Cam ignition timing 'deflection' (wobble)?

[joedrum]

gee great post .... yes one of the great places to see belt effects is on cnc machines ....they are at mercy of a belt adjustment or they dont do anything but cause problems ....

 

[C5Performance]

AApple » Tue Feb 17, 2015 1:31 pm[/url]":22txrma6]

C5Performance » Fri Feb 13, 2015 10:29 pm[/url]":22txrma6]
What I do not believe without measuring myself is how that "wobble" converts to DEGREES of ROTATION.

I been following this discussion, and Paul finally hit on what I have been wondering the whole time. Sure, you can have cam journal, and cam bearing wear that will cause some MINOR left/right-up/down movement of the cam ends, but there's no way that would change to actual rotational value of the cam. Granted a true "wobble" will mess with a points type ignition, but it was mentioned(if I read it right) that the cam/bike in question was having 6-9 degrees of rotational variance...which in my mind would have more to do with belts than worn cam/bearing journals. "Wobble" indicates something not rotating in a perfect 360 degree circle...not something that is changing the rate of rotation at times. If you have a bent wheel, the wheel wobbles....but it still rotates in the same circle(on the same axis) as a straight wheel. If you have a worn wheel bearing, the wheel can move on both the left/right, and up/down plane, but the center of the wheel would no longer be in the center of the AXLE(cam, if you will)....THAT'S a rotational variance.

I have long said that timing belts can effect timing, whether too tight, too loose, stretched, whatever, BUT...I don't believe any of that will effect it enough to cause a noticeable difference in how the engine runs. You might be able to measure it with some fancy equipment, but in the end, for our purposes, I can't see it making one dadgone bit of difference.

Thank you for reading the fine print. Everything you said is exactly what I believe. Up, down, side to side movement will not equate to "rotational variations" but would affect points timing. So my theory is the measured variation of timing (using a timing light) is the result of the sum total issues: cam movement + belt deflection + points variation.

Here is a partial Dynatek quote from Joe's NGW link as they try to explain why one trigger is set correctly and the other is incorrect:

Once the first timing procedure is done, which is accomplished by moving the
Dyna-S plate, the second module will generally be extremely close when
checking the timing. If it needs to be adjusted, there should be enough
movement (by design) in the power module to allow this. If the module cannot
be moved far enough to set the timing, this is where the timing belts come
into play. However, there is also the rare possiblility that when the power
module was assembled, the pick up in the unit shifted slightly during the
poting process. If you had to file the module side to get it closer to the
fixed module, this may be one reason why. In the future, while you can safely
file to side of the power module, it may be best to return the Dyna-S assembly'
to us for examination and testing first.

When using any Hall Effect ignition, even OEM Honda, Dyna fails to mention an important fact about the use of magnetic triggers....

Magnets change physical properties based on heat and surrounding magnetic interference.

As a magnet heats up, or is affected by the magnetic field created by the spinning rotor of the pickups, the magnet pulls in one direction or the other. You can test several triggers and record "repeatable" variations based on the position the magnet was glued into the rotor, the heat of the engine, and rpm of the rotor.

This is not necessarily a manufacturing flaw!

This is the reality of a magnetic based ignition. Why do ignition manufacturers have adjustable timing plates for the second trigger? Do you think they pay extra for that feature because 1 in a 1,000 ignitions might have shifted slightly? I believe it is to compensate for the inherent limitations of the magnets they use. Although I am not a magnet expert, I'm told the use of better Rare Earth magnets can reduce this variation greatly. Cheap magnets create larger variations (get what you pay for).

So you have belt flex, cam wobble, and magnetic variations that once again cause your timing light to move around a bit. Will it cause issues? That depends on the sum of the issues: belt + cam + magnetic variation.

Once again, I am not blaming Dyna or anyone else for these variations. The engine used to find 9 degrees of wobble actually had mechanical points, not magnets. I am stating that 9-10 degrees of ROTATIONAL variation because of cam journal wear is a hard pill to swallow. If we can find an engine (like the one in Dan's video) with visible wobble, we should do the following:

record static variation in timing
start engine and measure again at idle
measure at half and full throttle.

Now correctly adjust the belt and measure the above items again. Once that is done we should install an optic ignition and measure one last time.

That would sort out what is belt deflection, what is cam movement, and what is trigger variation.

 

[dan filipi]

I think we have come to an impasse in this discussion until some specific tests are done as laid out by Paul, otherwise the whole deal is hearsay and opinion.
I hope this thread doesn't die because I really would like to know exactly, need someone to take the time and make the effort to carefully test and document it. I don't have a 1000 so I'm out.

 

[bronko37]

I think for having a pile of mass produced parts whirling at several thousand RPM between your legs if you are wanting anything more than what you got you are just too hard to please. Its a pretty god dang precise machine IMO. That's why they still make em...

With my machining background I will say that there are too many variables to measure it accurately in using any method. You can come up with some general ideas about what may cause these minor irrelevant issues, but I just don't see the point in :head bang: over it. This topic can only lead to :Awe:

 

[mcgovern61]

Something to add regarding the timing belt tension (sometimes I feel like such an idiot).

I always wondered why the tensioners were set using the spring load and then locked down tight (defeating the need for the spring)? Every other belt tensioner I have worked with is spring loaded (heavy duty) and maintains tension all the time.

Then I realized, the load change and RPM change on the timing belt would cause a spring loaded tensioner to change based on the load. If the tensioner changed with belt load, the timing on the cams would also change! Fixing the tensioners correctly in the first place maintains a constant tension on the belts which would keep the cam sprockets always turning exactly the same as the crank pulley with little to no variation other than from thermal expansion of the belt.

Am I saying that right??? :roll: :beg:

 

[joedrum]

:builder:

 

[dan filipi]

Interesting on this 1200 engine, the expansion of the engine makes adjusting the belts with the tensioner when cold VERY tight when the engine is hot, so tight the belts and idler will sing and you can damn near play a tune on the belt.
Too tight imo.

The last time I adjusted them I used the spring exactly as laid out in the manuals and they were too tight when hot.
So I tried adjusting them when hot and checked them in the morning. Cold there is well over a 1/2" deflection in the belt, too much by what we read on the forums and just 'seems' too loose so I split the difference. They seem good now so it makes me wonder if the spring was originally intended as a starting point but should be re-adjusted when hot?

This topic has made me curious how much this engine expands.
Once I get some time I'll measure crank to cam difference cold and hot.

 

[Ansimp]

Just a thought on your cam belt variances. There is very little variance on the driven side of the belt with crank to cam relationship and the belt flap that is witnessed is usually on the unloaded side of the cams. Many cam belt driven engines use a spring/hydraulic tensioner that has the potential to vary the belt tension as required and not locked in place tensioners like the GWs

 

[C5Performance]

I could install stock coils and points back into my GL1000, then swap in a C5, but tomorrow temps are expected to be -35 F so my bike will not be running for at least another month.

A real test will be nice to get under our belt.

 

[julimike54]

C5Performance » 14 minutes ago[/url]":3gmlrfqb]
I could install stock coils and points back into my GL1000, then swap in a C5, but tomorrow temps are expected to be -35 F so my bike will not be running for at least another month.

A real test will be nice to get under our belt.

I like that idea...

Regarding tensioners on timing belts it would only work if it's running open loop control, I say that because the hostile environment of our equipment caused any kind of 'auto' tensioner to be another variable in the motor control, they also change characteristics with temp. swings from ambient to 500 degrees F (sometimes in poor installations it was even greater), but the customer is always right :roll:
I think end of day you'll be able to measure, but by the seat of the pants ride nobody could tell that you got rid of the timing variation. I think to get that much variation you'd be dealing with a poor performing engine to begin with & by the time it's all eliminated you're back to a good performing engine, that's the feel you'd get.

 

[ekvh]

Sounds like fun, but if anyone here is a member at wingworld, you might be able to access the tests that Robert Overby did. It was in '95. I forget which month.