Mikuni conversion, fueling question

[fasterdammit]

I'm undecided which path to take here.

The stock Paso set up (on mine, at least): tank -> petcock -> filter -> pump (electric) -> Weber

The stock Monster/SS set up (mid-late 90s): tank -> filter -> vacuum-operated petcock (driven by 1st inlet manifold) -> vacuum-operated pump (driven by 2nd inlet manifold) -> Mikuni fuel rail

I have all the parts for both setups. Since I'm converting to the Mikunis, my 1st thought is the Paso's stock pump could be replaced by the Mikuni vacuum-op petcock/pump system. This would eliminate one drain on battery, too.

My question: which is preferable in this situation? Electric pump -> carbs, or vacuum-op system -> carbs? Or a combination thereof? Tank -> filter -> vacuum-op petcock -> vacuum-op pump -> electric pump -> carbs (Although ... that sounds like serious overkill.)

As always, all thoughts & advice greatly appreciated.

[koko64]

Many people with Monsters get rid of the vacuum operated fuel tap in areas where there is ethanol in the fuel. I'm not sure if that is the main reason, but on the Monster forum people generally get rid of them. They seem to fail by either jamming open or closed. Some failures flood the motor with fuel while others starve the carbs. People often convert to a manual fuel tap. An in line tap could work ,but access is an issue with the bodywork. If you find a reliable vacuum tap you can trust then you could put it anywhere.

The oem Monster fuel pump is a very high flow but low pressure (3 psi) pump. It's ugly but very effective. It's also expensive when new. Rebuild kits are very cheap however. It's a Mikuni hexagonal type. I read somewhere that it flows enough to run a V8! Mikuni also make a smaller rectangular pump that flows 14-16 litres an hour that a is low cost alternative. Should be enough for a 750. California Cycleworks has them.

I've also heard that these pumps can be affected by ethanol. I have never had or seen a problem with them yet down here.

Hope this helps.
Cheers.

[fasterdammit]

Thanks for that. So, I gather: ditch the vacuum-petcock (I'll just keep the Paso's stock unit on the bottom of the tank), keep the filter (obviously), and swap the Paso's stock pump for the Mikuni unit? Any benefit to using both pumps in series?

Regarding ethanol, I've been adding Startron to my tanks to good effect - unless I know I'm giong to blow through the tank in the next couple hours. But the ethenol was really starting to degrage performance and reliability ... but after a couple tanks w/ that stuff, back to normal!

[fasterdammit]

Next question: is 300°F a suitable temp for intake manifold gaskets or should I look for a higher temp resistance?

[koko64]

The Mikuni will be good with the vacuum pump. The extra Watts will be good for your battery and starting. One pump is enough.

I like being able to turn off the fuel tap overnight.

Others will know if the Weber prefers a non pulse electric pump.
Buy the oem inlet gaskets if you arent sure. I buy stock gaskets when in doubt or from a reputable aftermarket supplier. I use some Permatex Aviation gasket on paper/fibre type gaskets. Others will have good sources Im sure.

I like external fuel filters for ease of service. A mate converted his 2002 GSXR1000 to a $10 GM auto external fuel filter. Nice work and saved $200!

[fasterdammit]

Others will know if the Weber prefers a non pulse electric pump.

Won't need it when it's sitting in a box on a shelf!

[lane1feathers]

I'm about to start my mikuni conversion. I was going to leave the paso petcock (fuel tap coming out under left side of tank) insitu, thinking it was vacuum operated, but when I drained the tank the other day to replace fuel lines, the fuel poured out using gravity alone when tap was turned on. I will be installing a vacuum fuel pump. Will I need the vacuum operated petcock from the monster (as per manual diagram) as well or not. If I don't include it, will fuel overcome the carb when sitting overnight and end up filling the overflow tank and all over the garage floor? Any advice would be great.
Thanks guys.

[Mc tool]

The stock fuel tap is fine , as it has been for the last 20 odd years . Did you ever have a pool of fuel on the floor before ( what over flow tank ? ). The mikuni's have a float valve to stop the flow of fuel once the float bowl is full ( remembering , as you have just discovered the fuel was never turning off )...... same as the weber , unless your float valves fail ( jammed open with dirt ...... hence the fuel filter ) there will be no puddle on the floor or in the motor ,Same as the weber. The fuel pump is there because as the fuel level goes down it will go below the height of the carb(s) and as you have cleverly noticed gravity makes the fuel flow out the bottom of the tank ,but it will not make fuel flow uphill to the carb(s) once the tank starts to empty so we need a pump, and weather this pump is an electric pump or a vacuum operated pump doesn't matter as long as sufficient fuel reaches the carb(s) at the correct pressure , And historical reliability in service would suggest that both pumps are capable of doing this....... The Paso has a electric pump feeding the weber with a return line , the SS has a electric pump feeding mikuni's with a return line , the monster has a vacuum pump feeding mikuni's and others here have a vacuum pump feeding a weber , AND I really don't believe weather you use a vacuum tap or an ordinary one will make a shit of difference.
( OH OH ! look out ! the sky is falling )

[Skins]

I use the original fuel tap. I never turn it off, and the float valves in my Dell Ortos control the fuel just fine. Only had a problem once with dripping fuel, and reseating the offending float valve was easy, and fixed it.

[lane1feathers]

WOW, thanks for that Hamish, why didn't I think of that .....entertaining as ever! I love your sarcasm when you're off your meds...even if it is directed at me very helpful none the less. Keep up the good work bro


Thankyou Skins for your response, appreciated


Just as a side note, I am a crane operator/ heavy haulage platform operator NOT a Ducati mechanic so if I ask some dumb questions along the way...I appologize

[Mc tool]

sarcasm ? me ?... directed at you ?....... WELL and Im not off my meds ( I wish ) and , if I take the flash wrapping off my job description , Im a washing machine fixer , or rather was , now Im supported by ACC ( accident compensation corporation , a government enforced compulsory accident insurance , yeah it is a #ucken rip off ), but a crane Mmmmmmm that would be cool . The last personal experience I had with a crane was in 1980 when some of my co workers sneakily put the hook under the back of my safety harness , hoisted me up and then lowered my into a river and then a Gorse bush ( prickliest plant on earth ), and yes , you may infer from that my becoming a smartarse is not a recent event and I sure don't mean to put idea's into your head , and ( seriously ) I hope it was helpful , that is always my underlying intention
Hamish