Topic: Lost on timing and tappets

[Jv550]

So I'm working up to a carb rebuild & synch, and I'm told I should adjust the timing and tappets first. I put a Dyna S on last weekend and I think I got the timing right. Using a strobe, I got the 1.4 and 2.3 marks on the timing mark at idle - they bob around a little but they're both right there, only when I try to adjust the higher rpms (2,500 - 3,000) neither will hit the advance mark. It's like it stops a few clicks away and won't go any farther.The Dyna manual says the advance mark won't line up exactly, but does anyone know how not exactly they mean? The bike is idling and running great, so I think it's ok but just want to make sure.

Now the tappets. I've never done this before. I tried using a Haynes and the little manual that comes with bike, but I'm just not getting it. For one thing, which is the inlet and which is the exhaust tappet? And for another thing, it says to watch the tappet til it hits bottom and starts to lift, then look for the 1.4 mark to line up. But it's nowhere near lining up. Does that mean I turn the engine until it hits that mark and then make the adjustment? And does TDC means both valves are in the middle of their respective upstroke/downstroke?

Sorry if these are dumb questions. It's a 75 550k. 

[kuyarico]

Regarding the tappet adjustment, the front tappets are for the exhaust and the rear for the intake. Line up the 1.4 mark and check cyl 1's tappets for some play. Both intake and exhaust should have a slight amount of play. If they do not, then your number 4 cylinder is at TDC. Check 4 for play. If you do find some play then adjust those tappets accordingly. Rotate the crankshaft 360 degrees and do the other side. Do the same for the 2.3 cylinders. .05 mm intake .08 mm exhaust according to my Clymer. There are a lot of threads and methods of this procedure.

[Jonesy]

When I installed my Dyna-S, I timed it to the full advance marks, with the engine around 3000 RPM. This way I knew I was getting full advance where it counted. I think when they say "not exactly", they refer to the way the full advance is marked. As long as the pointer is between the two hash marks, it's sufficiently advanced.

The inlet tappets are on the side with the carburetors, and the exhaust ones are on the side of the head where the mufflers attach.

When the T mark is lined up for cylinders 1&4, both pistons will be at the top. However, one will be on the compression stroke (with both valves closed and the tappets loose) and the other will be on the exhaust stroke, with the intake tappet loose and the exhaust tappet applying pressure to the valve. So, if you are doing cylinder 1 (at the outermost left cylinder) and one tappet is tight, roll the engine over one turn and try it again.

"TDC" Stands for Top Dead Center, meaning the pistons are at the highest point in thier cylinders. The igniton timing is set to fire a bit before the piston reaches this point, as it takes a brief moment for the air/fuel mixture to ignite.

[Jv550]

Thanks guys. That helps a lot.

In regard to the timing Jonesy, when you say you timed it to 3k at full advance, did you have to mess around with the magnets or just rotate the plate?

And does it matter which I do first - timing/tappets?

[Jonesy]

I just moved the whole plate for timing 1&4, and then moved the pickup for 2&3 to fine-tune that side. I did get lucky with one Dyna unit that didn't need any secondary adjustment.

If it were me, I'd do the valves first. They are to be done on a "cold" engine and I prefer to do the timing with the bike running and up to operating temp.

[750goes]

Adjust your camchain as well when motor is cold before you adjust your valves........

[martin.g.g]

For tappets I use the thread pitch method as this compensated for rocker wear and you end up with a more accurate gap and thus less rattle. Finlay I run the engine up to operation temp and tweak the tappets using a screw driver to the ear and listen to the noise each tappet is making (place the screw driver to the rocker cover at the point were the rocker shaft is on the tappet you wish to adjust). Don't over tighten or you will have a very quite engine but you may well burn the valves out and the bike will not fully rev up under load. Better a little rattle than no rattle.

[OldSchool_IsCool]

Thread Pitch Method..... Hmmmmmmm

You mean bottoming the tappet adjuster screw then backing it out a certain fraction of a turn to get the .05 and .08 mm gap?

[OldSchool_IsCool]

Not guna tell us, eh?

OK, lets try this.  Does anyone know the thread pitch of the tappet adjuster screw on a '77 550K? 

[Jv550]

I didn't have a test light so i used a multimeter set to voltage as someone suggested in a past thread. Red to the coil junction black to the engine case, pushed the rotor clockwise to open it up and rotated the plate until the voltage shot up. But I couldn't get all the settings to jibe, and it was hard to start once it was set, so I got out the timing light and reset everything that way.

I don't notice a major difference in performance since I got the dyna in. The idle seems a little smoother... I'm going to have to wait until this weekend to take another crack at the timing, and I'll try again with the tappets then too.