G'day Stinga

Where has your post gone?

I've serviced the 42HSR on my 1200 Sporty. I followed the link that Scotty set up and printed off the manual. I did all the work with the tank on, but I reckon your tank would get in the way. Removing it would give you a chance to clean the fuel tap screens. I'm glad I pulled the carby apart as there was a bit of crap in the float bowl and some fine metal fillings creating a grinding past in the slide tracks. I found the small small torx head bolt that holds the needle in stuck. I just carefully levered the tab to one side to get the needle out. You are right, a dyno would be the most exact, but pricey, way of getting the right needle position. I've only heard good things about the Yorst Power Tube, so if I was going to the expense of a dyno tune I would fit one then.

I bought 101 H-D Evo Performance Projects from Fishpond.com for $10. The book says: "Mikuni's HSR42/45/48 series is an updated version of the 40mm carb...As with all Mikunis, it is infinitely tunable, offering not only swappable fuel jets, but air jets as well, for each circuit. Ironically, that may be its biggest downfall for Harley riders who think it's too complicated. Well relax, 99% of the time these carbs require no special tuning to work exquisitely well."

Good luck,

Dude

hi, the mic carb 40/42/45 mm comes with the main air bleed to the main  needle jet  blocked on all of them,                        iv'e been opening them up for years you can buy the main air beeld jet's or jet drill them out  to size & can put  8 x  0.025"  holes in the needle jet tube  from bottom to top in pair's  ,  hole's low in the tube will be richer than hole's higher  in the tube ,   & use a  0.5mm air bleed ,  you will need to go up in the main fuel jet , they close this off on  all the harleys only ,       it's a big part of tuning a carb  try & fix the bent tag for the needle  tap the screw head with a steel driff to made it  come easy, try it with the needle set 1 below the middle c- clip groove,    bring the needle up 1 ,         cheers

G'day,

Thanx for the replies Dude & daddyracer56, Dude tried to remove me post because there didn't seem to be any interest in the topic unlike the overwhelming discussions, options and trumpet blowing on  the specialist mathematical equations and quantum physics of how to design and build a hot rod Harley donk, that level of physics would even give Stephen Hawkins a huge fucking migraine HA HA.

Had the motor done up back in 2000, and going on what the Mukuni manual states about the carb tuning being OK straight out of the box, I dont think any changes were made to the fine tuning of the carb. I have a few reasons for this thinking, 

1. When adjusting the Pilot Air Screw it takes more that 2.5 to 3 turns out to get the engine speed to change
2. Motor pulls cleanly when cold with little or no choke
3. Black sooty spark plugs
4. Poor ecomomy 12.5 ks/lt @ 110, pre build 17 to 18 ks/lt

So if I am going to go to the trouble of removing the tank to change the "E-Ring" I think I will get the next leaner sized jet needle and one of then Yorst Power Tube thinges or fuck it and take it to the Dyno man.

Thanx

Stinga

hi, idle jet size should be around either 25 -27.5 or 30  , main jet around 170,-180,   the way i do it is go small idle jet 1st ,  check the running for a flat spot just off  idle  about  up to 1/4 throttle ,   load it slight up a slight hill  with load in  2nd gear & check for a flat spot  if you don't get one with a 25  try a 22.5  don't forget to dring the air bleed screw in  with the smaller idle jet,   adj idle  air bleed screw  only when at opp temp  with bike in  up right posie  at idle speed, adj  slighty torwards the rich side of adj & test ride slow up a hill ,   

 it's the only easy way to find just the next size up from being lean,   it's easy than going rich idle size 1st, because you can be a bit on the next size  up idle jet  & bike will still use the extra fuel,    ,      asp with  big bore & cams etc,     big air cooled motors don't mine a bit of extra fuel,      drag pipe's don't like to be rich there tuning window is more narrow than with mufflers as e.g.         cheers hope this helps you

untill you set-up carb proper just use 2 only bowl screws to make it a bit easy ,  the needle itself has nothing to do with under less than a 1/4 throttle  the 1st section of throttle is handled buy the idle jet,    needle is for about 1/4 throttle & up  , needle& needle  jet+ main air bleed & main jet  size work the later throttle openings ,

Yo Bro.  

G'day All,

Well went to Thunder Tech in Mundaring today to let Pete have his way with me old girl and sort out her private bits, shit it was hot down there. He made the first bench mark run @ 9.09 am and got 86.4 hp at 5400rpm and 92.5 tq at 4050 rpm but the fuel/air ratios were well below the12's at the cruising range, so some re jetting was needed to get fuel/air ratio up into the 13's.

Pete changed the main jet to 157.5, slow jet to 22.5 and the pumper to 50, then he had a couple more runs on the dyno and got 85.92 hp @ 5500 rpm and 91.31 tq @ 4050 rpm on the last run but more importantly he got the fuel/air ratio at the levels they should be, at around the mid 13's.

Now I can read and I can see a slight loss in hp and tq but the last run was at 10:49 am and the air temp was @ 30.76 and the main point was to do something about the MPG, which was achieved.

Same motor with S E mufflers I was getting around 12.5/13.5 lts/k, changed mufflers to S & S got 14.24 lts/k on the trip down to Mundaring then after the dyno tune and a 35 c plus ride back home I got 15.7 lts/k so I guess I can say my original quest to improve fuel economy has been achieved. So when I filled up the old girl she had used 1.25 lts less to do the same amount of k's as pre-dyno and at $140.9 per litre for BP ultimate it's going to take a few k's to recoup me dough but now I also have a bragging sheet.

I am not connected to Thunder Tech in any way what so ever but if ya looking for top notch service and advice that is delivered to you by good people and not some bloke with a pony tail, greasy skin and shows about as much interest in you as the last fart that he dropped, unless you have a wallet the size of a shoe box, then give them a try.

Thanx again to all that contributed to this thread

Stinga

G'day,

A bit of an update on how the old girl is going and whats been happening to her, went to Perth today to get a new Avon rear tyre but before I went i had completed a 48 k service over the last week and in the service ya have to change out the plugs. Well I thought that I would try out them NKG Iridium plugs that I got from M & M Cycles, $ 9.50 US each. Well on the way down the temp was about 23 with no wind and sitting on between $ 1.15 to $1.20 with a few overtaking manoeuvres ( $1.80 with 3 road trains bumper to bumper) and running on BP ultimate and I got 16.36 ks/lt. Got to Mundaring and filled up with Peak 98+ went and got the tyre fitted at Vic Park then rode back to Tammin and filled her up again and the numbers showed 17.56 ks/lt with the same type of running including similar passing manoeuvres.

Don't know if it's the placebo effect but 17.56 ks/lt it's a lot better than the pre dyno numbers of 13 ks/lr and and even better than the after dyno numbers of 15.7 ks/lt but it's money well spent.

am running a 42mm mikuni HSR mechanical slide not vacum 160 main and a 52 pilot starts without a choke and is to rich the bike runs good at 100 klms an hour 8 litres over 100 kilometers but full throttle I get fuel coming out of the aircleaner at this time the motor is stock put am unsure where to get the jets anyone in nsw have them for sale ?

There is no way in hell you should be running a 52 pilot jet in a HSR Mikuni  !

In fact, I don't think you can buy a 52, sounds like a CV size ?

These guys are pretty good with jets etc'

http://www.mikunioz.com/

 

hi Ratty give us a ph call , i run a 45 pumper mik on my 1999 Dyna street dragbike

 

For the people to follow up where im goin the trike runs a 1340 evo standard in 150 psi twin exhaust long with mufflers and the 52 pilot was a jet out of a box which was maybe an imperial size from what I have no idea. I am running the 160 main jet, 20 pilot jet, needle is in the middle setting fuel pump backed off will go for a ride to daddy racer today and will be a good test run. Thanks everyone for there help.

runnin a little lean on the pilot next size up 22.5 am thinking of leaning up the main to a 150 feels over the top when trying for full noise