T mark and Timing

[gimphand]

Gameplan is that I am taking off the head to get bored. I get to the point where I take off the cap on the crank and the one where you line align the T mark on the flywheel. When I rotate the crank, I see two mark about 1/4 to 1/2inch apart. Is this the T mark? which one?

[Honda#4]

Theres a F mark and a T mark line the T mark with the little line on the stator cover, make sure the motor is at TDC on the comp stroke the valve rockers should be loose.

[Dew2008]

When you align the T mark up I am confused. You have a | T You align the T not the | correct?

And with the valve cover off the cam lobes should be down correct? I have had a hard time with this.

[Bounce400ex]

Line up the | with the marks on the cover. Take off the valve service caps. If the rockers are loose you're fine.

[Dew2008]

The cover has a notch which is wider than the | does it go in the middle, To the left, to the right. The manual should be more specific on this topic.

All 4 rockers should be loose?

[GPracer2500]

Originally posted by Dew2008
The cover has a notch which is wider than the | does it go in the middle, To the left, to the right. The manual should be more specific on this topic.

All 4 rockers should be loose?

You don't need to be that precise. All you're trying to do is unload the valve springs for removing the cylinder head cover. Getting the piston to TDC on the compression stroke accomplishes that. But bear in mind there is a dwell period at TDC. The crank can move this way or that way a little and the piston will still be more or less at TDC.

As long as the rockers have a little play in them you're fine.

[Dew2008]

So just as long as the | is in the notch and the cam lines are lined up its in time? I know with automotive engines you have to be exactly or the engine will miss and not run right.

I am a auto mech but this 4-stroke timing has spun me for a loop. Just wanna make sure I have all this right before I do all this work.

[GPracer2500]

Originally posted by Dew2008
So just as long as the | is in the notch and the cam lines are lined up its in time? I know with automotive engines you have to be exactly or the engine will miss and not run right.

I am a auto mech but this 4-stroke timing has spun me for a loop. Just wanna make sure I have all this right before I do all this work.

My advice was specific to disassembly procedure, not assembly. When disassembling the only reason to even think about the position of the piston and cam is to get the rockers onto the base circle of the cam so valve spring pressure doesn't lift the cam cover off as you unbolt it. For disassembly, it doesn't matter if you're at exactly TDC or not. Technically, you could disassembly the top-end without any regard to the position of the piston and cam. It's just better to unload the valve springs first.

When you're assembling and getting the cam timed, more precision is warranted. Line up the " | " mark that is next to the T with the other mark to find TDC. If the lines on the cam sprocket are even with the head it is in time.

Alternatively, you can forget about the "T" mark on the flywheel and measure the position of the piston itself. Remove the spark plug and stick a plastic straw (or similar) down there till it rests on the top of the piston. Use the movement of the straw as you rotate the crank to determine the position of the piston.

[Dew2008]

Gotcha...


So the "|" Mark Lines in the middle of the notch on the crankcase? I understand TDC and I understand what your saying but if I have to use a straw to find position on the piston why would honda waste there time to notch the crankcase? Just a little confused in there design with this. I have already pulled it all apart and waiting on parts. Cam marks were about 4-6 teeth out of time so I obviously jumped time. Chain is shot Im not sure how its still in one piece.

So find TDC, Line cam marks with head (- -) and put it together? Just would rather do it once if you know what I mean. Thanks

[GPracer2500]

Originally posted by Dew2008
Gotcha...


So the "|" Mark Lines in the middle of the notch on the crankcase? I understand TDC and I understand what your saying but if I have to use a straw to find position on the piston why would honda waste there time to notch the crankcase? Just a little confused in there design with this. I have already pulled it all apart and waiting on parts. Cam marks were about 4-6 teeth out of time so I obviously jumped time. Chain is shot Im not sure how its still in one piece.

So find TDC, Line cam marks with head (- -) and put it together? Just would rather do it once if you know what I mean. Thanks

Yes, align the | with the middle of the index notch on the case. Although, I think you'll find it won't make too much difference if you're not perfectly centered on the notch. Manufacturing tolerances and wear will sometimes prevent all of the relevant marking points from aligning 100% perfectly. BUT if you're one tooth off one way or the other--that will be obvious. When your timing the cam and something isn't lining up 100% perfect, just move the cam one tooth. Chances are now it will be way off and you know that the previous position is as close as you can get to "in spec" without using an adjustable cam gear.

I only mentioned the straw down the spark plug hole method as an alternative to using the flywheel indexing marks since you seemed unclear on how they should be used. It's sort of a "when in doubt, just measure the position of the piston itself" method.

[Dew2008]

Gotcha man, I just know how precise you have to be with a auto and a **** hair off and your screwed so I assumed it would be the same in this situation. Although that would explain a few issues I have been having. I have been trying to align to the tee and it aint worked to well lol. Thanks man