jamie99roadstar wrote:
Can any HSR 42 be used, or do they differ based on what model of Harley they came off of? And, do you have to change anything with the intake (for mounting the carb)

I am sure that the jetting they come with can vary. The nice thing about this carb is that you can get different needles (Mikuni made), with different tapers, for fine tuning.

The only real difference other than that (That I have seen) is that a model made for a Road Star uses the Road Star throttle cables.

I have tuned quite a few, but this is the first time I have purchased one. So I am sure I am going to learn more.

Gram

jamie99roadstar wrote:
Can any HSR 42 be used, or do they differ based on what model of Harley they came off of? And, do you have to change anything with the intake (for mounting the carb)

I forgot to add a couple of notes to this Jamie. Both carbs have spigots on the back that will slide into the stock manifold and mount just as the stocker does. I don't know if the front throat is in exactly the same position, but I guess I will find out quickly.

Gram

Gram wrote:


This is the first time I have heard this Erbman. In fact I understood the factory (and aftermarket for sure) ignitions only have two timing curves. Can you help me understand what you learned about this?

Gram


Got this info a way back, don't remember from whom tho. Though there are 2 curves, within these curves the ignition modules see voltage to adjust the timing to fire the plugs. The firing vs the voltage it see is probably in the thousandths of a second. I don't know where he came upon the every .2mv chnage, just remember the numbers. I had the voes and now the tps mod, night and day difference on acceleration and performance from take-off, even gained about 4mpg in city riding (under 45mph)It takes aprox 4.5v for the module to see to go into WOT

Gram wrote:
jamie99roadstar wrote:
Can any HSR 42 be used, or do they differ based on what model of Harley they came off of? And, do you have to change anything with the intake (for mounting the carb)

I forgot to add a couple of notes to this Jamie. Both carbs have spigots on the back that will slide into the stock manifold and mount just as the stocker does. I don't know if the front throat is in exactly the same position, but I guess I will find out quickly.

Gram

Thanks very much for the info Gram. Another I need to look for this winter.

Gram wrote:
jamie99roadstar wrote:
Can any HSR 42 be used, or do they differ based on what model of Harley they came off of? And, do you have to change anything with the intake (for mounting the carb)

I am sure that the jetting they come with can vary. The nice thing about this carb is that you can get different needles (Mikuni made), with different tapers, for fine tuning.

The only real difference other than that (That I have seen) is that a model made for a Road Star uses the Road Star throttle cables.

I have tuned quite a few, but this is the first time I have purchased one. So I am sure I am going to learn more.

Gram

The tapers are all the same, the difference is the straight portion of the needle, that is the portion just below the grooves that effects from idle to 1/4 throttle (cruise speed) . I got mine from Bulldog, I believe what he did to mod the cable brkt was to spread it open a bit for our cable end to fit, he also used a spacer to move the brkt about a half-inch away from the carb body compared to the way it comes stock. One issue with out stock cable is the bend at the end of cable since it will now connect from the side, all I did was not to route the cable thru the 1st guide on the frame tube, this allowed enough flex without binding to come in from the side. Basically there are 2 HD models, one for the sportsters, and one for their big twins. I think it is only the pump nozzle that is different, smaller for the sporty.

Thanks Erbman!!

Gram

Gram wrote:


The only real difference other than that (That I have seen) is that a model made for a Road Star uses the Road Star throttle cables.


Gram

That's true, It also comes with the choke cable, and the float/needle is setup for the fuel pump...

Thanks for the info. I've got the 42 on the bench and cleaning it up a bit and checking it out. I think I can put my stock choke cable on it, there's the same nut type setup for it, I will check as soon as I can get back into my shop....work first, play later I'm gonna do the tps mod got the info from here: Click on HSR42 tps adapter

Steven

if you use the stock manifold, cut off those 2 nubs that are used to align the stock carb, it will let the 42 seat flat and possibly avoid leaks.

Thanks I will do that!

Steven