No Fuel Flow??

Hello all,

This is my first post here so I apologize if it is a little long. Let me start by getting you guys up to speed. I recently bought an 86 XJ700 that had been sitting for the past 10 years or so, and still had about a quarter tank of gas. Well needless to say the whole fuel system was full of gum, varnish, and dried gas. So I took the carbs off and cleaned according to the tutorial on here. I also soaked most of the parts in sea foam for a few days. I dont recall anything in the write up about separating the carbs from each other, but I did not do that. Well once everything was nice and clean I put it all back together and mounted the carbs on the bike.

I left the fuel tank and airbox uninstalled for now. Next I squirted fuel into the main line coming off the carb until it filled up. I did this so I could try and test run before I got everything else back on (I am not sure if this is even a correct way to test). Well I could see the fuel level come to the top of the line and stop there. So I tried to start. It sounds like it will run, but does not. I shot some starting fluid in there and it runs on that, but the fuel level never drops.

I opened 2 of the drain screws on the bowls and there was fuel in there and then the level dropped a little bit. So the bowls are filling correctly, but for some reason the carbs are not sucking up the gas the way they should.

Am I doing something wrong by testing this way? Also I just had the vacuum line just hanging there. But I figured that line is only to open the petcock anyway. So is there something I am missing here?

Thanks in advance guys.

 

Sounds like you need to revisit your carbs. Float levels are incorrectly set and main/pilot jets are still clogged.
While it is not necessary to "break the rack" durring a carb overhaul it is necessary to remove ALL jets,emulsion tubes, , idle mixture screws, floats, neelde/seat. carb slides. These parts need a through cleaning and inspection it order to work properly. The carb bodies need cleaning also, blowing the internal passages with cleaner and compressed air. After you are positive everything is clean and unclogged reassamble the carbs, set idle mixture to 2 1/2 turns out, bench sync, wet set floats. Install them and they will run. Skip a step or take shortcuts and you will have to do it again.

 

I believe floats are correct because there is fuel in the bowls and the fuel stops filling. I soaked all the jets for days and they are all clear. Emulsion tube was also soaked and cleaned very well. I followed Rick's write closely and I dont think I really left anything untouched. Although I did not bench sync. I thought this was only neccessary if I broke the rack.

 

Did you pull all of the parts out of the carbs and squirt carb cleaner through all of the passages? Do you have and air compressor and blow gun?
Sea foam is not going to do a lot to clean dried gas out of those passages. Carb dip will but you'll need to really work on making sure every passage is clear and fully open for the fuel to flow right in those carbs.

MN

 

Bench sync is always necessary on a unknown set of carbs. The others are right, Sea-Foam will not dissolve the dried fuel and varnish deposits in the carbs. You need a good carb cleaner for that. Be careful it will eat rubber parts, watch out for those throttle shaft seals. Compressed air helps to get all the crud out from inside tha carbs. Make sure the pilot jet is clear, just because you soaked it does not mean it is clear. The small orifice is hard to clear without some kind of help(air or small wire)

 

Ok let me clarify a little. The Sea Foam I used was not the regular one, it was deep creep. That stuff does an excellent job of disolving dried gas and varnish. But I also sprayed a few cans of carb cleaner through all the passages, and blew them all out with a compressor. I cleaned all the jets with a small piece of wire, and a needle. I had them all to where I could put a flashlight under them and see the light come through so I knew they werent clogged.

 

Let me say this much. I am positive the main jet (#107) and the emulsion tube it screws into are very clean and definitely not clogged. So that should at least pick up some fuel shoudlnt it?

 

Sounld like you were through in the cleaning. Can you see light through the pilot jet? It provides fuel to the idle circuit. The main jet only comes in at higher engine rpms.
Verify the float levels( very imporntant) , open the idle mixture screws to 2 1/2 turns. IT should after all this.

 

I did see light through the pilot jet as well. I also did Rick's test and put the jet in my lips and squirt some water through it with my mouth, and a stream came out as he said. I wet checked the floats off the bike, but I will check again with them mounted tonight. I also preset the mix screws at 2.5 turns out.

 

It probably won't want to run without the airbox connected.

 

But I can get it to run for a few seconds on starter fluid. I figured once it got going it would be able to keep itself going. Or does the airbox have that big of an effect on it. It seems like fuel is not getting sucked up through the jets. Is there a way to determine if it is?

 

^- This is your issue.

CV carbs like nice smooth air provided by the airbox and the airbox to carb boots. Open to the air like yours are they don't work well. I had the same issue when I first got my bike.

 

Ok so I will try with the airbox connected. I just wanted to try without and see if it would run before putting that all back together.

I guess I will need a new filter first too right? The old one was filthy. Can I find that at an auto store, or does it have to be ordered?

 

You won't find a proprietary filter for an '86 Yamaha at the auto parts, sorry.

 

Ok. I will have to figure that one out later. For now I will just use the stock one to try and get it running.

 

Ok so I connected the airbox and so far same result. Will start with starting fluid, but dies once that burns off. Am I missing something here?

 

I read back through but maybe I missed it.

Did you clean the jets in the bottom of the fuel bowl? These feed the enrichment circuit.

And the float levels are verified with the clear tube method and gas?

 

Yes the jets in the bowl are clean, and I did verify the gas with the tube.


So here is some new results.

I plugged the vacuum line coming off #2 with my finger and that helps a lot. I can now keep it running in the high rpms. About 2500 or above. If I let it drop down it dies. Will not idle on its own. Also the lower the rpms the less responsive the throttle is, and vice versa. I tried messing with the pilot screw, but I am not really sure how to adjust that. I have it preset to 2.5 turns out. Should I be adjusting that? Or is there another reason it wont idle?

 

turn the main idle speed screw in the center of the rack in a little bit until it idles on it's own and adjust the mix from there.

The 700's are yics yes? with an open vacuum line you have massive amounts of unregulated air in your mix. All the vacuum nipples should be covered or connected to your synch tool when you get to that point.

 

Sorry I forgot to mention I did try and screw the idle speed screw in and that did not help any. And yes it is yics. The nipples are all covered up too.

 

Ok so I forgot to mention one thing. When I mounted the carbs I didnt have any gaskets, and couldnt find them online. So I used a very thin coat of gasket maker on the manifold and carb flange. Could this be causing a vacuum leak?

Because if not a vacuum problem, then it must be that all 4 pilot jets are clogged, and not letting it idle?

Is there a way to test if it is leaking around the flanges? Maybe holding a lighter to it while running? I know that is an old car trick to find vacuum leaks.

 

You used gasket maker on the carbs to the boots? Should just be a screw clamp there.

Unlit propane torch works. If you have it running.

 

Well I disconnected the flanges from the manifold. The ones that are mounted with allen head screws. Figured it would be easier that way.

 

If you had he good fortune to be able to remove the Intake Manifold Allen Bolts, ... Replace them with quality HARDENED fasteners or Stainless.

Treat the Threads in the Head and on the Fastener with Anti-seize Lube.

 

Yea the allen screws came out pretty easy actually. The bike sat in a garage for 10 years.

But anyway, how about those mount gaskets? Is that what I should be focusing on next? If so, can I just buy a sheet of fuel safe gasket material from napa and cut my own gaskets?

 

Ok lets just say your carbs are clean and sync is close because you bench synced them. It almost sounds like your valves are too tight. I have had that happen in the past when I tried to fire up a bike that had been sitting for some time I found out why it was parked in the first place. The PO Admitted that the reason the bike was parked was it would not idle???? I asked the question was it ever back to Yamaha to get tuned up. The answer was asa you might guess. "It was too expensive , so I never brought it back" Not sure if thats your problem but you might want to do a compression test and check the valve clearances.

MN

 

I do believe carbs are clean. I havent done a bench sync because I did not break the rack. Is it possible to still sync with the rack on the bike? I am going to try and check for vacuum leaks today, and maybe a valve clearance check if its not too hard.

 

http://xjbikes.com/Forums/viewtopic/t=1 ... valve.html - valves with pictures.

Bench sync is what puts you in the ball park for a running sync. Should be done even if you didn't split the rack on carbs of a previously unknown condition. Meaning you weren't the last one to work on them prior to this.

 

Now the bike is running, forget the bench sync and just do a running sync.

If its way out, it may be safest to get hold of gauges or a carbtune unit.

 

Or use atf in your home made. If it did injest some smoke out the tailpipe is your only issue.

 

ATF as is in automatic transmission fluid? You guys are losing me here. What do I do with that?

Dont I need to get the bike running smooth before I can do any kind of sync? Right now I can only keep it running by giving it throttle. And its hard to keep it at a steady rpm that way because gets pretty unresponsive below 2000 rpms. So I have to give it more throttle then by the time it catches up the rpms shoot up to around 5.

Im not sure how I can sync that way.

 

Yes ATF as in transmission fluid. It goes in your home made sync tool. It's bright red so it's easy to see in the tube and causes no damage to the engine should it get sucked in.

I've read back through this thread, and I'm now suspecting your carb manifolds are not sealed to the head. Letting in air. Which would make the bike very lean and hard to start/run at idle. The pilot jets can't supply enough fuel for that air and most of it isn't even coming through the carb.

 

Ok I will have to search for how to make that sync tool. But I wont be able to do the test until it will somewhat idle right?

First I guess I gotta figure out if the manifolds are leaking, and then try to seal it up. So is the lighter the best method for checking for leaks? And will one of those long grill lighters work?

 

as long as the lighter is letting out fluid while not lit I don't see why it won't work.

 

Ok so I messed with it more today and same result. Bike would not stay running below 2k. So I pulled the carbs back off, and so far the pilot jets all look good. I can see thru all the jets. I cleaned the tube the pilot jet screws into by poking some 0.0020 saftey wire thru the hole. How can I be completely sure that tube is clear?

I also found that pretty much all the metering ports for the enrichment tubes in the fuel bowl are clogged still, but since that is only used for cold starts I dont think it is causing idle problems. I am working on getting those clear, but it is very difficult. I know chacal has a tool, but I rather not order anything if I dont have too. How do you guys clean those?

So far I havent found anything that I would think would cause the bad idle. But when I reinstall I am going to use gaskets for the manifold flanges. I guess I hope that is what the problem was.

Any other suggestions?

 

Manifold gaskets as you mentioned.

Large amounts of air introduced after the carbs makes it very lean and not able to run at idle.

I would remove the manifolds from the carbs and install them with gaskets. RickCoMatic has a write up some where on how best to do it.

 

Can't I just install the carbs with the manifolds mounted? I was just going to put the gaskets on the intake with some high tack gasket sealant and then mount the rack and manifolds on there. I just think its much easier to leave it all together.

 

I think you'll have a better chance of getting them sealed by installing them individual then the carbs in to them.

 

You mount the manifolds on the head before installing the rack. Be sure to use a torque wrench so you don't over tighten anything.

I've just read back through the thread. You haven't fully serviced your carbs, nor does it sound like you "wet-set" the float levels correctly.

You're trying to "short cut" the process and it just won't work. You have to do it right, and in order. You can't jump ahead.

Valves in spec yet?

 

Why havent I fully serviced my carbs? I now have the metering ports clear, and I am positive the fuel jets are both clear. I shot air through them and felt it come out the other side. The air jets up top are also clear. Everything else inside them is nice and clean.

I am going to reassemble them today, reset the floats, and hopefully get to reinstall them today. I guess I will mount the manifolds first. It is just so much easier to leave them on the rack.

I havent had a chance to check valves yet either. I guess that will be next if it still doesnt run right after this.

 

You will continue to be frustrated until you do this carefully and in order.

I said you hadn't fully serviced your carbs based on your descriptions of what you've done. You haven't fully disassembled and thoroughly cleaned them; the phrases "good enough" and "should be OK" keep popping up.

You're still jumping over steps and trying to take shortcuts.

For instance, FROM THE FACTORY BOOK(S

 

Ok so here is an update.

I got the carbs all back together and installed. The bike now idles nicely. I believe the cause of the problems before was the lack of manifold gaskets. The enrichment circuit is also working well. The only thing I do notice though, and Im not sure if this is normal, but when it is idling if I move the choke to the "choke" position the rpms will climb pretty high. To around 3k I think it was. Is that normal?

The bike is idling well though with the choke off so I am happy about that. Now it is on to tuning. I may get a colortune plug, and I will get around to checking those valves when I have more time.

 

What is the air temp where you are?

That is normal for an engine that is already warm. The "choke" is adding fuel.

 

I am in Maryland. I guess it was around 65 when I was running. Good to hear that its normal for the rpms to rise when the choke is turned on

 

Well, hell, depending on where in maryland we could have saved three pages of thread! If you're near baltimore and want some hands on help let me know.

 

I'm a couple of hours north... can help too

 

I really appreciate the offer guys and I will definitely keep that in mind. I am located in southern MD. By the Navy base in Pax River. You may not have heard of it. But I am about 2 hours from Baltimore.

I am hoping I may get a test ride in the next couple of days. I just need to get the gas tank cleaned out, bleed the front brakes, and put it back together.

 

I'm familiar with it. I've been farther to lend a hand.