your shit and take up your pichforks and torches and shoo this poser out of your performance oriented forum. I would like to add that i did that as an educated guess. I was aware i was changing the performance of the fork by shortening it, and the stance of the motorcycle. So ofcourse rake/trail were going to be effected. No i didn't do the math before hand, but i have now. And as you see above it shows that in regards to performance i've actually improved the bike. Making it slightly easier to steer (aka more nible), but still well within the sweet spot of a stable trail, ofcourse at the cost of some front end comfort.

    So now that I have answered your questions, could someone enlighten me on what i have done wrong. If anything.
    Last edited by BalkanMoto; 10-25-2018 at 06:29 PM.

  11. #70
    Senior Member brad black's Avatar
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    you've told yourself that what you did was right.
    BalkanMoto likes this.

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