Another valve check problem

[Fatallybitten]

A short recap of a long story. I messed up my release of the cam chain tensioner by relying on the advice of an inmate who was told by a Yamaha tech that the easiest way to release the tensioner was to rotate the engine counterclockwise. That was a mistake. The cam chain tensioner did eventually release but not before the chain jumped a bunch of teeth on both the intake and exhaust sprockets. This was compounded by the fact the chain jumped a different number of teeth on each sprocket and then things were so messed up the engine would no longer rotate clockwise through 360 degrees before stopping. So I had to remove the cams with the crank not set to the K mark. In the process I have completely lost track of where the engine is in the 720 cycle. I can identify when the cylinder 1 hits TDC by going through the spark plug hole. Same with cylinder 2 (270 degrees later) But I have no idea whether the cylinders are on the intake or exhaust stroke when they hit TDC. Reading through old posts I came across this comment by an inmate:

"The cam is always off every 360 of crank rotation. Yes it is a 720 degree cycle but it is the cam that determines which half of the cycle the motor is on not the crank. If you turn the crank 360, you are exactly where you were on the crank but cams rotate 180. The cams should line up every other rotation and it makes no difference which one that I can see. I see no cam sensor on this motor so I assume the timing is driven from the crank sensor. So the ECU does not know which cycle it is on. How can that be? Spark and fuel injection happen on both cycles. Spark is "wasted spark"and fuel injection is set up for twice per cycle."

Does this mean I can just line up TDC on cylinder 1 using the T mark on the crank and rotate clockwise 650 degrees until the K mark lines up as per the manual and then re-install and time the cams? I am concerned there could be a difference between the intake and exhaust cycles notwithstanding the comment above and that I stand a 50/50 chance of installing the cams on the exhaust stroke rather that the intake stroke if, in fact, that matters. Anyone have an answer?

 

[Fatallybitten]

So, while waiting for someone to chime in with the definitive answer I have been spending more time with the manual. Page 5-19 of the 2014 - 2016 manual describes installing the camshafts. The starting point is aligning the K mark on the pick up rotor with the crankcase mating surface b by turning the crankshaft clockwise. Then comes the TIP.

"When piston #1 is before 71 degree of TDC ON THE COMPRESSION STROKE, align the K mark with the crankcase mating surface."

The manual does not differentiate between the compression stroke on the intake stroke and the compression stroke on the exhaust stroke, so perhaps it doesn't matter, as long as you start when the K mark is before 71 degrees of TDC on cylinder 1 and the K mark is properly aligned with the crankcase mating surface which is easy to do through the spark plug hole.

 

[RED CAT]

Dave

I had the same thing happen and ended up at Blackfoot doing the cam reset for me. Yamaha mechanic there Brett. Bike is perfect again. He was the one who told me to rotate CCW to release the CCT. But you should have it zip tied to the sprockets in a few spots. Doubt you'll be able to do the reset yourself. Was a hard lesson.

 

[Fatallybitten]

I think I will be able to get it back together if I get an answer to the question of whether there is an intake compression stroke and an exhaust compression stroke or just compression strokes every 720 degrees and it doesn't matter to the ECU as long as the timing is set on the compression stroke. If there are different compression strokes for intake and exhaust, then the question will be how to determine which is the intake compression stroke and which is the exhaust compression stroke within the 1440 degrees of rotation that it takes to complete a four stroke cycle. I am hoping the answer is it doesn't matter, but we will soon know since I am sure someone on the forum has the answer. Cheers, David

 

[Pterodactyl]

It does matter. Read the service manual as it describes how to find TDC to check the valves. Once you align the timing marks to place the #1 piston at TDC you are told to check the position of the cam lobes to confirm that you are not 360 degrees out. The only reason they have you find TDC before going 71 degrees beyond is to confirm you are not 360 degrees out.

I don't want to be a jerk here, but I think the nature of your question indicates this job is beyond your skill/experience level. But, on the other hand, if you do it without damaging your engine you'll be pretty experienced.

 

[Fatallybitten]

The issue isn't whether I am 360 degrees out. That is easy to check by testing the position of the #1 piston through the spark plug hole. if you are 360 degrees out the piston will be at the bottom of the stroke. The crank has to turn 720 to come back to TDC on the next compression stroke. There are two compression strokes in the 1440 degrees the crank turns to go through both an intake and an exhaust cycle. My question remains.

 

[Pterodactyl]

Squeeze, bang, blow, suck.

Good luck.

 

[RED CAT]

The whole problem on the Gen 2 bike is the new CCT which is much harder to reset and release once back on the bike. There has to be an easier way to release it. I did a full valve adjust on the Gen 1 without any hassels. I agree with Dave. How do you know which is actually the compression stroke and which is the fire stroke on number 1. Dave, if worse gets to worst, I have a trailer and can get you over to Blackfoot. They did a great job on mine.

 

[Juan]

Fatallybitten, I would suggest you change your username

 

[Checkswrecks]

I'm lost with your question. It's been a few years since I did the valves on my Gen1 and haven't yet had to do them on the Gen2, but I don't remember anything about 1440 degrees. In any 4-stroke.


Once #1 is TDC, it was just a matter of checking the cam markings and lobes to the book references to make sure no teeth had slipped. From what I remember, in your case it would just be the same as an install of a cam after replacing shims.

 

[Fatallybitten]

I think one of my assumptions was wrong. I read somewhere on this forum that each cylinder took 4 revolutions of the crankshaft to go through the intake - compression - power - exhaust phases. I am now questioning that assumption since two (720 degrees) rotations of the crank turns the cams through 360 degrees hence the intake valves and exhaust valves have opened and closed in that 720 degrees of crank rotation . I am not sure that changes anything since there are still two TDC's in each 720 of crank rotation. And so, I am still left with the question. Is there any way to tell if which TDC is at the beginning of the power stroke and which is at the beginning of the intake stroke ?

 

[Fatallybitten]

Checkswrecks, our posts crossed. Yes, the cam re-install is simple if you haven't turned the crank without the cams in place. Since i have done that I am left with the question.

 

[OldRider]

I think one of my assumptions was wrong. I read somewhere on this forum that each cylinder took 4 revolutions of the crankshaft to go through the intake - compression - power - exhaust phases. I am now questioning that assumption since two (720 degrees) rotations of the crank turns the cams through 360 degrees hence the intake valves and exhaust valves have opened and closed in that 720 degrees of crank rotation . I am not sure that changes anything since there are still two TDC's in each 720 of crank rotation. And so, I am still left with the question. Is there any way to tell if which TDC is at the beginning of the power stroke and which is at the beginning of the intake stroke ?

There is only one TDC. The position of the cams determine if it's the compression stroke or the exhaust stroke. Make sure and use a ziptie on the intake cam to avoid having to start all over.

 

[Checkswrecks]

No problem - all good and maybe I'm forgetting something.


But in the end, the #1 comes to TDC once per crank rev and has no idea whether it's in compression or exhaust, as those are terms defined by the cams. Hence, my comment about simply bringing the crank to TDC and then installing the cams to align with their marks.


LOL- Just saw that OldRider posted the same.

 

[Fatallybitten]

Okay, I got that far in my thinking and then I read the manual some more and realized there is a sensor under the crank sprocket that presumably is connected with the ECU and would send a signal every 360 degrees of crank rotation. Presumably the ECU controls fueling and spark based on that input, so it still may matter which TDC within the 720 degree of 4 stroke cycle is the compression stroke and the exhaust stroke.

With everything stripped off the bike would the ECU still send a signal to the spark plugs at the TDC at the end of the compression stroke, or would all the error codes just shut it down? I could re-install the cams and then turn the crank with one of the spark plugs connected and see if I get spar at the right TDC. But that assumes that the ECU would ignore all the other error codes it would be receiving with the bike in pieces.

Thoughts?

 

[XTZELEE]

+1 exactly what Chainwrecks and Oldrider said - you are over thinking this.

 

[Fatallybitten]

Oldrider, Checkswrecks and XTZELEE, thanks for the comments, which all tell me it makes no difference. Before I act on that advice, and at the risk of overthinking this, help me with this thought process. Everything above the crankshaft is mechanical. The only sensor is the one at the bottom of the crankshaft. What does it do? If, as I suspect, it sends a signal to the ECU every time the crank goes through 360 degrees then the ECU is programmed to act on only one of the two signals it receives during every 720 degree 4 stroke cycle and ignore the other in terms of fueling and firing the spark plugs. If that is the case, then it would matter which TDC I used to re-install the cams. What am I missing?

 

[Pterodactyl]

I mentioned this in my earlier post and I think it is worth repeating. No ill will intended, but it is quite apparant that you do not have the knowledge base on which to base tackling this problem without someone alongside you to help. I'm no great mechanic, but I'm getting better all the time with the help of others. Help from a forum is great and can bring you a long way, but sometimes it is just enought to cause trouble. Part of learning is knowing when you are in over your head and being confused over the basics of how a four stroke engine works (1440 degrees?) is an indication to me that you should seek competant help fixing your bike. Remember: Squeeze, Bang, Blow, Suck; each takes 180 degrees .

 

[Checkswrecks]

Oldrider, Checkswrecks and XTZELEE, thanks for the comments, which all tell me it makes no difference. Before I act on that advice, and at the risk of overthinking this, help me with this thought process. Everything above the crankshaft is mechanical. The only sensor is the one at the bottom of the crankshaft. What does it do? If, as I suspect, it sends a signal to the ECU every time the crank goes through 360 degrees then the ECU is programmed to act on only one of the two signals it receives during every 720 degree 4 stroke cycle and ignore the other in terms of fueling and firing the spark plugs. If that is the case, then it would matter which TDC I used to re-install the cams. What am I missing?

If it's what I'm thinking of it makes no difference what you do, as the plugs fire at whatever BTDC it is they are timed for every time the crank approaches TDC. It's regardless if in the compression stroke going into power, or toward the end of the exhaust stroke before drawing a fresh mix.


You sound like you've done valves before in something else, but if not (or for others who have not done valves) make SURE you can SLOWLY turn the engine through at least four turns - gently - with the plugs out - when you get the cams back in. You want to make sure the cam positions are not putting a valve in the way of a piston. STOP if there is resistance in the rotation and back off a bit to see why.


Then check the cam timing marks again before putting the cam cover on.

 

[Fatallybitten]

Valve checks on a KLR - dead simple, on a KTM 990 - much more difficult, but no drama compared to the S10.