Valve adjustments

[mr. softie]

Like Easy said...

and if a valve clearance (or "lash") gets tight (below minimum spec.) the valve and/or valve seat in the head will burn & start leaking, especially the exhaust valves. Leaky valves equal lower compression and a top end rebuild (valve job).$$$

They burn because the valve is not closing fully thus allowing a flow of high temperature/high pressure gas to erode the metal.

And again as Easy stated, by the time you notice a loss of performance the damage is done. Hence the necessity of scheduled valve lash measurement and if needed, adjustment.

Too large a lash will lead to noisy valves and accelerated wear of valve train components, plus a decrease in horsepower :shocked:

I have checked mine twice (at 6500mi and 9500mi) and they needed a small adjustment each time to be right on spec for the way I want my bike to run. I set mine towards the smaller end of the range, knowing I am going to check them on a regular basis. A larger gap may allow a longer interval between services but hurt top end performance. The range of allowable lash enables a small amount of "tuning" to be done. You can vary the amount of time the valve is open(duration) by varying the lash. Smaller gap=longer duration, bigger gap=shorter duration.

Reducing the lash (smaller gap-longer duration) will increase top end (upper RPM power) horsepower and make for a quieter valve train. Almost like a "bigger" cam! :rawk:
Increasing the lash (bigger gap-shorter duration) can improve low end torque and acceleration, and easier starting, as well as a longer service interval :2tup:

I found that a bicycle nipple wrench works well to keep the small square end of the threaded adjuster from turning while you tighten the holding nut.

[mr. softie]

Here is an excerpt from the downloadable manual


2-5 PERIODIC MAINTENANCE Remove the valve inspection caps The valve clearance specification is different for intake and exhaust valves. Valve clearance adjustment must be checked and adjusted, 1) at the time of periodic inspection, 2) when the valve mechanism is serviced, and 3) when the camshaft is re-moved for servicing.

Valve clearance (when cold):
IN. : 0.03-0.08 mm (0.001-0.003 in)
EX.: 0.08-0.13 mm (0.003-0.005 in)

NOTE:
* The piston must be at top dead center (TDC) on the compression stroke in order to check or adjust the valve clearance.
* The valve clearance should only be checked when the engine is cold.
* Remove the valve timing inspection plug and generator cover cap
Rotate the crankshaft with a box wrench to set the piston at top dead center (TDC) on the compression stroke. (Rotate the crankshaft until the "T" line on the generator rotor is aligned with the triangle mark on the generator cover.) Insert a thickness gauge into the clearance between the valve stem end and the adjusting screw on the rocker arm.
If the clearance is out of specification, adjust it to specifica-tion as follows.

ADJUSTMENT The clearance is adjusted using the special tool and offset wrench.
• Loosen the locknuts
• Insert a thickness gauge between the valve stem end and the adjusting screwon the rocker arm.
• Adjust the valve clearance by turning the adjusting screw using the special tool while holding the locknuts

CAUTION Both the right and left valve clearances should be as closely as possible.
• After the adjustment is completed, tighten the locknut securely.
• Rotate the crankshaft 720° with a box wrench and check that the clearance is within specification.

See Manual page 20 for more detail

[mrlmd1]

OK, now you've educated and convinced me. Thanks. One of these days I'll have to get mine done, I have ~4000 miles on my '99, don't know it was ever done as routine maintenance by the previous owner.
How much is needed in special tools, how much do they cost, where do you get them, vs. having the dealer do it?
I have average-above average mechanical abilities and can read and follow directions, but is it worth the investment in the tools, time, etc, if I may only do this once every year or two?

[Easy Rider]

Originally Posted by mrlmd1

I have average-above average mechanical abilities and can read and follow directions, but is it worth the investment in the tools, time, etc, if I may only do this once every year or two?

Only YOU can make that call. For me, it's not.
Ask a dealer in your area what they charge and take it from there.
It is not "difficult" but can be a little tricky......especially the first time.
It can be problematic if you have LARGE hands.

[Chris]

Hi guys,
Lots of good info here. I did download the Service Manual - what good advice that was.

Soon I'll get with my motorcycle maintenance expert and I will ask him all the questions that were raised here. He is going to give me a lesson on how to do it.

Chris, Atlanta

[alanmcorcoran]

Originally Posted by Easy Rider

Ask a dealer in your area what they charge and take it from there.
It is not "difficult" but can be a little tricky......especially the first time.
It can be problematic if you have LARGE hands.

Didn't Mr MD used to do open heart surgery?

[JWR]

I would like to know if your motorcycle maintenance expert sets the valves both the same.

IN. : 0.03-0.08 mm (0.001-0.003 in)..................003
EX.: 0.08-0.13 mm (0.003-0.005 in) ..................003

Some mowers use the same setting for intake and exhaust.

[mrlmd1]

To AC - Yes he did, and very well thank you.

I just wondered how much trouble this is, and like the old adage, if you want something done right, you do it yourself (vs. possibly having the dealer screw it up worse than it wasn't before)
We'll hear from Chris on how his went, how difficult he thought it was. I have no problem doing it, just wondered how much effort, expertise, and expense for the tools it took.
And in surgery, it's the same as this - watch one, do one, teach one..

It would be nice, the next time someone does this, maybe Chris with his expert mechanic, to take some pictures and post it in the "How To" section.

[Easy Rider]

Originally Posted by mrlmd1

It would be nice, the next time someone does this, maybe Chris with his expert mechanic, to take some pictures and post it in the "How To" section.

I thought there was one there already.
Do you do brain surgery too ??
I think mine needs a replacement. :biggrin:

[GZ250]

I have 20K miles and never had valves adjusted. I don't know when its time to have them adjusted. For the last couple of months I am getting less milage so now I was thinking to have them checked by the dealership.