Attention All Mikuni Users

[Travel'n Man]

Attention all Mikuni Users:

We were all at a loss when Todd (Wold Creek Racing) passed away, and the knowledge that left with him for our Mikuni Carbs….not to mention all the parts that he had.  I know there are other authorized dealers of Mikuni parts on the internet, but without the knowledge to share there are just another parts shop with no first-hand knowledge for the sale.

I have found a great new resource on Mikuni PHH carbs and he is willing to share his knowledge and is also an authorized distributor for Mikuni – David Premo

A few weeks ago I called up Dave Rebello and asked him if he was interested in me purchasing a few parts and pieces for my Mikuni from him – he said “not really” due to he is really an engine shop – I asked him who he would recommend to push that business to - he said “David Premo” and gave me David’s number.

After a few conversations with David and advise for my jetting – David came up with a small jet order for me, and some advice on my current jet settings. Over the weekend,  I make a couple adjustments to my pump nozzle rod, upsized my pump nozzle and changed the duration of the fuel being injected at launch, edited an air jet and it was like my Mikuni’s woke up for the first time (even more so than the original jetting that Todd send me when I bought my Mikuni’s).  I’m stoked on getting some new jets in from David mid week (USPS Priority) to see how the total jetting package that David recommends will affect my overall performance and the air fuel ratio mix. 

I called David yesterday and told him I had reduced my Air Jet per his guidance (I have good collection of jets through trial and error) and it was a HUGE difference – he said “wait until the new jets come to you mid week – you will really feel the Mikuni’s kick in then – you will think you have turbo’s”……………yep – I’m pretty stoked to say the least!

For any of you Mikuni guys/gals our there give David a call – he is a world of knowledge – easy to talk to , has a complete inventory of Mikuni parts, and will steer you in the right direction for performance of your Mikuni set up.

dave@tuning4performance.com

925-890-8074

[RyanT67]

Great info, thanks for sharing!  
 

[madkaw]

Yes - thanks for the heads up.

Even Todd admitted that he was more a race tune guy than a street tune guy. It's hard to find that kind of knowledge anymore.

Sent from my iPhone using Classic Zcar Club

[Travel'n Man]

Anybody following:

First of all David Premo is a genius - without a doubt.  I have spent $$ hundreds in past jetting with the hope of finding the correct jetting combination.  Digging and hoping to read a post somewhere that would be the "magic one".  It's all the blind, leading the blind..........David Premo is the real deal for anybody wanting to tune their Mikuni's right......the first time.........period.

His advise is spot on.  The knowledge he has for our fuel systems is dead on perfect.

My AFR meter is more consistent with less wild swings - the sound of the car is much better - faster power - much better acceleration - faster startup - less smoke - less fuel smell - plugs look better - faster idle time........and all this for a few jets and a few parts and pieces along with few phone calls!  David nailed it with 3 sets of new jets for me (naturally through trial and error I have way too many jets at this point from previous purchases.

Now I have a jet collection that I have accumulated over the past few years that absolutely has nothing to do with the true jetting of my car..........like I said - the blind leading the blind needlessly!

If you want your jetting done right - make a phone call to David - you will be surprised what has been hiding in your Mikuni's for years!

See my attached worksheet for details ( I do have an issue with my cylinder #3 that I will have to work on this winter)

Looking forward to getting a little dyno time in this summer to see what the difference is based on my last one from a few years ago with improper jetting.

 

Mikuni Tuning Master - BEST EVER 03MAY16.xlsx

[madkaw]

Looking at your chart, the only number that surprises me is the 160 air jet. With that l28 , you might need that main jet coming in sooner . 

My numbers( AFR) , are close to yours. Like to see a better start up when warm, but it's not terrible. My Mikunis are going bye- bye in the near future , so someone else can play with tuning. I'm going FI

[RyanT67]

All of your numbers were really throwing me off, then I saw you were running 40's.  The air/fuel jetting numbers seem sort of low.  Do 40's usually run 32 for large venturis?  How is you car pulling up around 5k to redline?  

[madkaw]

The 40 Mikunis usually come with 32 chokes/venturis . They aren't the biggest, but Mikunis also have booster/small venturis .

[Travel'n Man]

For street use the 40's are perfect.  IMO a lot of folks always think bigger is better. To be able to use the full band of the cam and to keep the carbs flowing on the speeds they are designed for 40's are perfect for me.  If I were tracking my car on closed courses I would want bigger carbs and a larger cam to maximize air and fuel flow. 

The car pulls like a champ through all RPM's with no issues on the transitions from Pilot - to pump nozzle - to Main Fuel.  Remember the Pump Nozzle determines how much fuel is dumped at launch/acceleration.  You can watch the AFR go rich for about 1-2 seconds and then stabilize when the pump nozzle is doing it's job correctly and dumping that extra fuel based on the nozzle size you have elected.

My new base line is dead on for my car.  I will not be moving these jet setting unless a dyno reads something different.

Edited May 8, 2016 by Travel'n Man

[madkaw]

Actually, I believe the pump nozzle size dictates the length of time the fuel is dumped into the engine . So if you want all the fuel at once you go with a bigger nozzle. You can adjust the linkage for a larger - longer stroke = more fuel

Glad to see he is a non-believer in the 1 turn out pilot rule. I tried to accomplish this  and it just doesn't work as good as a smaller pilot and more turns - for starting anyway

[Travel'n Man]

Steve

Actually David and I did not discuss the pilot screw setting - I have a wide range of Pilots and could never get my car to run smoothly with any of them set at 1 turn out.  The engine was not in a happy place at all with the "1 turn theory".

[gundee]

I wish I could get 32mm Chokes for my 44PHH. I am at the smallest at 34mm they make for the 44's.

I think the 32mm choke would be pretty much ideal for the street. Throttle response would be much better,

which I like more than a few extra HP at the top end where I never drive it anymore.

[madkaw]

Did you say throttle response!!