Air fuel mix, what do you think is going on here?

[CoreyP]

My bike has be modded by the PO. What I have is one bag with original needles and springs. I also have a bag with needles and springs that look like a cobra set up. The needles have notches with a snap washer that you can move up and down. The question there is what is on the bike now?

I ask because I did this. The bike came with the D tool or whatever you want to call it to adjust the pilot jet so no doubt that has been fooled with.

Of course I had to play with that to get an idea what is going on here but just one cylinder. I couldn't really feel when the D tool locked in so I have no idea how many turns it took to get it screwed all the way back in. After reading around the forum 2 and 1/4 turns is right for stock jets. I did that and within a hundred miles I was snap crack pop back fire on decel.  Took the plug out along with the rest of them and the plug I fooled with was heavily covered with dry carbon, totally black and powdery.  Okay from this forum again I read that if you up graded the jet you probably need to set the pilot jet at 1 and 3/4. So I did. I also trade out the number four plug for the number 6 after I cleaned up the number 6 plug.

That didn't work long. End result is the carbon fouled number 6 plug that went into number 4 looked like it should. Number 6 was all carboned up now.  So I know it's not the plugs. To much fuel to the number 6 cylinder.

Backed it down to 1 and 1/2 turns. Carbon fouled on me again. So today I turned it down to 1 1/4 turns. I guess I'll keep going down till the plug doesn't foul.

Anyone have an idea what is going on here? Did the PO put some giant pilot jets in this bike? Maybe there is a combination of things that were done to bike that would make the pilot adjustment very low? I just not sure what is going on except I should have never fooled with the A/F mixture screw.

[Ricky-D]

Probably good to mention if your exhaust is stock, or not.

Serious fowling of the plug so quickly indicates a carburetor badly needing attention.

Stock needles have no provision for moving the clip.

Slow jets are #35,and the main jets are #100.

Engine condition is the most important factor when attempting carburetor adjustment.

An engine compression test on the cylinders is probably warranted.

[sandy]

It sounds like you have no idea what the PO did. Now you need to start over by setting everything back to stock. Check needles, and pilot screws. If you still have popping, replace vacuum lines and intake runner O rings. Set the pilot screws to 2 turns out to start. If you have adjustable needles, set them on the 2nd notch down from the top. If you have a K&N air cleaner and low restriction pipes, thn 2.25 turns and the 3rd notch might be right.

[CoreyP]

It sounds like you have no idea what the PO did. Now you need to start over by setting everything back to stock. Check needles, and pilot screws. If you still have popping, replace vacuum lines and intake runner O rings. Set the pilot screws to 2 turns out to start. If you have adjustable needles, set them on the 2nd notch down from the top. If you have a K&N air cleaner and low restriction pipes, thn 2.25 turns and the 3rd notch might be right.

Running a glass pack exhaust.

You did read what I did. I started with a perfectly well running bike and played with A/F mix. Only one cylinder. I started at 2 and 1/4 turns and now I'm down to 1 and 1/4 turns. I didn't touch anything else so this bike is set up weird. I don't know how exactly this was setup. Was running great to me, changing that one thing has thrown off the one cylinder. If it ends up running well on one turn I'm really going to wonder what has been done here. I do not want to do anything with any of the carbs until I have some idea what is going on with this setup. This is not the time to take all the carbs off and rebuild them. They were running fine.   The only variable is the change in the A/F mix. The question is what was setup if I have to go to 1 turn or lower maybe? I'm just trying to figure out what was done by the PO.

[Gregory Scott 16248]

If you can check the exhaust temperature with a digital heat gun at the cylinder header pipe after it is warmed up. The temperature for all cylinders should be about the same. If cold increase mixture or hot decrease mixture. Just a place to start.

Greg

[Ricky-D]

If you can check the exhaust temperature with a digital heat gun at the cylinder header pipe after it is warmed up. The temperature for all cylinders should be about the same. If cold increase mixture or hot decrease mixture. Just a place to start.
Greg

If all you did is mess with that one carburetor, it's pretty simple to get it back close to where it was.

Start with a baseline setting.

Run/ride the bike enough to know if the setting is correct/incorrect

Adjust in small increments.

Repeat until satisfactory results.

***

[98valk]

what air filter? only OEM should be used. I remove the EPA noise reduction screen for more airflow.

lightly seat/close all of the idle mixture screws.

open to 2 turns open.

put all needle clips on third step from top.

this will give u a base line and then go from there.

http://www.factorypro.com/tech/tech_tuning_procedures/tuning_carbtune,CV,lower_rpm_engines.html

[indybobm]

Do you still have the OEM petcock? if so, try moving the vacuum hose for the petcock from Carb 6 to Carb 5 to see if the fouling changes to #5. thinking the petcock might be bad dumping fuel down the vacuum line.

[Ricky-D]

My feeling is that the previous owner, attempting to keep the popping to a minimum,

with the glasspack mufflers, probably thought the engine needed to run more richly,

and acted accordingly.

On cold start ups, all the plugs are probably drenched.

***

[CoreyP]

If you can check the exhaust temperature with a digital heat gun at the cylinder header pipe after it is warmed up. The temperature for all cylinders should be about the same. If cold increase mixture or hot decrease mixture. Just a place to start.
Greg

If all you did is mess with that one carburetor, it's pretty simple to get it back close to where it was.

Start with a baseline setting.

Run/ride the bike enough to know if the setting is correct/incorrect

Adjust in small increments.

Repeat until satisfactory results.

***

That's what I'm doing, it just seems odd to me when guys are running 2 1/4 turns and I might down on 1 turn. I'm betting the pilot jet has been up sized. Once I dial this in, I'll go from there.

I'm wonder if someone else has set their bike up like this? This bike has been dyno'ed a few times and the curve is just about straight up off of idle. By 2900 RPM the bike hit 85 HP and 46 torque. Earlier dyno's didn't hit power that fast and the A/F mixture got much leaner from the first dyno to the last. 4 dyno's all together.

More a science project at this moment. I'm not going to get more power out of this. More a matter of if it's running at it's former performance.  Of course minus some for age. I haven't looked at the needles because there is an after market trim piece that is glued to all three caps. I don't really want to risk breaking that if I don't have to. Looks like some seriously sticky double sided tape was used to hold it on there.   

[CoreyP]

My feeling is that the previous owner, attempting to keep the popping to a minimum,

with the glasspack mufflers, probably thought the engine needed to run more richly,

and acted accordingly.

On cold start ups, all the plugs are probably drenched.

***

I don't even use the choke at start up. Starts right up and idles around 700 then will move up to 900 soon after I start riding.

The bike didn't back fire till I played with the mixture. at 2 1/4 turns I got a nice rifle bast on hard decel into second gear. LOL. People were probably calling the cops over that one. At 1 1/2 turns I can still get the blast but it's more in the small arms fire range. Going for 22 cal. now. LOL. Actually I want the back fire to be gone.

I guess the the Po may have put really big pilot jets into the carbs and then used the A/F mixture to tone it down? I don't know why actually you would do that?

[CoreyP]

1 and a 1/4 turns got rid of the back fire.

I'm going to get some temps off of the exhaust pipes, see if everything is about the same.

I think this bike has really big pilot jets.