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Discussion Starter #1
what are some relatively inexpensive things to do to your bike to lighten it? i mean besides shaving off blinkers. and passenger pegs, but what are some obtainable, to the average man, things to lighten up an old steel and iron bike?

anyone have an unobtainium, Formula one race car sort of weight reduction skills applied to their bike that they are particularly proud of and would like to show off?

anyone run a fiberglass tank on the street?? i don't like dying in a burning ball of fire, but are they really terribly ill-advised for the street?
 

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I run fiberglass on the street. I am not fond of it but some tanks just are not made in metal.

as far as lightening...well that depends on the bike. One area oft overlooked is the chain guard. Having been slapped once by a chain letting go on a buddy's bike I advise people to use them, but they never need to be as big and solid as they need to be, you just need enough to keep your foot from getting slapped and the part that is there does not need to be solid all the way through.

Fenders - stock fenders are heavy, fiberglass replacements are a good idea where advisable.

Renthal makes aluminum dirt bike bars in 7/8ths that have a similar bend to superbike bars. used ones are cheap on ebay

alloy rims - some bikes they are more accessible than others, look for similar models that use alloy rims laced to stock style hubs (the cb750A vs cb750K for example - same hub but the A has alloy).

lights, replace what you can with LEDs. Taillight, signals, idiot light etc. Drilling three idiot light LEDs into the back of a stock headlight shell is a heck of a lot lighter than the stock dashboards on some 1970's-80s jap bikes...espically if you don't feel you need the gauges or have switched to mini gauges.

Drill holes in anything not structural.
 

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my triumph bobber with 5.5 over forks and 35 degrees of rake is sized for a guy from 5'10 to 6'5 and only weighs 305 pounds

I'd say it puts 40 horses and maybe change to the back tire

it's geared really tall

and it wouldn't surprise me if it puts 45+ ft/lbs of torque out back

I have a 53 inch Vtwin in a fbed that comes in under 370 and that's with a boat anchor buffalo wheel, cush drive rear wheel

and several pounds that can be unbolted and it still run although sans light and passenger carrying ability

have another vtwin fbed that weighs 340 not very wet

not sure if you've built too light?

answer...... rattle can primer until a bike has been proven..... and the willingness to go back with Mr Tig, more metal, and maybe a new idea

that first harmonic is a real MFer

and don't think for a minute that singles, twins, and even multis don't have them

an inline four makes very intense and destructive harmonics because it does its thing on two axis

and the higher frequency doth tend to lull many builders into complacency
 

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the ultimate in lightness I have seen in an old bike was cody's kh500/750 hybrid:



if you search on the kawi triples board there is a pretty extensive writeup or just ask about one component and I can give you some details I have saved. in this incantation it was about 360lbs wet and he could have gone lighter.
 

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holy SHIT!!! i have to go clean my keyboard now...thanks a lot
 

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the nice part about that bike is that there are some obvious tricks and some not so obvious ones.....

obvious:
- tank, seat, alloy hubs, etc....
- drilled everywhere, all extraneous tabs removed....

not obvious:
- motor: the motor is a 750cc h2 motor. Fits the 500 frame because they use the same mounts. People can;t see inside an engine so where ever you can get an advantage take it.

- Frame is a 1976 K500 frame. Although identical looking to the other h1500 frames the 76 kh frames had more bracing in an attempt to make the h1 a better handling bike. It is the strongest of the kaw triple frames, but not the lightest. However, the factory was able to brace that frame in ways that the average homebuilder may not have access to which means it may be lighter than a comparably braced frame done by someone in their garage.

- Wheels. The alloy excel rims are obvious but what isn't is that the hubs are off a smaller lighter triple. The stock h2 750 hubs weigh a ton, but the smaller triples have much lighter rear drum. The front actually runs an ex500 caliper so there wasn't a need for as big a drum as the stock 750 runs.

- lights...LEDs plus small car fog lights (PIAA maybe) for the headlights. No turn signals because most h1/h2 bikes didn't come with them anyway.

just some examples of what is out there that makes a truely great bike...

if you think this is an isolated example thing about some of these things:

- cb650 motors have the same engine mount locations as an earlier cb500. The cb650 is a bigger crusier bike but the cb500 is much lighter (and down on hp compared to the 650 mill)

- kz440LTD motors will fit into standard kz400 frames. 40 extra ccs never hurt anyone.

- a lot of earlier suzukis like the gs gsx and early gsxrs you can build 7/11s out of (1100 mill in a 750 frame).

- with DOHC cb750s, always buy an F if you are looking to build a cafe. The F chassis uses a thicker wall tubing and is much stronger and better handleing than the K bikes despite looking very similar. The same does not apply to SOHC cb750s, however the 77-78 cb750Fs can benefit from some of the parts devloped for their later DOHC bretheren (although a majority of the parts on those bikes do not swap over).
 

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If your trying to lighten up your ride - some of the newer sport bike parts from exhaust to foot pegs (and brake actuators) are really light. I'm totally amazed with the weight of the exhaust compared to my kerker exhaust. Point being - change out some of your standard parts like foot pegs, airbox, exhaust, rims, forks and etc can shave off a ton of weight. It seems to me a little bit of waste to spend time sawing off mounting points and such - I don't think much weight are saved vs the time to do it.

I have a cb750 71 project I'll be working on this winter with weight savings as part of the project. The next best thing to hp increases is weight loss - I plan to attack both ends of the spectrum. Since the budget is limited - this will be a real challenge to see how much I can reduce my weight and stay within budget.
 

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the cheapest weight reduction on a motorcycle is your own weight. A good diet and exercise routine can make a big difference in how your bike handles and goes.

Bob - I can see how a few tabs here and there won't make a difference, but in come cases of these bikes you can usually cut off a big portion of the frame aft of the rear shock mounts. If you look at the kh500/750 pic above there is a significant chunk of frame (maybe close to a foot) missing just past the rear shock.

weight location can sometimes be as important weight reduction. As much as I like the look of a battery hidden in the tail, the lower on the frame you can get that chunk of lead the better. The lighter a bike is on top, the faster you can flip from side to side.
 

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Geeto -
I was going to add that my last posting, I'm at 220 (with a 34" waist) now and since riding season has started, I've already lost 1" off my waist line. I could lose another 20lbs with no problem. I also agree - the lower the weight is on the bike, the lower your cg becomes and gives you better handling. For my project, I'm really thinking about a mid-frame gas tank, oil in the frame and moving the battery under the engine - how all that's going to work (????) but it will be cool anyways to try.
 

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Discussion Starter #12
that kawasaki is super nice.

i know as far as tabs, tailpieces, and lights go they add up. i read a lightweight camping book book and it said "take care of the ounces and the pounds will take care of themselves." which i think is applicable here.

anyone figure what sort of power to weight ratios your getting? whats the appropriate formula?
what is the advantage of reduced "unsprung weight" besides simple weight reduction?
 

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http://en.wikipedia.org/wiki/Unsprung_weight

the more unsprung weight you reduce, the stiffer you can make the suspension without sacrificing ride quality.

unsprung weight on a bike would be the tires, wheels, swingarm, shocks, brakes, sprocket, etc....basically everything below the suspension that also included the suspension. Sprung weight is the rest of the bike.

If you do a search here there is a company that was talked about a while ago that uses a lot of titanium for building ducati parts....I believe they had a sub 300lbs ducati. The advantage of titanium is that it can be made thinner than a comparable aluminum part with equal strength (although titanium cracks, it does not give). Yoyodyne sells a lot of TI parts that you could probably use on your bike if you were willing to spend the money...considering it is an xs400 I would not be willing to spend the money

There is also reciprocating weight. The heavier something is the harder it is to get it to change direction. You lighten your crank and the bikes revs faster, you lighten your wheel and the brakes work better.
 

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I don't know the "correct" formula for power to weight but I usually just divide the weight by the hp and that tells me how many lbs per 1 hp I am carrying. Really the only time I use it is when I am comparing my vehicle to another vehicle and it makes a nice quick and dirty ballpark estimate. If you are going to calculate use the actual wet weight of the bike (or even better, bike + rider).

Gasoline weighs approx 6lbs per gallon so remember - the longer you ride the faster you will be able to go...until you have to fuel up again.

don't take any mfg's word on weight. If you are really serious about doing weight reduction then baseline your bike, weigh it with everything on it in stock trim, and then start making changes. YOu can use two bathroom scales (one under each tire). The advantage of two scales vs a truck scale or a race track scale is you can set the front/rear weight bias.
 

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Many years ago when I started racing a friend told me "Everything on a bike has to be accelerated and deccelerated. So make it as light as you can. Including yourself." I saw an old NSU Supermax racer that belonged to another friend. All the nuts and bolts were titanium and despite the fact they didn't weigh anything the factory still drilled the tops of the boltheads to save that little bit more. Little bits add up. As Dennis Jenkins was quoted "There is nothing lighter thn a hole". Worth remembering.
 

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There is a very thin line between making it light and making it break - if it's a modified street bike drilling too many holes could be a problem. A track bike - at least they have medical on site in case your front end falls off...
 

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quote:Originally posted by Hoofhearted

"There is nothing lighter thn a hole". Worth remembering.
i thought it was, "very few holes are worth remembering." that might have been on a different forum.
i bet if you drilled every single bolt you could save about 5lbs.
another trick is to machine your front brake rotors thinner. this is probably more suitable on certain bikes then others. cb750's had stupid thick rotors that could be shaved down about 50% and save a couple pounds.
strip turn signals.
engine side covers can be lightened.
use smaller chain
get aluminum sprockets and drill them even.
light crank, light rods. most cranks are so seriously over built. I'm not the one to ask, but i would think lots of weight could be removed here so long as its all balanced afterwards.
lighter skinny tires.
aluminum swingarm
get rid of wiring.
run total loss.
kick only. (but actually remove the starter...duh)
Loose weight. (this one is hard for us all)
 

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I have a way of losing 220lbs of ugly fat off my cb - make it remote control...
 

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quote:i bet if you drilled every single bolt you could save about 5lbs.
i doubt it.
quote:the cheapest weight reduction on a motorcycle is your own weight.
g-man has it goin' on again....improves the whole program.
-parks
ps some holes are prone to fill with dirt. that can get heavy.
 

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If you're racing you can save a whole lotta poundage by getting rid of the lead acid battery and using Lithium-Ion batteries from R/C airplanes (running constant loss of course).

Michael
 
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