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Can anyone tell me their main jet size cooresponding to this carb? Mine have a mismatched set 142 & 145 and are running too rich. I have adjusted it very carefully but it is still running rich. Someone told me that it should be in the 135 range. BTW this carb is on my 90 750 Sport which is the same motor as the Paso.

I rejetted my Dell's a few years back so I have that info....somehwere. I headed out to ride today, 50 in NY in January!!! Yesterday it was 70!!!!!

I'll post the sizes tonight.

I've been sneaking up on the jetting on my 1990 Sport.
Current jetting in my 36 PHM Dellortoswith 2into1 exhaust
160/162 main (richer in back)
60 pilot
265 atomizer
K5 needle in middle postion
60/4 slide
Champion plugs
Needless to say, quite a bit more rich than what you are running. And I'm going to go one richer just to make sure, although it runs pretty good now.

If its running rich, make sure your choke plungers have good rubber in them, and that the spring is setting them complete down to their seats. If you haven't already done it, take the carbs completely apart and blow all the passage ways clear with some carb cleaner or compressed air.

What plugs are you running? The Champions made a big difference in my bike. Much better than the NGK plugs. If you have a single pickup, you can't change the timing on that bike, so that won't make a difference.

Make sure you are using fresh gas, and your carb boots are good.
What aircleaners and velocity stacks are you running?

Hope this helps.

I found my notes and this is what I'm using:

PHF36BD

Main: 155
Pilot: 60
Choke: 75
Needle: 261 AB1
Jet Needle: K-27 Clipped at 2nd lean position.

K&N Pod type air filters
F1 Slip on cans.
No internal engine Mods.

ducinthebay wrote: What aircleaners and velocity stacks are you running?

I have Malossi pod air filters on some kind of hard plastic elboy connected to the intake side of the Dellortos. To be honest, I am really new at the whole carb adjusting procedure. I've read several methods and believed that I have adjusted them properly but I just can't get rid of popping through the air filter that happens at idle. Once the motor warms up, most of the popping disappears but it is very annoying for someone who likes their machines to run perfect.

I tried the "bear hug" method or whatever you call it to make sure that the slides raise at the same time. I have adjusted the idle screws as best as possible (according to the procedure given in this forum). I just got a carb mercury stick in so I am going to see how close I adjusted them. I am running NGK spark plugs, platinum (sp?). I have replaced all the gaskets in the carb, along with valve needles and floats. However, through all of this the damn popping pervades itself. I am assuming that "popping" through the intakes = running rich. In other words, the popping specifically is a freakin flame that comes out about of the intake and is very disturbing. Fortunately, it is below the flash point of igniting any other gas or fumes that may be in the vicinity of the tank (at least I hope). When I break the carbs down, I can see black residue on the slides and on the inside of the carbs which I am assuming is from the gas not being properly burned.

Yo, Yeller,
When was the last time you had your valves adjusted? Have you changed your belts lately? You should probably also check the tension if you haven't in a while. I know mine settled down quite a bit after a valve adjustment. Also, have you checked your timing? How much do you trust the previous owner's abilities?

The only real test for proper mixture is a plug check. Start with the main jets, then work your way down through the needle, slide, then pilot jet. Install a fresh set of plugs, and leave your farings off. Find your self a nice long hill, run as close to full throttle as possible, chop the throttle closed, pull in the clutch, and hit the kill switch at the same time. Coast to a stop, and pull out your plugs and look at their color. If they are white, its lean. If they are black, its rich. If it looks like a nice latte, you are good. Once you get the mains right, then run at mid throttle and look at the plugs to see how the needle is doing. Then run it on a flat road at about 2 grand to see what the pilot is doing. Always start with your pilot 1.5 turns out, and your needle in the middle postion.

I am running the Champion plugs and they work a lot better for my bike. they are also pretty cheap if you find a shop that carries them. I think I paid $1.50 ea. last time.

Cheers,

Thanks for the tip. The valves are perfect, I put MPB collets and new belts on. I have not checked the timing though.

the Champion plugs are the RA6HC.
In my Paso these worked better than all other plugs I tried from Nippon Denso to NGK, NGK plat.
In case you didn`t do it yet the often posted wiring mod may be of some help. (although not the solution of backfiring)
The rubber sockets between inlet manifold and carb are ok ?

paso750 wrote:the Champion plugs are the RA6HC.
In my Paso these worked better than all other plugs I tried from Nippon Denso to NGK, NGK plat.
In case you didn`t do it yet the often posted wiring mod may be of some help. (although not the solution of backfiring)
The rubber sockets between inlet manifold and carb are ok ?

Thanks Paso750. I'm going to check the rubber gaskets again.

OK, I'm back to this topic. I'm still running rich after the following things:

1) perfect valve adjustment and new belts with proper tension.
2) synched carbs with mercury carb stick
3) adjusted air mixture screws out 1.5 turns and fine tuned while engine warmed to best position that doesn't cause pops while blipping throtlle and to the point where I can vaguely tell an increase in rpm
4) at full throttle, everything is excellent. Pulls hard. Occaisionally, I will fill a jolt, like the rear tire is spinning and then it catches but the tire isn't doing that. I think it's in 2cd gear, I hit throttle, engine rpm increases acceleration good then a jolt and I really get a seat of the pants increase.

Problem:

1) Plugs are black and look a little wet
2) back fire through intake after four or five blips of throttle
3) verticle filter (using pods) seems to be a little wet and black
4) if I downshift at around 5 or 6 and don't apply throttle I can hear pops as the engine rpm decreases
5) have to slip clutch with increase rpm to keep from stalling out

I've replaced all rubber gaskets in the carbs, new floats, new float needle valves. I've got 142 and 145 main jets, going to have to pull them again to see what else I have in regards to the pilot etc. Pretty sure I have K5 needles. Carb boots look fine, have filter pods and Champion RA6HC plugs. I have supertrapp slip ons. Using 93 octane. I'm going to check to see if the choke plungers are seating correctly because at idle there is a faint sound that seems like the choke is on. Kinda of the "airy" sound that you hear when you put the choke on. There are new seals on the choke plungers.

Make sure that you are running a return line from your carbs back into the tank. The Sport has to run a fuel pump, and the pump will easily overpower your floats and make your bike run really rich. Run a T to run the excess pressure back into the tank, then another T to split between the two carbs. On the Sport there are two outlets near the middle of the tank. One is the return line, the other is the vent.

Have you checked your float levels?

Cheers,

ducinthebay wrote:Make sure that you are running a return line from your carbs back into the tank. The Sport has to run a fuel pump, and the pump will easily overpower your floats and make your bike run really rich. Run a T to run the excess pressure back into the tank, then another T to split between the two carbs. On the Sport there are two outlets near the middle of the tank. One is the return line, the other is the vent.

Have you checked your float levels?

Cheers,

Yes, and yes. Have return line and floats have been set. Thanks.

Well Davy, I think you covered everything that I can think of. If you haven't already, I would replace your coils. They are an item that dies over time, and 18 year old coils shouldn't be trusted.

If its running rich on the mains, then I would say you need to get some smaller jets. Have you done some plug checks? Take off your fairings, Find a nice long uphill, and ride up it as fast as you can. At the top, chop the throttle, pull in the clutch, and kill the motor as fast as you can. Pull over and pull out your plugs to see what they look like. If they are still black, then you are just too rich. If they are the color of milk chocolate, its just right. If they are white, its too lean. Always get the main jet right first, then figure out the needle and needle jet, then pilot jet, then air mixture screw. Always make only one change at a time and take notes. Its a slow process. If you have someone in town who knows what they are doing with jetting, have them help you with it. It will go much faster.

Jet changes are a pain in the ass as you have to take off the tank and the carbs to change the jets, put it all back together, then take it for a test run and plug check. If you dedicate a full day to it you will get faster and better at it.

You can get new jets and Dellorto parts at Herdan
http://www.herdan.com/

Cheers,