The OBSERVED Valve Clearance thread

[Pterodactyl_imp]

On the three occasions that I have checked clearances I have followed the Workshop Manual procedure. Looked OK to me. Will be doing another check in the next two weeks so will advise further.

Cheers

[Houtman_imp]

I think that I will not check the valve clearance till 25000 miles, unless I hear some strange "noises "

[Django]

I think that I will not check the valve clearance till 25000 miles, unless I hear some strange "noises "

Neither do I. However, this type of valve drive leads to smaller clearance when wearing down. So you won't here something strange until it was to late. With no clearance at all you'll get a pipe in the valve.

[the Ferret]

Pay attention to hard starting, rough running, lower fuel mileage etc symtoms of reduced valve clearances. That is what my mechanic has recommended.

[dave]

Hi Max, thanks for your reply.

Can you please clarify "the machine that produced two of the finest camshafts in history"? Are you referring to the two camshafts in the CB1100?

So i cannot even remember how i went about measuring the gap but i vaguely recall using the small sections of the lobes so the cams must have pointed away from the buckets.

Max, you did your complete valve clearance inspection without the help of a FSM? WOW! That's amazing! You must have a lot of experience working on motorcycles! What do you think about the small, metal bracket with the two nuts attached to it hiding on the bottom side of the heat shield? The FSM was not very clear about this (the illustration was terrible), but at least it mentioned it.

We now need someone else to shed light on the right way to check the valve clearances and i am happy to take notes and put them in the recipe book for next time.

I'm betting someone on this forum will respond, possibly after using a dial indicator to measure the cam lift versus degrees of rotation.

If I can get out of work at a decent time today I will finish the job up and start the bike tonight.

[SportsterDoc]

Clearance is measured with valves fully closed and the lobe not starting to open or just closing. Therefore the lobe of the cam for that valve is ideally 180 degrees from valve full open. You will find that the measurement changes little, if any, if the lobe is only close to 180 degrees, such as 160 to 200 degrees.

Too tight a clearance could lead to a valve not fully closing, allowing escaping exhaust gasses to warp/burn a valve. This is the more serious concern.

Too loose allows the valves to be "hammered", although that may be more of an issue with rocker arms on SOHC, rather than direct cam operation to the valve stems, via shim/bucket on DOHC.

If the lobe is close to raising the valve or just leaving letting springs close it, it will leave a wider gap. That may be audible, although the sound of the fuel injectors is so loud, it may be difficult to hear.

I like to use a stethoscope* to listen to a new motor, which may help detect a change as the miles accumulate.

*A large screwdriver, with blade on the heads and handle to an ear will allow a lot to be heard.

Just my 2 cents

[dave]

[quote='Pterodactyl' pid='205324' dateline='1526291373']
On the three occasions that I have checked clearances.

You have checked your valves three times? How many miles on your bike? This is the first time I have checked the valves on this bike, and it has 17,000 miles, and I do not look forward to ever having to do it again. After working on the CB1100 I will never say again that inspecting the valves on my VFR800 is difficult. I would rather inspect AND adjust the valves on the VFR than to just inspect the valves on the CB1100. The VFR cams are gear-driven, and are easily removed. I dread the day I will have to actually adjust the valves on this bike where the cam sprocket and chain have to be removed first, before removing the cams.

[Cormanus]

Pterodactyl has more than 100,000 kilometers (62,500 miles) on his bike. I've got just over 86,000 kms on mine and have had my clearances checked three times. I'm about to have them checked again. I wish I had the ability to do the job myself. I'd almost be tempted to have a go this time, but there are too many other things happening.

[dave]

Hi Cormanus. You must have a competent mechanic that you can trust. I'm a backyard mechanic who has been working on motorcycles for 45+ years, and this was the most challenging valve inspection I have ever done. I am sure it would go a lot faster the second time, but that is probably 2 or 3 years away from now and I'll probably forget everything I learned. Can you tell me how many hours labor you are charged for your valve inspection, and how much it cost you?

[PowerDubs_imp]

Dave,

I am curious as to what was challenging? I'll be removing my stock cams and installing new ones soon.

I've had my valve cover off before to swap from black to brushed. Wasn't horrible, but I know that is only the beginning.