valve clearances

[DeanR]

Many here speak about few if any valve adjustments are generally needed on the ST1100.
Seems quite stable.

I recently did my first ever valve adjustment. '99 1100 with 71k miles. Not sure if they had ever been checked by original owner. I bought it at 15k.

Intakes were (spec 005 -007)
cyl 1 ... 5, 6
cyl 2 ... 5, 5
cyl 3 ... 6, 6
cyl 4 ... 5, 5

Exhausts (spec 009 - 0011)
cyl 1 ... 6, 6
cyl 2 ... 8, 8
cyl 3 ... 8, 8
cyl 4 ... 7, 7
I centered everything.
Question is, what would cause the exhausts be so far out? Seems to not be the norm.
Has always run fine.

 

[RobbieAG]

I had the same issue with mine. All intakes were good; all exhausts were too tight. I know most owners don't seem to have a problem, but that's why we check. Mine always ran fine too. I didn't have complete maintenance history for the bike, so I don't know if they were ever checked, or if the previous owner mis-adjusted the exhausts. I checked them at 50k. This was on my 2001 1100 which I no longer have.

 

[W0QNX]

I assume the engine was completely cold. If so it seems your bike is the 1 in 100 that had tight valve clearances. Or the prev. owner reved the bike sky high all the time and slammed them valve parts shorter.

I think pretty much on engines now days the exhaust wear comes from valve seats wearing a bit. Assuming they wore down .003" in 71,000 miles that would still be pretty good.

 

[Bush]

Question is, what would cause the exhausts be so far out?

Exhaust valves run hotter than intakes. Think about it. Every intake valve opening has cool fuel mixture flowing past them, whereas every exhaust valve opening has HOT gases flowing past. The only time a valve can cool is when it is on its seat. Hence wider gaps for exhaust to keep them on their seats a bit longer. Not enough gap and an exhaust valve will get white hot and then blow metal away.

Consider yourself lucky you decided to check them. That one at .006 was in grave peril.

 

[Bush]

Many here speak about few if any valve adjustments are generally needed on the ST1100.
Seems quite stable.

This does seem to be true from all reports. However, I believe it is only true if the initial clearance check was done at the prescribed mileage. Following that, the clearances do seem to hold very well. Yours may never have been done though. My '95 had a few valves off on the first inspection and a few shims were needed, but no changes were needed following that and 175,000 km, before I sold it.

 

[DeanR]

Not sure about an initial check before I owned it.
I checked em 4 years/about 30k ago. Almost all exhausts were at the low end of spec. Particularly that #1 cylinder. I made no changes then.

I certainly haven't overreved the bike (other that the occasional missed shift) and I'm quite sure the original owner didn't either.

Wondering if I might have further clearance tightening to look forward to with this engine in the future and if that would get to be a problem, other that needing to adjust again.

 

[red one]

Just for info...had mine done at 14K miles because I had some ticking noise. Stealer found them all adjusted to spec. I have about 68,843 miles and they have not been inspected. At this point i'm on the fence about getting them inspected. My Corolla has 191,000 miles valves never been inspected. Toyota Stealership says they don't inspecting or adjustment. In fact they say they have never had to do it.

 

[Bush]

Just for info...had mine done at 14K miles because I had some ticking noise. Stealer found them all adjusted to spec. I have about 68,843 miles and they have not been inspected. At this point i'm on the fence about getting them inspected. My Corolla has 191,000 miles valves never been inspected. Toyota Stealership says they don't inspecting or adjustment. In fact they say they have never had to do it.

Inspecting valve clearances is not a hard job, but having a deft touch for using the feeler gauges is important. Changing shims IS a bit more tricky, but still doable with proper tools, particularly a torque wrench. If you have the Honda Service Manual, follow that for guidance on the clearance inspection. Then, if you find some out of spec and aren't comfortable proceeding with the next step, take it to your dealer, not mentioning what you found and see if he confirms your findings. This would tell you how well they did, or didn't do, the job.

 

[SMSW]

The only time a valve can cool is when it is on its seat. Hence wider gaps for exhaust to keep them on their seats a bit longer. Not enough gap and an exhaust valve will get white hot and then blow metal away.

I thought the wider gap for ex valves was because the whole valve runs hotter than an intake valve and thus it will increase in length more. The larger clearance allows it to grow and not 'float' above the valve seat, but make solid contact which, as you said, allows heat to flow from the valve to the block. (Perhaps I should dig up a book, get the coefficient for linear expansion for steel, find out what temps valves routinely feel, and do a few calculations before I repeat what I read eons ago).