Valve Shim replacement

[cobrawide]

OK I have ordered new shims as some of the gaps on my bike were out of spec.. I am curious what to expect when the new ones are installed. Will the engine run or sound more "even" or will I notice anything at all.

Thanks

[FJmonkey]

If they were really off then you might notice a little bit, a carb sync has a larger effect. When the carbs are out they are feeding the 4 cylinders unevenly, each cylinder is doing its own dance to a different beat. Imagine listening to R&B, Rap, Rock, and Blues all at the same time...

[cobrawide]

If they were really off then you might notice a little bit, a carb sync has a larger effect. When the carbs are out they are feeding the 4 cylinders unevenly, each cylinder is doing its own dance to a different beat. Imagine listening to R&B, Rap, Rock, and Blues all at the same time...

Thanks FJ that makes sense. I was having trouble syncing the carbs before I looked at the shim gaps. Could incorrect valve clearance cause that?

[FJmonkey]

Unless your valves are really shot, burnt, etc... carbs will sync, when you make changes like valve adjustments then sync again.... Once you get the carb sync down you can sync them quick enough to not need an aux fuel thank.... 

[cobrawide]

In the past I didn't really have issues synching but this flatside carbs( not original ones) are a real pain to do. I was hope that the valve shims were causing it. Oh well.
On a side note what would you consider as valves gap been badly off, 1up to2 mm larger gap?

[FJmonkey]

In the past I didn't really have issues synching but this flatside carbs( not original ones) are a real pain to do. I was hope that the valve shims were causing it. Oh well.
On a side note what would you consider as valves gap been badly off, 1up to2 mm larger gap?

Depends, too tight means the valves stay open too long, hot gasses blowing past the valves. Loose exhaust valve blows gas into exhaust chambers. Loose intake, blows gas in to the air/fuel supply, not good but also provides lots of indicators that something is really wrong.... And both lead to burnt valves. Too loose is a loss of HP and tapping valve noises..... Not as catastrophic... A tappy valve is a happy valve, you know that one is safe....

[andyb]

In extreme cases, too much clearance and/or worn valve springs can lead to the shim becoming disloged (spitting a shim), which causes a fair chunk of carnage.  Slightly too much clearance functionally decreases the valve lift and duration, which costs power.

Not enough clearance means that the valve never closes fully, so it tries to channel the heat of combustion along the stem rather than through the seat and into the head.  Burned valves are the result.

Follow the spec, it's there for a reason.