engine and drivetrain Mikuni Dual 44's Flooding

[bmwfan]

I removed my dual 44's Mikuni's to change intake to head gaskets and the O-Rings on the heat block spacers between the carbs and intakes. This was for a presumed vac leak ( rough idle and with backfire flame shooting out at the heat block on #4 cylinder carb ).

After reinstalling everything, It starts right up, again with single backfire from #4 but ran fine the all of a sudden the engine starts to sputter and RPM dropping. While looking at the carbs wondering what's going on gas starts flowing out of all 4 intake ports like little waterfalls. Shut down engine and still flowed out for a few more seconds. I would guess a couple of ounces of gas in all.

I searched some old threads which pointed to float level adjustment, an obscure post on vac leak causing flooding, as well as to high of a pressure from fuel pump. Well I had around 2weeks ago replaced an old electric fuel pump with an Airtex E84070 pump. Max psi , depending on where you look, of 5 to 7 psi. Mikuni manual Rec's are 2.84 to 4.98 psi.

I checked the float adjustments, per manual, they are at 13mm on each side, manual states 12mm +\ 0.5 . I left them at 13 as the would close the floats sooner and trying to get 0.5 adjustment is a bit rough. Also removed jets and cleaned and sprayed out ports. I had a fuel pressure gauge that I ordered along with the new pump, but hit the wrong PSI button and received a 0-100 psi gauge . I hooked it up anyway, but thinking that it may not be very accurate at low psi.

Started her back up. Same exact thing, #4 backfire then idled a bit rough then rpm drop, then the waterfall of gas. I opened the throttle a few times checking the pressure gauge , looked the be between 7-10 psi. This may answer my own question. But before removing the carbs and putting them back on the '02 was running fine except for a bit of a rough idle which I thought may be coming from a vac leak.

Next simplistic step for me is a fuel pressure regulator, but there seem to be a lot of pros and cons on these. And the selection for low pressure regulators are few. As well as Airtex stating not to use one on the E84070.

Specs:

Mikuni 44's

Main air jet. 230

Main jet. 145

Pilot jet 55

Starter jet. 160

Bought 2002 2 months ago, that is they way it came

Any thoughts on what is going on?

Walt

Edited September 15, 2013 by bmwfan

[LimeySteve]

Look on ebay for a Malpassi (Itallian ) Filter King they are brilliant, cost about $85 usually, I've got mine from people in Canada. Used them when I was in England, my Dellortos set to 3 psi my Stomberg 97's on my 32 Ford Roadster set to 2 psi .They Work .

[bmwfan]

Thank you,

I'll have a look

Walt

[Emyers]

Rick,

  I am also running Mikuni 44s, have for nearly four years now.  I am running the Carter P4070 pump, same pump I used for the Weber 40/40 DFAV the Miks replaced. No external regulator and absolutely no issues with fuel pressure.  Just a thought.

Earl

74 02Lux

02 M Roadster

72 Volvo 1800ES

Edited September 16, 2013 by Emyers

[bmwfan]

Thanks Emyers,

 

other than both needle valves/seats going out at the same time ( sitting dry for 2 days in 110degree heat, don't know if tip of needle valve is rubber or metal )floats seem adjusted right , high input fuel pressure seems to be the most logical for now.

 

So, I ordered the Malpassi filter king, 67mm, as reccommended by LimeySteve. Best price from dellorto.co.uk, $49.71 pounds uk. Might take up to 2 weeks to receive. In the mean time will replace the needle valves and seats. And try it out before the Filter Kings is installed so I can narrow down what exactly what the issue is.

 

Any thought on wheather the Starter discs or vac leaks at manifold mounts can cause flooding?

 

Walt

[DaveBMX]

Just to counter point i bought a filter king years ago for my dual solex's and it actually didnt regulate the fuel at all. It could have been a duff but it was brand new but it did not bring the pressure down sufficiently at all. i fitted something like this and it was perfect. cheap too!

 

http://www.ebay.co.uk/itm/8mm-10mm-Manual-Adjustable-FUEL-PRESSURE-REGULATOR-Carburettor-Carb-Fuel-Pump-/271095762730?pt=UK_CarsParts_Vehicles_CarParts_SM&hash=item3f1e910f2a

 

 

regards

 

Dave

[LimeySteve]

Word of warning on the rotary dial type regulators, the ethenol in our wonderful "gasoline" is destroying rubber parts in fuel systems, there have been a lot of incidents where the diaphragm has failed & sprayed fuel on exhausts with terrible consequences. I have used tons of filter kings & had one that acted up on one car , moved it to another & it was fine. not sure why but generally the FK is brilliant.