Shim replacement - trying to keep it simple

[Cadbury64]

I need to replace shims in the rear intake valves only. I've recently undertaken manual CCT installation and while I was in there I checked all 8 valves, and just the rear inlet valves need attention. I've read the Honda manual which refers to pulling the front valve cover to confirm timing, and if I can I'd like to avoid going through the pain of carb and radiator removal that that requires.

So my question is, is it possible to pull just the rear inlet camshaft out and leave everything else in place? I was thinking that if I could cable tie the intake cam sprocket to the chain, and leave the exhaust cam/sprocket in place, and keep a little tension on the chain, to keep the timing unchanged? Does that sound feasible/sensible? Or am I over-thinking this?

I've probably been spoiled by my gear-drive VFR800; no chains and sprockets to worry about, just gears!

[sirch345]

I can't see you need to remove the front cover to replace a shim on the rear cylinder providing you follow my instructions on setting up the valve timing in this link first:-
http://www.vtr1000.org/phpBB3/viewtopic.php?f=31&t=8326

Follow the instructions up to and including number (9) in that link. You will need to remove your manual CCT after you have set the valve timing , but don't alter the CCT adjustment. Keep the cam chain taught when you remove the inlet cam so the chain doesn't drop off the crank sprocket. I'm not 100% sure if cable tying the cam chain to the inlet cam sprocket will allow you enough movement to access the shim area, thinking about that I doubt it will.

Before removing that side bolt on the cam chain guide, make sure you cover the cam chain tunnel with a clean rag, you don't want to be dropping it down there,

Chris.

[Cadbury64]

Hi Chris

Thanks for the reply. I was planning on unbolting the cam sprocket, then the cam saddles and lifting the camshaft right out so access to the buckets should be normal. I just wasn't sure whether the cam would slip out sideways while leaving the sprocket cable tied to the chain so I didn't lose the timing. Seemed to me that if the chain and sprockets stay connected, and the chain stays in contact with the engine sprocket, then the timing couldn't change.

Regarding checking the front cylinder, I think the Honda manual is trying to ensure that the rear cylinder stays 270 degrees behind the front, hence the check to ensure the front timing marks are to the outside, then rotating the crank 270 before setting the rear timing. Otherwise it would be possible to time the back cylinder 360 degrees out of phase, at which point I presume ignition will be an issue. I guess if you can be sure the crank hasn't been rotated during the rear cam-out then there's no need for the check.

Cheers, Terry

[sirch345]

Hi Chris

Thanks for the reply. I was planning on unbolting the cam sprocket, then the cam saddles and lifting the camshaft right out so access to the buckets should be normal. I just wasn't sure whether the cam would slip out sideways while leaving the sprocket cable tied to the chain so I didn't lose the timing. Seemed to me that if the chain and sprockets stay connected, and the chain stays in contact with the engine sprocket, then the timing couldn't change.

Regarding checking the front cylinder, I think the Honda manual is trying to ensure that the rear cylinder stays 270 degrees behind the front, hence the check to ensure the front timing marks are to the outside, then rotating the crank 270 before setting the rear timing. Otherwise it would be possible to time the back cylinder 360 degrees out of phase, at which point I presume ignition will be an issue. I guess if you can be sure the crank hasn't been rotated during the rear cam-out then there's no need for the check.

Cheers, Terry

Hi Terry,
I hadn't thought about doing it that way (removing the sprocket from the camshaft). You probably could so it that way, and yes probably more chance of keeping the timing right if you use cable ties. Also make sure you mark the cam sprocket and camshaft before removing the sprocket, you don't want that going back in the wrong position, although you sound like the sort of person who has already thought of that

I can see by checking the front cylinder valve timing with the rear is as you say like a secondary check, just to make sure all is correct before re-starting the engine. The timing marks at the alternator cover should give you a fair idea to whether or not the crank has moved. The crank shouldn't really move IMHO, but I'll leave it up to you to decide if you want to do the secondary check

There is a wasted spark on these engines, meaning a spark from the ignition is created everytime the piston hits TDC, well just before to be precise. So if you get the valve timing 180 degrees out it will still run, although it won't like running over 6,000rpms or thereabouts.

Good luck with it,

Chris.

[darkember]

Yes you can do it that way. Just remember to set TDC on the cylinder you are working on then bolt everything down with ties and what ever else you gave to hand. I would also tie down the cams on the cylinder you are not working on just as a precaution. I know this means taking the tank off but it is good practice.

[tony.mon]

Yes you can do it that way. Just remember to set TDC on the cylinder you are working on then bolt everything down with ties and what ever else you gave to hand. I would also tie down the cams on the cylinder you are not working on just as a precaution. I know this means taking the tank off but it is good practice.

Why on earth is it good practice to tie the cam chain to the sprockets on the one you aren't working on? The chain on that cylinder cannot jump as long as you leave the front CCT in place- and there's no reason to do anything on that cylinder.
You aren't going to move the crank during the process- it will stay where it is.

Regarding losing the timing, you can't.
The crank will stay where it is, and you merely set the cams in the correct (lobes up and towards each other, line on the sprocket lined up with the top head surface) but make sure that you pull the cam chain in the right direction; towards the rear of the bike.

[darkember]

Yes you can do it that way. Just remember to set TDC on the cylinder you are working on then bolt everything down with ties and what ever else you gave to hand. I would also tie down the cams on the cylinder you are not working on just as a precaution. I know this means taking the tank off but it is good practice.

Why on earth is it good practice to tie the cam chain to the sprockets on the one you aren't working on? The chain on that cylinder cannot jump as long as you leave the front CCT in place- and there's no reason to do anything on that cylinder.
You aren't going to move the crank during the process- it will stay where it is.

Regarding losing the timing, you can't.
The crank will stay where it is, and you merely set the cams in the correct (lobes up and towards each other, line on the sprocket lined up with the top head surface) but make sure that you pull the cam chain in the right direction; towards the rear of the bike.

Point taken it is a little over kill but he wants to do the shims on the front exhaust valves by just unbolting the cam off the sprocket so he will need to secure the sprocket.

[Cadbury64]

Thanks for the input chaps. I guess the key to keeping this simple is taking off the correct sprocket bolt before rotating the crank so that the lobes are in the correct TDC spot then taking the second bolt out to pull the cam, and not touching the crank until all are bolted back in.


Sent from my iPhone using Tapatalk

[Cadbury64]

I can confirm that this worked like a charm.


Sent from my iPhone using Tapatalk

[Cadbury64]

Just in case anyone is interested in my simple method for swapping shims out to avoid loss of timing between the cams and crank:

I do one cam at a time. Rotate the crank to line up the timing marks on the cam sprocket; you'll notice one sprocket nut is up and accessible, the other is rotated down into the cam box. Rotate the cam until you can remove the one that was inaccessible before (don't forget to stuff a rag down the camchain tunnel to catch any dropped bolts first!).

Now rotate the crank to get back to the correct position for cam removal. Tie cable-ties around the chain and sprocket at the 12 O'clock position on each. Use extra cable ties and tie the sprocket/chain for the cam to be removed to a fixed point e.g. on the rear head intake cam I tie onto the breather hose on the back of the airbox. That keeps some up and forward tension on the chain and makes sure the chain can't fall down/off the crank sprocket. Release the camchain tension, then remove the second sprocket bolt, and the chain guide and camshaft holder. The cam can now be slipped out of the sprocket and the cam bearings, leaving the chain and sprocket more or less in their usual place. You can now remove the bucket(s) and shim(s). You could probably get the same result by tying the sprocket to an object that would bridge over the cam tunnel alongside the sprockets provided you still had access to the sprocket nut.

For reassembly, slip the cam back into the sprocket and then fit the first sprocket bolt (20 N-m with threadlock). Refit the camshaft holder and torque up the three bolts (21 N-m no threadlock). Re-tension the chain, then remove the cable ties. Rotate the crank to access the second sprocket nut and install, and check the torque (20 N-m). Check and adjust the chain tension (6-7mm), then refit the chain guide. Always double check that the timing marks on the sprocket match the one on the alternator!

I've followed this method three times and it takes the stress of lost timing out of the operation.

[popkat]

Sounds time consuming and like extra work to me, tipex mark the cam sprockets and cam chain, count the pins or links between the sprockets for reference then remove the cams with sprockets on, on installation put the cam furthest from the cct in first gently pulling the chain for tension, but not rotating the crank (front cylinder exhaust cam, rear cylinder inlet cam), line up tipex marks and count pins/links so you know it's all correct.
Some bikes are difficult to remove the cams with the sprockets, these always take longer faffing about removing sprockets.

[Cadbury64]

I understand what I did was time consuming but I'm on my own without adult supervision and don't want to stuff up. This way, I can't get it wrong.

With your method what happens if the chain drops off the crank sprocket and you don't pull it back to the same location? Then the cam timing will be off even though your tipex and pin count would tell you all was well.


Sent from my iPhone using Tapatalk

[popkat]

If the chain drops and moves round a link or two no problem (just make sure it's not kinked or caught up), you would have counted the pins/links between the sprockets and you have the marks on the cam sprockets that sit level with the cylinder head so easy to time up, the crank won't move by itself but if you want to be double sure put a long socket on the end of the crank nut when you start and tape it in place.