Saturday, February 4, 2012

Valve Clearance Adjustment Tips

Well, as you know from an earlier post, I checked and adjusted the valve clearance on my Kawasaki Ninja 650R last month.  The procedure is well documented in the Ninja 650R service manual, but here are a few tips that made -- or would have made -- the job a bit easier and safer.

Before you start turning any wrenches, clean off the areas of the bike you are going to work on with an air hose and brushes.  This helps prevent dirt from falling into places it shouldn't be while you are removing bits and pieces. 

Next, realize that you might drop something during the procedure.  That may simply be a nuisance, but it can also be potentially serious if you drop something into the wrong spot inside the engine.  One of these spots is into the throttle bodies.  If you drop it there, there is a chance it will get into the valves and cause real trouble.  So stuff it... 
...with a couple of rags before proceeding.

After removing the seat and fuel tank, the airbox is removed from atop the engine.  Beneath it, the cover over the camshafts becomes visible.  There are several brackets and other items that must be removed to get the cam cover off. 

Even though the Ninja manual says to remove the throttle cables, I instead removed the right-hand radiator support screw to give sufficient clearance to remove and replace the cam cover from the top rather than out the right side.  The fit was tight, but possible.  Be careful not to damage the radiator fins with the corner of the cam cover.

If you wish to remove the cam cover the way the manual advises, out the right side, there is a bracket in the way.  The red one in the center of this photo. 
From a riderforum posting by MCRider. 

However, this bracket is not used on the Ninja, and you can bend it out of the way or remove it without harm.  

Another place where trouble could occur is if you drop something into the cam chain tunnel that runs down from the cam sprockets to the crankshaft.  This could require more extensive disassembly of the engine if you cannot retrieve a dropped item there.  So, stuff a rag into that space as well.

Keep a magnet nearby in case you drop something anywhere else.  The magnet comes in handy, too, to help extract the buckets from their guides.  If those terms sound cryptic, read on and learn. 

Measuring the current valve clearances is done according to the manual instructions, using feeler gages of various thicknesses between the cam and the valve lifter with the cams at the positions it describes.  The use of feeler gages takes some finesse, since you can fairly easily compress the valve springs trying to force a gage into a space that is smaller than the gage thickness.  You want the gage to just slip in with a light amount of friction.  That indicates that the gap is about the same as the gage thickness.  If the gage slips in easily, the gap is larger than the gage thickness.  This is one technique where it pays to have someone who is experienced show you the method so you can get the feel of it for yourself. 

If any of the clearances are not within the specifications, you must proceed with further disassembly. 

Since you have to remove the camshafts to adjust valve clearances on many motorcycle engines, one shortcut is to make sure the camshaft sprocket does not come out of time with the camshaft drive chain.  You have to loosen the camshaft chain by removing the chain tensioner to be able to move the camshafts aside one at a time, but you can prevent the chain from leaving its correct position on the camshaft sprockets by threading a wire tie through an opening in the cam drive sprockets and around the chain.  Like this:

That simple expedient helps save the time to reset the timing upon reassembly.  That is not to say that the timing shouldn't be checked once the cams are back in place.  If the cams are out of time, the engine will not operate and internal damage could result.

If you don't secure the cam chain like this, then do make certain that you loop something -- a shop towel will do -- under the cam chain and use the towel to drape the chain over the edge of the cylinder head to keep the chain from dropping down into the crankcase and to keep the chain engaged with that sprocket hidden way down there on the crankshaft. 

Another important part of making the clearance adjustment is keeping good notes.  Your feeler gage measurements must be recorded for each valve before you take anything apart.  For any valve whose clearance is outside the correct range, you must then determine what shim is currently installed between the valve lifter or follower (often referred to as a "bucket") and the valve stem for each valve.  That is why the camshafts have to come loose -- so you can get to the shims, which are beneath the cam followers on this engine.  The shims may be marked, but I had to measure each one of mine with a micrometer, again diligently recording their thicknesses.

I recorded the data on a chart, showing before and after clearance measurements and shim thicknesses:

Here are a couple of photos from the procedure written by Black Lab for his Suzuki V-Strom DL-650 on the Stormtroopers* forum.  This one shows a magnet being used to lift out the bucket from its guide. 

This photo shows the shim stuck to the inside of the bucket by the oil film between the two. 

It is a very good idea to take more photographs during disassembly than you think you need in case some don't turn out or don't show what you are puzzling over a few days later when you are trying to put things back together again.   My memory seems to be getting shorter and shorter these days, so the camera becomes importanter and importanter. 

A chart in the manual tells you what new shim thickness to put in place, based on the measured clearance and the thickness of the current shim.  You can also do a simple calculation to determine this, though it is easy to get your plusses and minuses mixed up, resulting in installing the wrong shim thickness. A simple spreadsheet can also help.  (See below.) 

Only after you have made the clearance and existing shim thickness measurements can you determine whether any of the shims can be moved to another valve to provide the correct clearance there, or whether new shims of other thicknesses are required.  I moved three to other valves, left one alone, and purchased four shims to get all mine within spec.  The shims cost about ten dollars each, postage included; the lowest price I could find.  Mine came from Ron Ayers

Remember that the valve clearance generally decreases with use, so thinner shims are usually required to bring the clearance into the specified range.  This seemed backward to me.  I thought valve train wear would have increased clearance.  Apparently it is not the usual case that the valve train wears.  Instead, the valves wear into their seats.  This decreases valve train clearance. (Some clearance is necessary to allow for expansion as the valves and valve gear get hot. If there is no clearance then there is a risk that valves will not seal properly, will not transfer combustion heat to the cylinder head as well as they should, and hot gas could blow by them, which could damage both the seats and the valves.)   

Since too little clearance in the valve train risks serious valve and head damage, it is a good policy to aim for the high end of the clearance tolerance when selecting new shims.  I found all four intake valves to be near the low end of, but within, the clearance tolerance, so I changed the shims there to introduce more clearance -- still within spec -- to avoid the possibility of their becoming too tight between now and the next check. 

Here is a good article* from the ALL THINGS MOTO forum that shows how to perform a valve adjustment on a Suzuki RMZ450 single cylinder motocross bike.  The procedure is quite similar for the Ninja, and other overhead cam engines that use shim/bucket valve gear.  There, you will also find the spreadsheet* that helps you select the correct new shim thickness in case you don't want to otherwise calculate it or don't have the service manual. 

Once the cams are back in place, the clearance is again checked to make certain you have not made a mistake.  After that, reassembling everything with new seals is all that is required before getting back on the road. 

I say "all that is required."  An understatement, for sure. 

A big difficulty for me was getting the cam cover gasket to stay in its groove in the cam cover while reinstalling the cover to the cylinder head.  A little old fashioned rubber cement in the groove saved the day. 

Also, reaching the various hoses that attach to the airbox was a challenge.  You need tiny hands and hemostats to put back some of them. 

While I had things apart, I also did some other maintenance:  
  • Replaced the spark plugs 
  • Cleaned the crankcase vent reed valves
  • Cleaned and re-oiled the air filter element 
  • Degreased all of the parts removed 
  • Re-cemented one heated grip
  • Checked the clutch free play
  • Did quite a bit of general cleaning (mostly leftovers from my occasional gravel road excursions)
I took my time on this work because I was unfamiliar with the procedure and with the engine.  I suppose I took around fifteen hours all together to do just the valve clearance work, including reading the manual, doing Internet research, ordering the parts, being very careful to document the order of things, keeping the fasteners with the parts they held, and double (sometimes triple) checking myself as I went along.  Next time will be faster.

The forum poster who calls himself Black Lab that I mentioned above has some additional good advice:
Pick a [time period] where you know that you will not have interruptions. Work at [a] pace that you are comfortable with. When you feel yourself tensing up, walk away from the project for a little bit, then return.
Now, the acid test: Will it start?

One push of the magic button provided the gratifying sound of a well-running engine.  I was careful not to rev the engine initially to make sure everything that had been disassembled was receiving oil. 

I couldn't resist taking a picture of my ride after the mechanical work was done but before the plastic was put back on.  She looks a bit menacing that way, in the half light of the evening. 

The next day, my first trip after the mechanicing, was an enjoyable 138 miles around the mountains north of home on some familiar rods and some less so. The engine seems a bit peppier with things adjusted, replaced, and cleaned. 

She should be good to go for around 26,000 more miles now.

See y'all out there riding! 

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Charlie6 said...

great post!

To my eyes, way more complicated and intensive process to check valve clearances than on my vintage Beemer airhead....probably why the last time it was due on my V-Strom, I had the dealer do it! I really must try it next time....sure is a lot of stuff that has to come off to get at the valves though.....
Redleg's Rides

Colorado Motorcycle Travel Examiner

Anonymous said...

Just a note, after adjusting valves the Carbs or throttle bodys need to be synchronized.

Anonymous said...

Nice Post!
I am just working up the courage to check the valve clearance on my Z750S.