Valve Cover gasket woes and Carb? Problem

Discussion in 'General VMax Questions' started by Will, Jul 22, 2019.

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  1. Jul 22, 2019 #1

    Will

    Will

    Will

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    Hello all, I picked up a 93 vmax (33,000ish miles) as a project that needed the drive line repaired. It didn't take me long to get that all put back together and I got to take it out for a drive this weekend. Now, I've got a couple of issues to address and am looking for opinions of some vmax gurus.

    1st problem is a bit of a pop/miss on cylinder 3 at idle that gets more noticeable/louder up to 1/4 throttle and goes away after that. Definitely leaning towards a clogged pilot circuit on that one and I'm going to try the shotgun cleaning method to remedy that. Funny thing is that cylinder makes a hissing noise I can hear out the exhaust after shutting the bike off. Related any way or any idea what that is?

    My other problem is my cam cover gasket blew at the half moon part. The gasket looks pretty old and cracked so I was just wondering if it's just an issue of weak old gaskets or if my crankcase is overpressurized. It's normal for the case to have some pressure right? And it'd be enough to blow put a weak gasket?

    Sorry for the long read and appreciate any help. Thanks
     
  2. Jul 24, 2019 #2

    one2dmax

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    Might need some carb cuircuit cleaning so run some seafoam through it first. You can also try a procedure many call the "shotgun" which can be found on youtube. Also a carb sync if the rest checks out.

    The gasket can blow out if old and dry enough but it's not common. The vent usually can control it. if it's been sitting for quite some length of time the rings may need a bit to get cleaned up and reseated to slow down some of the blowby.
     
  3. Jul 24, 2019 #3

    Will

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    Thanks for the reply.

    I do have seafoam in it but I'm gonna try the shotgun while the bike is down waiting for a gasket. I did a sync on the carbs and it ran better but the problem was still there.

    As long as I can blow air in/out of the breather tube my breather system is working, correct? I'm hoping it's just a gasket issue and nothing major. I may have had a little too much oil too, (filled to top line) and the PO had switched to synthetic oil when he bought it.
     
  4. Jul 25, 2019 #4

    lonfu

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    Hard to balance the carbs until they are cleaned out. I use 2 diff methods depending on how long it has sat with fuel in the bowls. As an old timer what I do, with the engine off, is pull the idle mixture screws and shoot carb cleaner in them followed by some compressed air. I then shoot some down the throat of the carb and move the diaphram needles by hand a few times to loosen them up. This I do 3 times an each carb of the 4 carbs. Then balance them.

    The first time I had to clean them out about 28 years ago, they were so plugged that I had to pull both the idle mixture screws and the diaphams/main jet needles and clean both jets with carb cleaner and compressed air. Used 0000 steel wool on the needles. After than I've learned to drain the carbs, easy to do on a vmax, when I'm not riding for more than a couple of weeks.

    Most old bikes need the valves adjusted, not always a simple thing to do but they run much better afterwards. Gonna have to bit the bullet and buy a 4 gage carb sync..... I have an old style mercury unit... just can't rev it while hooked up...

    good luck
     
  5. Jul 26, 2019 #5

    Fire-medic

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    I'd just rather pull the carbs and split them into two pairs, and disassemble them, and into the ultrasonic tank they go. That way you address anything needing attention in the carbs, and it's not 'a wish and a prayer' that a can of solvent and a little red straw fix things.
     
  6. Jul 26, 2019 #6

    lonfu

    lonfu

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    To each his own..... If you are going to pull the carbs then plan on replacing the rubber that connects them to the intake manifold. They usually have some dry rot and when you disturb them there are usually problems. For myself, summer is when I prefer to ride so getting it back on the road fast is my priority. Rebuild stuff is for the winter temps...
     
  7. Jul 26, 2019 #7

    Fire-medic

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    After owning a bunch of these, and after working on them all, I never had to replace all four rubber gaskets from the carbs to the VBoost manifold at the same time. One, maybe two, that's it. I suppose if you're in the middle of gila monster baking climate, maybe the toll on them is worse, after all, it's a 'dry heat.' Maybe the humidity of Florida helps to keep them supple, despite the heat.

    I can have a pair of carbs on the bench from a running bike, and split into pairs, and stripped of jets and the jet blocks, ready for immersion in the ultrasonic bath, in about an hour and a half. I'm not particularly fast, nor do I try to-be, but if you've done it dozens of times, you become quicker and more-proficient. Being-able to blow all the passageways clear, and holding in your hands those pesky plugged-up pilot valves, and visualizing they're clean is a better use of time than "pluck your magic twanger Froggy!" using a spray can; yes, that's my choice.
     
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  8. Jul 27, 2019 #8

    Will

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    So just an update so far...

    I've replaced the blown gasket and performed the shotgun on the right side carbs (one of the carbs being the cylinder I was having trouble with) After I did that I started the bike and the pop/miss seems to be cleared up. Cool. I went to go clean the left side carbs and I discover a 1/4 inch tear in the diaphragm for cylinder 1. So I'm waiting on parts again...
     
  9. Jul 28, 2019 #9

    Fire-medic

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    You can use roofing cement or another flexible drying rubber glue, (did someone say Flexseal?) and it should work. Keep you on the road.
     
  10. Jul 29, 2019 #10

    Will

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    I thought about doing that but being the busy guy I am the part will probably get here before I have a chance to work on it again anyway.
     
  11. Aug 1, 2019 #11

    Will

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    New diaphragm in, carbs tuned and synced and she is running a ton better... But the pop comes back. I'm going to check for an exhaust leak next. That cylinder responds to richening the mixture and I recall when putting the bike back together I could wiggle that header pipe quite a lot.
     
  12. Aug 12, 2019 #12

    Will

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    After some spirited test rides I think everything is sorted...
    Valve cover gasket is holding fast. Must have just been old and cracked enough to fail and the po's switch to synthetic oil probably didn't help things.
    Carb seems to be tuned and balanced pretty well...
    The pop/miss I think was due to a cracked spark plug cap arcing to the cylinder head. Sealing the crack seems to have fixed things for now and I'm going to be looking into doing the cops mod.
    Also put in new friction discs and did the dd mod and she rips now! Thanks for everyone's help.
     
    Last edited: Aug 12, 2019
  13. Aug 12, 2019 #13

    Fire-medic

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    If it works, ride it until something else needs attention.
     

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