1985 XJ 700 rough running tough to start won't stay running

Hi folks,
ok past the title this is what I have done so far:
removed and fully cleaned the carbs 12 times
I have a yuasa battery on a smart charger (full charge)
cleaned the petcock
cleaned the tank
Replaced the intake boots
removed the canister (cali model) and plugged all the hoses
still not running
I have had this bike since about 2000, I have taken apart and cleaned the carbs a lot of times, I can't find any leaks in the boots (starter fluid method)
It could probably use a new air cleaner but the one in there is after market and not dirty
It will start for a few secs on full choke when cold, then die
it's acting like it's running out of gas
I have been perplexed with this for almost a year and missed the whole season so far. If anyone has any ideas please help!

 

Re: 1985 XJ 700 rough running tough to start won't stay runn

After you cleaned the carbs, did you set the float levels? Are the floats in the right way?
Check the fuel valve on the tank to make sure your getting fuel.
Do you still have the vacuum line hooked up to the fuel valve?
You could try running it on PRI for a test. See if it stays running.

 

Hi man, thanks for the reply.
Yup I have done all of that, the only issue with the petcock is that the rubber gasket is shot so it does not really close w/o the vacuum but it does not overflow or anything so it's no big deal.
Even on Prime it does the same thing, I have a clear fuel filter on the fuel line, and there's gas flowing through it. The vacuum line is still hooked up from the manifold to the petcock (even though it doesn't do anything due to the washer).
Still won't stay running
Thanks for the thoughts!

 

hrm, 12 times... maybe luckey number 13 will work , that sucks man.. I have a 700 and i friend something electrically, and i still cant find it... probably gotta get a new harness,
but as for your problem, no idea

 

Re: 1985 XJ 700 rough running tough to start won't stay runn

You say you have a washer on the vacuum line from the intake? Make sure tha thing is clear all the way through. I know mud wasps like to plug up just about everything from gas lines to bleeder valves. Try switching the vacuum line to number 2 cylinder.

Do you have good compression?

Have you replaced the vacuum/fuel lines? It sounds like it might be the pilot jets.

Do you have spark on all the plugs? Have you checked the plugs? I had an airhead that did something similar, and it was running way rich and fouling the plugs. Replaced the plugs, adjusted the fuel mixture and it was good. One other thing to check and it is an oddity|

the fuel mixture screws in front of the carb bodies, right behind the manifolds. Next time you have the carbs off, pull them all the way out. Ensure you have a manual so you can see how and what goes back in there. There should be a tension spring, an o ring and a very small washer. They all need to be in there to work properly. My airhead had parts missing off them and a pinched o ring. thing wouldn't idle to save it's life. Made sure all the parts were in there correctly, adjusted the mixture to roughly 3 turns and it was good. I'd make sure those pilot jets are good and clean.

I'd check the float levels too. Before you pull the carbs, crack open the drain screws to make sure you have fuel down there.

 

Hi Guys,
Thanks for the input! Yup floats are at the right level, I haven't changed the mix screws (still factory sealed) All the vacuum lines are clear and no holes and the plugs look pretty good and gapped properly. The pilots were my main concern for all of the cleanings, so they're clean as a whistle (whatever that phrase actually means; I have never cleaned a whistle). There is fuel in the bowls and I can see fuel in the line (clear filter between tank and carbs).

 

i'm confused (not unusual lol).
If the "mix" screws are still capped,how can the "pilots"
be clean,as they are one in the same?

 

Did you sort this problem as mine has similar problems

Daz

 

Re: 1985 XJ 700 rough running tough to start won't stay runn

the pilot jets are just next to the main jets in a similar 'hollow' tube. The fuel mixture screws are in front of the actual carb bodies just behind the manifolds.

 

Yeah the Mix screws are not the same as the pilot jets, they are the first thing to clog so I figured these were why the idle was dying after the enrichment was closed, but after repeated cleanings they are quite clean and I have a filter from the tank to the carb.
So far I haven't been able to figure this one out. When I do (and after I'm done making up for lost time riding everywhere) I'll post what I found out. Till then if anyone has an idea please chime in!

 

Did you clean out the enrichment circuit in the Fuel Bowls?? Take a B string from a guitar and poke the inside and squirt it with carb cleaner. Could not be getting aby fuel from the Fuel Enrichment Circuit. Just IMO

 

Remove the Inline Fuel Filter.
Try "Blowing" through it, ... to test its porosity.
Cheap ones get clogged when thy get wet.

 

Wow... it seems this thing is being troubleshooted to death here. After you start the bike are you keeping the choke on? Also, is it YICS equipped? You might need to clean the YICS passage out. just pull a good piece of cloth through it but one that doesn't have strings hanging off and won't lose fibers in the passage.
Also, try giving it a little throttle and adjusting the choke down once it starts. Your choke and idle mixture are on the same circuit and if you are flooding the engine it will sound like its running out of fuel. But you'll also smell the gas.

Ever throw the choke all the way up and the engine dies? Its a quick reference for me when tuning carbs. A quick wide open choke will kill the motor...

If you run it on 'pri' you'll be running rich unless you disconnect the vacuum line. Try clamping the vacuum line and just running it on prime. If your petcock is bad you will either have a blockage if the valve is stuck between positions, or you can be drawing in too much fuel if the passages are rotted and cracked. Clamping the vacuum line, or taking it off and capping the nipple and plugging the line, will allow you to run the bike on a gravity type system instead of the constant velocity. I did it for a while out of laziness. I hate rebuilding the petcock. Haha

Also, How is the gas you have in that tank? If it has been sitting in there for more than 3 months, get new gas. And use 93 octane. And if you can get the stuff without ethenol, do it. Those bikes were made at a time when gas was just plain gas. Not this low octane with corn addative, etc... I run shell 93 without ethenol

Remember it's a Yamaha. Its cold blooded. They don't warm up fast and I am sure anybody here can give you a hard starting story. Its a carburated Yamaha's life story. If you can get it running, don't let it die. Keep on top of it and your hand on the throttle... just try keeping it running. If your carbs were cleaned and set right, it might just need a good running.

Those jets do need extra special attention, though. Just as SLKid said, you have to poke a guitar string (exactly what I use...) through. You should be able to hold them up to light and see through them.

 

Re: 1985 XJ 700 rough running tough to start won't stay runn

Chuckles has some good things in there.

I think it's being re'd to so much because it's winter time and most folks have their issues sorted....

 

Hi Guys thanks for the input! Yeah I can see through all the jets, no guitar string needed. They're clean, actually the old gas theory might be on the right track, also the fuel filter clogging idea is a good one I'll try those and get back to you. Yeah the cold start issues are nothing new for this bike (that's why I eventually switched to a Yuasa battery). As of right now it is not starting at all but it was starting with the enrichment at about 3/4 but then would die... if I added throttle while it was running (even up around 3000) it would die...which makes me think: too rich. And that might be from running it on PRI but it never had this problem before.
Here are my thoughts: I will get new plugs, a new fuel filter, some new gas and try it again. It might be something that simple!
Thanks again for all the input folks!!

 

-float levels checked dry or with fuel using the clear tube method?

-bench sync'ed?

-VAC sync'ed? (I realize it's a bit hard to do if you can't get it to hold 1500rpm.)

-fresh gas, new plugs, as above.

 

Ok, new issue: I managed to get it running on full choke (enrichment) but it was running really rough, so a quick feel of the exhaust pipes and only the outside cylenders are runnign the inner 2 are cold. So my first thought was the coil (since the middle two share a coil) so I pulled the middle plugs and turned it over, nope nice hot blue/white spark. and the plugs were covered with gas so it's getting gas and spark (and compression) but not firing. Maybe it's the timing? But how can the timing be correct for the outer 2 and not for the inner 2?

 

Sounds like you've fouled the plugs to me. Clean em up with some fine sandpaper and let the gas on the plugs and in the cylinders evaporate. Plug in. and try again. If it still fouls em up, carb issue.
Uuuuse the Fiiiitz.
He brilliant and speaks the truth. Check your floats.
-Chris

 

I had the same issue with my bike. Come to find out it was the coil. It would put out a spark but not hot enough. Checked the resistance on the secondary, sure enough open circuit. When I changed the coil out it runs like a scalded monkey, and has not giving me any trouble since. I also cleaned/rebuilt the carbs a dozen time before this. You can have the carbs running like the finest Swiss watch, but wont do no good if you can't fire the mixture.

 

The Timing is FIXED.
The Timing is regulated by Electronic Impulse.

If you have a Situation where: "It will only run on Choke", ...

You have considerable work to do in order to have the Carbs supply Fuel to the Holes like they are supposed to do.

Thoroughly Clean your Carbs, including:
Fuel Bowl Enrichment Well Metering Ports.
Siphon Tube.
Emulsion Tube (Remove Main Jet & Washer -- Press Tube Out Top)
Remove Pilot Jets and Topside Pilot Mixture Screw:
> Flush Connecting Passageways.
> Flush Main AIR Jet Passage
Refinish:
> Remove AlumaOxidation from Bores
> Search "Clunk Test"
Also:
> See if Petcock Tower Filter is in Place.
> Pull Float Valve Body's and Clean "Beanie Screens"

Get yourself in a POSITION for Fine Tuning.

 

Well said Rick. That may look like a lot, but it is all fairly simple and straghtforward. Especially when you already have the carbs off. Spend a lot of time on your carbs. Get to know them. They are the heart and soul of these bikes.
Besdies
Age old rule. "Start simple first" Do everything you can without spending a lot of cash, then move on to expensive things Ruling out all the simple things as you go. First prob I have with the bike, any prob at all, I check the fuses. Feel meh?
-Chris

 

Wow Thanks for all the input guys! The wonderful news: I finally got it running! Turns out almost everyone here was right; the bike had a lot of issues. First the battery electrolytes were low, topped those off; the carbs were clean but the Shell around the corner had water in the fuel (when I drained the floats I noticed the fuel was cloudy, I dumped it in a cup and sure enough it seperated out); so I got new fuel (from somewhere else); The plugs were old so I changed them out; New airfilter. After all of that it started right up (I also pulled the carbs and cleaned them again for good measure. I'm waiting on new oil filter so I can change the oil, that'll make her happy.
Thank you all again I don't know what I would do without this website! If nothing else it just reaffirms what you know but keeps you from missing something stupid...in this case a lot of somethings!

 

Re: 1985 XJ 700 rough running tough to start won't stay runn

good show! Now, you just have to wait for it to warm up if you are back east (didn't see where you are at). Yeah, they are pretty simple MOST of the time. It's just getting your paws dirty and experienced enough to know what you are doing that takes the time.

 

Re: 1985 XJ 700 rough running tough to start won't stay runn

I hoping you will be able to help, i've been messing around with my xj700 for about a year now. I've went through the carbs multiple times, ive replaced the plugs multiple times, and other this' and thats'.

my bike runs great, it idles ok, the major problems are that it only gets about 10mpg, and that at take off it "cuts out" or "bogs down" until about for a second or two, and then seems to run great, or great for how it has ran since i've owned it.

I the plugs foul out as fast as i put them in, and the mixture seems or is really rich, i mean in the garage or i guess the neighborhood stinks bad 8O .

I'm going to take the carbs off again and take the mixture screws out and see if all that stuff is there. I guess my main questions were if you got terrible mileage before you found that you were missing pieces, and also any other ideas, i still haven't messed with the floats, another thing i'm going to do with the carbs off.

Hopefully this reaches you, i really wanna ride my bike. Thanks for any advice, Scott

 

may be running rich mine acted ssimilar to this took three tanks of gas 2 cans of seafoam one night I was warming it up to ride home it was blowing so much smoke I thought it had blown a gasket got on it to get home quick it sputtered and smoked then it cleared up runns like a top after I readjusted the idle screw. Check all the jets blow air in every hole,make sure there is no trash in the needle valve . there a lot of tiny holes ti wont take much stick open or stop up good luck I know it is frustrating

 

I am sure its been said but sounds like floats are 2 high or to much play between the float pins and the float or the tab might be bent crooked. If they are spot on anything the might be changing it. If your plugs are fouling that quick . Try this start it up get a small pair of vice scrips clamp off the rubber hose to the carbs drive it see if it runs better you wont be able to go for maybe a block but see how it works that will tell if its in the float position. You didn't get your air jets mixed up when you re did your carbs did you? Just searching for a simple solution . Whats the compression like ?

 

Hi Scott,

You should start a new thread with your problems so it doesn't look like an old issue.

If you are getting that bad of mileage, your float levels have to be way off (or the needles aren't even there)

It's amazing that it runs at all actually.

You need to use the clear tube method to set the floats and of course confirm all the bits and pieces are in your carbs to start with.
I'm guessing your floats are so far off that you need a major re-set which is a PIA so here is a little method I used this spring.
http://xjbikes.com/Forums/viewtopic/t=30833.html
You still have to finish with the clear tube method to confirm but this will get you in the ballpark quickly and confirm the needles are shutting off the flow.

Is this a "california" version? there are some odd emission control stuff on those that might mix you up.

 

ok i started a new thread with my original post, well i've got new issues, strangely enough this makes me happy, at least it's something else i can work or on or look at other than the same ol stuff.

i will post what i find out on the new thread. thanks

Scott

 

cutlass, do you mean to put the vice scrips on my fuel line?

and believe it or not the needles are there!! you would think that there not with how much fuel runs through it.

pretty sure everything is in the right place, i mean i put it back the way i found it, i can take a look at the manual again just to make sure that stuff is where its supposed to be.

thanks everyone, Scott

 

yea try clamping off the fuel line see what happens

 

learned a lot as i’m having the same problems i’m going to replace coils and hope this is the problem

 

anyone know where can i buy a new coil dor my air xj700n