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Discussion Starter #1
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.

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Discussion Starter #3 (Edited)
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....

Carlos
 

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hell yeeeeha. very cool . keeping them tolerances tight
 

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Discussion Starter #6
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.

Carlos
 

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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?
 

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Discussion Starter #8 (Edited)
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.

Carlos
 

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Discussion Starter #10
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.

Carlos
 

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well, ken builds championship winning engines and isnt hiding his "secrets", he is aware most people cant do the kind of work he does so he is happy to share his knowledge with the world. he is a man of integrity and thats another reason why he is successful.

john
 

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Discussion Starter #12 (Edited)
The best Jig or Fixture will get you close, the final truing and adjustment to specifications is what brings the crank to specs.

For a closer look at the Honda specifications, and how to inspect the crankshaft for T.I.R. and Twist, see the Honda service manual, it clearly tells you the inspection points including the the 2 main jornals, and at the taper point next to the keyway.

Checking between centers, with 3 indicators at the same time and holding to Honda specificationsof .001" or less is how we do it..."no smoke and mirrors", just good machining, assembly and inspection skills.

Here is a picture from the Honda service manual showing the inspection point at the taper end, clearly the video posted is not inspecting the crank to Honda specs.

As an example; a .001" runout at the main bearing jornal will compound to .003" or .004" at the taper end or 60 MM or 2.360" down the shaft, that is why it is important to check as illustrated, on the taper end of the shaft, otherwise the crankshaft has not been rebuilt to specifications.

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Carlos
 

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what you failed to recognize in the video is it was a demonstration. he was explaining one issue with the crank. if you view his other videos he applies similar techniques for inspection. also, he was explaining the accuracy of his rebuilding technique.

john
 

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Discussion Starter #14 (Edited)
In none of the videos I have seen, does he or anyone else for that matter inspect to Honda specifications nor does he show an inspection procedure adequate enough to meet Honda specifications.

What we posted clearly shows the correct method of inspection, and is NOT a "demonstration" in any way, it is an actual rebuild, with an actual inspection process, comforming to Honda specifications.....in other words Real Life crankshaft rebuild.

Carlos
 

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Discussion Starter #15
Hummer:

Our die fixtures the crankshaft halfs, a partial press of both halfs occurs, crank is inspected, induction heated coil expands crankshaft crank pin bore, halfs are rotated or twisted by hand, back into press fixture, back into inspection centers, ect....the process continues until the crank is true, straight and the T.I.R. is under .001" on all 3 indicator points per Honda specifications.

Carlos
 

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Discussion Starter #16 (Edited)
Hummer,

The only thing I know for sure is that we inspect to the Honda specifications, and at the inspection points specified by Honda. I also know that inspection between centers on an inspection center stand is the most accurate method of inspection. I also know what tolerances we hold our crankshaft builds to, at the very least to .001" total T.I.R. all of these knowns are facts, since it is what we do and have control over.

I will also add I will stand 100% behind our crankshaft builds to be as good or better as far as tolerances, and rebuild to like new based on the OEM Honda crankshaft. If the customer has the BDTM crank inspected, and it does not exceed the tolerances listed by Honda, he/she can return it for a full refund. The accuracy of our crankshaft rebuilds, and the inspection method is top quality, and it shows in the finished product.

The $185 cost includes the Rod, needle bearings, and rebuild as listed. The finished crankshaft is an example of a real customers cranshaft rebuikd at $185...

Carlos
 
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