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Have a wierd problem

Discussion in 'XJ Technical Chat' started by szabon, Jun 4, 2010.

  1. szabon

    szabon New Member

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    I'm new to this. I just bought my first bike, a 1985 Yamaha Maxim 700cc. The only problem it had was a really low idle. You had to keep the engine reved to keep it from dying, which was a little rough every time you hit a stop sign. After about a half hour of riding, it would get better, but it would still die alot.
    My friend said to take the tank off and mess with the screw that was attached to the clutch to fix the idle. The bike was hot at this point, and we messed with it untill it would idle fine at half-choke. This took us a while, because we had to take the tank off, mess with the screw, then put the tank on. Most of the time, it would rev up real high as if the throttle was cranked up, but we found a happy medium finally.
    This worked great and I road it for about another 2-3 hours and then took a 1.5 hour break. went back to the bike and tried to start it, and it did not want to start. I had to hold down the start button and then throttle it when it cought, and i had to keep throttleing it to keep it going, or it would die. I road to my friend's house, and as I got into the neighborhood, I pulled the clutch in to downshift and the bike died. I coasted in and tried starting it while rolling with no luck. parked it at my friend's house, pulled off the tank and messed with the idle screw untill it idled right, but it was harder this time because it kept wanting to rev high, and it would not start easy. i finally got it where it was good i thought and started to ride it. shortly after I pulled the clutch in and it reved way up. went a little farther, with it reving real high each time i pulled the clutch in, unless i pulled the clutch when it was real low rpm. then the bike started bouncing on its own without me touching the throttle. it seemed like i was bouncing the throttle but i didn't touch it. i tried then messing with the throttle and it was not responcinve to me at all. then the engine died, and i couldn't start it at all. kept triying to start it untill the battery was too low. i tried jumping it, but i couldnt get it to ride. I let it sit last night and have not messed with it. does anyone have any idea what i can do? also, when i took the tank off there was a plug going from the tank, but i don't know what that plugs into....any help would be amazing.
    Thanks!
     
  2. skeeter

    skeeter Member

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    not to be a jerk - but a few more paragraph breaks would make this a LOT easier to read.

    this makes no sense at all.

    that being said - i have no idea what you adjusted - but to adjust the idle, there is a screw between the middle 2 carbs, backing it out lowers the idle, turning it increases the idle. there's no point adjusting the idle if the engine isn't completely warmed up.

    a lot of the symptoms you describe sound like the idle is adjusted too high.

    however, being that you just bought it and it's your first bike, it's pretty likely that there are other things going on.

    your initial symptom sounds like the pilot circuit is clogged up and your carbs just need a good cleaning.
     
  3. ManBot13

    ManBot13 Well-Known Member

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    Ditto what skeeter said. Also, if you've got the choke in and the idle screw turned down and the bike races - this suggests an air leak (choke is really and enrichment circuit - adding more fuel, and the air leak means more air - more of both is just like opening the butterflies).

    A bike that is "new" to you, sold by a PO who was able to just get it running, will need a lot gone through. You may prioritize running right - but please don't forget stopping and steering control (check and reburb your front and rear brake systems - check for rear brake delamination), steering head bearings, and use a good set of tires.
     
  4. shnuffy

    shnuffy Member

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    Checking the rear brake for delamination is crucial. If it's become delaminated over the past 25+ years, it can seize your rear wheel when you're riding.

    That said, your carbs need a good cleaning. This is the place to find all the information you need. There's several fantastic write-ups and we have our very own parts guy, chacal, who can get you any part you will ever need for your bike. He's also the cheapest and fastest, and I'm not being paid to say this.

    Welcome and good luck!
     
  5. szabon

    szabon New Member

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    Thanks guys. I did adjust that center screw (thats what i meant when i said "My friend said to take the tank off and mess with the screw that was attached to the clutch to fix the idle"). I tried adjusting a little more today, and then I started messing with the other two screws...hopefully I didn't mess anything up. if it is the carbs that need cleaning, why would it run fine all day yesterday, and not even start today? should i just start with cleaning the carbs, or is there something else i can give a try first?

    Thanks again
     
  6. szabon

    szabon New Member

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    I just realized the screws i have been messing with are the Synchronizing Screws....Looking online, I guess I need to bench-sync the carbs? think im on the right track?
     
  7. ManBot13

    ManBot13 Well-Known Member

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    Yeah those sound like the sync screws. The idle screw is under the carb between bowls 2and3. While there is some ASTRONOMICAL chance that your carbs are perfectly clean and you just screwed up the sync playing with those screws - be warned...it's not unusual for these bikes to need quite a few things.

    Adjusting the carbs won't work without a valves in spec, all carb passages clean, slides that go clunk, and all air leaks sealed. And be careful with all intake and exhaust modification (meaning not absolutely stock). Mod's usually lead to rejetting at least
     
  8. szabon

    szabon New Member

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    so, take the carbs out, clean them, bench-synhc them, and good to go. What is this "clunk test" i keep hearing about? I assume it is related to you saying "slides that go clunk", but this means nothing to me...

    Also, where do i find a good write-up on doing all this? i searched and found a good bench-synching one, but nothing else....

    Thanks
     
  9. RickCoMatic

    RickCoMatic Well-Known Member

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    The Clunk Test is a finishing-up of a thorough Carb Cleaning.

    The Diaphragm Pistons need a frictionless Bore to rise and fall in.
    After some years, Aluma-oxidation forms and causes the Pistons to stick or bind.

    But, you need to do a complete cleaning of the whole rack.
    Disassembling everything, Cleaning and getting the rack ready to be reinstalled and Fine-Tuned.

    You can make that Bike really ZOOM and run like a jeweled watch after:
    Cleaning
    Float Height Setting
    Bench Syncing
    Mixture Setting ...
    and, ...
    Vacuum Sync

    If you plan to do most of it yourself, ...

    Get a Genuine Factory Service Manual.
     
  10. skeeter

    skeeter Member

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    slap your friend.

    your synch is now screwed up for sure.

    the good news is that you needed to pull your carbs anyway (to clear the pilot circuits).

    DO NOT RUSH TO GET YOUR CARBS DONE SO YOU CAN GET BACK TO RIDING! take your time - force yourself to go slow and be painstaking. before you put your carbs back together, ask yourself at least 10 times "am i really sure i'm done here?"

    then, after you put them back together, ask yourself another 10 times, "am i really ready to put these carbs back on?"

    you should know where every hole and passageway goes and what it is for. it will help you trememdously down the road diagnosing other carb problems on this bike and others.

    if you don't know what something is, post a picture here and myself and others will be happy to fill you in.

    with that said - a bench synch will get you close. you will need a YICS port blocking tool and a set of vacuum gauges (or search 2-bottle synch tool) to get a perfect synch. bear in mind that you should check your valve clearances before you synch your carbs.

    now you also have a good excuse to pick up an impact driver (your float bowl drain screws are likely stuck). it is a wonderful tool that will come in very handy and save a lot of headache in the future.
     
  11. bigfitz52

    bigfitz52 Well-Known Member Premium Member

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  12. szabon

    szabon New Member

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    Thanks guys. Looks like i have a project for me tomorrow. where do you even get a service manual? also, I saw this post for bench synching
    http://xjbikes.com/Forums/viewtopic/t=6 ... synch.html
    won't this work, or do i need this "yics" tool? or am i in a completely different direction as to what the yics tool does. i am so stupidly new at this it isn't even funny....
     
  13. Zyggy

    Zyggy Member

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    A bench synch will get you close, but not perfect. It will get rid of your high idle problem that you were describing earlier. Use a business card cut into 3/4" wide strips to get a consistant gap on your butterflies when bench synching.

    You will still need to do a final synch with vacuum gauges, carbtune, or homemade synch tool.

    From experience, I would also do a spray test to fix your 'choke' problems. You need to double check and then triple check, and then quadruple check this passage way to make sure that they are CLEAN. Trust me, it's frustrating to get everything back together, try to get the bike to start and have it turn over and over and over to no end because you missed checking such a simple, yet CRUCIAL step. Like I said, I'm speaking from experience here! :D

    Have fun and don't be afraid to ask the 'stupid questions'; that's the only way you will learn how to take care of these bikes properly.
     
  14. skeeter

    skeeter Member

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    you don't need a YICS tool to bench synch.

    a bench synch should get you close enough to run the bike and ride it. but it won't perform as good as it can.

    the "true" synch is done with the carbs on the bike and the engine is running - with vacuum gauges connected to the ports on your intake boots.

    the YICS tool isolates the intakes from each other (plenty of reading available on this - make a pot of coffee and search "YICS")

    the reason the bench synch will get you close but not perfect is because a bench synch should, in theory, get all your butterflies exactly the same <-> however, all your cylinders are not exactly the same. some valves will be tighter or looser than others. the compression in all 4 cylinders is not exactly the same. the final synch adjusts the butterflies so that the vacuum pull of each cylinder is the same. (this is why a proper synch is a waste of time if you plan to adjust your valve clearances - if you change any valve clearances, your synch is now *off*)

    you will definitely need to do a bench synch - what is going on now is that your carbs are so out of synch that some of the butterflies are open too far and it's like you have the idle for those individual cylinders set too high. they want to race and pull the rest of the engine along for the ride.

    when you get the carbs off you should look in at the butterflies - up at the top of the butterfly, in the carb throat, you should see a teeny tiny hole. it's right below the idle mixture screw. that's where the fuel from the pilot jet comes out. you want to make sure you've got good flow through that hole. if you open the butterflies, you should see 2 or 3 more teeny tiny holes - these are also for fuel from the pilot jet when you are just off idle.

    to bench synch, i try to set it so the tops of all the butterflies cut that first hole exactly in half. seeing how much a turn of the screw affects the position of the butterfly in relation to that hole should give you a feel for how sensitive the synch adjustments are.

    anyhow - you're getting way ahead of yourself - focus on cleaning the carbs now

    also - try not to get carb cleaner in your eyes.
     
  15. dmschuler

    dmschuler Member

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    There are no short cuts! Take your time and read, and then re-read, everything these guys say to do. My bike is finally running after several false starts. Buy yourself a decent depth gauge for checking the floats! I used a steel ruler the first time around and it was less than perfect...


    And the carb cleaner in the eyes comment - wear safety glasses! Take it from someone who didn't and got a visit to the ER for that!

    Good luck!
     
  16. parts

    parts Member

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    Just in case Ill state what has been well stated already.

    NO SHORT CUTS ALLOWED,AVAILIBLE ,ACCEPTED, unless you feel
    like doing them over and over again.-dont let your friend do anything
    but hand you tools lol.
     
  17. szabon

    szabon New Member

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    so, the carbs look to be stupidly clean....that combined with the fact that they came right off leads me to believe the previous owner cleaned them recently. (when i say came right off, i mean i read how to take them off and everyone said get ready for a struggle, and i got positioned, and almost fell backwards...) so im going for the bench synch now and will do the vac synch after i fashion a tool....wish me luck!
     
  18. szabon

    szabon New Member

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    bench-synched em, and no luck. bike won't even start. i used paperclips to bench synch them, like that one post said. i messed with the idle screw (the right one this time) and nothing. got it going a little bit, but it went to 500rpm and then died....any suggestions?
     
  19. ManBot13

    ManBot13 Well-Known Member

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    You can't SEE clean - the passages that have to be cleaned can really only be "tested" with a can of carb cleaner. You peeked at them and didn't see anything wrong - so you expect it to work? Many POs take their bikes in to get a "carb cleaning" and they get sprayed out and dipped and LOOK clean - but passages internal to the carbs that you cannot see are not clean. It might run out of the shop - but quickly the problems will develop again. After spending lots of money that these shops - the owner off loads the bike onto an unsuspecting victim. "It runs - just needs some adjustment."

    You need to make sure all the small passages in the carb are clean. These include the emulsion tubes, all jets, pilot passages, and enrichment circuit wells are COMPLETELY clean.

    In addition to that, there is rubber in the carbs that needs to be in good condition. You have to make sure the diaphragms do not have holes, the throttle shaft seals, fuel tube, and pilot screw o-rings, float needles and seats are in good condition, and that all of the settings on the carbs are at a good starting point. For all rubber in the carb save the diaphragms - it is easier and more economical to replace than hope it is ok.

    We also don't have a lot of info on your bike. Given how "easy" your carbs were to pull off for the first time - I'm gonna guess that you don't have an airbox. It complicates removal - but helps performance. If my assumption is correct, please read threads on PODS so that you get an idea of what you are trying to deal with.

    Look, I know you are looking to the experts on this site for the EXACT answer to your problem - but the thing you will hear from all of them is that you need have a good STARTING point when it comes to diagnosing a running problem. You should check your compression, check for spark, check and adjust your valves, clean and rebuild the carbs, then try to get the bike running. It is nearly impossible to troubleshoot an intake system issue when you likely have more than one issue.
     
  20. parts

    parts Member

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    Nicely put Manbot.
    Thats exactly why we do our own work. (besides costs).
    Yeah,a mechanic is the easy way out if you can affford one.
    And you can have a very false sense of security saying "oh, I
    had the dealer do the work"
    A buddy took his 2005 v star in because there was a bit of
    greasy goop around the rear tire. It was a single d-shaft bearing.
    They talked him into a total rebuild for over $1000.00.
    And,the wheel was covered in grease whne they handed it back to him.
     
  21. szabon

    szabon New Member

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    ok, by easy i meant i did not have to pull too hard. i have an airbox, and that is not the issue. the porblem i had last night was i didn't prime the carbs after synching them.
    got there this morning realized this, primed them, and the bike started up just fine. vac synched them and everything seemed great, except now i saw a bit of smoke in the air.
    didn't know where it came from so i let the bike cool thinking that it just got hot while working on it in the garage and running it with no air flowing over it. i then grabed some new sparkplugs because the ones on the bike were black and nasty. came back and the bike was cooled a bit, threw on the plugs and took her for a spin.
    drove for about an hour total driving, watched a movie, then went to drive it home and it was difficult to start again. got it going, and got it home, and i noticed smoke from the front of the engine. didn't have a lot of time cause i had to go, but when i came back, i noticed that there was an oil leak coming out of the engine. I don't know what part this is cause i'm bad at this, but i took pictures.
    dont know how to upload pics here so i photobucketed them
    this one is me standing at the front left of the bike looking at the engine
    http://i863.photobucket.com/albums/ab19 ... 100149.jpg
    this is me standing at the front right looking at the engine
    http://i863.photobucket.com/albums/ab19 ... 00150a.jpg
    these next ones are me standing in front with the camera right above the front wheel.
    http://i863.photobucket.com/albums/ab19 ... 100151.jpg
    http://i863.photobucket.com/albums/ab19 ... 100150.jpg
    http://i863.photobucket.com/albums/ab19 ... 00149a.jpg
    So, i'm thinking i have to take the engine apart to get at this gasket and replace it. I will definately go ahead and clean out the carbs completely like you guys are telling me while i am doing this project.
    Any ideas on where to get a good service manual to help with with the engine take-down?

    Thanks again guys
     
  22. 85MaximXX

    85MaximXX Member

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    How did you set your mixture screws that you turned recently? Even when you have the carbs incredibly clean you will have to adjust the mixture screws properly. Do plug chops or colortune. You can't expect to just throw them back on and be done. I manual is your best friend. with book in hand almost anyone can repair these machines. It is all worth it when you get them right they fire right up run smooth. Keep at it and take your time as mentioned there is no short cuts do it right and you will be rewarded.
     
  23. szabon

    szabon New Member

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    i bench synched them and then put them on the bike and vac synched with a tool i made from one of these forums. what does "plug chops" and "colortune" mean? also, i'm thinking my main problem is this oil leak for now no? i got a manual online with directions to pull the engine apart, and was thinking i'll give this a go and replace that gasket. where would you guys go to get a new gasket?
     
  24. ManBot13

    ManBot13 Well-Known Member

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    85MaximXX is talking about your pilot air mixture screws. They adjust the amount of fuel that is drawn up at idle and are different than your sync screws (which adjust the amount of air that each cylinder allows to pass at idle). There is one mixture screw per carb body, in the front in a well next to the enrichment plungers.

    Do you see oil gushing out of a gasket? Is all that grime new? If you really think you have an oil leak, you need to clean the engine (simple green works well if you wash it off quickly - <20 min - it will oxidize aluminum). Oil leaks tend to flow downward and pool in a location different than the actual leak.

    Unless you are out of oil...a small leak shouldn't cause starting problems. You likely need to at least adjust your mixture screws - if not clean and rebuild the carbs - the enrichment circuit is a likely culprit.

    I'm not sure oil leaks on the outside would cause a white smoke. Perhaps an exhaust leak if you notice it in the front? I would hold off on tearing down the engine if you can - how was your compression? Did you check your valve clearances? The HIGHEST possible spot to leak oil on these engines is the valve cover gasket - if that was the source you can replace that without even taking the engine out. So really pinpoint the source of the leak.
     
  25. tibor

    tibor Member

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    look under the engine, could be that you have oil leaking onto the exhaust, if this is the case when the exhaust heats up it will smoke... not a big deal but annoying.
     
  26. szabon

    szabon New Member

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    i've been messing with the idle adjustment screw, but i didn't know there were more than the one...am i thinking something different? how do i synch those?
     
  27. ManBot13

    ManBot13 Well-Known Member

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    Ok...terminology here. Idle adjustment screw is what is in between carb bowls 2-3 and has a big knob on it. It directly opens #3 butterfly - but due to the linkanges in the throttle shaft, it takes all the butterflies with it. It does not affect the mixture, only the opening of the butterflies to increase or decrease the idle engine speed.

    The pilot air mixture screws (4) are recessed. They might be capped. They might be hard to turn, and you can strip the heads out easily. Make sure your screw driver fits the head perfectly (grind a spare one down). Check out RickCoMatic's "Whole 9 yards" carb cleaning guide (search that phrase - "9" not "nine") - he goes into great detail on how to remove them if they are stuck.

    These adjust the mixture (lean->good->rich) at idle and off-idle. They adjust one per cylinder. There are several ways to tune (search these out, or someone else might provide links soon), the colortune plug, plug chops, or by ear. These are in order of increasing difficulty and skill, and decreasing initial cost. I would recommend the colortune plug - it is well worth it.
     
  28. szabon

    szabon New Member

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    when i mess with the mixture screws (after i check valve clearences which seem like a project) what position should the idle screw be? or does that matter? also, where do i get the colortune plug?
     
  29. ManBot13

    ManBot13 Well-Known Member

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    Idle should be 1050 rpm (it should be in your manual or on a side cover - which bike do you have again - hint hint). As you adjust things (sync and mixures) your idle will likely increase the closer you get to ideal running conditions (because the cylinders will start working together, instead of over compensating one way or the other). So always keep your idle at a touch over 1k - so you don't bring other fuel circuits into play.

    Chacal sells the colortune plug. Send him a PM
     
  30. szabon

    szabon New Member

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    so, as i'm messing with the micture screws, i am also messing with the idle screw to keep it just over 1000rpm, then when i'm done messing with the mixture screws, i set the idle to the 1050 rpm perminently?
    but before i do this i mess with the valve clearance. and if the clearence is not what it should be then i need to buy special pads? and how do i know what the valve clearence should be and what pads to buy?

    I know i sound like an idiot, but this is all brand new territory for me...thanks guys.

    two more things, if the valve clearence is bad, this could cause that oil leak i saw? and what oil shoul i use for the bike. its a 1985 maxim 700cc with 31000 miles on it.
     
  31. ManBot13

    ManBot13 Well-Known Member

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    Unless your engine was clean and shiny and after one ride you ended up with what's in the pics, I suggest you degrease the engine, and trace EXACTLY where the oil leak is comming from.

    Search for "airhead valve adjustment" bigfitz52 wrote. The chacal has the shims - there is a chart that will give you the spec and which shims.

    You really need a manual - I see the Yamaha one recommended - RickCoMatic posted a link to where you can order one (around $90). Or you can get a Haynes (around $30). But you need a manual, you'll learn alot faster, and alot of the basic questions you are asking would be covered. Don't worry about a lack of knowledge, we all start somewhere.
     
  32. ManBot13

    ManBot13 Well-Known Member

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    Sorry...no haynes for you bike...but I can't edit my post because of the window size since I'm the first post and can't get to the edit button...anyone else get that?
     
  33. szabon

    szabon New Member

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    i got a manual, someone posted a free one somewhere...and i checked the valve clearances and every one was too close. i couldn't even get my .006mm in most of them...and two where exhaust and were .008, so i'm going to get those shims out (which is terribly difficult, only got one out so far and it took me forever. i'm using the zip tie trick, and a knife and needle nose pliers, if anyone has tricks for this, let me know), and figure out shat sizes i need and have chacal send me the shims as well as a colortune plug. after the new shims are in and everything is good there, i'll tune up the carbs and see where it takes me.

    also, where exactly are the mixture screws. i thought i found them, but turning them out only makes the carbs leak gas, so i'm guessing thats wrong....

    and you guys are awesome. i never would have gotten anywhere near this point without you. I've learned so much in such a short time its amazing.
     

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