Dark Horse Crank.

[Fisherking]

I just got a Dark horse crank4 inch with 3500 miles on it . It has been ballanced crank pin welded trued and some weight taken off. I got this from a vender on another forum as he said he just through one out. I almost fell off my stool. He said he could go grab it and if I had an adress in the U.S.A. he would ship it to me at caust.. I jumped all over it.
My question is, I have done a 95 build Static comp at about 9.8 and 9.2 corrected 185 psi at 750 feet .
I'm running Andrews 57 cams . Intake raised 3/8 of an inch ported with 1.9 intake and 1.585 exh.
I'm planing on getting another set of engine casses and put the new crank in that . with my build would you put the Timken angeled bearing kit in the the crank cases or just leave them as they are ?

Thanks F.K.

 

[dolt]

If you are going to get another set of cases, consider a couple of options.
1. I am not sure what you are gaining by purchasing another set of cases to replace a 4" stroke crank with another 4" stroke crank; the only difference being one has been trued, balanced and welded (BTW, Dark Horse does not weld cranks unless specifically requested by the customer; they "Pro Plug" their cranks). If purchasing another set of cases, why not case bore for a set of 4.125" cylinders and build an all bore 107" motor.? MTC will sleeve, bore and hone your cylinders to 4.125" for about $400 but you will need to send them your new pistons.
2. That crank has been balanced to a balance factor based on the weight of the reciprocating mass, i.e., piston, pin, rings and locks. If the weight of your piston assembly varies from the weight used to balance the DH crank, you will experience some vibration at a certain rpm range and it can be nasty. Hoban Brothers provides a data sheet with their cranks with all the specs. It would be a good idea to see if the source vendor can provide that sheet.
3. In either case, you do not need the Timken conversion for a 95" motor; use two "Lefty" crank bearings and save a bunch of money.

 

[Fisherking]

If you are going to get another set of cases, consider a couple of options.
1. I am not sure what you are gaining by purchasing another set of cases to replace a 4" stroke crank with another 4" stroke crank; the only difference being one has been trued, balanced and welded (BTW, Dark Horse does not weld cranks unless specifically requested by the customer; they "Pro Plug" their cranks). If purchasing another set of cases, why not case bore for a set of 4.125" cylinders and build an all bore 107" motor.? MTC will sleeve, bore and hone your cylinders to 4.125" for about $400 but you will need to send them your new pistons.
2. That crank has been balanced to a balance factor based on the weight of the reciprocating mass, i.e., piston, pin, rings and locks. If the weight of your piston assembly varies from the weight used to balance the DH crank, you will experience some vibration at a certain rpm range and it can be nasty. Hoban Brothers provides a data sheet with their cranks with all the specs. It would be a good idea to see if the source vendor can provide that sheet.
3. In either case, you do not need the Timken conversion for a 95" motor; use two "Lefty" crank bearings and save a bunch of money.

Thanks Dolt , I'm getting the other set of cases so that I can build the lower end and still ride . I can just switch out the bottom end for the other bottom end when finished .
Now that sounds interesting 107. I have an extra set of jugs and two extra sets of heads . I figure when I get the motor in my bike finished , I will be working on the other one on the bench. I can take my time with it as I get extra $$ . I can send the factory crank for ballancing then maybe go the 107 route.
Sounds like a new project in the works .

F.K.