Just switched to yz timing and..........



70 replies to this topic
  • jchantzWR400F

Posted January 10, 2004 - 02:35 PM

#1

Now I can't get it to start. I just got done kicking the SOB until the kicker side foot peg broke. So I'm thinking to myself "self, that's just about your luck". Anyway,if there's anyone who's made the switch, and has then had problems with getting it to start, then I would appreciate some input here.

I did make the mistake of going through the cold start procedure (choke on, two turns of the throttle) after rolling it out of a 70 degree garage (doh!!!). Usually though, if it floods I just pull the hot start and it will fire up. Not this time. I haven't checked the plug yet and my jetting was perfect before the timing switch.

  • gfergtr74

Posted January 10, 2004 - 02:43 PM

#2

Check the plug. Sure sounds like she's flooded.

  • jchantzWR400F

Posted January 10, 2004 - 03:03 PM

#3

1 other thing that I noticed was that I was able to kick it over with the hot start pulled without having to use the decompression lever. Once wouldn't have concerned me, but, I must have kicked it over 10 straight times without having to use the decomp lever. I'm beginning to wonder if there's something that I over looked while reassembling.

  • Bill

Posted January 10, 2004 - 03:06 PM

#4

Pull the valve cover and count the number of pins between marks on the cam and make sure your correct. If you don't have proper tension on the cam chain prior to tightening, it could have affected your count. Change the plug and try again. My bike fired first or second kick.....it was a long time ago :)

Bill

  • gfergtr74

Posted January 10, 2004 - 03:11 PM

#5

Is this thing pushing thru the stroke real easily? Perhaps something is wrong with the decompression.

  • jchantzWR400F

Posted January 10, 2004 - 03:32 PM

#6

I will pull the cover and count pins to double check. While I'm there I will pull the plug (since this is the only convientant time to do so). I will report back after that.

Also, it only seems to be going through the compression stroke easy with the hot-start pulled. Go figure....

  • tctrailrider

Posted January 10, 2004 - 03:46 PM

#7

The issue with being able to kick it through without the decomp would be an issue for me. Wonder if an exhaust cam bucket is hanging up. The hot start button is not relevant to this, its on the carb. and a completely different issue.

  • jchantzWR400F

Posted January 10, 2004 - 03:52 PM

#8

The issue with being able to kick it through without the decomp would be an issue for me. Wonder if an exhaust cam bucket is hanging up. The hot start button is not relevant to this, its on the carb. and a completely different issue.


If an exhaust cam bucket were hanging, how would I check it, and how would I fix it. I guess I should say that I'm only moderatly mechanically inclined. That is to say, this is the first time I've had the head cover off of a motorcycle. I can however follow directions pretty well. (Thanks to the motoman393 site for yz timing directions)

I do know this, if I check the plug later, and it's not fowled, I will switch bad to WR timimg to make sure it's not that. I have never had problems starting this bike.

  • Guest_Guest_*

Posted January 10, 2004 - 05:24 PM

#9

Did you adjust your valves at the same time and remove the de-compressor? If so its posssible the spring on the decompressor is installed on the wrong side of the head casting. I did this once and it would hold the valve open and not start..Just a guess, good luck

  • jchantzWR400F

Posted January 10, 2004 - 05:59 PM

#10

I did not adjust valves. Is it possible that I did something else to the decomp device. In the process of advancing the exhaust cam 1 tooth, I did have to wiggle it around quit-a-bit to get it back into the cam chain and seated properly again.

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  • Indy_WR450

Posted January 10, 2004 - 06:44 PM

#11

Hey Chantz, I would try to set it back to WR timing and restart it to check that nothing else got messed up. Then while the engine is still hot switch it back to YZ timing and start it. It takes about a half hour. The engine should still be easy to start. Make sure the cam tensioner snaps tight before putting the cam cover on. As you know Yamaha 4 strokes are troublesome starting in cold weather anyway.

  • jchantzWR400F

Posted January 10, 2004 - 07:11 PM

#12

That's pretty much what I had in mind Dan.

Let me ask everyone this. In the yz timing instructions that I have in mentions one of the first steps is to get the engine to TDC. My question is this, for this mod, when the object is to advance the exhaust cam 1 tooth, does it really matter whether or not the engine is TDC.

The reason I ask is because in my manual it shows a picture of what the timing marks should look like when the engine is at TDC. I am lining up the "I" in "HI" which is what I see through the timing plug. In the manual picture it says that the "E" and the "-" should be parallel with the cylinder head surface. When I think it's at TDC (as in "I" in "HI" aligned, the "E" on the exhaust cam sprocket is not exactly parallel, and the "-" is in this form "I". It also is not exactly parallel with the cylinder head surface.

Any takers?

  • jchantzWR400F

Posted January 10, 2004 - 07:14 PM

#13

Oh,and by the way, I did just pull the plug and it was black and sooty. I'm sure this is why it won't start. At this point, I'm trying to figure out why I can kick it through without pulling the decomp lever. I first thought it was just if I had the hot-start pulled. Now I can kick it through without the hot-start pulled. Is it possible that either the timing is off, or that during reassembly, I screwed with the decomp?

  • Gadsen

Posted January 10, 2004 - 07:26 PM

#14

1 other thing that I noticed was that I was able to kick it over with the hot start pulled without having to use the decompression lever. Once wouldn't have concerned me, but, I must have kicked it over 10 straight times without having to use the decomp lever. I'm beginning to wonder if there's something that I over looked while reassembling.



Well, I have a WR426 with YZ timing and there is no way you can kick it over without the decompression lever. Did you do the wrong cam, or index it the wrong direction? :)

  • jchantzWR400F

Posted January 10, 2004 - 07:35 PM

#15

I advanced the exhaust cam sprocket clockwise 1 tooth. Any thoughts on why when the "I" mark is centered in the timing hole that my engine does not seem to be at TDC. What I've done now is to turn the engine until the punched timing marks on the exhaust and intake spockets are at 9:00 12:00 and 3:00. The cam lobes are facing away from one another. I can currently count 13 pins between the 12:00 timing marks on both cams. Which means when I started, I must have been at 14 pins (in the cam chain between marks). It should have been 13 stock right? To get to yz time it needs to be 12 pins between 12:00 punch marks on the cam sprockets.....

Clear as mud right?

  • Indy_WR450

Posted January 10, 2004 - 08:51 PM

#16

I doubt that your engine is not at top dead center on the I mark. It has run fine all these years and you would have had to break the woodruf key to get it to move. Check that the cams are at their peak compression of the bucket for the intake and ehaust cams when you are at the I mark. Make sure you did not accidentally change both cam timings even though you have 12 pins between the cam marks they may be out of phase with the TDC position.

  • tctrailrider

Posted January 11, 2004 - 05:14 AM

#17

What I've done now is to turn the engine until the punched timing marks on the exhaust and intake spockets are at 9:00 12:00 and 3:00. The cam lobes are facing away from one another. I can currently count 13 pins between the 12:00 timing marks on both cams.


In this position make sure the timing mark is on. Its easy to get the whole assembly one tooth off. If it is correct put a tie around the intake gear and chain so in doesn't move. Remove the exhaust cam. Check both buckets with a magnet to be sure they move up and down freely. You mentioned that you did not reschimm during the change. If the buckets were not removed the compression issue is most likely related to the decomp setup, so check this closely to make sure it does not hang open a little. There should be a little slack in the cable. Reinstall exhaust cam with 12 pins for YZ timing and give it a new spark plug. Once both cams are in and the tensioner set, check the compression before you go any further. Careful when putting the gas tank back on, not to bind the cable and hang the decomp open.

  • jchantzWR400F

Posted January 11, 2004 - 05:15 AM

#18

Well, before I even started I marked the position of the cam chain on the cam sprocket so that I would have a reference of original timing. After that, I advanced the exhaust cam sprocket (clockwise) 1 tooth. I then reset the cam chain. I never even took the chain off of the intake cam sprocket.

On the subject of original timing, I guess that I'm confused on what TDC should be. It seems like if I line the "I" timing mark up in the hole, then look at the punch marks on the cam sprockets they are not always the same. Could it be that for every rotation of the engine (start at the "I" mark and rotate until the "I" mark comes back to center) the cam sprockets only make a half turn. Point being sometimes when the "I" is centered I've got punch marks close to 9:00 12:00 and 3:00. Other times, the punch marks are closer to 9:00 6:00 and 3:00. Again, the picture in the manual does not look exactly what mine looks like when I've got the "I" centered.

For reference, my bike has always started and ran great before I tried the yz timing yesterday. I have never fouled a plug, and the jetting was always spot on.

  • tctrailrider

Posted January 11, 2004 - 05:28 AM

#19

Could it be that for every rotation of the engine (start at the "I" mark and rotate until the "I" mark comes back to center) the cam sprockets only make a half turn. Point being sometimes when the "I" is centered I've got punch marks close to 9:00 12:00 and 3:00. Other times, the punch marks are closer to 9:00 6:00 and 3:00.


This is correct. With a 4 stroke the crank makes two full revolutions to complete a cycle. At TDC the cam lobes will point out. Turn the crank 360deg. and the timing mark lines up but the cam lobes point in.

  • jchantzWR400F

Posted January 11, 2004 - 06:12 AM

#20

Could it be that for every rotation of the engine (start at the "I" mark and rotate until the "I" mark comes back to center) the cam sprockets only make a half turn. Point being sometimes when the "I" is centered I've got punch marks close to 9:00 12:00 and 3:00. Other times, the punch marks are closer to 9:00 6:00 and 3:00.


This is correct. With a 4 stroke the crank makes two full revolutions to complete a cycle. At TDC the cam lobes will point out. Turn the crank 360deg. and the timing mark lines up but the cam lobes point in.


Thanks for confirming that. In my own lame way (+/- 4 beers last night) that's the conclusion I came to.

Does anyone have a theory on being able to advance the exhaust cam 1 tooth, and not having to worry about whether or not the engine is at TDC when doing so? The instructions call for the engine to be at TDC. If all you're doing is advance the cam sprocket 1 tooth, does it matter?




 
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