Timing Question

[corey]

I'm setting the timing on my 79SF. What degrees do I need to calibrate the timing light to?

Also, as a quick aside: is there anyway that the timing plate could be put on in the wrong alignment? I had it off the other day while checking my advance unit, and I'm not sure I got it set back the way it is supposed to be. ????

[TopCatGr58]

Corey,

With the bike warmed up, and idling around 1K, it should be lining up with the F mark. Then disconnect and plug the vacuum advance, and rev to 5.2k, should be at 31 degrees for Special.
This is per the manual!
T.C.

[Winterhawk]

It might not be a bad idea to put a dial indicator in the #1 cylinder at top dead center and set the pointer to the "T" before using the timing light.

[randy]

Corey,

Are you asking about how to calibrate your timing light? Some of the expensive ones ( SUN ) have an advance adjustment on them. If yours does, set the advance on the light at 0 degrees and read your advance directly from the timing plate.

You shouldn't have a problem installing the timing plate, it only has a few degrees of adjustment. Snug it down with the mounting screws in the center of the range and that'll be good enough to start. If you also removed the pointer, do what Winterhawk said and re-time your engine ( TDC on the compression stroke on #1 cylinder ), then re-install the pointer to 0 degrees.

As far as the advance mechanism, unless you disassembled it, it only goes on one way, there's a locating pin in the crank.

If you did disassemble the advance mechanism, it's possible to reassemble it with the reluctor 180 degrees out of phase. You'll know because the engine will backfire through the carbs when you hit the starter. Don't ask me how I know this

[corey]

It is a SUN timing light. I will set it to zero.

Also, I didn't remove the pointer nor dissassemble the advance, so I should be good to go, I guess. I'll give her another try. I'm starting to think my gun is a little fubarred, as a friend of mine busted it pretty hard in a cooling fan... :S

Thanks!

[randy]

Corey,

try flipping the spark plug clip the other way round. sometimes it helps. also, get it as close to the plug as possible.

[corey]

Will do, Randy.

Recent developement: while playing around with the bike earlier, I decided to check for spark. Much to my chagrin, none of the four had a consistent spark. One and four offered an intermitent flame, but for the most part NOTHING. Now riddle me this, Batman: can completely off base timing result in no spark whatsoever? My analytical side tells me that the ignition will spark no matter what, it just won't necessarily be at the right time.

I just received new spark plug caps this evening that I will put on, and I'll be acquiring a new set of plugs tomorrow. Hopefully this will rectify my problem and keep me from having to by new coils/ignition unit!

One more thing... I found that my bike is running NGK BP7ES plugs. The book calls for BP6ES. What's the difference?

[randy]

Corey,

Chances are that the new caps will make a big difference. The fact that you have spark AT ALL is good, means your coils / ign unit are working. Hint: when you install the new caps, cut 1/4" off of the wires. That will expose new wire for the caps to bite on.

Install the recommended BP6ES. The 7's are a colder plug, may induce fouling in a stock engine. Of course, that depends on the way you ride, jetting, exhaust, etc. But it's usually best to stick with the stock heat range plug (eliminate variables).

Make sure you set the gap on the plugs.

Weak spark is likely why your timing light is not flashing.

[corey]

...and now I see how the pieces fit. I'll see how it goes tomorrow. Thanks a ton Randy, you help to put my mind at ease!

I'll let you know...

[pggg]

Randy and Corey, if the spark plug on the lead happens to be carboned up - the light wont work. Dont dare ask me how I know that.

[corey]

Interesting and worth noting. Thanks PGGG, that comes in handy.

I replaced the caps today, still no spark. I think the plugs are fouled out badly.

...and now I anxiously await my new plugs.

[DiverRay]

Cory
How old is the battery? If you are dropping below ~10.5V when cranking, no spark! You may want to put a VOM on the battery while you crank if it's over 2 years old.
just my .02
Ray

[Dan Hodges]

Originally posted by TopCatGr58
Corey,

With the bike warmed up, and idling around 1K, it should be lining up with the F mark. Then disconnect and plug the vacuum advance, and rev to 5.2k, should be at 31 degrees for Special.
This is per the manual!
T.C.

I would be very interested in knowing what he get's when he checks it at full advanced,as the shop manual gives two different answere's on the total timing for a 79 SF.If he get's only 31 degrees at 5200rpm,that will confirm my suspicion of why the 79SF was slower than the orignal 78 E which had 36 degrees at 5000rpm and ten degreess at idle.My 81 SH has 40 degrees at 4000 RPM and 5 degrees at 1000 RPM.The 81's had a timing plate that was not graduated in degrees and the timing was not adjustable.So, I installed a 79 timing plate on mine that was and slotted the timing mechanism/plate where I can adjust the timing to whatever I want and the 40 degrees at 4000 RPM is what it likes.A different combination might like something different,but it would not vary by more than 5 degrees.There is some power to be had or lost with this timing thing,you gotta look for it very closely.

[corey]

Alright, got her all timed up. I couldn't get an accurate reading at 5.2k rpm, as my advance is screwed up. Thanks for your help everyone!

[pggg]

Dan, running a 2H7 centrifugal unit(131-01) advanced 5 deg in a 3H5 motor gives a high rev boost but not by much. Running a 3H5 centrifugal unit(131-02) at 5 deg advanced in a 2H7 motor doesn't seem to change anything. A 5 deg advanced 2H7 unit in a 2H7 motor also gives a small high rev kick. 3H5 cams in a 3H5 motor with 2H7 carbs running a 2H7 centrifugal unit advanced 5 deg gives similar performance to 2H7 cams in a 2H7 motor running a 3H5 unit at normal advance. Running 3H5 cams in a 2H7 motor with a 3H5 unit advanced 5 deg with 3H5 carbs...

Ah F*#* it! I'm going to bed.