Checking valve clearance

[Mikey350D_imp]

Just got my Honda service manual, and it appears to be an excellent manual.
Its a long time before I need to check clearance but here are some things I have learned from wrenching on Honda CRF250's and CRF450's for many years. (head design appears very similar)
-You dont need special tool to back off the cam chain tensioner.
Use a small flat bladed screwdriver, back of tension then lock screwdriver in place with a small pair of vice grips (When valves need to be shimmed).
-Plug all oil gallies, in case you drop a shim: trust me on this one
-I found the best way to remove reluctant shims was with a piece of gorilla tape (clean off oil first)
-Shim size may be worn of by the time you check valve clearance, then you will need to measure shim with micrometer.
Record clearance gaps and shim sizes.
-Clean oil off cam chain and cam gear and mark position of chain on gear in 3 spots with a sharpie. Insures everything is correct when re-installing cams.
-Keep tension on cam chain as cams are removed, don't let in drop off bottom gear- tie up with a mini bungy.
-I always used a bit of assembly lube on shim, bucket, cam journals and cam lobes.
-Use a good quality torque wrench (I use Proto) in/lbs and ft lbs.

[Scoobynut_imp]

Mikey, Thanks for the great write-up. I don't think I'll be doing this myself as I have a Honda mechanic I trust to do things like this, but still, it's good to know the procedure.

[furious_blue_imp]

Thanks for the write up. I've always adjusted my own valves for screw and lock nut engines, but never shimmed valves. Since the cylinder head is so accessible on this bike, maybe I'll try doing the adjustment on a shimmed engine for the first time with the CB1100.
So just to be sure, when you tie up the cam chain after cam removal, you have to be sure to keep the chain engaged on the lower drive sprocket, since you marked the chain to make it easy to put the cams back correctly.. if the chain slips off for some reason, I assume that the cam sprockets probably have some kind of alignment markings that you can use to get them positioned correctly when the crank is at top dead center. I hope the 'T' mark on the crank is accurate enough (I guess it would be since we use that to know when to measure the clearance to begin with ?)

[AZrider_imp]

Is 8k about the right time to check the valve clearance on bikes with the shims? I know the owners manual says 8k. I'm just wondering what others have found to be true of this type of valves.

[Deanohh_imp]

Go by the book, they are all different. Lots of yamahas call for 22 or maybe its 24k miles between valve check....shim and bucket type. My street triple is 12 or 14k.

[Mikey350D_imp]

For those who haven't done shim and bucket it can be a PITA.
For my CRF's I have chart with existing shim size, measured gap and spec gap. Then I just put in the correct shim per chart, but it doesn't always come out perfect, then you have to remove cam again and re-shim.,
I also never let the cam chain drop off the bottom sprocket, but the cam gears are marked so it shouldn't be a big deal, but I am always very nervous when cams are out, and add extra (sharpie) markings so everything goes back together EXACTLY the way it came out.

[_imp]

Go by the book, they are all different. Lots of yamahas call for 22 or maybe its 24k miles between valve check....shim and bucket type. My street triple is 12 or 14k.

Yah, the Genesis engines go 26,600 miles before the first check. 8,000 miles is not bad at all. Usually the first time there are a few tight valves, but thereafter if it's done right, it will probably stay in adjustment for much longer. Still has to be checked though. It is a quiet engine that is cause for concern with respect to the valve train. Tight valves will be nice and quiet because there is inadequate clearance between the valve and bucket. Better to set them on the loose side. Noisier, maybe, but the engine will run cooler.

[ridesalot_imp]

Hopefully, the Honda motor will hold its clearance as well as my FJR. I checked the lash at 45,000 miles (a bit beyond the recommended 26 K) and to my amazement all valves were in the middle of their range and very nearly the same measurement. BTW the bike has over 50 K now. It has had a steady diet of Mobil 1, MX4T 10w40.

[_imp]

Keep in mind that the valve clearance changes almost exclusively due to the valve seat wearing in, which reduces the clearance and tightens the valve. The valve face is beating the seat down causing the stem to get closer to the cam/bucket/shim. Choice of oil does not affect this at all. Materials used in the valve and seat make all the difference and the Genesis engines are first rate in this regard. Earlier Yamaha FZRs were terrible and many became difficult or impossible to start because the valves beat themselves into the seat so badly that they would stay partially open and the engine would not develop sufficient compression to fire up.

[Xyzzy_imp]

Just got my Honda service manual, and it appears to be an excellent manual.
Its a long time before I need to check clearance but here are some things I have learned from wrenching on Honda CRF250's and CRF450's for many years. (head design appears very similar)
-You dont need special tool to back off the cam chain tensioner.
Use a small flat bladed screwdriver, back of tension then lock screwdriver in place with a small pair of vice grips (When valves need to be shimmed).
-Plug all oil gallies, in case you drop a shim: trust me on this one
-I found the best way to remove reluctant shims was with a piece of gorilla tape (clean off oil first)
-Shim size may be worn of by the time you check valve clearance, then you will need to measure shim with micrometer.
Record clearance gaps and shim sizes.
-Clean oil off cam chain and cam gear and mark position of chain on gear in 3 spots with a sharpie. Insures everything is correct when re-installing cams.
-Keep tension on cam chain as cams are removed, don't let in drop off bottom gear- tie up with a mini bungy.
-I always used a bit of assembly lube on shim, bucket, cam journals and cam lobes.
-Use a good quality torque wrench (I use Proto) in/lbs and ft lbs.

Here is what the "official" little Honda tool looks like. I had a credit on my part account at my local dealer so I ordered it. $100! (It does have a cool one-way bearing, though.)



Since most Hondas use this tool I don't feel too bad about the expenditure.