Help: front cylinder valve adjustment

[Rmcapozzi]

Valve adjustments on a motorcycle motor are done the same as on a car especially for tappet screw type). For shims and bucket type, sometimes you have a special tool to remove the shims and other times you have to pull the cams to remove the shims. But the basic principle is the same. You line up the markings, make sure your cams are in the correct position and then check for clearance.

The issue in this thread is certainly bizarre. I'll be adjusting the valves this weekend. I always pay close attention to getting the alignment marks set but will make doubly sure just in case on the NT. When you have to pull the cams, THAT is when you can really get things messed up which isn't something you need to do on the NT...fortunately.

I was all set to do this on my bike but now maybe I won't. My bike had 2100 miles on it when I bought it and I have no idea if the 600m inspection was performed or not.

I would not think it's possible to adjust a valve to the point where it touches the piston head. The fact that it runs to me means it's probably fine. I've adjusted valves before but never on a motorcycle. Are motorcycle engines different than other small engines? In my experience you can adjust a valve to the point the engine doesn't run but you couldn't actually cause damage. To cause damage you would have to actually disassemble the cam chain and move a cam. That was not done in this case. For piece of mind I would take it to the Honda dealer and pay a 4 hour inspection fee. They can do as others have said and do compression checks to make sure everything is seating properly.

Thanks for posting your woes. This is how we can all learn. Don't feel bad we have all made mistakes it's part of being a home mechanic. Yesterday I dropped a socket down into my fuel tank on my NT...

 

[DirtFlier]

[..it sounded good.... Except I THINK I'm hearing a knocking noise that was not there before. I say "think" because I'm not sure it's really there or my head telling me that I screwed up and messed up a valve on my earlier try...]

If a valve got bent during your episode at the "wrong FT" mark, you'd have a one-cylinder motorcycle so it'd probably shake like crazy when it was running. The mind can play all sorts of tricks and that noise could have been there before but was never noticed.

 

[Herb]

I would not think it's possible to adjust a valve to the point where it touches the piston head. The fact that it runs to me means it's probably fine. I've adjusted valves before but never on a motorcycle. Are motorcycle engines different than other small engines? In my experience you can adjust a valve to the point the engine doesn't run but you couldn't actually cause damage. To cause damage you would have to actually disassemble the cam chain and move a cam. That was not done in this case. For piece of mind I would take it to the Honda dealer and pay a 4 hour inspection fee. They can do as others have said and do compression checks to make sure everything is seating properly.
NT...

The idea that the piston couldn't have hit the piston no matter how much I adjusted the valve is the type of information I'm praying for. Would others agree? So maybe that noise that I think I hear is just fear and paranoia and not real damage. Even if no valve damage, there is still the puzzle as to why my FT mark is inaccurate. So maybe I start driving it again and see how things go. The weather sure was nice today!

 

[Phil Tarman]

Herb, the only vehicle I've heard of which had valve/piston clearance issues in recent times was the first generation Ford Escort. If a timing belt broke, which they did with some regularity, pistons and valves bounced off each other with catastrophic results. But that doesn't mean it couldn't happen on the NT. Do you have an at least semi-trustworthy dealer whose mechanic you could talk to?

 

[Chucksklrst]

Herb, the only vehicle I've heard of which had valve/piston clearance issues in recent times was the first generation Ford Escort. If a timing belt broke, which they did with some regularity, pistons and valves bounced off each other with catastrophic results. But that doesn't mean it couldn't happen on the NT. Do you have an at least semi-trustworthy dealer whose mechanic you could talk to?

The ST1100/1300 are also zero clearance engines. Don't know about the NT motor. But If timing is correct one could not adjust the valves that far out to interfere with the pistons.
If you are in time the pistons will be moving down when the valve is opening. Out of time is a completely different story.

 

[Rich]

The idea that the piston couldn't have hit the piston no matter how much I adjusted the valve is the type of information I'm praying for. Would others agree? So maybe that noise that I think I hear is just fear and paranoia and not real damage. Even if no valve damage, there is still the puzzle as to why my FT mark is inaccurate. So maybe I start driving it again and see how things go. The weather sure was nice today!

Not categorically. But they won't hit if they're too loose (clearance is too much) and you'd probably need to adjust them so tight that they never quite close before simply being out of clearance could cause them to impact the piston. Normally in these types of engines (where the valves occupy the same space as pistons do when the pistons are safely elsewhere) the things that can cause valve-piston collisions are:

• Valve float. Usually from going past redline. This is because the spring doesn't close the valve fast enough to avoid the rising piston. Weak or broken springs also can cause this. This has happened to me in a BSA (one of a long litany of stuff that broke on my British bikes).
• Cam chain/belt failure or other weird things such as the cam sprocket coming off or a valve guide coming apart. (I had the latter happen in an airplane in flight one time, though in that case there was no valve/piston impact. In an engine such as ours it likely would cause impact.)
• Misassembly of the cam drive system. This would have to be at the factory or someone removed the cam and installed it improperly. Not a normal thing to do in the NT, but fairly routine in bikes with shim-and-bucket adjustment such as the NT1300.
• Valve keeper jumps out of the valve. This has also happened to me and can cause destruction of stuff even in engines where the valves and pistons DO NOT normally compete for the same area.

 

[elizilla]

Given the age of the bike (not very old), the fact that it was running the day before Herb worked on the valves, and the motor's reputation for longevity, I am still betting on a non-catastrophic cause at work here.

I'm with Bob. He's missed something or gotten confused in his process, but he shouldn't be any worse off than when he started, and the bike was running fine when he started.

 

[dnktng]

If you hand cranked it before you closed it up, and pistons weren't hitting valves, there is no reason to think it should happen when running the engine.
Since it was running OK before you started the valve adjustment, there is no reason to believe that the cams are not timed with the crank. If you're not sure there is a new noise in it, start it as normal, put on your normal helmet & ear plugs( if your normally wear them), and try a easy ride. If the valves are slightly off, you should notice it. If something catastrophic was going to happen, it probably would have happened on the first start after you completed the work. Good Luck.

 

[Rmcapozzi]

Loose valves are better than tight valves. All you're doing with the valve adjustment is making sure the valves are able to completely close and remain so for the optimal amount of time to help fend off over heating the valve. I don't see how you're going to hurt the motor as long as you haven't changed the timing as mentioned above.

So even if you increased the tappet clearance when the pistons aren't at TDC, you're not going to get a piston/valve impact because you would be reducing the lift. The motor may not run at peak efficiency resulting in poor burns and low fuel economy but you aren't going to cause catastrophic failure.

 

[Rich]

Loose valves are better than tight valves. All you're doing with the valve adjustment is making sure the valves are able to completely close and remain so for the optimal amount of time to help fend off over heating the valve. I don't see how you're going to hurt the motor as long as you haven't changed the timing as mentioned above.

So even if you increased the tappet clearance when the pistons aren't at TDC, you're not going to get a piston/valve impact because you would be reducing the lift. The motor may not run at peak efficiency resulting in poor burns and low fuel economy but you aren't going to cause catastrophic failure.

Generally true, as long as the clearance is not ridiculously excessive. I once adjusted the valves on my Honda 160 per the manual. One day the bike was barely running. I opened up the valve cover to find that the top 2 mm or so of the valve had broken off and was sitting there. It turned out that the manual (like all do) had the valve clearances in mm and inches and the inches value was off by a factor of 10 (misplaced decimal) for the exhaust valve. This engine had very tight settings. As I recall the clearance was supposed to be something .002" but because of the misprint I had set it at .020". The rocker arm then actually had some velocity when it arrived at the valve stem, sort of hammering it open instead of accelerating the opening smoothly. This caused the top of the valve stem to fatigue and pop off. Fortunately, this did not happen at the keeper groove or the valve would have been swallowed.

 

[Rmcapozzi]

Good point. I guess if you adjusted a valve fully open to the closed tolerance, you could have a problem.

Generally true, as long as the clearance is not ridiculously excessive. I once adjusted the valves on my Honda 160 per the manual. One day the bike was barely running. I opened up the valve cover to find that the top 2 mm or so of the valve had broken off and was sitting there. It turned out that the manual (like all do) had the valve clearances in mm and inches and the inches value was off by a factor of 10 (misplaced decimal) for the exhaust valve. This engine had very tight settings. As I recall the clearance was supposed to be something .002" but because of the misprint I had set it at .020". The rocker arm then actually had some velocity when it arrived at the valve stem, sort of hammering it open instead of accelerating the opening smoothly. This caused the top of the valve stem to fatigue and pop off. Fortunately, this did not happen at the keeper groove or the valve would have been swallowed.

 

[ARKNT]

Generally true, as long as the clearance is not ridiculously excessive.

If a valve were adjusted when the cam was lined up incorrectly, and the valve was actually "up on the cam lobe" then the clearance would be greater than desired and would likely clatter quite a bit because the 1st part of the cam profile is a more gradual ramp. That would explain Herb's clatter.
This may be a case to get another set of eyes on it to verify what is going on and to get peace of mind about it. Peace of mind can be worth a lot while riding in the middle of nowhere.
Even with the clatter, there is a pretty good chance there is no damage, other than a lot of time working on it.

Brad

 

[nyst100]

You're kidding. This is how the thread ends? No answer? WTH?

 

[Warren]

Thats what happens with old guys. They just eventually run out of gas or forget things. Sometimes right in the middle of telling a story

 

[Stex]

I just did my first valve inspection/adjust at about 2000 miles...........I adjusted a couple to the middle of the spec and I thought I knew what I was doing but when I started it, it sounded louder (tick) than before inspection......I was running it without the plastic so could that be why it sounded different? How did the above incident end?

 

[ARKNT]

I don't have details but there was no damage to the motor.

Brad