TUNING QUESTION

I got my carbs all cleaned up and bench synced by what I read here and there. I set the floats the best I could, verified the valve clearance and then completely cleaned the carbs taking them apart.
I am not sure if I set the butterflies correctly though. I backed off of the idle screw so it did not touch and found that they were closed no gap. I set a gap of .0015" on all 4. Is that correct?? What would happen if it was off by some small amount. Say I read wrong and it was at .005. i used an old feeler gauge.
Anyway the bike fired right up nd was running pretty good but it did backfire off the start so I backed off of the pilot screws and it is now running better. I did a plug chop and 3 out 4 plugs are still on the white lean side. I need to adjust but I want to make sure of how critical the buterrfly position is before I keep tweaking. I would hate to compensate for a bad adjustment down stream.
Thanks

 

The butterfly issue. The bench sync is only to get the butterflys close enough to fire up once they are on the bike.
It sounds like you did alright since the bike is running. Job well done.
Im sure I will be corrected.
You know to get the butterflys even closer is to do a running vacuum sync.

Sync 1 to 2... 2 to 3 and then 4 to 3. This process worked the best for me and it should put your butterflys spot on. Oh, in case you have not heard... you should also be using the YICS blanking tool during the sync.

The popping you hear is from a lean mixture more than likely.
Your motor will not last long running like that so its best to be running slightly rich.

 

Im pretty sure it`s running lean because as I said the plugs are on the white side. I guess I can go out on the adjustment screws a few degrees and do another plug chop. As far as the stupid YICS toOL lol I cant see spending big bucks or even trying to find one.
I have heard of people using some sort of oil filled shirt or something but I have not reall searched that yet. I was hoping for an easy way out. Do you think it would be safe to set them on the rich side just to get me going for the weekend or should I really put some time in it and try again.

 

I made another small tweak and went and got some gas. Not a pop at all so thats a good thing I think. I cruised down the backroad at about 5krpm for most of the 10 minute ride and coasted in my driveway killing the engine. I pulled all 4 plugs and they are still white-well 1 is pretty black but thats how it was before the carb cleaning.Is the way I drove it o.k for a plug chop or am I off?

 

Sounds simple enough.
adjust the white ones mixture screw to the left a good half turn.
adjust the black sooty one to the right a good 1/4 turn.

I suggest making these big adjustments BECAUSE you could ruin your motor running lean. Its best to run slightly rich so Im trying to give you directions to get there ASAP.

 

TOO LEAN!

That's way too Lean.
Can you "Hear" any difference.

I'll bet the Bike accelerates like the Space Shuttle.
You're Burning Clean.
Too Clean.

When the Ignition occurs ... The Charge is going-off like a Flash Bulb.
Fast and HOT.
If you don't add some FUEL ... the Bike looks for Fuel where-ever it can find it.
The OIL Sheen on the Cylinder can get burned-away ... leading to catastrophe.

If the Mixture isn't getting Richer adjusting the Pilot Screw Out ...
You have some issue preventing Fuel from being drawn up.

Pilot Passages clogged
Pilot Fuel Jet Clogged
Wrong Mixture Screw
Flipped O-ring
O-ring torn and clogging orifice
Severe Air Leak

 

Thanks Ill do it in the morning.I swear this is like a repeat of tuning my Porche 914 air cooled engine. What a PITA. LOL but at least I can get to this engine.here is a picture of when I had to replace a bad cylinder that had no compression.

 

RickCoMatic

It was poping when i accelerated before but now it sounds real nice and accelerates smooth off the line and when I get on it at higher rpm`s. What If I do back way off of the screws and see if it runs richer. If I move the adjustment screws I cant reall hear a noticeable pitch difference in the motor and the rpm`s dont seem to change. Could my floats be way off and thats causing a fuel issue???? I would think if I was not getting eough fuel I would have some serious back firing or something though and it would not be smooth through the whole rpm band. I dont really have any special tools to tune it so I am tweaking it by ear and probably not a great idea but its all I have to go on. This is where I started.
3 tuns out on all 4 mixture screws. I made a small tweak and the back fire went away and it runs real smooth now. I have not made any adjustments to the float levels because I could not get the drain plugs out to make a meter. Heck I was not even sure how to dry set it because I was not sure where to measure the 17.5mm from.
Any help would be great because I want this to run tight for bike week coming up soon.

 

I just got the carbs off again and attempted to get the drain screws off of the fuel caps. I was able to free one of them so thats a good start. I bought some clear tubing and hooked it up to that carb #2 and filled the carbs with gas. This is what i found. The carb with tube now attached filled until the gas was level with the screws from the cap. I think that is good. The carb next to it #3 overfilled and fuel started to come out of the ports on the face where the air cover would go ( I have cone filters not stock). This is obviously a problem for that cylinder but it looks like # 2 is fine. I will need to move the cap from #2 to the other carbs because I cant free the screws in the others plus the heads are all torn up. I went to the Yamaha dealer to buy new screws and they were llike 22 each so I walked.

 

Get 4 New Drains fm Len, on here.

Stainless, Allen

Bring the Carbs down too my garage and we'll remove them with a Special Tool.

 

Mafia101,
If you can get a good vac sync gauge and a colortune plug you can set everything perfect. You won't have to worry about messing up your motor. That alone is well worth the price of the 2 gauges.

 

What size main jets do you have?

ab

 

If I remember I have 120 mains???? Not 100% sure but thats what I remember.

 

I don’t think those are big enough.

What exhaust do you have?

ab

 

I opened the carbs and they are 120 mains and I have a Dunstall exhaust. If the mains are too small would that cause it to run real lean? I guess I could back way off of the air mixture screws and se what happens. My guess is that the more air the richer the mixture. I will reset the screws at 4.5 turns out from bottom and see how that responds.
The more I read about pod filters the more it makes me concerned and thats what I have.

 

I was hoping a carb guru would reply, everybody must be ridding.
I would be but I’m going through my carbs ONE :cry: MORE :cry: TIME :cry: .


Your 120’s are way too small.
I’m running 126 main and 41 pilot with a 4 into 1 exhaust and a drop in K&N filter.
In my 750 the 126’s are a little small.

In a few weeks I’ll be ordering 128’s, 130’s or ? from chacal.
http://xjbikes.com/Forums/viewtopic/t=14561.html

about 1/3 of the way down the pg.

DON’T quote me but the pilot screws are for idle and ¼ or less throttle.
Any more throttle and your on the main jet.

ab

 

E-mail Len at info@xj4ever.com and ask him what is suppose to be in there. He will know.

 

More fuel = richer mixture
more air = leaner

Pods suck way more air making the bike run very lean

 

Ya, no, you are saying this wrong.... The more air the leaner the more fuel the richer. But you are correct about backing out the screws.... You want to turn them out to make them richer (more fuel). In for leaner (more air).

 

sometimes I dont really word stuff right but at least I`m sort of going in the right direction. I will look into getting bigger jets. It sounds like a good starting point might be 126`s or even a little bigger. Time to shop around and figure it out.

 

The more AIR the Leaner the Mixture.

Getting the Full SUPPLY, and ...
Getting the Full BENEFIT from the Fuel Supplied is the obstacle.

Bringing up and into the Intake Air Stream the Fuel made available by the Main Jet is most important.
AIR needs to pass-over the Emulsion Tube Exit Orifice, ... with sufficient speed to LOWER Pressure at the Orifice.
AIR needs to be present in sufficient volume to flow through the Main AIR Jet through the passages to the void surrounding the Emulsion Tube.

Without these two necessities -- the Mixture delivered to the Engine is not right.

AIR needs to RUSH across the Emulsion Tube Orifice and below the Diaphragm Piston's Orifice.
The Air lowers PRESSURE and Fuel gets Siphoned-up, ... and the Piston internal pressure lowers causing the Piston to rise.

AIR must be present to bleed through the Emulsion Tube's Drilled Metering Ports to:
Aid the Siphoning
Atomize the Fuel

Otherwise:
The Siphoning doesn't occur
The atomizing is too weak and ineffective
The Diaphragm fails to completely rise

The resultant LEAN Condition CANNOT be alleviated by Inserting a Larger Main FUEL Jet.

The obstacle that needs to be addressed in order to solve the Lean Condition you are battling is controlling AIR.
Intake Air Shape
Intake Air Speed
Main Air presence
Main Air Volume

Solving the AIR Problem isn't going to happen adjusting Fuel related components.