single Mikuni HS42

[sokota]

anyone running the single 42 mikuni set up? pros and cons over twin flatsde set up? Leaning towards the single carb, stage 2 hotcam, and bumping the revs 500. any insight will be devoured .. bike is 96 scorpion sport , going to get some track time in. It is running great with the well sorted stock carbs , is the performance improvement considerable ?

[Jimbo]

Hey, I'm using the Mikuni single carb on my Skorpion along with the megacycle mild cam and 2mm overbore high compression piston. Also have the M4 exhaust slip-on. My bike runs real well, much stronger than my other Skorp with the stock carbs rejetted. I went up one tooth on the front sproket because of the fast back roads I ride and occasional track days. I just recently put in Hyper Pro fork springs and oil (20 wt), EBC Pro-lite front brake rotor and EBC sintered brake pads. I'm waiting any day now for my Hyper Pro rear shock to come in the mail. I do my track days at V.I.R. in Alton, Virginia. Maybe I'll see you there one day. Jimbo

[OLDMTNCARVER]

Hey Jimbo,
What are you useing with the 42 Mikuni as a manifold? I'd comment about the stock carbs and jetting mods but I think that my head would explode.
OMC

[OLDMTNCARVER]

Jimbo.
Scratch the 42mm...opps
omc

[Bill Jurgenson]

I'ver run both setups for quite few miles, er years.
Just went back to the TM34-65 from the BikeWorx Kit with TM42 (aka HSR42, the Harley crowd name for it - it is exactly the same carb)
Have run both with stage2 and 3 Megacycle cams, with stock piston, with 1mm larger Wiseco and with 104mm J&E.
Remapping the CDI to a limiter at 8400 is a must for every serious rider regardless of tuning or no. Or simply using a TDM 3VD box. Plug and play.
For general road use, the dual carb is better and also easier to deal with.
As I have written several times, it will work with an otherwise stock engine in the stock airbox with remapped CDI and return about 5hp more along with much better mileage. My Sport with completely stock engine ran an honest (not speedo) 120mph with the TM34-65 jetted 110 and 115, 25 idles and 50 pump nozzle.

The big single will not act properly with any kind of restricted i.e. legal exhaust.
At least not with an otherwise pretty much stock engine. Serious porting and much bigger headers are necessary to cope if the can is to be any where near legal - at least over here. Been there - done it...
With an open illegally loud exhaust, the big one is easy enough to set up however. That is how I used it, too,mounting the quiet can for inspection and the lookalike open can for everyday. That is how I do it regardless of setup otherwise.
The big sinlge worked great on the racer with no problems at all. Not that the racer would get very far on the open road, even with lights.
It depends on what you want and how much you want to spend and how much you can do yourself in terms of machineshop.

[sokota]

Thanks for replys. Bill seeing you have tried both set-ups , would appreciate your opinion on the performance differences between the single TM 42 compared to the twin carb TM 34-65. Iam guessing the twin carb set-up might allow more top end ....? I really enjoy this bike , its motor is tight so do not want to get into the bottom end this season [like the installation of a carillo rod]. The exhuast is custom fabricated and free flowing , yes a bit loud . My plan is to run the stock bore and compression , a stage 2 cam and choose a carburation system then let it spin maybe 1000 rpm more ,hoping the "soft" compression will be easier on the rod and lower end. The single carb appeal is simplicity and cost but leads to the curiosity of performance difference .Thanks for anymore input.

[basser23]

Hi
Two questions..where in Maryland are you located?
Next, you say you have a custom fabricated exhaust...who built it?
I am looking for a new system..currently running the stock pipes with a Holeshot can...
I'm west of Gaithersburg for reference..
Chip

[sokota]

Hi Chip, I live northeast of G-burg , in Mt. Airy. Headers are stock , the Kerker can has been modified. Mark

[basser23]

Hi Mark,
Well we are almost neighbors! My brother lives in Mt Airy off Penn Shop
Once I sort the Skorp,we'll have to get a ride in somewhere..
Having carb issues..aka dirt....
Chip