I got a cnc mill, lathe, tig welder and a boatload of imagination.
That's a bit of a worry The actual static pressure will mean 3/5ths of SFA it's what happens under dynamic pressure is the key, but no body is going to know until you do it.A look at a stroker 'shee crank might give you a safe limit on the proximity to the edge of the web.
Why no balance shaft.IMO unless your running a 90 deg crank that's a retrograde step. RZ/TZ cranks will spread apart when revs are applied, and from the factory they have no balance applied to them.
The beauty of the KR engine with the balance shaft is that the rocking couple issue was addressed, this allowed the crank width to increase making room for decent transfer ducts.
I was going to leave it off because I thought the crank had to be balanced to accomodate it. The KR crank is rather "thin" in places. The RZ crank even after cutting will be heavier overall I think. I'm just now moving into the stage where I have all the parts in front of me and more exact measurements can be taken. I expect many things to change in the next few weeks. Luckily I don't know enough to understand that this will never work!! Actually a person that builds RD's, RZ's and such said it should be ok. I believe him. [-o<
whats the stud spacing for the 54 barrel - same as KR?
maybe if you turned the web down from 6.5 to 4.5 clearance meat you could press on a 2mm ring around the whole web - like a composite pipe (shrunk inside another) the compressive force of the ring might balance the loss of material in that thin island of material
if the reciprocating units (rod, piston etc) where lighter than stock KR there probably not so much issue with 6.5mm compared with stock 8.2mm
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Last edited by KR-1R on Fri Nov 20, 2009 12:01 pm, edited 1 time in total.
WHOA THERE!!! I wasn't planning to work on this until next week after I dig the KR crank out of the shed! Here are a couple pics though. I haven't even opened the cylinder boxes yet. I do know the piston is lighter and the rod looks lighter as well but I won't know until I tear everything apart and measure/weigh the componants. I'll be working on this in my spare time over the next several weeks and will post more info in a specific thread on the engine build. The KR base gasket is on the bottom, KX on top.
With a balance shaft the crank is left 'unbalanced' and the balancer shaft does all the work.
I would believe your very own tuning guru(and Geeza's mate) Wobbly before I would believe anyone else on high end tuning. The AIR cooled RD cranks are the only cranks that left Iwata balanced correctly, all the problems with that POS crank that went into the LC and RZ was wallpapered over by those little tie bars going from the engine to the frame on all LC and RZ models.
From the quick look I had last night I think it is definantly worth a go, has the piston got a 15 or 16mm gudgeon?What's the comp height of the piston? The stock RZ rod is 110mm and the RD 400 has a 115mm rod both with a 16mm gudgeon. Using a spacer plate under the cylinder will give you some room to blend/adapt the bolt spacing and transfers.
You might need a packet of ceramic inserts for the webs, as those webs are HARD.
I have an RZ crank here 1 in bits and the other together.
The wrist pins are 15mm on the KX. I was going to have the crank balanced once the setup was completed. I wouldn't know where to begin to get proper balance with a KR balance shaft, turned down RZ crank and a KX topend.
You'll need a KTM 125 110mm rod then.
Balance will be easy, reciprocating mass / rotating mass. Expressed as a percentage. The components used are of little consequence.Only the maths matters. Work on 60%. If you can wait a bit I can crunch some numbers for the balancer, but why not just go 90 deg no rocking couple, no balancer or no balancing required.Simple.
The last thing you want to have to do with a completed true twin crank is start drilling filing or machining. Balance must be done in the machining phase.
Don't be confused with primary and secondary balance, primary is where the mass of each component is matched, secondary balance is the killer(as MJ's link shows) and MUST be addressed with an RZ crank.
The actual static pressure will mean 3/5ths of SFA it's what happens under dynamic pressure is the key, but no body is going to know until you do it.A look at a stroker 'shee crank might give you a safe limit on the proximity to the edge of the web.
Actually a person that builds RD's, RZ's and such said it should be ok. I believe him. [-o< 
