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TECHNICAL MOTOBRICK WRENCHING In Remembrance of Inge K. => The Motobrick Workshop => Topic started by: mejetski2000 on August 21, 2015, 09:16:31 AM
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Would like to lower my K75S about an inch or so. I know many shock companies can build shorter shocks but I'm wondering how to do the front forks. Can I cut the fork spring spacer, or spring AND spacer or do I need to get custom stations ? I have Progressive springs in there now. The suspension travel and current height looks like a 1" drop won't be detrimental.
TIA Pete
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greetings...
id just drop the triple tree down 1" on each fork tube...
a 1" drop can be detrimental to your foots if you getts lazy and donts keep the balls of the foots on the pegs when canyon racing...
j o
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Hey Johnny thanks for suggestion ! That's my final option but I'd like to maintain the appearance of stock setup if possible. I really don't carve hard on this bike since it's a husband/wife thingy lol. (Luckily I have other bikes for that)
Pete
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(Luckily I have other bikes for that)
Pete
Quite the list of other bikes. How big is your garage?
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Alternatively, you could just put 70 series tires on her front and back. You'll lower the bike but not mess up the geometry.
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It's not possible to raise the fork tubes by lowering the triple-tree with S-handlebars. The S-bars are in the way.
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Tim's correct, even a half inch would be tight. I'm going to get with Ted at Beemer for the shock and additional info I think. I imagine I'm not the first short KB rider who's done this LOL. I have $900 budgeted which should get me set up.
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(Luckily I have other bikes for that)
Pete
Quite the list of other bikes. How big is your garage?
Actually have 4 right now, but the K13 is up for sale. Bought a KTM 390 Duke in May.
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You could cut the PVC spacers down a little.
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My thoughts exactly : )
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flip the bars over...
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I got an e-mail from Beemershop and was advised against lowering the bike, which I don't understand since several companies are selling shorter than stock height shocks. Anybody running a 1" short shock that can give some feedback ?
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greetings...
the reason is it changes the moto geometry and can cause whack... the beemershop wants no liability with regards to whack caused by something they suggested...
some folks here have lowered their motobricks... they will speak up when they see this thread...
j o
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Funny I should notice this thread this morning.
I lowered the front end about 1/2" when I first got my 75RT last year. Today I was riding with no hands to check alignment. At about 40mph the front end started to oscillate. Did it three times. Scary.
Looks like there is not enough trail to stabilize the front end with the forks lowered. Not noticeable when holding the grips even up to 110mph, but let go and things get a little loose.
Will be checking fork alignment and raising the front end this evening. My advice: don't drop the front end.
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Gryphon Thanks for posting your experience. Did you shorten the spacers and are you running factory or progressive springs ? I believe the RT has substantially different geometry than the S model, ie travel and fork length specifically. Are you running a standard length shock or shorter ?
Thanks, Pete
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I believe the RT has substantially different geometry than the S model...
I don't. the RT has a larger radiator and a lot more fiberglass.
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Hey Tim, what I've seen so far is that the S forks have less travel and a different fork oil volume than a later RT. Every manufacturer I've checked also have different part numbers for their spring kits and rear shocks also. I agree that the RT likely has more front end weight than a S model for sure. Not sure how relevant the RT suspension is compared to the S.
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I thought you meant frame geometry. Angles and such.
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Nope, sorry should have been more specific on my end.
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As far as I can tell, the front forks are standard "94 RT. I recently installed and balanced a new front tire. Fork oil has about 12,000 miles and front end damping is good. No leaks/good seals. Besides the lowered front end, the only other notable factor is that there is a very slight, barely perceptible play in the steering bearings.
In any event, I am raising the front end and retightening the axle clamp screws forthwith.
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I installed Progressive Suspension springs in mine about 20 years ago. I'd like to replace them with fresh springs when I add the new shock. I have new Honda 10wt to go in as well. I'm hoping Progressive can advise how much to shorten the spacers.
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Generally, are all forks for two valve bricks, '85-'89' the same? Or, as the mark aged were forks upgraded internally? Have never read a synopsis of the development of these forks through the series.
I know forks stamped S are different. Are later forks better than early forks? I got early forks, '85, progressive with bottoming springs, seem to work for me, just wondering. Reason I ask is got a pair of '87s laying around and maybe a switch out would be cool with the integral aero brace and fender. This is on a early '85 KRS.
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Gryphon: There should be zero slop in the steering head bearing. The R models will oscillate violently with any slop there, to prevent it I pre-load the steering stem on the R. The K is different. On the K tighten the steering stem bearing shell lightly by hand till it stops - don't force it further. Then tighten the Fitting bolt to 33 ft-lbs followed by the Hexnut to 33 ft-lbs (pg 374 Chpt 10 Figure 58 Clymer). The fitting and nut is used together to prevent preloading the shell bearing during assembly. Take a test ride and check for oscillations.
I'm a fan of lowering these K75s, dropped my steering crown as far the handlebars would allow. Next step is to grind a LITTLE on the handlebars to allow more clearance, maybe cut the shock strut after that. I find no adverse handling issues when riding the lowered frame, think the shorter wheelbase is a plus. For taller riders the extra knee bend might mean trouble, I'm 5'-10" with no discomfort. Cutting the spacers changes the fork dynamic, it removes preload in the fork spring that in turn changes the ability of the fork to isolate the chassis and rider from road vibration.
Would have started a new topic but discovered this old thread.
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So to lower a K75 RT, with fairings removed, sounds like springs in the back and a fork adjustment would do the trick. Combine that with a lowered seat setup and maybe shaving the seat a bit… would y’all say that’s the best way to lower the bike without sacrificing the handling? And running lower profile tires?
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Running lower profile tires gets you about 1/4".
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You can get about 10mm by raising the forks in the triple clamps, and about a half inch by putting a shorter shock at the rear.
You might need to modify the center stand as a lower bike needs to be raised that much more to get it on the stand. Remember, you are lifting about 550 pounds even if it is less than a half inch.
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So to lower a K75 RT, with fairings removed, sounds like springs in the back and a fork adjustment would do the trick. Combine that with a lowered seat setup and maybe shaving the seat a bit… would y’all say that’s the best way to lower the bike without sacrificing the handling? And running lower profile tires?
What you need to do depends upon how low you need the Brick to be. Removing the OEM standard height seat and installing an OEM low seat and its assembly will lower seat height by 2 inches.
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Everything I’ve read here and elsewhere… total drop from standard is about 3 inches all things combined. Does that sound right? Glad I’m doing this math now because I’m not sure this would be low enough to get my partner’s feet on the ground. 🙃🫠
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The 2" lower seat height gained by installing the OEM low seat and its assembly applies only to the rider, not the passenger. That seat has a V-profile into which the rider nests; the passenger's seat is not lowered as much. At least one member here has added lifts to his boots. In addition to cutting down and narrowing the seat profile, raising the tubes in the fork, and using a shorter shock, that did the trick for him. Perhaps the passenger should consider having boots customized with thicker soles and heels.
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I meant as rider, not passenger.
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I meant as rider, not passenger.
If the lowering you've calculated isn't enough, carving more from the seat and modifying the riding boots are what is left without greatly compromising handling and ground clearance.
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Boots with thicker heels help but you can also add shoe lifts. However you might have to go up a size in boots. Buy the lifts first and take them with you when buying the boots and try them out for fit. I have a 1" shorter YSS rear shock and have dropped the forks through the trees. After doing this I bought a straight leg stand and shortened it by cutting out a piece but I also made up plugs to reinforce the weld. I also had to modify the side stand by bending it a bit more to get the lean angle right. I used a butane torch and a 3/4" pipe bender bending slightly letting it cool and trying it until the correct lean was achieved.This led to further modifications on the stand foot to stop it scrapping. And this led to the stand buffer having to be modified to accept the side stand. Done right all this should not compromise your handling, however very occasionally when at extreme lean angles it may scape. The bike has also been fitted with a Corbin seat which may be slightly lower.
Regards Martin.