I got a Paso in my garage!

[ahdoman]

About 5 years ago I sold my pristine 88 Blue Paso and have regretted it ever since and have longed for another one. I got my opportunity today and snatched up another 1988 this time in red (I'll get pics later, right now it's in pieces). I'm trying to get it to run. I've been through the carb and here's what's in it;
Mains - 145
Air Corrector - 170
Idling Jet - 55
Pump Jet - 40EW
Starting Jet F7/110
When the fuel pump is running I've pulled the Main Jets and the fuel is at the bottom edge of the emulsion tube. When cold it starts with the choke but runs rough then dies. Here's a couple of questions I have;
1) With the pump running but the engine isn't and I crack open the throttle I don't see any fuel squirting into the barrells. Should I?
2) When the engine is turning over and the throttle is wide open I see a little weak "spray" activity from the one barrell but not the other. Checked the fuel level in both tubes and it's right below the emulsion tube.

Any ideas?

Update - I've confirmed I have fuel flow through my venturi's. On the bench, I can spray carb cleaner through them and I have cleaned them out. But there is this small passage (A) in the accel pump that leads to the pump jet. In the bowl of the carb is another small hole (?) that doesn't go anywhere. Should it be feeding the backside of the accel pump?

[jayh]

Yes it should be feeding from the float chamber through that little hole and into the pump housing,via that hole in the top left above hole 'A' ,with the brass non return valve in it .I'm tipping that the little ball in the non return valve is jammed,you should be able to shake the carby and hear it rattle.Spray some carby clean or compressed air through from the float chamber side to free it up,and then some through hole 'A' and check it is coming out both the pump nozzles evenly.

check your float level is 46 mm or slightly less as measured from bottom face of top cover to furthest point on float,with top cover balanced on its edge and fuel inlet end at highest point,so needle is lightly seated.(spend a little time getting all this right).I'm running mine at 44 mm but you have to be careful you dont go to far as fuel will overflow through the nozzles into the venturies.This will help eliminate lean spots,mid revs.

55 idles should be right at 2 1/2 turns from seated on the idle adjust screws.You checked the idle jets were clear when you took them out didn't you,and the little o rings were still there ?
It should fire right up and idle with the float level set and the idle jets clear,they are a different circuit of the carby to the main jets.

If you look down the emulsion wells,with tubes removed,you can see the passages leading out to the venturies,try and blow some carb cleaner through them and make sure they are working also.

That appears to be a larger than stock pump jet,it may cause stumbling taking off in first and second gear.

Thats a very lean jetting combo you have there,I'll be surprised if it runs real well,but try it first(if it ain't broke don't fix it !) J.

[ahdoman]

Thanks for the reply Jay. I've been reading through your adventures with the Weber and I must say you are a very patient man but I really appreciate your contributions!

The check valve for the accel pump was the problem. It was sticking in either the closed or open position. That's what was confusing me. Sometimes I would have response and then it would go away. If I took the cover off there was always fuel behind the diaphram. Everything is flowing good now.

Everything is clear and flowing so today I plan on syncing the barrels. It was too late last night when when I finally got the check valve working correctly. This bike has the F1 pipes on it. My neighbors would not have been happy.

I'm going to get a set of the 185 main jets and go with your latest recommendations. I live in the high desert in California. During the summer our temps get around 100 degrees (F not C!) and average 75 year round. We're heading into summer now.

Do you have a picture of your most current accel pump cam mod? I want to do that as well.

[jayh]

give me a day or so and I'll measure it exactly.Whats your altitude there? that might explain the current jetting.We are only a couple hundred ft above sea level ,otherwise your climate is very similar to ours.

My latest is 165 mains 185 Air correctors 56 idles.185 mains is far too rich. J

[ahdoman]

I'm at about 1800 feet above sea level.

And just for clarification right now I am running;
145 Main Jet
170 Aircorrector jet
55 Idle Jet

[jayh]

This is a really easy cam to copy,just file the short stubby end to 10 mm (3/8" long) and parallel with the bottom edge of the cam.Then the overall rise in the gradient of the cam is 4mm (3/16 ").Both surfaces are filed flat,no curves,with the exception being the join of the two surfaces ,where a round file can be used to create a smooth transition between the two.Don't create a hole or low point at this point.To avoid this I start on the short 10mm bit and carefully 'draw file' back up the gradient until it is smooth.This will probably lengthen the 10mm section slightly,but it really isn't that critical. J.



Try those jets first,I'm not sure how much your altitude will effect the jetting,suck it and see

[ahdoman]

Thaanks Jay! I files the cam down per your specs and the throttle got a lot smoother. Before I filed I took a look at where the AP arm follower was; As soon as I would crack the throttle I was already on the cam so it was never coming all the way back. I put the 185 Air jets in and it helps but I'm at 4 turns out on the A/F screws. Does that mean I need some bigger main jets?

[jayh]

The idle screws only control the amount of fuel at idle,4 turns out is too far ,it suggests that a larger idle jet should be fitted but its a long way out for 55 idles,you may have a different taper on the screws or your air bleed screws are open to far.You should start with both air bleeds seated and only open one of them a tiny bit to balance the barrels at idle.One should always be closed.

For 55 idles at sea level, a 170 main jet is required to supply enough fuel for smooth transition from idles to mains.Evidently there is very little change up till about 2500 ft and at 5000 ft jetting changes are essential.

The larger you go with idles the smaller the main required, 56 idle/165 main ,57 idle/160 main.
Any size idle jet can be made to idle smoothly by adjustment of the screws,but there will be problems further up the rev range,as the mains start to work,with either too much or not enough fuel causing a stumble.The Idle jets supply the fuel right up to 3000 rpm and above.A change in idle jet size will reduce or increase how far up the rev range they work .Likewise with main jets.Your job is to find an idle jet large enough to supply fuel to within reach of where the main jets start to work and or a main jet big enough to supply fuel back down the rev range to within reach of the idles.A small overlap of jetting is required to avoid any lean spots,too much overlap will cause a rich spot.

The above sizes will get you close if you have modified the pump cam and raised the float level.

because of your altitude you may find one size smaller on mains better,but I would stick to the above
jets unless you are having problems,better too rich than too lean to start with.

Stock jetting was 57 idle/ 150 main ,but this was relying on the accelerator pump to supply the extra fuel required,along with all of the other problems associated with the extra fuel when it wasn't required.

Once you get the idle to main jet combination sorted,you can play with the Air Corrector size.If you are
too small on air correctors,you will start to bog down on full throttle openings,too big and you will start to get overheating and possible engine damage.I have found 185 AC's to be about as small as I can go without bogging issues on hard acceleration.A smaller size will run fine for most riding,but when you go to overtake,or other wide open throttle scenarios you will notice the difference.Another problem with larger AC's is that they also lean the mains at lower revs and therefore create problems with the mains/idle overlap.

It really isn't as complicated as you are probably thinking it is after my explanation,start with the above guidelines,and you should be very close.

Alpha1750 on ebay is very good to deal with and has all of the jets needed at very good prices.
Only takes 10 days to Australia,so you should be quicker.

I would get some 56 idles,165 mains and 185 AC's if you can't get it running right with what you have. J

[ahdoman]

Thanks for the reply Jay. I am getting a stumble between 4k to 5k.

I confirmed my float level at 46mm.

If I close the idle screws back down to 2 1/2 turns it starts to run really rough and won't stay running below about 1500.

I only have one air bleed open about 1/3 of a turn to equalize. I used my sync tool to find that.

It's running a lot better off of idle now with the cam correction.

I was trying to remember; if I'm getting popping in the carb it's too lean and if it pops in the muffler too rich? I'm not sure where I heard that please correct me if I'm wrong.

[jayh]

yeah thats right carby lean / exhaust rich, but not set in stone, there are exceptions.

bigger mains,bigger idles will fix it,or 44 level float may improve it enough, but you will still be lean me thinks . J.

[jayh]

If you are going to be riding it until you can get bigger jets I'd put the smaller AC's back in it too,the 185's will be too big for your 145 mains and could be contributing to your problems.

The very early pasos had 60 idle 142 mains 160 AC's

your mains are 145 at the moment,so your AC's should be 160/165 and 60 idles to cover the lean hole
(which corresponds with what I was saying earlier 145 mains/60 idles,150/59,155/58,160/57,165/56,170/55 175/54 will all work)

The problem with going larger than 57 idles is a lot of popping in the exhaust on the overun,once warmed up.
The problem with going smaller than 55 idles is a larger main and therefore an AC greater than 185 is needed and this opens the lean hole up thus negating any increase in mains.

This is why I have settled on the three combinations I recommended earlier. J.