Guess I should have worded it differently,,,

As far as strength goes,,, has not seen any rash of crankshaft failures...

I was just commenting on the common run out that they have been seeing,,, checking before any performance enhancements, and putting together a Baseline for future reference...

yes .006 is within Harley spec...

 

What what run out have you been seeing?? any consistency??

 

How many miles do you think the PS crank goes before rebuilding?
The pro stock cranks are probably tapered pin/nut crank different animal than a pressed crank. There have been plenty drag bikes making over 200 hp with tapered pin cranks but they are not asked go 100,000 miles. Right now the 3 piece SnS crank is s good crank but guess what? They went back to a 1.671 pin. Also went 4140 on the wheels IIRC. I've got a good friend that has put 200000 miles on an 2003 deuce. Most of it is as a 107 all bore. He'e managed to kill a stock crank and an Sns 5 piece. He's had Dark Horse rebuild the cranks each a few times. It's interesting that his cranks pinch out of alignment. Mine spread. Neither cranks twisted so we are not abusing the drive train or shocking the wheels with power shifts or hard off the line starts. The cranks simply flex which indicates that the crank pin could be larger.

I've got the crank pins out of both cranks that have failed. You can see where the pin starts to wear from flexing in the wheels. At 125 hp one lasted 22000 miles, At 144 the other lasted about 11000. Both bikes were in the street so they weren't run WOT all the time. There were run hard at times (but not all) and both have a number of dyno runs. Going from a 1.5 to a 1.671 pin only gets you 11% increase in strength. The problem is that going larger presents it other issues, like roller speed,

I've tested a 48 on a flow bench, It flowed more than a bored G. As far as which one makes more HP? It really depends on the build.

 

 

 

Freight will be a PITA.. Could you measure the crank pin diameter?

 

Had a customer build his to a 124. Cam in to tune. He rode it a bit and brought back because it ran rough. Trashed pump and plate and .016 run out. So, problems do still exist.

 

Jason,
Did it spread, twist or pinch?

 

WRONG-

TC STREET PRO-"S&S press-together style flywheel assembly with 1970-up big twin sprocket shaft - Billet aluminum rods with 1.500" crankpin"
4 CAM-"Pork chop” style S&S Pro Stock press together flywheels with a relatively short 4.375” stroke – includes 8.500” long S&S billet aluminum connecting rods"

"Overview-
FEATURES AND BENEFITS ƒ The special shape of the S&S Pro Stock flywheel results in increased rigidity and allows flywheels to be balanced to very large pistons and rods ƒ Flywheel diameter may be specified between 7.875" to 8.125" (larger diameters must be used for the longer strokes) ƒ 1.500" pressed-in crankpin, 1.250" diameter big twin style pressed-in sprocket shaft, and a special pressed-in Pro Stock pinion shaft ƒ Pinion shaft is .850" longer than stock pinion shaft for a Harley-Davidson® Sportster® models ƒ Although the S&S Pro Stock flywheels are used in a S&S four-cam crankcase, they are designed to use big twin width connecting rods. Connecting rods typically used for 45° Pro Stock applications are S&S 8.000" or 8.500" billet alloy rods. However, any big twin width connecting rod designed for a 1.500" crankpin may be used. Refer to current special order sheet for options available"


Again,
For the third time, crank pin size , in and of itself is not the reason any crank design performs better than another.
For the dozenth time.....which brand crank is better than the S&S? Maybe you and your friends with 125 HP can tell us...lol....
Man Max, you used to be one of my idols....bring hard data to back up your claims. A no BS, take no prisoners data killer. Now....you just ramble on like a "Forum expert", with zero back up.
You are better than "should be, might be, think so, or the worst "a couple of my friends".....damn.

Why do you continue to use this S&S product if you and your friends continuously have various problems, failures and feel the product inferior?
You say "right now" the TC crank is OK but then spend a paragraph on how bad it is and your various failures. You are talking out of both sides of your mouth. You of course understand a crank is simply another of many "wear" parts on a vehicle? Lifters, cranks, rockers, pistons, rings, comps, bearings, and on and on.
Again, I have destroyed a HD Evo crank, S&S Evo crank, TC crank, and a Prostock S&S crank-and again, thats on me. I own my ****.
My current TC S&S crank had 30k on it before my rebuild of the motor and another 10 or so since, and zero issues. Way more power and abuse than you and your "friends", and zero issues....but guess what, it will fail eventually (IT IS A WEAR PART WITH A LIMITED SHELF LIFE), and I will smile, thank it for its service, and replace/rebuild it as new. Done.
Zero excuses and zero BS bagging on a product on my end.

Since you don''t obviously have the courage to answer what crank is better than S&S on a V Twin HD, I suggest you take Larry's offer and actually attempt to answer the OP's question (with real testing of load, twist, shock, brake, metalurgy, crio, etc)-which of course you have no way of doing without some serious testing facility help, (maybe an old engineering friend at UCSD, using their multi million dollar testing facilities?)
-M8 crank strength compared to TC-

I sure as hell don't have the answer (sounds like the M8's are holding strong), never pretend I do, and like I said, no one here knows either, but "experts" will for sure chime in and give their opinions.

 

Ok so the SnS prostock crank is pressed. Again. how long do you expect it to last? 50K? 200 miles? Just how far have you seen them go? Number of times down the track? You're the racer with all the experience. You should know..
[ Got the "you're" right ]

You totally missed my point as far as SnS cranks go. I'll say it again.. I just used it as a reference to pin diameter issues. Early SnS cranks failed because they could not handle the power and a major part of it was due to using a 1.5 inch crank pin. For me it's pretty obvious that the second version of the crank has a larger crank pin that they saw this as an issue. I sure as heck saw what I thought was an issue on the cranks that I and my buddy had fail.. That is direct experience. If you want to argue my diagnosis, go ahead. Oh wait, you don't have any engineering experience. My bad. From what I can tell your experience is to spend money til it stops breaking.

Thanks for telling me that I need to waste time to get a takeoff crank to do something that would require my time to give a single wasted point of analysis. I'd still need TC crank to compare to. If close I'd probably need 10 of each. Personally it's too much work just to prove you are wrong. I'll leave you with the point that HD advertised a point on the M8 cranks being stronger due to the larger crank pin. It make sense to me. For you? I don't know. BTW They only increases the diameter to 1.75 inches. So the strength is only slight.. My bet is that the only made it large enough to keep production failures at an acceptable level. Still, the M8 kits seem to make more HP than the TC kits. We'll only really know after someone collects data on crank failures at various HP.

So is the crank stronger? Engineering wise yes. A little. HD even said so.