MSD TIMING BACKING OFF AT RPM?

[KennyM]

Here are two ways I have done to see changes in timing.
On a single cylinder go kart engine with a fixed magneto and flywheel advance key, install a degree wheel and find zero on pointer in the standard way then start engine and check the timing with a trigger timing light against the key installed and with the usual manuel setting procedure.
Rev the engine and watch the amount of retard take place.
Sometimes the a coil can be selected to minimize this effect and sometimes the flywheel can be changed to find one that has different magnet actions against the coil.
.
A second way to see timing changes on a distributor engine is to prepare a cap with a 5/8" hole at the base of # 1 plug tower so a timing light can strobe the action.
Fix time the engine and use a light to see the distance the rotor tip changes from the tower conductor.
This should tell something about the distibutor to cam relationship change that might occurr and any hystersis that may be present but has to be tracked down to tell which and what is causing any changes seen in the rotor to post relationship.
Or build in a correction compensation action in the timing advance method.
I would expect that a good timing light has very little to no effect in adding to what is seen.

[racer189]

Does a "Hall Effect" type crank trigger sensor experience the same hysteresis lag of the magnetism as the non magnetic trigger? I'm surprised that more people don't use a Crane or Mallory distributer that uses a light trigger as opposed to the magnetic sensor that MSD and most other distributers use. Is there an issue with using the light type of sensor? I've heard that many NASCAR teams use the Crane system.

[racinnut15xm]

So guys that are unable to use a crank trigger what do we do?

[jet1]

If you are allowed to use a programable ign you can program the retard out of it. Or you can switch to a haal effect type dist.

[racinnut15xm]

If i buy one of those "msd" lights if it is truely a MSD ignition problem will this issue go away?

[cuslog]

I chased this problem for awhile.
Brought the cam endplay down to about .006.
New composite dist. gear. Lowered the dist. down .100 to center the pattern. Shimmed the gear down to about .010 endplay.
Made an adjustable nut / bolt for the front of the timing cover so it bottoms on the backside of the water pump to eliminate cover flex -- set it @ .006.
Still got it.
Was using an ATC dial-back timing light -- bought the "good" MSD light -- still got it (timing rolling back about 4 - 5 degrees as RPM goes up).
I've tried a couple of friends lights as well, both dial back and fixed with no change, so I don't think its the light.
But I must say, I DO like my new MSD light -- 2 less wires to tangle and worry about burning and its a really BRIGHT light. On my chromed ATI dampener, its almost blinding.
I'm now thinking its the "hysteresis" in the electronics and I've decided to just "live with it".

[levisnteeshirt]

try a crane distributor ,, problem = over ,,, I like a good point distributor ( use just one set of points ) with a MSD if the rpms aren't through the roof ,, the points only see 5 v , low amps on the white wire ,, a set of 48 oz accel points last a long time , and they start instantly like this ,,

[levisnteeshirt]

an HEI may not look too sexy, but they have less problems with this that I have saw ,, but of course like what has been posted , a mag trigger is the best

[dieselgeek]

(1) try reversing polarity on the pickup because no matter how we try to match it to color codes, etc. there seems no rhyme or reason to the problem
(2) people call it "hysterisis" but the real issue is inductive delay. Not that it matters what to call it.

[racinnut15xm]

an HEI may not look too sexy, but they have less problems with this that I have saw ,, but of course like what has been posted , a mag trigger is the best

I tried an MSD HEI i borrowed from a friend and it was still doing it.

Is a MSD HEI just like having a MSD box though? Should i find a STOCK or closer to stock HEI?

I have the bolt in the bottom of the water pump for cam walk. I set the play in the MSD dist w/ the new gear to .020 cause thats as close to .015 i could get with what i had. I guess my next move is to pull all the plugs and put a socket on the crank and hold the dist and see how much play is in the whole system.

[racinnut15xm]

I know i wasnt the original poster but thought i would report back.

I tore the pan and timing chain cover off. Pulled the cam gear off and the pin for the cam was sitting sideways. Wiggled it and it fell out in the floor, broke in half. Chain seemed loose too. I put the backup motor in and will go to work on this one this winter. Think it needs more attention to how long the oil pump driveshaft is, a better oil pump, and better chain/gears.