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Over raving/vacuum leak

Discussion in 'The Garage' started by Winnipeg_79_XS400, Apr 11, 2018.

  1. 1979 xs400F

    So I am now TRYING to get the carbs sync. Once I let the bike idle/warm up and shut off the choke, the bike takes off/over rev's.

    New battery-good charge
    New coils-Both primary's and secondary's checked out on install. Going to chack again
    Electronic Ignition!
    Valve spacing has been set/redone.
    Emog air pods (starting to hate.)

    Before starting the bike;
    • I backed off the idle screw first.
    • Then set the Air mix screws-tightened hand tight, then backed out 1-1/4.( PO had them at 3-4 turns out.)
    • Then tightened in the Sync Screw (wrong name)- All the way in then out 3 turns to start.
    I start the bike let warm up, then set the idle. I then rough sync (with hands/back pressure from exhaust). I then shut off the bike, attach the Manometer and fine tune!

    Tried to take it for a test ride down the lane. The throttle is VERY slow to respond!

    This is where the bike is, now taking off at high rev. I have read this can be a vacuum line issue.

    I have a new HD Peanut tank (inside has been lined) and new petcock (fuel filter installed too). I also have a vented fuel cap. I have capped off the vacuum ports on the carb holders.

    As always, Cheers!
  2. I have read about the spray the carb holder with WD-40, to see if their is a leak. I'll post later tonight with results!

    (Almost makes me want to get a turn key!)
  3. NewHavenMike

    NewHavenMike 1976 XS360C

    Those pods are only hurting you. Did you bench sync them first? This will get them close enough to where you should only need a turn or 2 on the sync screw. Did you set the float levels? Did you set idle to 1000-1200rpm when you synced? Are you sure the timing is set? 1.25 turns on the mix screw seems like its not enough. I think you should go around 2.5 to start.

    Have you replaced the carb boots? These can be deceiving.
    Winnipeg_79_XS400 likes this.
  4. I did bench sync first (after re-jetting the carbs last season), and set the float levels.

    I have electronic ignition, so its good for now (no need to static time). I read that, once the carbs are synced to use a timing gun to finalize!

    I am currently not using the H pipe with the pods. I may throw that on and see what happens!

    Air mix screws. I tried to adjust them to see if it helps, no luck
    Last edited: Apr 11, 2018
  5. NewHavenMike

    NewHavenMike 1976 XS360C

    My bike seems to run OK with just the H pipe. I had to take the filters off one time and had the bike running. It was still revving and idling just as it did with the filters.
    I go in this order: maintenance, valves, timing, carbs, recheck timing.

    The idle screws only help at idle and just after taking off. You can do plug chops. You can also smell when its too rich.

    Timing is VERY important lol. I can tell by how it sounds and feels when the timing is off by just a few degrees. It makes a big difference.

    The thing here is, tuning is only good when you do it in a finalized setup. Its worthless to tune with one set of filters, and then change them over.

  6. You, and a number of other have mentioned plugs.

    I've done the valves and timing. I read you don' time with a gun until your done tuning your carbs, is this correct?

    I'm going to re-install the H pipe with these shit uni pods! Pull the plugs and clean them (So I can pull them later And know if it's black/rich or white/lean.)

    I will then start tuning again from scratch, and try spraying they carb holders for leaks.
  7. So I decided to start from the begining.

    While taking apart the carbs, I noticed (I think) the gasket may not be fitting correctly.

    You can see me pointing to the same hole in the carb body with and without the gasket. Could this be in some way causing an issue (not the source)?

    I tired to flip it so see if it fits correcty and it does not.

    Attached Files:

  8. After some digging, I found that the gasket was not placed correctly, that was fixed.

    Carbs were cleaned, bench synced.

    Put back in the H pipe with the shit Uni Pods.

    The bike will now only run on full choke. When I try to put in in half way and give it gas it dies.

    Also, it is still over reving!

    Ideas please? I thought about static timing the bike again but its electronic now. No points.
  9. NewHavenMike

    NewHavenMike 1976 XS360C

    You need a timing light after doing a static time. Static time is not good enough. What electronic ignition do you have? When I installed my Pamco, I had to move the pickups quite a bit to get both cylinders firing at the right moment. One cylinder could be firing after TDC like mine was.

    If youre absolutely positive your carbs are clean, it could really only be your timing or an airleak. Even with the wrong jets you should be OK. The diaphragms in the carbs could have small holes in them or they could not be set in place.

  10. First of. Thanks for the help.

    When I cleaned the carbs today, I gave those diaphragms a close inspection and they are intact.

    I was under the impression that; You static time, then sync the carbs, and THEN time with a gun.

    This is my ignition I have.

    I have a timing light, but where do you attach them? I was under the impression from the ignition instructions that you don't/can't need to static time... clearly I have too. Any points or tips?
    Last edited: Apr 12, 2018
  11. NewHavenMike

    NewHavenMike 1976 XS360C

    The gun I have uses clips that connect up to the battery and another inductive clip that goes over a spark plug wire. It gets the signal from the plug wire. Notice the 2 battery clips and an additional clip for the wire here: http://www.jegs.com/i/Bosch-Actron/885/CP7528/10002/-1

    You can power the timing light using any 12v battery. Ive powered mine from my car battery before. As long as the inductive pickup clip is connected to the bike youre fine. MY timing gun has an advance knob so make sure that you have it set to ZERO.

    If you still have the mechanical advancer, that could be sticking and retaining full advance when you let off the gas. I stripped my mechanical advancer down and cleaned everything and lightly oiled it and let it sit. Then I bought the Pamco with the E-advance so I no longer needed it.

    Ive switched back to points recently, so good thing I didnt get rid of anything.
    Winnipeg_79_XS400 likes this.

  12. Ok. What your talking about is not static timing. Static (engine not running). It's a timing is a light bulb and 2 wires with allgator clips.

    I'm picking up with what your saying. I'll strip and clean my mechanical advancer before hand.
  13. Cleaned the advancer, and now it won't start. Time to take a few days off from the bike and find a truck to take it to someone! Done Son! I'll admit I'm well beyond my abilities at this point!
  14. Pulled the plugs (one at a time) to see if I am getting a spark. No on the right, intermittently on the left!:cussing:
  15. xschris

    xschris a lifestyle not a trend

    As for the carbs.... Check to make sure the pilot mix screws have not broken off into the carb bodies as this happens with the 77-79 carbs. When bench syncing the carbs hold them up to a light and look at the butterfly's. Each should have just a little light showing through them. Use your sync screw in the middle of the carbs to do this ( its the small one). There are no turns out numbers for this screw or your idle screw. The only screws that has this is the pilot mix screws which should be around 3 from a lightly seated. Also as always make sure the carbs are clean and you have removed every part to clean them. Another thing to check is your float bowls. Make sure fuel will pass from the hole at the top of the lip to the hole at the bottom. You can use carb clean for this and compressed air will help clear them out. This is part of you pilot system.

  16. Did all that yesterday, minus the air mix being 3. Plan is for new plugs tomorrow and see what happens!
  17. Checked my coils and they are good. And no spark.... So plugs perhaps? Thoughts?
  18. xschris

    xschris a lifestyle not a trend

    After that you need to sync the carbs with a manometer. Warm bike at idle 1200 rpm's. Stock jets with H-pipe and either stock style filters/boxes or uni foam filters.
    Winnipeg_79_XS400 likes this.
  19. NewHavenMike

    NewHavenMike 1976 XS360C

    OK, so you have a Pamco with a mechanical advancer...

    It may sound really hard to overlook, but since Ive gone back to the points setup and have had to deal with the mechanical advancer and the timing cam, Ive forgotten to tighten the bolt that holds it all together a bunch of times. Id get it all ready to go and get the timing perfect and put the cover on and get ready to go for a ride. Next thing you know, it wont start?!? The cam and advancer were slipping off of the key on the camshaft and the advancer wasn't turning at all.

    Get the advancer on the keyway and tighten it all up. Make sure that the timing wheel still turns freely as if its advancing. Ive also noticed that when I had the E-advancer, I needed a lot more battery power than I do with the points. If you've been starting the bike and idling it, your battery could be getting low. Even if you only started it a couple of times and still turns over normally..

    Do you have original coils? If so, you can unscrew the plug caps and snip about 1.5cms off the end wire to get fresh wire to screw the caps back on. If you have aftermarket coils, you can do this to both ends of the wires. Id get new plugs too. Dirty plugs are no good and I wouldn't waste any time cleaning them because that wont do anything. New plugs and gapped properly. Don't leave the ignition switch on when the bike isn't running either.
    Winnipeg_79_XS400 likes this.
  20. So I am back to static timing. A friend explained to me how to do it with the PAMCO. That said I have used both a test light and a multimeter and the light/current does not go out at all.

    Checked that the coils are connected correctly to the ignition.

    Light goes out when the bike is turned off.

    Anyone have an idea for this curve ball?

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