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Motorcycle Forum / General / Yamaha / August 200783 XT550 not starting!
I had a pre-ignition condition at low rpm and decided to check for carbo build-up in the Cylinder. And yes there were a lot on the piston and around the values. I scraped it of. I also replaced the gaskets bottom of the cylinder and top and had some trouble figuring out how to set the crankshaft sprocket timing mark without removing the flywheel, but I find the spot. (same as the |T on the flywheel.) Now it just won't start any more. 1. Spark is strong, 2. no changes in the carbs (so they should work and if I open the drain, its flowing) and 3. I tested the compression (130psi) dry and wet (little oil). I am sure its higher, but its not accurate with the rubber plug and holding it while kicking. The manual say 156psi. I bi-passed the sidestand switch. It some times puffs a few times as if it wants to go, but then dies. I thought it must be the compress being to weak to keep going. After every 5 or 6 try it will back-fire real loud into the exhaust (why?) Any other ideas? Please! >and had some trouble figuring out how >to set the crankshaft sprocket timing mark without removing the >flywheel, but I find the spot. (same as the |T on the flywheel.) Now >it just won't start any more. Recheck your cam timing. The electronic ignition will fire a spark everytime the crankshaft rotates the alternator rotor past the pickup coil, but you get twice as many sparks as you need because the camshaft is rotating half as fast as the crankshaft. When all four valves are closed and the piston is around 10 degrees Before Top Dead Center, that's when you need to get your spark. But you get an extra spark when the exhaust valves are open with this system. Anytime you remove the head, you want to remove the cam chain tensioner before you pull out the camshaft, Then, when you reinstall the head, you line up the piston to Top Dead Center, install the camshaft and camchain on the sprocket and tighten everything down and the LAST thing you do is reinstall the cam chain tensioner. Otherwise, the tensioner will pull on the cam chain and pull the cam out of timing. >It some times puffs a few times as if it wants to go, but then dies. >I thought it must be the compress being to weak to keep going. After >every 5 or 6 try it will back-fire real loud into the exhaust (why?) If you are getting a weak mixture out of the carbs, it won't fire the first time the spark plug fires, but may fire after two or three four stroke cycles. I tend to think that your camshaft may be out of time with the piston movement though. But it's hard to say, considering that the ignition system normally fires a waste spark when the exhaust valve is open. > >and had some trouble figuring out how > >to set the crankshaft sprocket timing mark without removing the [quoted text clipped - 32 lines] > -- > Message posted viahttp://www.motorcyclekb.com So it actual does not matter if I set the camshaft upside down, because it fires both sides(I tried both side and the bike sounds the same, few puffs and die). I will open up AGAIN and put the chain tensioner in after everything is in. On the flywheel there are three marks, a 1 with a circle around it, next a |-| sign and last the |t (dead top center), do you know what the others are for. I will move the cam chain one chain link earlier. My reasoning is if it fires little too early it will ping(but go), but if it fires to late it will not start. Am I correct? >So it actual does not matter if I set the camshaft upside down, >because it fires both sides(I tried both side and the bike sounds the >same, few puffs and die). I will open up AGAIN and put the chain >tensioner in after everything is in. Did you take the camshaft sprocket off the camshaft at any point? It looks to me like there is a punch mark on the sprocket that should be straight up (in relation to the axis of the cylinder) when the piston is at top dead center. Then there seems to be a punch mark on the camshaft itself, so the mechanic knows to align the cam sprocket to the shaft before tightening the bolts. http://www.bikebandit.com/partsbandit/showschematic.asp?dept_id=653868 #1 camshaft punch mark? #2 cam sprocket punch mark? As the engine turns, the timing marks should line up every second turn of the crankshaft, because the camshaft turns half engine speed. >On the flywheel there are three marks, a 1 with a circle around it, >next a |-| sign and last the |t (dead top center), do you know what >the others are for. One would probably be the static *ignition* timing and the other would be the timing at some higher RPM, like 2000 or 2500 RPM when the electronic ignition advance circuit in the CDI box allows the spark to advance. Is there a hole in the side cover where you can shine a timing light to see if the advancer is working? >I will move the cam chain one chain link earlier. NO! Don't move the cam chain one link earlier, you might bend one of your valves when the piston hits it! The camshaft sprocket has 30 or 36 teeth on it. One turn of the camshaft is two turns of the crankshaft. So you'd be advancing the cam timing 20 to 24 crankshaft degrees. >My reasoning is if it fires little too early it will >ping(but go), but if it fires to late it will not start. Am I correct? Well, the owner of a motorcycle shouldn't have to worry about tinkering around with changing the cam timing when he does something as simple as decarbonizing a cylinder and putting the parts back together. Pinging shouldn't happen at all, but pinging doesn't occur until the engine is hot. If you have the timing marks aligned correctly and the mixture coming from the carburetor is rich enough and you have the right heat range spark plug, and you're using the right octane gasoline, the engine shouldn't ping. Light pinging comes from carbon in the cylinder, overheated spark plugs, excessively advanced ignition timing and lean fuel air mixture. You can adjust the fuel air mixture in your carbs to reduce pinging to the minimum, you can use the right spark plug heat range and you can check the CDI box to see if the ignition advancer is working correctly. If the fuel air mixture is slightly lean and the engine is running slightly too hot, pinging will cause small specks of carbon to burn on the spark plug noses. The specks will look like tiny grains of pepper. The engine sounds like it has a loose valve. Really bad pre-ignition begins to melt the top of the piston. You see tiny balls of melted aluminum sticking to the spark plug nose. Then, if you keep running the engine hard when it's pre-igniting, the engine will start to make horrible sounding groaning backfires before it melts a hole in the piston. http://www.sportbikes.net/forums/showthread.php?p=2848946&posted=1#post2848946 You might contact this guy to see what he knows about the XT550, he restored one and got it running. > >So it actual does not matter if I set the camshaft upside down, > >because it fires both sides(I tried both side and the bike sounds the > >same, few puffs and die). I will open up AGAIN and put the chain > >tensioner in after everything is in. > > Did you take the camshaft sprocket off the camshaft at any point? Yes I did, had to, to get to the piston. Should have looks more carefully on how it was (to late know!). > It looks to me like there is a punch mark on the sprocket that should be > straight up (in relation to the axis of the cylinder) when the piston is at [quoted text clipped - 8 lines] > > #2 cam sprocket punch mark? I found the two marks on the crackshaft and the three on the camsproket (I have the bikes technical manual). The camshaft can go 2 ways, the manual said compression side, I did that and for luck I tried the opposite side as well. Both sound exactly the same, few puffs then it dies. I just tried it again (takes an hour and half to get to it). Everytime I remove the tensioner first and replace it last. I moved the chain first 1 link the the left - closed, kicked my ash off opened it up again moved it 1 link to the right off were I started, closed it, kicked my ash off again. No go, no difference, it puffs a few times and dies! > Is there a hole in the side cover where you can shine a timing light to see > if the advancer is working? What is the advancer? There is a hole in the side cover to align the Dead top center with the timing marks on the Cam Sprocket. It did not ping before I started opening the cylinder to clean it, I was just trying to see what happen if I shift the chain incase I have set up little off the mark in the first case. I can't be that further that that off, can I? I will set it back as the manual describe (very limited but), and try again. I will send the other guy an email, hope he responses. Thanks for your help! >I found the two marks on the crackshaft and the three on the >camsproket (I have the bikes technical manual). The camshaft can go 2 >ways, the manual said compression side, I did that and for luck I >tried the opposite side as well. Both sound exactly the same, few >puffs then it dies. Well, putting the cam shaft in upside down won't hurt your XT550 because it's a single cylinder engine with an ignition system that fires a waste spark. But putting the cam in upside down on a twin cylinder engine might be a different story. >I just tried it again (takes an hour and half to get to it). >Everytime I remove the tensioner first and replace it last. >I moved the chain first 1 link the the left - closed, kicked my ash >off opened it up again moved it 1 link to the right off were I >started, >closed it, kicked my ash off again. Like i said before, moving the chain one link either way will advance or retard the valves by 20 to 24 degrees and you could bend a valve. > No go, no difference, it puffs a >few times and dies! Maybe your carburetors are dirty? Maybe you're using the choke wrong? Diaphragm carburetors with starting enrichener valves work best with the choke plunger pulled all the way out and the throttle butterfly all the way closed. >What is the advancer? The ignition advancer on your bike is an electronic circuit in the CDI box. >There is a hole in the side cover to align the Dead top center with >the timing marks on the Cam Sprocket. If you can see the timing marks through that hole in the side cover, you should be able to use a timing light to see if the advancer works. But you would have to get the engine to start and idle. >It did not ping before I started opening the cylinder to clean it, I >was just trying to see what happen if I shift the chain incase I have >set up little off the mark in the first case. I can't be that further >that that off, can I? Like I said, ONE sprocket tooth off changes the valve timing 20 to 24 crankshaft degrees and you could bend a valve, if you haven't already bent one. >> >and had some trouble figuring out how >> >to set the crankshaft sprocket timing mark without removing the [quoted text clipped - 44 lines] >earlier. My reasoning is if it fires little too early it will >ping(but go), but if it fires to late it will not start. Am I correct? http://www.thumperpage.com/ go there, get the correct info and fix. >http://www.thumperpage.com/ >go there, get the correct info and fix. Well, that was sure easy for *you* to type, but where's the answer? >>http://www.thumperpage.com/ >>go there, get the correct info and fix. > >Well, that was sure easy for *you* to type, but where's the answer? try the ask a question part in about thumper related questions. ask big ed. i thought you were a big boy. >try the ask a question part in about thumper related questions. >ask big ed. i thought you were a big boy. I don't have any problem, so I have no question to ask. > some...@some.domain wrote: > >try the ask a question part in about thumper related questions. [quoted text clipped - 4 lines] > -- > Message posted viahttp://www.motorcyclekb.com I replaced the stator, because I had one and after 3 kicks it started. Need to look at my idle jet! >I replaced the stator, because I had one and after 3 kicks it >started. But you said that you had a strong spark in your original post. Why would a different stator make any difference? >Need to look at my idle jet! Most starting problems start with a dirty idle jet. The engine stalls, so theowner turns up the idle RPM, which decreases the vacuum downstream of the throttle butterfly. Then the starting enrichener device won't work. |
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