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Not getting fuel on cylinder 1

Discussion in 'XJ Technical Chat' started by Kerry L Moline, Sep 11, 2018.

  1. Kerry L Moline

    Kerry L Moline New Member

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    I have been trying to get my 750 Seca out of moth balls for a couple months now and finally just fired it up the other day but it doesn't seem to be getting fuel on cylinder one. I have verified there is spark and even swapped plug, wire and plug cap from cylinder 4 to confirm the problem stays with cylinder one. Exhaust pipe doesn't get warm at idle or at 2000 to 3000 RPMS unless I shoot a little carb cleaner into the intake then it does but cools back off. I have confirmed there is fuel in the bowl and in fact just set the floats after rebuilding the carbs so the level is right. Not sure what I might be missing here that would affect both the idle and main circuits. Any suggestions would be welcome.
     
  2. tabaka45

    tabaka45 Well-Known Member

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    I would suspect that the pilot circuit is plugged. The bike runs primarily on the pilot circuit up to about 1/4 throttle so you can easily get to 3000 with little throttle with no load on the engine.
     
  3. XJ550H

    XJ550H Well-Known Member Premium Member

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    use the choke to see if the exhaust pipe gets hot.

    did you set the mixture screw 2-1/2 turns out from a soft bottom?
    check fuel level for that carb. .
    it does sound like pilot circuit
     
  4. Kerry L Moline

    Kerry L Moline New Member

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    I set the mixture screw 3 turns from soft bottom but adjusting it in or out from there (anywhere from all the way in to 4 and a half turns out) seems to make no difference.
    I set the float levels before I reinstalled them and they were all at 3mm from the flange so unless it changed during the install it should be good but I'll check it again for completeness.
    Not sure what you mean by using the choke to see if the pipe get hot. It won't actually start without the choke so it's been on most of the time until the engine warms up enough that I can turn it off.

    I thought the main jet came into play a lot earlier than that but I did some testing last night to see if I had a vacuum leak in the diaphragm that I couldn't see. I pulled the top off and put a piece of plexiglass over it to seal the diaphragm so I could check the vacuum piston for movement and I had to get the RPMs up to almost 5000 before the diaphragm would start to flex. Got pretty much the same results on carb four. I did notice after revving it up that far a few times the pipe seemed to be a bit warmer than it had gotten before so maybe it is just the idle circuit is clogged.

    I won't be able to work on it tonight (company coming for dinner) but tomorrow I'll see if I can pull the float bowl off that carb without pulling the rack and check the jet.
     
  5. tabaka45

    tabaka45 Well-Known Member

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    By "choke" he meant the enrichment circuit. By opening that a little bit extra fuel will be fed into the cylinders. That actually should be enough to get some combustion in all the cylinders. By the way, did you do a good bench sync before reinstalling the carbs. It might be that the butterfly on that cylinder is completely closed at idle. But that would not explain a cold pipe with the throttle open. Also, loosen the drain screw on that carb and make sure you have a good flow of fuel. If so, I'm afraid you are going to have to pull the carbs and give special attention to the pilot circuits.
     
  6. Jetfixer

    Jetfixer Well-Known Member

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    Just throwing darts here , I'd pull the carbs pull float bowl and check float needle , make sure your jets are in the correct position , make sure the jets have not fallen out( once I was experimenting with jet sizes and failed to fully tighten jet down it fell out and bike only ran on 3 cylinders ..similar to what your problem is.)
     
  7. tabaka45

    tabaka45 Well-Known Member

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    Also, is the plug for the dead cylinder dry (no fuel) or wet (too much fuel)?
     
  8. Kerry L Moline

    Kerry L Moline New Member

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    The engine won't start without the choke and won't run without it until it gets pretty warm. So that means I'm not getting fuel through the enrichment circuit either. Hadn't thought of that. I did a bench sync so they should be pretty close. I drained the bowl and then closed the drain and turned the fuel back on, waited a minute and then drained it again and got quite a bit of fuel but I didn't leave the tank on with the drain open to see how much was flowing through the valve.

    I don't think I mixed up the jets but anything is possible. I'll check tonight if I can get the bowl off without pulling the entire rack otherwise it will have to wait until the weekend.

    I pulled the plug and it looks dry. I also ran it briefly without the plug in to check for spark and didn't smell any fuel coming out of the plug hole either.
     
  9. tabaka45

    tabaka45 Well-Known Member

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    I'm pretty certain that you are going to have to pull the carbs and at least look at the pilot circuit for the dead cylinder. Actually, I would look at all of them.
    While they are off, you might try boiling the carb bodies for 15-20 minutes. If there is any gum in the passages that should remove it. But just in case, be prepared to spray some carb cleaner through the passages as soon as you remove them from the water. It has worked real well for me. I boiled my entire rack or carbs at one time after removing the bowls, gaskets, slides, floats, jets and emulsion tubes.
     
  10. Toomanybikes

    Toomanybikes Well-Known Member

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    This little passage is often overlooked.
     

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  11. Kerry L Moline

    Kerry L Moline New Member

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    I checked the float level and it matches carb 2. Both are low but I attribute that to the angle they are sitting at on the bike on it's center stand. There is a steady flow when I open the drain with the fuel on so I don't think supply is an issue. I managed to pull the rack last night, mostly in the dark, but I couldn't get the last bolt out of the bowl with it on the bike no mate how creative I got with tools. The pilot jet wouldn't pass light even though it would pass air. I blew a bunch of carb cleaner through it and it now looks much better. This might have been the jet I pulled from another set of carbs and thought I had cleaned but maybe not through enough. Anyway that explains the idle circuit.

    I'll check the main assembly and the pickup tube and well for the enrichment circuit, (thanks for pointing that out @Toomanybikes) tonight and tomorrow.
     
  12. fiveofakind

    fiveofakind Well-Known Member

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    Your statement does not make sense........if your bike is starting with the choke on, then your enrichment circuits are clear and not plugged.......you are confused on your statement above
     
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  13. Kerry L Moline

    Kerry L Moline New Member

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    Just carb one is having a problem. The statement was in response to @XJ550H suggestion to try the choke to see if the pipe on cylinder one got hot. Which it doesn't, so I'm concerned the the enrichment circuit on that carb is blocked.
     
  14. fiveofakind

    fiveofakind Well-Known Member

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    Chacal sells a drill bit small enough to clean out those enrichment circuits.......these passages are essential & must be clear for cold starting.......
     
  15. XJ550H

    XJ550H Well-Known Member Premium Member

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    are the holes in the wells of the carb bowls clean too?
     
  16. Kerry L Moline

    Kerry L Moline New Member

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    Well in addition to the pilot jet the well for the pickup tube for the enrichment circuit wasn't clear. It wasn't clear on 2 of the other three carbs either so I don't know why putting the choke on helped at all. Anyway everything is cleaned out now and it is running much better. I even got to ride it to the end of the street and back yesterday. First time it's been under it's own power in fifteen years. Now this morning the starter won't engage. :rolleyes: It did this the first time I tried to start it up. Ended up being the black connector under the tank. I don't have anything small enough to get into those connectors to really clean them.
     
  17. fiveofakind

    fiveofakind Well-Known Member

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    what black connector under the tank are you talking about.......if it were me, I would dremel every connection you possibly can.....a clean connection free of corrosion or rust is what you are after.....
     
  18. Kerry L Moline

    Kerry L Moline New Member

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    Hmm. Could have sworn it was black but it looks like it's the white 6 pin connector. Truth is all the connectors are probably a bit oxidized and in need of cleaning. I have a ton of dremel tips but nothing that would work very well for this. I just ordered these: https://www.amazon.com/gp/product/B0062Y599K/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1 I think they should do a pretty good job on these small connectors and be a little more controllable than the dremel.
     
  19. fiveofakind

    fiveofakind Well-Known Member

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    Take a pic of this connection you are talking about ........& post it....
     
  20. Kerry L Moline

    Kerry L Moline New Member

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