Everything affects everything, carbs

[ekvh]

To wrap up my recent posts on "1200 into a 1000 chopped." Some advice, get the spark and air leaks out of the way before messing with jet changes. I'm pretty sure this is dejavu, all over again, repeated, and multiplied. I'm a slow learner. I started assuming I needed jet changes this year when mine just wasn't performing as well as it should. I did an exhaust change and started noticing some backfiring on deceleration. Messed a bit with it and found I had some big gaps in my butchered intake manifold for the air filter. I decided to change it to an 1100 filter I had. What I should have done right then was go back to the jetting I had last year because after about ten days of constantly changing fuel jets and air jets and cutoff valve, I am finding myself close to being totally stock again. I went back to a 62 primary jet with a 120 air jet and it is reall good up to 5500. I still have a 130 main and a 68 air jet and a washer under the needle. That's a little more than stock on main jet, but I think the 1209 should pull a bit more??? Maybe not. Maybe the carb is just set to work with vacuum and is happy with the 77 cams and the extra 200 cc'a.

I'm leaving for a few days, but next I'll pull the washer. If that doesn't get it right, I'll go back to a 120 main and a 60 air and be right back to bone stock settings!

Changing jetting on these is tricky because there are two ( really three) circuits and they each continue to share and add to the mix.

At this point I'm pretty sure I jumped the gun on changing jets and should have found the intake leak first. Hope this helps someone else.

 

[mcgovern61]

All good information Eric, especially for those of us that haven't done anything yet and can learn from the trial and error that has already been performed!

 

[joedrum]

hmmmmm aint that the truth .....dealing with carbs ..cv carbs especially have more than one thing going on for every one move made ....when it get to tuning carbs it is a skill learn on every situation ...erics got a lot in play every move ...stock racks can leak rather bad too ....biggest surprise to me on oldwing carb tuning is how flow can happen up in the rpm zone over the car motors ..thats a bigger motor ....this tells me that oldwings require wide carburation spread ..from idle to redline ....this in itself ..stock or other ..makes dailing in oldwing motor good at the highest level of tuning a motor in i think ..... :headscratch:

 

[ekvh]

Back to my latest nightmare. Everything affects everything, right? How about a randomly firing spark plug? I am back to almost all stock settings now and was trying to smooth out the idle and sync. I kept getting a lumpy idle. Couldn't figure out why, but flat fours are known to be lumpy at idle. Finally turned one screw nearly all the way in, got a smooth idle but three cylinders. I had shut it right down. The light in my head slowly got dim. It was dark. So when I turned the screw out I picked that cylinder back up, but lumpy again. Pulled the plug wire, same smooth idle. Amazing how nice these will idle on three cylinders!! First I closed the plug ago some to see if it was too wide, nope. So I dropped an old plug in and voila, she ran smooth again. Put a new one in this morning and it runs great again. I still have a 130 main jet and I still have some backfiring on deceleration, but I think I'm going to leave it and drive it like this for a while. Two weeks of messing around with jets and air filter and probably all because of one bad NGK. I doubt I have 5000 miles on it. No visible cracks. Weird.

 

[Omega Man]

Ya gotta love those "ah ha" moments!

~O~

 

[joedrum]

well sheesh playing the game out till the end before knowing it all is always a good plan most need to learn ...seems most are to smart for that ... great job eric ..might not be full answer ..but it was this time answer :ahem:

 

[dan filipi]

Yep, same problem I had a while back. Lots of time wasted jetting.

 

[Ansimp]

I remember the Pig not wanting to run and a mate saying put new plugs in and me saying they are new plugs. Put new plugs in and the Pig fired right up, seems I had fouled the plugs with over rich mixture and changing plugs to new plugs worked :doh:

 

[ekvh]

I don't understand how plugs get fouled. Even saturated with oil, if you clean them, you'd think a spark want to jump. In the past few years there have been a lot of reports of bad plugs, often right out of the box.

 

[slabghost]

Electric items can be bad or just barely serviceable brand new. How many times have you replaced a light bulb only to have it flash just once and never work again? Plugs can often spark just fine outside while you watch but fail under compression. Always a good idea to try new plugs.

 

[Ansimp]

ekvh » Sat Jul 18, 2015 4:38 am[/url]":2xpu6eva]
I don't understand how plugs get fouled. Even saturated with oil, if you clean them, you'd think a spark want to jump. In the past few years there have been a lot of reports of bad plugs, often right out of the box.

That was my theory too and I couldn't see anything wrong visually with the plugs I pulled, bike started straight up with the new plugs installed :doh: