I'm just about at my wits end with this thing

1985 xj700 airhead. 11530 mi. Oil, filter, plugs, carbs cleaned/changed and sync'd. Petcock rebuilt, new fuel lines.

stupid thing won't start unless i hit it with ether and rev it, then it just dies.
I had it running for about 40 mins last night after I swapped the plugs. The plugs are now white after going from the factory setting (the factory brass mixture screws were still there) of 1.5, 1.5, 1.5 and 3 turns to 2 turns on all 4 carbs.

WHEN the bike does run it stumbles from idle to about 3500, then takes off. Local shop owner said to check the float level. Dry, they were at 16mm on all but no. 3 which was either 15 or 14. Moved them to 18mm and did a wet test with a test tank...NO change, thing just won't go.

If you touch the choke, it dies, period, and I mean TOUCH the choke. I'm looking for suggestions. The carbs are clean, no ifs ands or buts, but again, I wouldn't be posting if I didn't need help, so fire away

One final note, I am in the process of changing the oil again to make sure that before the petcock was redone, there was no gas that any gas leaked in the case...and it was nasty, no material though

 

Bad gas mabye. Or ethynol laced gas. It's a long shot, but simple to rule out.

 

What about the enrichment passages in the bowls? I've had to chase mine with a piece of guitar string even after the bowls spent a day at our local bike shop's carb tub...

Also, make sure your fuel tank is venting properly, and your new fuel lines aren't getting kinked somewhere.

 

update
carbs are off, and completely apart. Everything is out of them. All passages appear clear, altho there were bits of crap here and there. Plugs are absolutely soaked. gas pooled in the bottom of the manifolds.

she has new gas. tank is vented. a can of carb cleaner later, I can say that the passages are at least clear. I'm hitting them with a compressor tomorrow.

float bowl height is my concern now. I'm at 18mm dry, thats +2 over stock.

 

Those Carb Presets that you pulled-out of a book are, ... at best ... a guess.
What you should do is get a ColorTune reading to know the Mixture is Rich enough to keep the Bike running.

Experiment until you can get a ColorTune.

Cut the Point off of a Golf Tee nice and square.
Add a coat of bright Nail Polish to the stem where you cut-off the end.
MEASURE ... Using a Machinists Ruler ... 14/100ths of an Inch.
Make a MARK, using a Razor Blade ... 14/100ths from the end.

Run the Line precisely around the Tee
Use the Razor and SCRAP-OFF the Polish from the Line to the End.
Create a Depth Gauge for the distance of 14/100ths.

Use the Depth Gauge to Set the Pilot Mixture Screws.
Raise or Lower the Mix Screws to a Depth of 14/100ths.
This is an experiment.

See how she runs with the Pilots set at that height.

 

The red arrow show points to the small tube that ahs abot three holes along the length of it. Clean it with carb spray. I stick the straw right on it and press as hard as i can, turn my head and spray. If you where goggles you will see fluid sparay out of the tiny holes. sometimes the are facing in different directions but that doesn't matter. then check where this tube goes into the bowl. That passage must alsoo be clear. Once again i stick the straw in there and let h have it.

 

I'm not that familer with these carbs specificall but make sure the main jet and piolot jet didn't get swapped

 

Siphon Tube POWER FLUSH ...

Take a Carb Cleaner Sprat Tube
Add a Length of SHRINK WRAP
Shrink a Short Length of the Wrap to the End of the Tube.

Slide the Wrap OVER the TUBE until it seats and "Give it Hell"

 

That little tube is called a siphon tube then?

 

Update-carbs are off. completely disassembled. All passages are clear, 19oz of carb cleaner can attest to that. No apparent cloggage. There were a few bits in the bowls and on the needle seat screens. I am running a new inline filter with new fuel line. All bowls have fuel

Plugs are drenched, absolutely soaked. gas pooled on the intake boots. I thought I was at 2 turns on te fuel mixture, when I was really at 3.

Dry float height sits at 18mm. Wet height looked close, but can you really measure 1mm below the body? It's not easy. I'm going to blow everything out with the compressor tomorrow and reassemble. I'll set the float heights to 20 mm vs the stock 16mm and see what the wet setting is.

Just for piece of mind, what is the numbers for the main and pilot jets? Pilots are smaller, no? What about the numbered jets under the vacuum slide?

 

Non-X 700's have Hitachi carbs, right?

The fuel jets (bottom of carb): pilots are smaller number and i.d.. They go towards the from of the carb. Mains are larger, and go in the middle.

The AIR jets (under the diaphragm): pilots are LARGER number and i.d., and also go towards the front of the carb. Main air jets are smaller and go behind the pilots...

 

Unless you hook-up a hose and look at the level rise up the hose; how do you REALLY know the Float Levels.

Fill them babies up and check them with the hose method.
You might get lucky and not need to do anything.

Then, again ... one or two or more might be off.
Mark the one that is best.
Match the others to it.

Once you have a BASELINE ... you can dial-in the other ones on that.

I use Windshield Washer Fluid and just Drain them into a clean tub.
Totally safe.
Quick.
The stuff goes in the car when you're done.

 

I've been chatting with desinger mike on this for days now. The needles appear to be corroded and we feel this may be inhibiting them for seating. I'm going to try and polish them carefully and run washer fluid through them from the test tank and see if they seat by hand and if there is any leakage. They are in good shape otherwise. The other thing I may do if that doesn't work is the golf tee trick to 're shape' the needle seat. I think this is where the issue lies. I did take wet readings, they appeared ok, but it is truly hard to tell '1mm below body'. I think the gas is leaking past the float needles...I'll find out soon. There is just far too much gas ahead of the carbs in the manifolds. The jets I had in the correct slots, I was just verifying, thank you. I'm use to mikunis on the x's, not the hitachis. Mikunis appear simpler. I've never had this much issue with a set before. Live and learn huh? I did find 4 rebuild kits (needle, seat and gasket) on flea bay for 56 bucks shipped, so if this doesn't work, or I can't get the needles to seat, I'm going that direction.

 

The needles on air-head Hitachi carbs (700's) are rubber tipped, not metal.

That may be the real problem..........!

 

Thanks Len. What I meant by corroded was the sides and what not of the needles are corroded. I'm thinking they are not seating correctly. Hoping to see if I am right or wrong today. Gosh, I hope I'm right, and they are leaking.

They are rubber tipped and the tips are apparently in good condition

 

I thought windshield washer fluid was the wrong density for measuring float heights (off by 25%), and you better FLUSH it all out with carb cleaner...after I tried this, I completely clogged up my carbs and had to clean out all the ww-fluid that had CRYSTALIZED all around the carbs and especially on the slides and fuel inlet screen. There could be differences bewteen brands of ww-fluid too.

My recommendation, is use gas and only gas to measure the float height.

 

I was de corroding the needles, when I looked into the seats, holy cow, there is a lot of corrosion in there! So much so that I could scrape it off with a pick (gently)...so, i put some 00 steel wool down there, made sure it was in there well, and spun it with my fingers, and voila! nice and shiny, and you should've seen the schtuff that came out. The steel wool changed color it was so nasty. I then polished up the hole with a golf tee. I re soaked the seats, then ran steel wool through them again and blew them out. Nice and clean. I remember one float height was lower than the other, and guess what? There was one seat that didn't have corrosion in it...hmmmmm. The needles were not seating and the engine was flooding. Simple as that. And if it isn't that, look for a ball of flame from Winchester VA.

 

dry float heights set at factory specs 16mm and they are +/-.5mm. Wet heights look very good. No overflow and all looks like a go. After I get the kids down, I'm putting the carbs on. I'll update in about 1.5 hours

 

Yeah, and put out that cigar while you're at it !
Cool avatar !

 

EVERYONE go outside and look towards N. VA, because there is going to be a fireball.

She won't start sans starter fluid. No. 1 won't fire, and when it runs, it hangs in the rpms. 3 and 4 look to be lean. mixture screws at 2.5. I'm pullng the tires off it and burning it.

Seriously though, if I can't get it in the next few days, it's being parted out.

 

Have you entertained the idea of a possible electrical problem. There is a lot of old crap on these bikes that have the potential to cause some rather baffling headaches.

It sounds like you have the "fuel" aspect covered, so make sure that you don't have any air leaks (the source of most of my problems). As long as your carbs are correctly bench synced, I would move on to spark and voltage.

 

I've got spark on all four. I'm replacing the plugs with the 8es vs the 7es tomorrow. the ones in there are not all that pretty. I thought about swapping cdi's

 

I switched to champion plugs this year, seems like the NGK's only last 1 year. New plugs always seem to bring new life in the spring (for me anyway)

The cdi is worth looking into, also the fuse block.

How is the battery? What about plug wires and caps?

 

Whoa, ....

25-Percent different.
No.

If the Gas contains 10~12 Percent Ethanol ... allowed by Law.
You're talking ... maybe 6 or 7 Percent.
Not 25 Percent.

 

I've heard a lot of talk about ethynol's poor performance issues with newer cars, but how does it effect our older bikes? It's kinda like an octane boost isn't it. And who know what your really getting at the pump these days.

 

Once the Season gets to where the Sun is out and the roads are dry; I spend as much time on the Bike as I can get.

I don't fool around with New England Summer Regular.
I go the extra Dime and get High Test.

 

Any additional thoughts on what might be the culprit here? I'm beginning to wonder if I have bad gas in the bike (I do regurally as well :lol: ). I'll swap plugs consult the local guru and try different gas. I'm starting to really hate airheads. I've never had this much issue with x's. I've had 2 airheads and they have been total beasts.

 

Hey MC, when you cleaned the carbs did you take the mixture screws out and inspect to see if there's any of the same crap in that circut? I did some carb work this weekend on some Hitachi's. Those little mixture screws make a big difference.
Make sure the Oring at the bottom comes out ,you might have to pick it out with a dental pick. Put it back in this order-screw,spring,steel washer,oring. Turn them all out 2.5 turns.
Don't get discouraged. I do lots and lots carb cleans at work. Which carbs do I have to pull twice...............mine.

 

don't get angry - sounds to my like you fixed one problem and uncovered another problem. it was running too rich, right? with wet plugs and gas in the manifold. now that you fixed that, you've discovered that the carbs really wanted to run lean, but the floats wouldn't let them.

#1 not firing: try swapping the spark plug wire with #4 - that will tell you if it's carbs or electrical.

i had an idea you might want to try - the way the pilot circuit is routed through the carb - it's hard to get the compressed air to go where you want it. i.e. if you blast air into the pilot fuel jet, most of it blows out the pilot air jet and it's hard to block the air jet off to force the air through the port(s) in the carb throat - the tiny tiny holes that you really want to make sure are clean. if you have a spare jet that you can clog up with solder or something - install that as a temporary air jet and then shoot air into the pilot fuel jet - that will force all the compressed air out the fuel port and really blast it clean. i'll be doing this next time i have my carbs off (why do i always get an idea after i re-install??)

 

#1 not firing: try swapping the spark plug wire with #4 - that will tell you if it's carbs or electrical.

I totally forgot about this, thank you. I'll give that a go. Weird thing is that the bike ran on all four rich as can be. Heck, it might just be that the plugs are all fouled even after a cleaning.

The mixture screws were completely taken out in order, and replaced in order. I've had that issue before as well, but nothing was in that circuit. I pulled everything off the carbs without breaking the rack. Guys, you should see these things, they are beautiful. I'm getting a compression guage today with new plugs and I will run a test across the board. I am also going to see if there is a manifold leak somewhere, but I dont' believe there to be one. Desinger Mike is going to be sending me a rack to try off an 86 xj700n and we'll see if it is something there. I'm thinking it is something else other than the carbs due to the fact that everything is correct to my knowledge.

here is what I have on my to do list for this bike

new plugs and plug caps (snipping the end of each wire a bit to expose new wire)
-see if it will run
--if not, swap wire 1 and 4 so see if the problem follows
check for air leak if able
do a compression test

battery is good, mixture is at 2.5

seat and needle rebuild kits coming by the end of the week I hope. Hopefully the new plugs make a difference...

 

compression is at 120, 130, 130, 120. New plugs, new spark cap. New needles and seats on order. Carbs are off. Float levels (funny enough) are at 17mm on 2-4...1, which isn't firing is at 16. Bike runs on all four when ether is injected, then dies as soon as it is gone. hmmm 1+1 = ? anyone? I'm hoping anyway

I just swapped 1& 4 floats, and the float height changed. what in the world? I believe that the needles are toast. you can see a ring around the rubber portion of it where it sat in the seat for some time. I'm going to wait until I have the new needles and seats to go any further

 

644, don't part out the bike! You're so close to getting it going and when you do, you will be a bona fide XJ expert!

I'm really interested in following this thread while slowly gaining an understanding of the intricacies of our bikes (and specifically the carbs). The troubleshooting here is great.

I'm not incredibly technically experienced, so I suppose the only advice I can offer is to actively avoid getting tunnel vision. Don't focus on a single part, that may or may not be the cause of the issue, for too long.

In computer programming, it's common for people to spend way too long on a solution that is less than ideal simply because they didn't take that step back, that 30-minute break to let their brain reorganize and rethink the problem.

More of general piece of advice to anybody solving a any problem, really.

And that is my $0.02. Good luck!

 

shnuffy, this is the first bike to give me this much trouble, and I've owned I think 8 or nine xj700/700x's. I'll offer up one thing, don't overlook a single piece on these suckers. This bike has sat for 7 years and I saw things on it I have never seen before. I'm not parting it out, I was just very frustrated with it. I have every confidence it will fire right over when I get the new parts and on the bike.

 

Good news!

I just started working on mine yesterday after 7 years of (garaged) sitting. Nothing could possibly go wrong...

 

my order for new needles and seats went out today, or late yesterday from NY, that should mean they are hear by Saturday

 

I polished the vacuum slide bores while waiting for my parts. I also put the new needles and seats in yesterday. I reset the float heights 2x to get them right. Bike back talked me a bit, but did start after a few mins.

I've got 0 power from idle to about 4k though, but I believe it is due to needing a sync. I'm also running a bit rich, which I'll TS down today. I took her out for a ride and found that the lack of power was in every gear which tells me carbs.

I went for a 35 mi ride and was very comfortable on her. I love those pirellis and for 200 installed, I can't complain on the price.

A word on the rebuild kits...the needle 'tangs' for lack of a better word, need to be installed and they are a bit tricky to get into the correct position so they'll stay on, but otherwise, the price was right....
Oh, and she MOVES!

 

Did you set the float height with gas and the "clear tube method" or stop after the dry adjustment?

Did you bench sync while you had the rack off?

You're finally learning what everyone learns about these bikes eventually: You have to go through EVERYTHING, front to back and top to bottom, to reverse the neglect and deterioration.

FAILURE to do that; the neglect of one small thing, no matter how seemingly inconsequential, can bite you and probably will.

After fixing all the bites, you end up having done it anyway. I prefer to be the one in charge.