light cranks

seanmx57 · Post by **seanmx57** » August 9th, 2009, 6:53 am

anybody know what years has the light cranks? I'm pretty sure the 89 crank was lighter than the newer ones. How much lighter are they? Light enough to change the way the motor accelerates? I changed to a CR250 flywheel and am quite happy about that. Thinking about a lighter crank now.

http://www.youtube.com/user/500bigbore · Post by **Roostius_Maximus** » August 9th, 2009, 7:17 pm

i talked to a dude who does alot of the different teams stuff, says they'll "swiss-cheese" the cranks for the racers from the rod side, or on the 4 strokes they'll undercut the weights. theres always titanium.

100hp honda · Post by **100hp honda** » August 9th, 2009, 7:25 pm

any crankshop will lighten your crank to what ever weight you want.

MICK · Post by **MICK** » August 10th, 2009, 7:11 pm

Lightening a two stroke crank just seems like a fundamentally BAD idea to me...
Aside from producing a crank from lighter material, machinging the existing journals will substanially reduce CCR. I think to a large degree ideas like this rear their ugly heads because of fourstrokes. Race shops and the OEMs swiss cheese the piss out of fourstroke cranks no prob...but a two stroke has a much more dynamic form of operation.

I think an easier/safer choice is a light con rod. Titanium for instance. I've emailed a company in the UK back and fourth a couple times about con rods for the CR500. Arrow Precision says they can produce a custom steel rod that weighs 25% less than OEM.

Now if they could produce a crank, steel or Ti, that wasn't solid but honey combed inside like a helocopter's rotor...that would be suuweet

thestuz · Post by **thestuz** » August 11th, 2009, 4:17 am

i read of one guy who drilled 1 1/2 inch holes in the crank below the main bearing then welded tin plate to block the holes. apparently it made quite a difference. but bad for idle stalling.

dannygraves · Post by **dannygraves** » August 11th, 2009, 10:10 am

'88 and '89 were supposed to have lighter cranks.

http://www.youtube.com/user/500bigbore · Post by **Roostius_Maximus** » August 11th, 2009, 4:07 pm

hey, i happen to have 2 88 cranks and an 89 loose at the moment, i'm back to work tommorrow and will check em

seanmx57 · Post by **seanmx57** » August 11th, 2009, 4:57 pm

now we are getting somewhere. I'm not interested in modifying a crank other than to let STR set it up maybe.

dannygraves · Post by **dannygraves** » August 11th, 2009, 6:14 pm

yeah, weigh them so we can know for sure. no one has had any real data to back that.
unfortunatelly, even though the pn is listed as available, you can't get them from honda anymore.

crflattracker · Post by **crflattracker** » August 11th, 2009, 9:23 pm

back when pro flattrackers rode yamaha 360's some of the better motor builders would cut 125thoundths off the outer face of each crank wheel and then screw a magnisuim plate on to fill crankcase volume.

http://www.youtube.com/user/500bigbore · Post by **Roostius_Maximus** » August 12th, 2009, 7:21 am

k, i forgot i used the good 88 crank in my 87 engine, so it goes like this

crank used in my af had a hotrod, got it from frank,
'90 1025grams
'89 1100g from kball
'88 1095g from dahondaboy
'87 1035g from my california bike

dannygraves · Post by **dannygraves** » August 12th, 2009, 8:18 am

hmmm, '89 is actually heavier... hhmmm

http://www.youtube.com/user/500bigbore · Post by **Roostius_Maximus** » August 12th, 2009, 10:02 am

i'll ask kball again, but i'm sure this one is 89

MICK · Post by **MICK** » August 12th, 2009, 10:55 am

Roostius_Maximus wrote:'90 1025grams
'89 1100g from kball
'88 1095g from dahondaboy
'87 1035g from my california bike

...interesting, all within production tolerances. So in actuality they weigh the same.

http://www.youtube.com/user/500bigbore · Post by **Roostius_Maximus** » August 12th, 2009, 11:22 am

the 1025 one was perfect, its in my af (the only aftermarket rod in the bunch)
the 1100 one is useable and stock rod, the 1095 has the side washers thrashed, and the 1035 (87) , well it was real nice so it got set aside and the not as good 2nd '88 (didnt check it) one went into the 87 bike

100hp honda · Post by **100hp honda** » August 12th, 2009, 5:45 pm

Roostius_Maximus wrote:k, i forgot i used the good 88 crank in my 87 engine, so it goes like this

crank used in my af had a hotrod, got it from frank,
'90 1025grams
'89 1100g from kball
'88 1095g from dahondaboy
'87 1035g from my california bike

in the '90 shootout it says honda increased the crank weight from the previous year. so that meens '89 would be lighter. it doesnt say how much heavier the '90 is but aparently its enough for the magazine to mention it. maybe your cranks are mixed up some how.

dannygraves · Post by **dannygraves** » August 12th, 2009, 5:55 pm

in 20 years I would not be surprised if someone changed a crank.

http://www.youtube.com/user/500bigbore · Post by **Roostius_Maximus** » August 12th, 2009, 6:09 pm

ya, no doubt its been changed, if anything its decent to see that there is/was a difference in cranks

the only thing i found from honda mentioning cranks is listed in the ad of the '90
"revised crankshaft balance factor for reduced vibration"

100hp honda · Post by **100hp honda** » August 12th, 2009, 6:45 pm

MICK · Post by **MICK** » August 13th, 2009, 7:08 pm

Maybe we assume too much?

If Honda's goal was simply to shift the BF by adding weight they would have only added grams...not ounces. Not nearly enough weight to effect power output or delivery.

And in this case 75g on a CR500 crankshaft is within Honda's production tolerances.

...so some guys get the "light" cranks while others, and god only knows who, get the "heavy" cranks

100hp honda · Post by **100hp honda** » August 13th, 2009, 9:16 pm

MICK wrote:Maybe we assume too much?

If Honda's goal was simply to shift the BF by adding weight they would have only added grams...not ounces. Not nearly enough weight to effect power output or delivery.

And in this case 75g on a CR500 crankshaft is within Honda's production tolerances.

...so some guys get the "light" cranks while others, and god only knows who, get the "heavy" cranks

is there a handbook somewhere that says what hondas acceptable tolerances are ? im alittle confused on why you keep saying everything is well within honda specs.

lets keep on a roll and assume some guys got a '90 frame with the footpegs 3mm higher, and some guys footpegs were only 1mm higher because thats probly well within honda specs...right ? and some '90 frames only had the the steering head moved 2.5mm rearward, while other were moved 5mm.....because its probly within honda tolerances.

. guessing and assuming is the wrong way to conduct a legitimate experiment, if you want to find correct answers to the questions.

i commend roostious for his generousity in weighing the cranks, but as far as im concearned the whole experiment is flawwed.........simply because it sounds like he isnt 100% sure what year cranks he actually has, and one of the cranks doesnt even have a honda rod on it.

and one more thing: i see where you going with the "maybe we assume too much" comment but why would honda tell the magazine they increased the crank weight, if infact they actually hadnt ? some kind of weird publicity stunt ? the magazine claims the extra weight will smooth the power, obviously it would need to be a good amount of weight to affect the power. maybe you guys see it different, this is just the conclusion i come to.

http://www.youtube.com/user/500bigbore · Post by **Roostius_Maximus** » August 14th, 2009, 8:10 am

i've heard it said before that the hotrod is heavier than stock too, i'd like to know its loose weight, but i'm too busy riding it.

Now if we are talking about a revised balance factor i can see that making a difference in the weight of the crank aswell, if its beeing built with the force calculated to be no larger than the bearing area of the crank and the force tolerence within 1/2" of that, then change either the force spec or the tolerence and weight will have to be added to previously neutral space, can be a 1/2 gram even, but its gotta be there to change the spec of the balance, which doesnt involve the target rpm of the balance formula

basically, if you had new oem cranks plucked from stock bikes, not substitued part # loose crank inventory, i doubt that all 89 cranks weigh the same as eachother, but they might be so different from the previous year that you could tell, either way i'm sure it'd irrelivant if you are going to balance it now, no one is going to secure mallory metal to a canned 2 stroke crank so the only option is to remove weight, and in that process can possibly remove some inertia weight (either by holes, chucking it in a lathe and cutting it off the sides, wherever), but cautiously so you dont "flip" the balance, at that point it asks to remove wight were it doesnt exist and you have major work to invert+recover the crank to balance back in its fields

dannygraves · Post by **dannygraves** » August 14th, 2009, 8:21 am

speaking of crank balance... on my gen-3 I bought a brand new oem crank. It had a stock bore with a really old wiseco, the kind that was also cut on the sides on the exhaust side. Before I took it apart it has excellent compression, so I decided to reuse that topend. Unfortunatelly after I cleaned everything and put it all together it had shit for compression. I rode it like that for liek 4-5 rides and before the last ride I went to a new style wiseco 1st over. On the old top end it didn't really vibe much and was really a super smooth bike, but I was having tuning issues and no low end grunt, so I did the topend. Now w/ that boat anchor in there is vibes like a SOB! my hands were going numb and the vibration through the footpegs was really bad. every bearing in that motor was replaced when I was doing the conversion and the only thing that changed was that piston. I'm starting to buy into the idea of having the crank balanced.

http://www.youtube.com/user/500bigbore · Post by **Roostius_Maximus** » August 14th, 2009, 8:42 am

you had the OLD wiseco with the big wide pin window? that thing is only 439.7 grams with its pin, the new one with no window at the pin is 498 with its pin! thats a huge difference, funny thing is that the oem with its pin was 486.7, you'd think that the big heavy one would have been closer to the target of the stock balance, it usually holds that if you change a piston on a balanced rotating assembly its alot easier to go heavier than lighter, dont seem to work here

dannygraves · Post by **dannygraves** » August 14th, 2009, 10:54 am

ya...weird but yeah, I held th old and new ones in my hands and the weight difference was really noticeable.

BannedCR500Riders.com

light cranks

light cranks