Strange Valve Shim Adjustment

[MechMessiah]

I did a valve adjustment today and it mostly went fine but the exhaust for cylinder 1 is being strange so I wanted to run this by someone else for some ideas.

I started with a 2.7 shim in the tappet and could only get a .03mm feeler in there. I dropped it down to a 2.65 shim and then it jumped to a .10mm feeler. Is it just me or does that math not add up? I did check both shims with a digital caliber multiple times and they were true to size.

I did take a ride with the 2.65 shim and it made the cylinder 1 exhaust pipe really hot so I'm gonna be going back to the 2.7. I would like to get a little more clearance for that valve but I'm not sure what to do. Is it possible to get in between shims? Like a 2.68? Also what would cause that? A bad lobe, bent cam?

 

[hillsy]

Are you sure you checked the clearances with the cams in the correct / exact same positions?

 

[Burque73]

A shim with an X on it is in between sizes. 2.65X for instance is what you need. Did you by chance use a zip tie or the motion pro tappett depresser? With the zip tie, there's a possibility of dislodging some soot inside the head giving a false reading if the soot prevents the valve from seating. However, since you ran it for a bit, any soot would probably have been blown out. Just sharing my thoughts for what it's worth.

Heres a pic of the shim.

 

[Steve]

Don't worry about the "extra" clearance. Many of us will go up to 0.10mm. The extra clearance keeps the valve on the seat just a little bit longer, letting it run cooler. It also reduces lift, duration and overlap, making it run a bit better at lower engine speeds, where some of us spend most of our time. Not everybody hits redline at every shift. :-\\\

.

 

[MechMessiah]

Are you sure you checked the clearances with the cams in the correct / exact same positions?

Yes, I checked the clearances according to the manual with the lobe pointing up (position A in the diagram below). I also checked multiple times and cranked the engine a full rotation after swapping shims so they would be depressed and properly seated.

 

[MechMessiah]

A shim with an X on it is in between sizes. 2.65X for instance is what you need. Did you by chance use a zip tie or the motion pro tappett depresser? With the zip tie, there's a possibility of dislodging some soot inside the head giving a false reading if the soot prevents the valve from seating. However, since you ran it for a bit, any soot would probably have been blown out. Just sharing my thoughts for what it's worth.

That's good to know the X is in-between. I've got 3 cylinder heads worth of shims so I'll have to double check if I have one like that. I used the motion pro tool. And thanks for your thoughts. That's why I made the post.

 

[MechMessiah]

Don't worry about the "extra" clearance. Many of us will go up to 0.10mm. The extra clearance keeps the valve on the seat just a little bit longer, letting it run cooler. It also reduces lift, duration and overlap, making it run a bit better at lower engine speeds, where some of us spend most of our time. Not everybody hits redline at every shift. :-\\\.

I've seen that some people run with .10mm which is why I left it in and went for a ride but my exhaust pipe was really getting hot. I just installed a 4-1 mac system that came in a black semi glossy finish and just after a short 5 min ride it changed pipe 1 to matte black. The extra heat is what I'm really worried about.

 

[hillsy]

Those valve clearances either way should not have any notable effect on the exhaust temp - I'd say you have a lean condition from some other source.

 

[bobgroger]

Don't worry about the "extra" clearance. Many of us will go up to 0.10mm. The extra clearance keeps the valve on the seat just a little bit longer, letting it run cooler. It also reduces lift, duration and overlap, making it run a bit better at lower engine speeds, where some of us spend most of our time. Not everybody hits redline at every shift. :-\\\

.

WHAT??? You're joking, right?

 

[Steve]

Nope, not joking. I only hit redline every OTHER shift. :encouragement:

.

 

[MechMessiah]

Those valve clearances either way should not have any notable effect on the exhaust temp - I'd say you have a lean condition from some other source.

Yeah, that didn't seem right to me either. Good to hear that from someone else. This bike also has an issue with no top end acceleration. I suspect this is all connected and based on some reading I've been doing I think the main jet is undersized.

 

[MechMessiah]

I swapped the shim back to the 2.70 that was in there before and the exhaust is running cooler again. I'm still surprised how such a slight change made that cylinder run so lean that the pipe changed color in no time. But it did make me pull the trigger on buying larger main jets. The bike just feels starved through all gears but I haven't been able to find a good place to do a full throttle plug chop to verify my suspicion.

At this point, I'm just going off all the CV carbs tuning articles that say to start the process by finding a main jet that produces the hardest pull at high rpm.

 

[1948man]

I would describe your jetting, air intake, exhaust etc and let some of the gurus here suggest a likely jetting and needle shimming (or not shimming) so you don't have to buy a bunch of different main jets to experiment with. I admit I'm kind of cheap. Also, most of the gurus here may work more with larger displacements.