Pilot air jets and carb tuning

[sky02]

Hi guys,

I wonder if anyone experimented with pilot air jets.
The old 4 speeds idle circuits were something like that.

Canada 87-88:
REAR
PAJ1 60
PAJ2 1.7mm
Pilot jet 57,5
2 turns out

Front
PAJ1 55
PAJ2 1.7mm
Pilot jet 50
2 3/8 turns out

US 87-88 (more air in premixed idle mixture than Canada but that’s understandable due to hotter air in general)
REAR
PAJ1 60
PAJ2 2mm
Pilot jet 57,5
Not specified no of turns (hidden screw)

Front
PAJ1 55
PAJ2 2mm
Pilot jet 50
Not specified no of turns (hidden screw)

European 4speeds (rear is closer to US bit slightly richer, front is richer like in Canada but there is no disproportion in no of turns so it is probably still close to each other)
REAR
PAJ1 60
PAJ2 1,9mm
Pilot jet 57,5
1 3/4 turns out

Front
PAJ1 55
PAJ2 1,7mm
Pilot jet 50
1 3/4 turns out

US 4 speeds but early ‘90 (this is where it gets strange in US. Rear has waay less air in both jets, but the fuel jet also drops so maybe the mix stays the same, front has the same fuel jet but one air jet is much bigger second one is much smaller )
REAR
PAJ1 40
PAJ2 1.55mm
Pilot jet 55
Not specified no of turns (hidden screw)

Front
PAJ1 70
PAJ2 1.4mm
Pilot jet 50
Not specified no of turns (hidden screw)

As the spring is coming I am planing to weld two wide band sensor bungs in my slip-ons just before the H connector to tune each carb separately.
I will start from WOT down.
All older VS1400 have 140/125 main jets but i have some 142,5 and 127,5 and 130. My slip-ons have less restrictive inserts so i might need bigger ones. Maybe i will also try the KN inserts.
I think that i will try to get about 12,5 AFR at WOT

Next the needle jet and needles
Its P3/P0 in Canadian and European carbs (richer)
And P2/O9 US models (leaner)
I have both sets
Needles
Rear:
5D30 Canada (richest)
5D35 US
5D38 EU (leanest)
I have 35 and 38
Front:
5D21 first US (richest)
5D22 Canada
5D39 EU
5D51 later US (leanest)
I have 39 and 51 but can get 22
In midrange i will try to get about 13-13,5 AFR

For the idle and cruise
I have fuel jets
Front 50 and 52,5
Rear 55 and 57,5
Pilot Air jets n1
40 and 60 for rear
70 and 55 for front

I can also play with pilot air jets n2

I will try to get about 14 AFR at idle. I know that in this carbs you premix the air ( metered by sum of two pilot air jets) with fuel (metered by pilot jet) and meter the amount of that mixture by the mix screw. In normal riding conditions you always use two air jets in pilot circuit the only reason for having two of them is to cut one during engine braking and richen the mix.

But why they had so many combinations of that pilot circuit jets?!?.

[Herb]

I know that they had to keep changing things to meet the emissions standards. During those years the advance curve was changed. When I bought the 87 the HP rating was 72 hp over the years the hp kept dropping, my 99 is rated at 61 hp.

Huge difference.

I used to have a link to a history of the 1400 site and you could see the continual drop in hp and torque
but it no longer works.

the 87 had 72 hp and 85 ft lbs torque.

the 99 has 61 hp and 77 ft lbs torque.

Here are a couple of sites to show you the difference in HP and torque.

I bought an 87 in 89 that was a new left over bike. In 2002 I bought a 99 because the 87 had 154,000+ miles on it and was starting to use oil. I had the 87 for about 3 weeks before I sold it and my son and I took them out. The 99 only had 8,00 miles on it and the 87 out ran it on accel, especially high gear roll ons. Probably should have kept the 87 and rebuilt the engine.

I found the site I was looking for...

It says the 87 was 71 hp but I remember the flyers said 72.

[sky02]

I am well aware of those castration in later models but. I am considering here those early models, lets say ‘87-‘94, according to specs they should be similar.
Running through service manuals and parts numbers i have found that the only changes are (years vary depending on country).
1- exhaust (thats easy it gets quieter and more restrictive)
But most intruders run on some aftermarket pipes so this is irrelevant.
2- carbs:
Main jets are the same- ( only the late ‘90 models had smaller mains but thats the reason why they are the most castrated)
Needle jet/needle- early 87-88 had way richer needle in front but thats why most guys shim needle in front one step richer than rear. Or use aftermarket factory pro ones.
Pilot jets- early 87-88 had one jet larger on rear that stayed in EU models but this is also jetted or helped a bit with mixture screw
Pilot air jets- this is the only thing that nobody talks about in this carbs and it has changed event in those few first years of production BUT they are BIGGER in 87-88 so the mixture that you add to you air flow is LEANER and it doesn’t make sense if you consider environmental factors on tuning.
Rest is pretty much the same.
3- ignition timing
According to service manual and dyna 3000 manual there are two:
87-88 US and EU - 2o below 1500rpms and 30o above 4000
Later US - 2o below 1250rpms and 30o above 4000.
In dyna 3000 manual those are called no 1 (newer US) and no 6 (older US and EU)
https://www.micronsystems.de/custom/mic ... -1_3-2.pdf
Usually the bigger the advance of timing the more horse power you get (thats why dyna 3000 suggests curves 3and 4 with proper jetting). But the limitation is engine knock that depends on the fuel type. For example higher octane burns slower so the spark should be more advanced for optimum power. I dont know how it is with ethanol fuel but i think that fuel type is the main reason for that change in US as ethanol fuels are not popular in Europe.
There is no environmental reason here as the best for pollution and millage is to have a perfect bang with optimal use of fuel energy transferred to piston.

[Herb]

I think the largest change was with the timing curve with even less advance in total and the reduction in size of the jets was to compensate for the more retarded curve.

BTW, 72-61 is a 15% reduction HP. Huge difference.

[sky02]

It’s not that simply if you think globally.

In ‘99 so one of the weakest years.
The ignition is the same in all countries and it is specified as 2o below 1000.
All of them are 5 speed.
Canadian and US have 140/125 mains with leaner needles
EU have 130/112,5 mains with richer needle jeting

In ‘96 so that middle spec
The ignition in US is 2o below 1250
But the rest of the world have the old 2o below 1500
US is 4 speed
Rest of the world 5 speed
Jetting in US, Australia and Canada is 140/125
Rest of the world 130/112,5

I still think that ignition is connected to fuel type not the jetting.

Also I don’t consider the changes between ‘87 and ‘99 they are quite obvious. I’m thinking about those details that make ‘87 better than lets say ‘90 or mine ‘93.

[Herb]

Jetting and timing go hand in hand. I have no idea how many changes were made to the timing along with the jetting.

About all you can do is the old hit or miss method to find the best power.