Mikuni HSR 42 tweaking

[The Guy with the 883C]

I installed my Mikuni a while ago, and here is what I put in it to start:
22.5 pilot jet
97 needle on the second groove
165 main jet
#60 accelerator pump nozzle
2 turns out on the mixture

My question is that the bike, in the hotter weather of late, is running pretty rich.
A little blue smoke at start, and the enrichener can be pushed in after ten seconds and the bike will run. Plus the mileage is down to 39-41 mpg.

I plan on checking the plugs tomorrow, but I was hoping that someone could give me a direction to go on the jets etc. I have a bunch of different ones to try but I'm not sure of which direction to go to lean it out.

Thanks,

[LagerDrinker]

Originally Posted by The Guy with the 883C

I installed my Mikuni a while ago, and here is what I put in it to start:
22.5 pilot jet
97 needle on the second groove
165 main jet
#60 accelerator pump nozzle
2 turns out on the mixture

My question is that the bike, in the hotter weather of late, is running pretty rich.
A little blue smoke at start, and the enrichener can be pushed in after ten seconds and the bike will run. Plus the mileage is down to 39-41 mpg.

I plan on checking the plugs tomorrow, but I was hoping that someone could give me a direction to go on the jets etc. I have a bunch of different ones to try but I'm not sure of which direction to go to lean it out.

Thanks,

I cant answer much but from my understanding the mikuni needs a bit of occasional tweeking cause it doesnt compensate for altitude changes like the stock cv does. While you may not be changing altitude the air density is changing with hot and cold temps. My suggestion would be small jetting changes especially if bike is running good.

[jamman]

smaller jet sizes or dcrease the jet size,to lean it out.. Blue smoke is a small amount of oil burning on start up..

[jerseymutt]

Ok Guys,

I don't really know my Mikunis but isn't that an awful lot of carb on that bike (unless it has a lot of mods)?????????????????

Mutt

[jerseymutt]

Ok Guy With The 883,

I went to this web site Sudco Mikuni HSR Carburetors and they don't list the 42 for the 883 only the 1200. Also the 42 is the carb of choice for stock 1340's. I think that carb might be to big for your application. I don't claim to be an expert but I do know that too big a carb is not a good thing. But they don't seem to list the 883 at all.

I was reading the other day (somewhere) about kick start big twins with mikuni's and that guy used nothing over a 38. On the web site it listed 38 for pans.

Your set up may be working now cause it is running to rich which compensates for the lack of air movement through the carb. But I don't think you will be happy until you punch the 883 out to 1200, raise the compression and drop in a cam - of course I am assuming you've already done the exhaust and air cleaner. That won't get you back your fuel mileage though.

Mutt

PS I didn't read everything at the web sitebut check it out, you might find a solution there.

[LagerDrinker]

Originally Posted by jerseymutt

Ok Guys,

I don't really know my Mikunis but isn't that an awful lot of carb on that bike (unless it has a lot of mods)?????????????????

Mutt

for 883, Yes. i totally agree too much carb.

[The Guy with the 883C]

Plans are for the 1250 conversion this fall.
The carb was free :-) so I had to use it.
Mostly for the throttle response. I know the 883 can't take advantage of what it will flow, but according to Sal at Mikuni, it will work just fine, justs needs to be tweaked.

My question was to get opinions on whether I should adjust just the pilot air or change jets.

My question was answered in a PM, and I adjusted the pilot air using the idle drop method, and ended up at 1.25 turns out, and once the idle was adjusted, it seems to run much better. That is close to where Mikuni suggests changing jets but I'll try it for a while and see.

[jerseymutt]

OK, glad to see you got it worked out.

Mutt