crank

Sheik Yerbouti · Post by **Sheik Yerbouti** » Tue Mar 10, 2009 1:01 pm

Crank pin bores should never be 'bored out' but EDM wire cut.Much more accurate and won't upset any heat treatment.

Thats not entirely true.... Boring done on a decent machine with decent tooling will always give a rounder hole than Interpolating with a wirecutter. EDM also slightly hardens the surface because the cutting action as a lot like burning. Conventional machining will upset heat treatment less than EDM. If the wheel is too hard to bore (its probably only case hardened) it can be ground, which is again more acurate than wirecut.

TwoStroke Institute · Post by **TwoStroke Institute** » Tue Mar 10, 2009 1:41 pm

Jig boring would be the way to go but good jig borers seem to be thin on the ground these days. I like the EDM as the bloke I use takes a lot of time setting up square in 3 planes. I Also like the 'lines' the EDM leaves on the pin bore gives a very strong grip on the pin, IME they stay 'true' for much longer.I use 0.08mm interference fit.
Now tell me you have a jig borer

Sheik Yerbouti · Post by **Sheik Yerbouti** » Tue Mar 10, 2009 1:56 pm

Dont need a Jig borer. We have a really good boring head for the cnc mills and that does an awesome job.
Nothing wrong with wirecutting of course, it obviously works fine. But the hole you get is never perfectly round, it's a fact of the mathematics of the machine and has nothing to do with how well the guys sets it up.
We seem to be hijacking this thread with machining discussion.........

And I DO have a jig borer

TwoStroke Institute · Post by **TwoStroke Institute** » Wed Mar 11, 2009 9:06 am

I trust your judgement on that then. Email me your address there will be a few cranks coming your way. Maybe a hijack but makes it clear that it's a long way before anything is 'scrap'.

TwoStroke Institute · Post by **TwoStroke Institute** » Fri Apr 24, 2009 3:30 am

A good article by John Robinson on the RZ 500 forum

CLICKY LINKY THINGY

Sheik Yerbouti · Post by **Sheik Yerbouti** » Fri Apr 24, 2009 1:25 pm

Excellent read that. I was curious about why they build v-twin 2strokes. Now its obvious (well sort of)

the-elf · Post by **the-elf** » Fri Apr 24, 2009 4:51 pm

or a 90^ firing parrallel twin like the KTM's GP 250's

TwoStroke Institute · Tue Jul 14, 2009 11:04 am

After pulling a crank down, I have a few impressions.
Yes your correct Falconman ther isn't enough meat to EDM out the crank pin and replace it, but I'll ask a crank expert on his opinion on what can be done.
Big end bearings are shite, I am sure their unsecured construction leads to many big end failures.buzinc they are supplied that way from Kawasaki (the KDX has the same arrangement)
Rod is definatly a 106mm centre to centre.
The rest is very good.
Some upgrades, a KDX 200/220 rod is 109 mm c to c but more than likely heavier. Not many 106mm rods but a big end cage with the rollers captive would be a real bonus.
HTH

buzinc · Post by **buzinc** » Tue Jul 14, 2009 3:21 pm

TwoStroke Insitute wrote

Big end bearings are shite, I am sure their unsecured construction leads to many big end failures.buzinc they are supplied that way from Kawasaki (the KDX has the same arrangement)

Cheers for that. I can only guess, Kawasaki can cram more rollers in unsecured cages.
But looking through theses threads, as far as cranks go. The main bearings, seals, aftermarket rods - even the centre section, all available. Its the integral crank pin and web that might be a problem.

Buz

TwoStroke Institute · Wed Jul 15, 2009 11:26 pm

Have a US contact that will be coating big end bearings and thrust washers for me. Assures me he has eliminated bearing failures, in high output engines with press up cranks

Sheik Yerbouti · Post by **Sheik Yerbouti** » Wed Jul 15, 2009 11:39 pm

Have a US contact that will be coating big end bearings and thrust washers for me. Assures me he has eliminated bearing failures, in high output engines with press up cranks

And I have a contact on the other side of the rainbow, who assures me there are fairies at the bottom of my garden... Probably the same bloke.

Seriously though, whats the coating?

TwoStroke Institute · Post by **TwoStroke Institute** » Thu Jul 16, 2009 7:42 am

Only rainbow in NSW is at the Mardi Gras and rest assured that there will be more than enough fairies there for a bloke to meet $\:D/$

COATING

falconman · Post by **falconman** » Wed Aug 05, 2009 10:22 am

I've been working on another solution. I have an RZ350 crank that is built the same as a KR. The inner throws and rod pins are cast as one and a press-in rod to connect both cylinders. It looks as though the RZ throws can have the diameter turned down to fit in the KR cases. You get a 54mm stroke crank to boot!! Does anyone have the diameter of the KR crank throws and center pin handy? My spare is buried in the shed will require an expedition of historic proportions to retrieve.

I won't be using the balancer shaft so I was going to make an extra wide lab seal. Even if the KR center shaft won't fit the RZ uses a straight shaft that would be easy to make a longer version. Oh, and I'm told Banshee cranks are the same. If true stock ones should be everywhere as the Banshee crowd always goes stroker crank first chance they get! $\:D/$ I'll post some pics later when I get a chance to take them.

TwoStroke Institute · Post by **TwoStroke Institute** » Wed Aug 05, 2009 1:38 pm

I like the "Kiwi Ingenuity' there falconman. KR crank is about 88-89mm OD with a 25.30mm offset for the 22mm crank pin.
RZ crank has a 96mm OD with 10mm of meat on the outboard of the crankpin.Primary drive side ends are different though.
Questions are is 6mm outboard of the crankpin bore going to be enough to keep the crankpin bore interence tight? Then there is the simpler task of machining a new KR replica drive side to put into the RZ web.
Then just add KTM/RM/KX cylinders and away you go

falconman · Post by **falconman** » Wed Aug 05, 2009 7:22 pm

I got 2 Athena KX cylinder kits waiting for install. I've been building this in my head for a while and got it figured out. The part of the crank was my only worry. But I'm going to build it and see what happens. I was planning to keep a record of the pressure to install the pin then after a few hours of running (if no boom-boom

) take the crank apart and check the pressure required to separate the parts. The primary gear will be easy. I got a cnc mill, lathe, tig welder and a boatload of imagination. I've been planning this for over a year. Just had to wait until I got the lathe in place. Now I can make some chips and hopefully a KR with over 80rwhp. My ultimate goal is to break 90hp with a 250 and 100hp with a 350 version. $\:D/$

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