Running rich

[PasoRoo]

A while ago my Paso started having difficulty starting. It would start on the front cylinder and after a short while the rear cylinder would kick in. A week ago the rear cylinder wouldn't fire at all.

I've completed all the electrical upgrades and cleaned all the connectors. After the relay upgrade the voltage over the coils is pretty much the same as the battery voltage, which I choose to interpret as that my tinkering is working. Today I took the plugs out and they were black and slightly wet. Cleaned the plugs and: Hey presto, it fired on both cylinders first push of the starter button. So I'm assuming the bike is running too rich.

This leads me to a couple of questions: My bike has been converted to Dell's and they are 40 mm. Is that too big for the 750? How do I go about checking the carb setup? What other items should I check/change to stop the bike running rich?

It's not too long til summer starts on this side of the world and I'm trying to get these niggles sorted before then.

Cheers,

Mike

[jayh]

Hi, Don't know if you have this information already but the 750 f1's were essentially the same engines and had 36 dell's their jetting was needle k8/2nd groove,main 135/140,pilot 65.The leguna seca,montjuich,Santamonica had a wilder cam, and ran 40 dell's needle K5/2nd groove,main 148/155,pilot 65.So you could compare your jetting to this.
Higher revs would mainly be effected by the cam,and my experience with 36 dell's on my pantah 500 and 600 has shown that this is not the area that the plug fouling occurs,it seems to be down low especially at 50 - 60 kph speed limits,just off idle.If i spend to long putting around at those speeds in 3rd gear my plugs foul in no time.One thing I try and do is drop it down a gear and open the throttle up a bit more,this seems to help,But I still get a bit of a miss after slow running as I open it up for the first time,Iridium plugs also helped on my paso. Jay

[PasoRoo]

Hi Jay,

You may be right about the 50-60k city running, which is what I have done mostly in recent times. The weather is actually improving on this side of the world and the days get up to about 20 deg C, despite the frosty nights , so I might take it for a good run and see what the plugs look like.

The Iridium plugs sound like they could be a good idea regardless, so I'll try and get a pair. What type are you running?

Am I right in assuming you can take the jets out of the carb and see what size they are?

Cheers,

Mike

[jayh]

Just remembered about the iridium plugs .They are ngk dpr8eix-9,I got 4 of them from the states for about $50.00 AUD inc freight on fleabay.It's much cheaper if you can wait the extra 2 weeks for them.

I'm not sure how complicated it is to remove your dellortos from the paso,but on the pantahs you can loosen the clamp to the manifold,twist them off of the manifold and then pull them out as far as the cables will allow.This makes it possible to remove the bottom cover.But it is easier to then undo the choke and top cover screws,remove the choke, slide and needle assy.The rest of the carby then comes away and you can work on the bench.It is a little bit tricky to remove the slide off the cable,but as long as you have a good look at it before you do, it's pretty straight forward.The needle has the grooves at the top,and the retaining clip should be in the 2nd groove from top.The K number is stamped on the needle.The other jets are inside the bottom cover.Last time I purchased jets and needles,I got them from gowanlochs in sydney and they were reasonably priced.The rear carbys main jet size was different to the front because of temperature differences,but I can't remember which way around the larger jet went. J

[paso750]

40s are big for a standard 750cc engine which has no other modifications. That doesn`t mean it doesn`t work but it`s likely you won`t be able to get a good setup as good with i.e Dell orto 36s.

G.

[PasoRoo]

How would you rate them against 38mm Mikunis, G?

Mike

[paso750]

That`s a good question I can`t really answer as the Mikunis are quite different to Dells or the Weber. The Mikunis have membranes which move the slider and needle opening the main jet depending on the underpressure regulated by the throttle valve position. That`s a different working principle.
They do work very well though and they require only very little maintainance. I`m definetely a fan.

G.