|Valve timing adjustment |
|Description Valve timing adjustment
Author Matthew Date Sun Jun 19, 2005 6:19 pm Type Type 1
|Valve timing adjustment on
a Virago is not a difficult task and can be accomplished by a novice.
Valve timing adjustment is an important part of a tune up. While some
people tend to leave them as-is until they make too much noise, others
know that mechanical valves are prone to loosening at any time reducing
the bikes designed performance. Another basic reason for doing this
yourself is knowing that the job was done right. With just a few simple,
tools you will be able to set the valves to factory specs.
Feeler gages ranging from .002 to .010 thickness
Phillips Hd screw driver
10, 12, 17, and (22mm deep) sockets and 3/8" drive ratchet
4 and 5mm hex keys
13/16" spark plug socket or use from Virago tool kit
Shop manual for specs and reference
Place the bike on its center stand. Be sure it is on solid level ground.
It is very important that you work in a clean area free of dirt, sand, etc. Let the engine cool for better results. If you are new at this, it is always a good idea to layout rags for sub-assemblies being removed. This helps you to be organized and to know what bolt goes where. Lay the sub-assemblies on the rag as if it were mounted on the bike, keeping the nuts and bolts in their proper position. This will ease re-assembly and you won't lose parts.
Before you can adjust the valve timing, there are a few parts which need to be removed for easy access to the valve covers. If you follow this removal order, it will be easy to re-assemble by reversing the order.
Remove the air filter on the right side and the emissions pod on the left side.(84+)
Remove both side covers.
Remove the seat.
Remove the rear fuel tank bolt and prop the back of the tank up about two inches. (I use a piece of 2x4)
Remove the spark plugs. This will make it easier to rotate the engine.
Remove the cover from the left side case. (Three phillips hd screws)
Remove the 17mm crank access cover. Be sure to turn it counter-clockwise. There is a rubber "O" ring under it.
Remove all four valve covers located on the cylinder heads. They are those shiny looking things on the front and rear of each head.
Valve timing adjustment
Now we can begin the actual Valve timing adjustment process.
Assemble your 22mm deep socket and 3/8" drive ratchet and insert the socket throught the access hole in the left side case. You will see a window just above the hole. Be sure the ratchet is set to drive the socket in a clockwise rotation.
Do the back cylinder first. Rotate the flywheel at least one full revolution clockwise, watching the valves of the rear cylinder rise and fall. When both valves are in the closed position and the timing mark (TDC "Top Dead Center") is on the "T" mark, check the valves to make sure you are on the right stroke by wiggling both valves. They should move freely. If they do, and you are on the timing mark, then you are ready to check the lash, aka clearance. If you should go past the timing mark, then rotate the engine counter-clockwise 180 deg. from the timing mark and then reverse rotation to a clockwise direction until the timing marks line up. This removes all backlash from the rotating elements.
Lay-out your feelers from smallest to largest. This will make it easier to select a given size.
Exhaust valves have the most clearance because they get the hottest. Look for the exhaust pipe coming out of the cylinder head and that's the exhaust valve above it. Now, take the largest (.010) feeler and try to slip it between the valve and the rocker arm. Do not force it in. They call them feelers because you have to feel the gap distance without changing it by force or by being too loose. A slight drag is all that is necessary. Check the rear cylinder exhaust valve clearance.
Here's an easy way to check for the proper lash...start with the largest feeler, try it. If it goes in, then don't worry about it because it will have to re-adjusted. If the feeler doesn't go in then try the next size smaller. Continue this process until you have a feeler that goes in with a slight drag.
If the lash is within shop manual specs, then leave it alone and go to the front of the rear cylinder and check the lash of the intake valve. Use the same procedure as you did on the exhaust valve.
Looking at each valve you can see a nut and allen socket head set screw (4mm). Using a 12mm wrench, loosen the nut enough to allow the allen set screw to rotate at least a half a turn.
Turn the set screw in or out to adjust the clearance to shop manual specs.
Lock the 12mm jam nut tight and check the clearance again. The set screw tends to move during tightening of the jam nut. You may have to repeat the adjustment several times until you get the hang of how to lock down the jam nut without changing the set clearance.
Virago valve clearances are:
Intake .004 in. (.003 - .005 (0.10mm)
Exhaust .006 in. (.005 - .007 (0.15mm)
Intake .003 - .004 in. (0.070-0.10mm)
Exhaust .005 - .006 in. (0.12-0.15mm)
At this point you should have checked both the intake and exhaust valve clearances while the flywheel was on the "T" mark (TDC "Top Dead Center").
Rotate the flywheel and watch the front cylinder valves rise and fall. Stop turning the flywheel when you line the pointer up to the "|" mark. This is TDC for the front cylinder. Check both valves for looseness. If they are tight, rotate the flywheel 360 degrees clockwise to the same timiing mark "|".
Check the valve clearances on both valves and adjust according to shop manual specs.
Once you've done all the valve timing adjustments, and especially if you're doing it for the first time, it would be a good idea to rotate the engine to the rear cylinder timing mark "T" and re-check the rear cylinder valve clearances. If they are the same as what you adjusted them to the first time, then it is a safe bet the front settings are correct. Remember to check both valves for looseness. If they are loose, then go ahead and check them using the feelers. If not, rotate the engine 360 deg. to the same timing mark.
The hard part is over. Now you can put everything back together by reversing the procedure above. Be sure to check the rubber gasket on all four valve covers for cracks, breaks or any other obvious problems. Also make sure the seal area is clean. Chrome plated covers go on the exhaust valves.
You should expect to hear the valves clack away, but they shouldn't be loud. If they don't make any noise, then they are too tight. Chances are, that you did the ajustments right and that you should have no problems.
Cut ½ the length of the short side of the 4mm allen used on the set screw. Especialy on the front intake this would save time spent since the allen wrench was too long.