We rebuild all our own crankshafts in house at BDTM. Here is a sample of a customers crankshaft, before and after. We first measure the crankshaft for run out, twist, and measure the shaft bearing diameters for wear. We also inspect the Tins for any signs of shifting & damage. We then disassemble, clean, and partially reassemble with a new rod, needle bearings, and spacers.
Then it is mfixtured in a press die and the assembly begins, during assembly it in mounted between centers and inspected, as the assembly progresses. Final assembly and inspection between centers to Honda OEM specifications of .001" total T.I.R.
Final inspection to .001" T.I.R. This crank actually measures a Total Inch Runout of .0005" or half the Honda specification. It also looks and runs like a new crankshaft.
On our Big Bore builds we weld the tins, crankpins, and Static balance to match the heavier pistons used in BB engines like the Sphynx, Puma and Saber. performing all of our own crankshaft builds and having the best assembly and inspection equipment allows us complete control over our builds.
The pictures below show the finished crankshaft ready to ship to our customer....
Last edited by acecarlos; 07-19-2013 at 06:54 PM.
hell yeeeeha. very cool . keeping them tolerances tight
Awesome. How do u clean them? If i dont mind me asking how much is this service
Solvent tank cleaning first, then Ultrasonic cleaning, wire wheel brushing, and bead blasted after disassembly, and final Ultrasonic clean. This complete service is $185....
IMO only makes sense to rebuild if the Tins are not damaged or molested, and the crakshaft bearing shafts are not worn out. Most Honda OEM cranks are worth rebuilding, if not, purchase a new HotRod.
I was of the understanding that rebuilding a 250r crank puts to much stress on the tins when separating and pressing the crank back together. I had two rebuilt crankshafts fail because of the tin cracking and catching the rod and dynamite. What is your opinion?
It goes fast over bumps too
You are correct Dirt Man....if the Tins are not respected like a Babies bottom (LOL) during the rebuild, or if they have been damaged or molested, they are a lot more likely to fail.
We use jigs, and dies that support the crankshafts on the heavy metal outer surfaces, never touch the Tins. We also support and center of the main shafts and never off the Tins. We also don't pound on the Tins to align the halfs, we use a dedicated die with guide pins to align the crankshaft halfs to specifications.
IMO if you pound on the Tins to twist the halfs into alignment during assembly like a lot of other crank builders do, that is a Big No-No, and one that will result in Tin failure. The Honda cranks with Tins are the most sensitive, and need to be handled with a lot of care because of the Tins.
Last edited by acecarlos; 07-19-2013 at 07:38 PM.
Yup, that is one method jcs003, not the way we really do it.
First we don't use a cut-off wheel to cut the rod off and seperate the halfs, we use press the in pin out of the crankshaft by induction heating around the crankpin area, and lightly pressing. The localized heat expands the crank more than the pin....
Second we inspect per Honda specifications using 3 indicators to see true run out and twist. The way they inspect the crankshaft does not meet specifications and never willwithout the 3 rd indicator all the way down the taper end of the shaft, next to the key way slot....the .001" run-out Honda tolerance is at the tail end of the taper, and much harder to obtain or assemble a crank to that spec.
Getting .001" T.I.R. at the 2 main jornals is easy, almost all cranks fall in, close or within a few thousands, getting the twist out and holding less than .001" on the 2 main bearing jornals, and less than .001" at the taper end of the shaft is not. This should also be done with 3 indicators and between an accurate bench center such as the one shown at BDTM.
Thanks for sharing the video.