Cam Timing Issues

[flexibledoor69]

Hi guys,

have replaced 2x exhaust valves (from CCT failure) and I have a question regarding lining up the cams on re-install.

On the front cylinder when the crank is exactly on the FT mark the cams are ever so slightly twisted to the right as you're looking at them, but if I move the cams one tooth to the left then they are twisted slightly to the left. Neither setting gets them exactly flush with the head so its like its inbetween gear teeth settings.

On the rear cylinder the intake cam is perfect at RT, however the exhaust cam appears ever so slightly above the head level. moving the cam 1 tooth results in teh same issue as the front so its inbetween teeth position.

I've rotated the engine by hand probably about 20 turns and I can't feel or hear valves touching pistons anywhere so I think i'm ok but if anyone has any experience of this or can confirm or deny that i've set it right then your help is most appreciated.

Stu.

[VTRDark]

I take it your referring to the cam sprocket alignment marks. I had a similar problem when fitting manual CCT's http://www.vtr1000.org/phpBB3/viewtopic ... er#p202032

It should be all OK as long as you have manually turned the engine to double check that nothing crashes. The slight misalignment can be caused by a slightly stretched cam chain and general wear and tear. I think it's anything more than two teeth out is where it will cause problems.

(:-})

[flexibledoor69]

Yep, the rear is exactly as your is/was. so happy there.

The fronts line up perfectly with each other, but then the mark on the crank is out from where is should be. its only a little bit out so I will take the plunge and since nothing appears to be binding then i will give her a kick in the guts after I get the broken choke repaired

Cheers

[sirch345]

If the valve timing is out less than one tooth it will almost certainly be due to cam chain stretch, as Carl says.

I hope you followed this link when you replaced the CCT's for setting up the valve timing:-
http://www.vtr1000.org/phpBB3/viewtopic.php?f=31&t=8326

Chris.

[tony.mon]

It's important to ensure that the cam chain is pulled in its normal direction against the cam sprockets, so that the slack in the chain is taken up in the right direction, with the TDC marks exactly lined up.
If you go past, go round two crankshaft turns (one complete cam turn) until you have the marks on the flywheel exactly lined up.

So with the front cam chain, pull the chain towards the rear of the bike.
With the rear one, pull the chain towards the front (CORRECTION: THAT SHOULD ALSO BE TOWARDS THE REAR) of the bike.
Then set the cam sprockets to the nearest tooth.

If you want, you can slot the sprockets and set it up with a dial gauge so that the cam timing is once more in the correct lobe centre (like tdc for cams) at the correct number of degrees of crankshaft rotation, but that's quite technical, needs special tools and frankly, it's easier to just replace the cam chains.

But usually it's quite obvious as to which tooth is nearer the correct lined up position. I'd suggest taking a photo of each position and comparing them.

[flexibledoor69]

Slotting the cams? Jeez that sounds technical. I think i'll just replace the chains in time. On the plus side the guides don't appear worn so they must have been changed in the past few years (90,000k on the odo so far)

As for following the proper technique to replace CCT's, I didn't follow your steps at all as I hadn't searched the forums. My mistake was to follow the Haynes manual approach which resulted in 2x bent exhaust valves in the rear cylinder head, so thats why i'm double checking the cams are right before I fire it up cause I don't want to be in there replacing another set of valves

However I thought that when installing the cams, I agree you pull the front chain towards the back of the bike, however I thought you also pulled the rear chain towards the rear as well cause the tensioners are both on the rear facing side of the piston block.

Other than that the sprockets are set to the closest mark I can get.

[VTRDark]

However I thought that when installing the cams, I agree you pull the front chain towards the back of the bike, however I thought you also pulled the rear chain towards the rear

Yeh that is correct, pull toward the tensioner side so the slack is on the tensioner. The non tensioner side is then pulled tight.

That bloody Haynes manual, you wont be the first to have damaged valves following it. I would not follow any instructions in that manual. The only thing it is good for is the pictures and specifications, torque setting and wiring diagrams. The rest is Apparently they are supposed to be re-printing it with the mistakes taken out.

As far as the timing goes if you follow Sirches instructions in the link above you wont go wrong. And if your confused about anything just ask You just need to make sure your on the compression stroke for each cylinder. So for the rear, crank will be on RT and the cam lobes should be facing upwards and inwards. For the front, crank will be on FT and the cam lobes should be facing upwards and out, so opposite to what the other cylinder is set at.

(:-})

[flexibledoor69]

Eyyyyyy! He runs! Fired up first time after a few cranks to get the carbs filled with fuel again.

There is what feels like more engine vibration than I remember, however i've been off the bike for a couple of months so it could just be me chasing ghosts.

Thanks for the help guys, always appreciated!

[VTRDark]

That's really good news mate, well done. Did you put manual cam chain tensioners in as well?
I would expect the engine to sound slightly different as you have new valves and there's the chance you got the timing more accurate than what it was to begin with. And as you say, we tend to start imagining things and chasing our tails looking for problems. It's always better to be on the cautious side though.

Get that choke cable sorted next. easy job compared to what you have just done.

(:-})