'85 Yamaha XJ700

I have spark on all four but am having a problem getting #s 1 & 2 to fire and run. It will run on #s 3 & 4. Thusly the coils appear to be ok in that 3 and 4 are on separate coils. I have also gone through the carbs three (3) times and feel pretty good about the carbs. It almost sounds like when it runs, not very smoothly and on full choke, that the timing may be off. Could this be affecting the firing of 1 and 2? I am asking for comments if that the CDI could be partially faultly and affecting the timing. I think I read somewhere that the CDI affects the timing. Can the CDI allow spark on all four but be causing an issue with the timing and not allowing 1 and 2 to fire? Does the CDI either work or not work or can it partially work?
I have bread tied the butterflys to a loose feel and the pilot air screws are set to 2 1/2 out. The full choke to run, would I want to increase the pilot air settings out to richen up the mixture?
Any thoughts and comments much appreciated.
gene in Tampa Bay area of FL

 

Most CDIs I have ever had the pleasure of owning either worked or didn't, but I am not certain if these have a middle ground. Are the exhaust headers on 1&2 cold, leading you to think they are not firing? What did you do to the carbs, full tear down and rebuild or just spray with carb cleaner, and what kind of air box/intake setup do you have? OEM or pods? If pods, did you rejet accordingly? Valves in spec?
There's a lot of detail that goes into tuning these bikes, especially after 30 years of potential neglect.

Btw, most of the people that describe living "in the Tampa Bay Area" live somewhere in northern Pinellas county. NPR? Tarpon? Dunedin? I lived in Clearwater for a long time, and miss it terribly. Welcome.

 

Removal and full disassembly of the carbs. Yes the headers of 1 and 2 are cold when 3 and 4 are hot. I do have PODS and when trying to run do not have the PODS on the carbs. I agree to your thoughts on the tuning but shouldn't 1 and 2 at least fire and run, even if poorly? But I have also read that the '86 carbs for the XJ700 were vastly improved?? Even though I have spark on 1 and 2 I always question how big a spark one needs to actually fire the cyclinder?
This bike is a very good example of neglect and is currently, with replacement parts, a combo of 5or6 bikes.
I live in the Town of Redington Shores which is just a bit north of Madeira Beach and John's Pass. The bike is in the "man cave" in Seminole.
gene

 

have you checked the float levels on the carbs? they are very sensitive to float levels being low. also consider testing the spark lug wire ends.

FU

 

When I got my 85 XJ700N it had the 86 carbs and a Uni foam filter. After cleaning the carbs, and adjusting the valves I found that it was not firing on # 1 even though I had a good spark. If I opened the choke it fired. If I opened the pilot screw to about 5 it fired. Found that a large portion of the intake gasket was missing and it was sucking air. When that was replaced I had good fire on all 4. At that point I assumed that I had the '85 carbs, but when I posted a picture of them Chacal informed me that they were '86 carbs. Even with the carbs clean the fuel consumption was about 35 mpg and I am easy on the throttle and cruise at about 60-65.

I bought a parts bike with '85 carbs that I cleaned and installed but still was getting sooty plugs at 2 1/2 turns of the pilot screws. I bought a stock paper filter and the plugs got much blacker indicating a much richer setting. I have a colortune plug and starting at 2 1/2 I was adjusting by closing the pilots slightly but was having problems reading the already black plugs. Said the heck with it and using the colortune plug I turned the pilot screws in until I got the white flame and then out to just to get a blue flame. Then I installed new plugs and took a ride and read the plugs and continued to open the pilots--slightly, no more than the width of a dime-- until I got really good color on the plugs. All of my pilot screws are set between 1 1/2 and 2. My plugs look great and my mpg is now about 42-43 on the highway.

Chacal indicated that the 700's were tuned on the lean side originally although I have no way to verify that.

The fact that you are running pods will of course require some experimentation with the jets and pilots--something I would not want to deal with.

 

I tried to carefully set the float heights to 16 +/- 1 mm per the book. What height have others found successful?
Also what have others found to be the best pilot air screw setting with pods? Approx. to at least run reasonably?
gene, still in FL

 

the measurement is just to get you close, you still have to wet set the floats to get the proper level.

FU

 

"16 +/- 1 mm"

Where did the "16" come from? Typo I hope. The specifications are "1 +/-1" and I have mine set at 2.

 

Check your valves, and try with the filters on. You might be sucking too much air.

 

I will double check the manual but am pretty sure it was the 16mm +/- 1. That is a huge difference but on my other Yamaha's it can be at 22mm +/-. That would really explain some issues.
Different thought, do you still have the '86 carbs you mention in your previous post? I am not a purest and if they are easier I am not concerned about the mpg #.
Are you the US Marine I got some help from previously who did some flying when we were both younger and doing our thing for the government?

 

Ok, the 16mm +/- 1 is the float height, and I was thinking of the fuel level used in the wet setting of the floats. I made a gauge to set the floats at 16, but still had to make adjustments to get the fuel level at 1 +/- 1 mm. And as I said earlier, I actually set my at 2 mm. The 16 mm dry setting will get them close, but you really need to wet set them to get them perfect since the floats may float at slightly different levels.

Once a Marine, always a Marine. Flew the EA-5A in Viet Nam in 69-70. Interesting times. After active duty I eventually got in the Army Reserve and finished the 20+ years as an artillery officer and even got caught up in Desert Storm where I was an intel officer for a FA Battalion of the GA Nat Guard. Quite a change from flying.

 

I am starting to think that I may also be "sucking" air from somewhere. What or where is that "intake gasket" located that you are referring to? I am still not getting #s 1 & 2 to fire and have used the choke and adjusted the pilot air screws as you tried. I have also used "plastic dip" on the carb boots and even tried to spray WD 40 around the boot seal between the boot and the head intake area. Are you referring to the carb boots when you changed the intake gasket?
What is almost too coincidental is that it is both 1 & 2 ie different coils and there is spark on all four.
Anyone else with any ideas will be most welcome. I have, tired, to adjust the carb floats and butterflys carefully.

 

My air leak was the intake manifold gasket, between the intake manifold and the engine. I'm not talking about the rubber boots between the air filter and carbs, but the actual intake manifold between the carbs and the engine. The same ones that hold the carbs in place. If you have a butane tank you can use it around the manifolds and see if it makes a different.

 

Dont want to hijack your thread but did u come up with a solution? Im having the same problem on cylinder 4 and slightly on 1 and want to get it running

 

http://www.xjbikes.com/forums/threads/4-cylinder-exhaust-cold-please-help.85253/

 

Check to make sure coils are hooked up properly... Would be the first time I saw a coil hooked up to 1/2 and the other to 3/4. If it IS. That way, then Id say a bad coil AND hooked up wrong.

Etc.....