AFAIK that is just an approximation and seat of the pants talk.

Thanks all for your comments. Think I'll get a 42 as the 45 may be too big. 

Anyone has got a throttle indicator installed?

Hot-wheels, you've got mail!

Sorry for the late response - system would not let me log in at all yesterday.

I used the 42 Mikuni on my 1310. I was shooting for 13 to 13.5 on the AF meter for regular road use. I think I ended up settling more for 12 to 12.5 as I did not want to get too much into swapping the jets and tubes.

I usually use as light of an oil as possible as Long as it doesn't flutter the piston. It is preferable to use a known weighted oil for a more accurate diagnosis of problems but I've chosen to use Singer sewing machine oil for convenience and its cheap cost.

About the being rich at the Low end of SU carbs, you've got 2 options: either manually tune your needle downwards to achieve lean settings as you prefer and manually tweak the rest of the stations (fine sanding of needle) or you could choose the most suitable needle from minty SU needle chart then tweaking whatever stations to your preferred mixture (quite hard to find a totally ideal needle)

Complicated but I had success in this for my HIF44. This is the limitations of SUs. That is why I'm considering the Mikuni.

I did try no oil in the dampers, but found that 40 wt in the dampers works best. I think the thicker oil limits the rise of the piston and limits the fuel. But I know this discussion has been done before and some think the opposite.

jerry

At full throttle I run Dellortos and Webers at 12s for road use, SUs work well in the 13s.

@Jchealey, re your comment about twin HS4s being rich below 1/4 throttle, try running with NO oil in the dampers and #6 needles, it worked for me on my 1293.

Very interesting comments! 

Some other queries; how do you guys know you've got a 1/4 throttle open? Did you manage to install an indicator of sort?

Also, what's the AF ratio one should be working towards? For my current HIF44, I aim at 12 cos folks say SUs work best when a little rich. But how about Mikunis?

Keep the comments coming!

I did try the 45 mikuni on my car. 1380 with 286 cam, ported head, etc. It ran great above 3000 rpm, sounded like a race bike going up the street. I could not get the carb to run at low rpm well. I had no power at all up to 1/4 throttle. I bought many jets to try different sizes, and had an air/fuel measurement to watch during the trials. I dont think you can do one of these without the a/f meter. I finally gave up, although others have made it work. I went to dual 1.5 SUs. Got the power back at the bottom of the throttle,although still a little rich below 1/4 throttle. I find now that I ease the throttle up through 1/4, then you can press the pedal to take off like a rocket. I keep meaning to dyno the car to find out how it is really working. I was told there was a good dyno guy for mini's in Shingle springs or Placerville? Anyone remember the name? Jerry

A friend put an HSR 45 on his 1412 stroker, with ported head, 1.46 Toyota Corolla rockers and a Russell Engineering RE13 cam.

After driving around with my AFR meter fitted, found it was way lean and I drilled the main jet out to 3/32" (2.38mm) to get it right.
It replaced an HIF44, he is happy now.

Guys,

I now need to seek your advice. 

Am considering between a 42 and 44. I'm currently driving a 1380, 3rd stage head, daily driver. Currently have a HIF44 with a MED XT Cam on. I probably do approx 100km every day; mostly freeways.  

I do enjoy a spirited drive but there are lights everywhere too. And yes, I drive Wifey to work and my 3 yr old bub to school.

Which HSR should I choose?

PN for the rubber spigot is HS42/018-42K.

It came with the kit. Don't know if it has a separate part number.

Oh yes, does anybody knows the part number for the rubber mount holding the carb (between the carb and ms inlet manifold)?

Thanks!

Lovely guys! appreciate the love! Btw, Hotwheels; youve got mail!

Seems like many have moved on from Mikunis eh?

I have a complete kit (MS manifold, HSR42, UNI or K&N air filter) that's sitting on the shelf.  I also bought mine from V-Performance and used it when I still had a close to stock 1275.  I have since rebuilt my motor to 1310 with an SW8 cam and have decided to go with a Weber 45.  The Mikuni is very easy to tune although I like the Weber better for autocrossing.  Let me know if you're interested.  My email is in my profile.  It will come with extra needles, jets, jet tubes, accelerator pump jets for tuning.  

My engine was bored to 1310 with an Elgin 001 cam (mild road). For it I think I had to lean the main jet one or two sizes. I also adjusted the needle one notch, but cannot remember which way (up one or down one from center). I seem to recall staying with the original needle it came with.

I ordered my carb through Vintage Performance Developments. They have a supplier that does the initial setup. It may be much closer to your needs with a 1380 and more aggressive cam.

I used a K&N RA-066V filter with it.

Edit: I also remember that I did need to add an extra throttle return spring to assist the return to idle.

Oh alright. 

Off the top of your mind, could you remember what mods were needed for this carb to run in our minis? 1 thing is know is that we need to down size the main jet or something. Is there other modifications you can remember?

thanks heaps. 

I do not recall the jetting I ended up with. I have since sold that car.

When I did that Mini (a 1961 "bitsa"), I did a custom dash with an A/F gauge and wide-band O2 sensor. I tuned the carb using that and a jet/needle selection I got through a local Harley custom shop.

Thanks for the heads up Mplaye

Im thinking of buying my own kit to play around. 

Can you share what jet settings should i be getting if i were to buy the HSR42 off the shelf? (1380, 2.9 FD, 286 cam)

Thanks!

No cutting required for the HSR install. It is actually just a fraction slimmer than the HIF44.