HSR42 for shovelhead?

[poohbearjake]

Ive been running a Super E on my kick only shovelhead since i bought it and after some tuning it runs fine and starts up pretty nice but I feel like pushing my luck and trying some other carbs out. Plus, I'm kind of a stickler for having a perfectly tuned carb and with the E it seems like I have to choose between running lean or super black, sooty plugs. Least that's been my experience with it.

I have a nice keihin CV laying around which I've read works great for shovels but I'm curious if anyone has any thoughts on running a mikuni hsr42 on one of these old pigs. I've run them on all my evo bikes and love 'em, but I wonder if the 42mm venturi might be too much carb for a stock displacement shovel motor.

For reference, I'm currently running some pipes w/ mufflers so i have some back pressure, and I have a Dyna S ignition installed. Far as I know I have a stock cam and other internals, but I may have 80" jugs on a 74" bottom end. I haven't been in there to check yet.

Anyone have any thoughts or base line jetting/needle setting recommendations on either the CV or the Mikuni? Im in So Cal at/near sea level.

Thanks

[tzienlee]

personally I would say if you are going to buy a new carb, to go for a Lectron,
they are by far the best carb out there, & a new Billet one will be out for Harleys soon !!! VERY trick bit of kit,
pricy, yes to some, but not for what you get in the long run,
easy starting with a REAL choke system, better performance throughout the range,
better fuel economy ..... this is a film of mine the first time fired up with my Lectron,
it didn't even need the idle setting once the mag was retarded.....
practically tuned themselves, no jets to worry about, bolt on & go fast....
https://www.youtube.com/watch?v=zapYrI8o4Y8

[JBinNC]

The Super E is one of the most user-friendly carbs out there, so if you are having trouble tuning that, a carb change probably won't help you. But that being said, the Mikuni would be more straightforward to deal with than the CV. And I say that as a fan of the CV. But they take some fiddling to run well on a shovel. I'm assuming the 42 Mikuni is an HSR, and it probably came jetted for an 80 cu.in. evo. To run it on your shovel, you may (probably) have to make the intermediate jet larger, and raise the needle to make it a little fatter across the range.

One of the problems with the Mikuni or the CV is that they are a bit of a pain to mount on a shovel motor as the oil crossover line and the rocker boxes sometimes interfere. That is the beauty of the Super E, it fits the motor.

Good luck with it.
Jim

[ncmc47]

Mufflers aren't for backpressure, they are to quiet your exhaust. I don't know who started the rumor you have to have backpressure to run right. A motor runs best with no back pressure, that's why hotrodders spend considerable time porting and polishing!

[pan620]

Mufflers aren't for backpressure, they are to quiet your exhaust. I don't know who started the rumor you have to have backpressure to run right. A motor runs best with no back pressure, that's why hotrodders spend considerable time porting and polishing!

A motor runs best at wide open with no back pressure, not so much down low.

[poohbearjake]

The Super E is one of the most user-friendly carbs out there, so if you are having trouble tuning that, a carb change probably won't help you. But that being said, the Mikuni would be more straightforward to deal with than the CV. And I say that as a fan of the CV. But they take some fiddling to run well on a shovel. I'm assuming the 42 Mikuni is an HSR, and it probably came jetted for an 80 cu.in. evo. To run it on your shovel, you may (probably) have to make the intermediate jet larger, and raise the needle to make it a little fatter across the range.

One of the problems with the Mikuni or the CV is that they are a bit of a pain to mount on a shovel motor as the oil crossover line and the rocker boxes sometimes interfere. That is the beauty of the Super E, it fits the motor.

Good luck with it.
Jim

Like i mentioned, I'm not having any problems with the carb whatsoever aside from the fact that my plugs are extremely black and sooty. The bike starts and runs excellent, but I'd like to have a more tunable carb that would allow me to refine my fuel metering and get it closer to perfect (not that it matters all that much, I just have about 7 carburetors sitting around and feel like trying them out)

But your thought does make sense to me. I'm not sure what this carb was jetted for when I picked it up at the swap meet but I'm thinking close to evo settings with a fatter intermediate and needle position/size would do the trick

[poohbearjake]

Mufflers aren't for backpressure, they are to quiet your exhaust. I don't know who started the rumor you have to have backpressure to run right. A motor runs best with no back pressure, that's why hotrodders spend considerable time porting and polishing!

I tend to agree with pan620. If your building a bike or car for the drag strip, then straight pipes are great. For practical riding anywhere below WOT, you want something to provide a bit of back pressure. Here's a good video from S&S that actually ran some dynos and does a good job of demonstrating what we mean.

https://www.youtube.com/watch?v=KjKUKhHQLHg

[Supertouch]

You can also check out Dale at killer motorsports. Bought one of his CV’S that he hot rods, the manifold and carburetor are polished like a mirror. Have had two friends that swapped them out on there shovels from s&s’s. He builds them to your specs have yet to put it on but here only good things.

[heyyodho]

My settings for a 74” shovel.

HSR42
Pilot Jet: 25
Main Jet: 155
Needle: 97; middle clip
Acc. Pump: 50

[setmeonfire]

I run an hsr 42 on my shovelhead and luv it - kicks ass over the super e - kicks easy and performance is great
was a pita to fit with fatbob tanks but well worth the effort

[poohbearjake]

My settings for a 74” shovel.

HSR42
Pilot Jet: 25
Main Jet: 155
Needle: 97; middle clip
Acc. Pump: 50

Right on, thanks for the reference, man!

[poohbearjake]

Alright so I got the carb mounted up and thought I'd just update this thread for anyone else's future reference. I took a look at the settings that heyyodho mentioned above and thought that sounded a little lean for me since I'm at sea level and its winter n all. I ended up just running the jets that were already in the carb when I bought it (which I suspected were for a shovel anyway) and the bike fired right up once it was installed.

I'm running a 162.5 main, 30 pilot, 97 needle at 2nd to lowest clip, and a 60 accelerator pump nozzle.

I havent put a whole lot of miles down yet and will prob need to do some fine tuning but after a few test rides around town I can already feel how much happier the bike is with this carb on it. I liked my super E, but with the mikuni I already feel more power and the bike idles stronger and starts up easier so far.

Gonna throw some new plugs in her today and see how they look after putting down a few more miles.

Thanks for all the replies

[heyyodho]

Glad it’s working out. My settings started off really rich (still ran well but poor gas mileage) and I made my way down to the settings I posted. I’m in California at 30’ elevation btw.

Alright so I got the carb mounted up and thought I'd just update this thread for anyone else's future reference. I took a look at the settings that heyyodho mentioned above and thought that sounded a little lean for me since I'm at sea level and its winter n all. I ended up just running the jets that were already in the carb when I bought it (which I suspected were for a shovel anyway) and the bike fired right up once it was installed.

I'm running a 162.5 main, 30 pilot, 97 needle at 2nd to lowest clip, and a 60 accelerator pump nozzle.

I havent put a whole lot of miles down yet and will prob need to do some fine tuning but after a few test rides around town I can already feel how much happier the bike is with this carb on it. I liked my super E, but with the mikuni I already feel more power and the bike idles stronger and starts up easier so far.

Gonna throw some new plugs in her today and see how they look after putting down a few more miles.

Thanks for all the replies