To lighten crank or not to lighten crank

Blah blah, lighten this, blah blah cr gearboxes, blah blah blah.  The cheapest and easiest way to more power is a Go Faster Stripe.  There are lots to chose from and you'll probably find that different widths and designs yield different power outputs.  Or.....Just put the horn so that it faces backwards.  For a boost of extra power just sound the horn and lunge forward on a sound wave of power.  Or......pump your tyres up to 70psi, (you'll need a long straight for this one though.) and you'll go like a rocket.
 
Whether they'll make rods to fit a Laverda or not (and the blurb does say they're for roller bearing motors) they only last 100 hours. Not remotely usable for a street bike. Maybe a competition engine but not too many of us here are that competitive.

Ken
 
mcnicol said:
Whether they'll make rods to fit a Laverda or not (and the blurb does say they're for roller bearing motors) they only last 100 hours. Not remotely usable for a street bike. Maybe a competition engine but not too many of us here are that competitive.

Ken
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Different, loads, clearances revs, etc in a modern MX engine.  Reckon 100 hours in a modern, high-revving competition 4-stroke is actually pretty good.  Think the equivalent 2-strokes didn't manage half that!

Anyway, totally unsuited to our needs.

piet
 
sfcpiet said:
Different, loads, clearances revs, etc in a modern MX engine.  Reckon 100 hours in a modern, high-revving competition 4-stroke is actually pretty good.  Think the equivalent 2-strokes didn't manage half that!

Anyway, totally unsuited to our needs.

piet
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Unsuited to the needs of the majority, yes...But someone, somewhere...
As a rule of thumb, the bigger the motor, the less time it spends on full noise. What is specced for 100 hrs in a race single may well go several times that in a motor which spends much less time wide open.
Too rich for my blood anyway...
 
The info does say they'll outlast an equivalent steel rod under similar conditions. So might last for 30 years in an under-stressed road engine. However, there are a couple of dodgy claims in the blurb that kind of undermine the credibility of the rest of it.

•Since the lighter crank also makes it easier to manoeuvre the bike I can more easily find the best track in the curve.
•When accelerating out of a curve the problem of a wobbling front fork is decreased.

OK, it's just a customer feedback quote, but it seems a bit of a stretch to credit a conrod with improved handling!




 
Dellortoman said:
OK, it's just a customer feedback quote, but it seems a bit of a stretch to credit a conrod with improved handling!
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Depends if you've got them bolted to the bars....

Just reminded that Carillo used to specify a life for their rods quoted in hours - 100 seems to ring a bell.
You could send them back and they'd check and re heat treat for a fee.
 
Dellortoman said:
100 hours?  :o

Shit! I've had my Carillos for over a year. They're well past their use-by date.
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Conrods are consumables in serious race engines... if you are competitive and want to stay that way.  Have a look around the classic endurance pits, you'll find crankcases waiting to be fitted!  The top teams will swap out major components as soon as practise/qualifying is done.  Quite normal to do a full strip if a championship is at stake, nothing is taken for granted.  Preparation is the key to reliability.  It's the front runners that have the lights in their box on all night.

piet
 
In the MX world handling in THE AIR has some significance. .Throttle input has a big effect on what a bike does in the air and maybe having it spin quicker and easier does that.Less reciprocating mass wears the rider out less as well, thats why I have a 250 and not a 450.
 
Dean Brown said:
Blah blah, lighten this, blah blah cr gearboxes, blah blah blah.  The cheapest and easiest way to more power is a Go Faster Stripe.  There are lots to chose from and you'll probably find that different widths and designs yield different power outputs.  Or.....Just put the horn so that it faces backwards.  For a boost of extra power just sound the horn and lunge forward on a sound wave of power.  Or......pump your tyres up to 70psi, (you'll need a long straight for this one though.) and you'll go like a rocket.
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I feel strangely at one with this post  ???
 
a very well respected and highly sought after tuner, with many thousands of (four stroke) racing successes behind him, with old British iron and bang up to date modern Jap stuff, plus everything in between, including many IOM TT wins, seconds and thirds even in the same race, and multiple times in the same week, once said to me  "a polished crank looks very nice on the coffee table"
CLEM
 
I di  and he said that they are all good, but create problems that you wouldn't have when they come off
CLEM
 
CLEMTOG said:
I di  and he said that they are all good, but create problems that you wouldn't have when they come off
CLEM
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current day anti friction coatings don't come off Clem
 
phil37 said:
I think that a lot of  bollocks, semi bollocks or misguided thoughts are  spouted when it comes to crank lightening themes.
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I'm with Phil. There are so many opinions and everyone has one.

Lightened cranks have advantages and disadvantages, just like every other modification made to what the factory felt was the best all-rounder.
Riding on the road is completely different to racing. But when it comes to racing then the saying goes something like, "When the flag drops the bull s__t stops."
http://www.thedam.com.au/The_DAM/DAM_Laverda_3c_Bol_dOr.html
The exciting part of racing is to see the various methods that engine/bike builders use to achieve the results and which modifications actually work. ? and we must always remain prepared to change our minds if a particular mod does or doesn't get results on the board. i.e. if we get beaten consistently then we make considered changes, one at a time.

I suggest you take a Lav with a super-lightened crank for a long ride first and see if it suits the way you like to ride.  A rip up and down the street is not sufficient. If you love it, do it.




 
I feel the Love Greg :D
One of the best parts of racing was tinkering and trying things.
Sometimes it ran well but was faster or slower.
Either way,it was enjoyable.
Well,  except when is was slower!
 
roger ramjet said:
That's definitely true but unfortunately that's Internet forums. Everyone with an opinion wants to let you know it and they are often portrayed as "fact" or based on personal experience, when in fact this is not the case. You really need to know the answer to your question before you ask, so you can sort the wheat from the chaffe. Even on a forum like this one which is frequented by some people with a solid technical track record, their will be differences of opinion. That's life on the net
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Yes - But Greg and myself are just saying "try it first" and if you like it - then put your hand in your pocket. - we aren't expressing an opinion even!! As I said - just remove your alternator - its weight plus the magnetic drag will equal any crank weight reduction - as a bonus on the S1 triples you will keep the s/motor too. - obviously all this only applies to triples. Happy new year to you all - Phil
 
My 2 cents worth. I've seen some wonderfully prepared machines..built with "cost is no problem" super tuners that ran fine..and were out run by a low budget home built machines..with a very talented rider.

Solid race preparation is very important indeed...but it is always "the Indian not the arrow"...a very talented pilot with aggression, knowledge, a well prepared machine and smart competition tactics is worth 10hp/20hp.

Lighten the crankshaft? Sure..have fun and enjoy!

 
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