Pamco question

[jgimar]

This has probably been asked a thousand times but...
i have a basic pamco unit, pma, and capacitor setup on a 77D. Question is, there seems to be a bit of side play in the advance rod. is this acceptable or is there a need for a shim? it isn't extreme but enough to make us wonder if the slightest bit would effect the pamco proper function. any help thanks in advance.

 

[Marlin72xs]

I haven't looked at mine or taken the covers off in a while, so I don't remember if I had any side play. I would assume, that a little play would be good since we are dealing with different expansion rates of steel and aluminum.

My problem was in the slop between the shaft and the cam. The steel pins in the aluminum disk that replaced the advance mechanism became sloppy and I could see the timing mark bouncing back and forth at idle. I also assume that at a constant speed that it was also bouncing back and forth. Overtightening was out of the question, so I epoxied the steel pin into the slot about a year ago. All has been good since. I'm sure that the little bit of epoxy will snap off if I need to take it apart.

Good luck!

 

[jgimar]

I haven't looked at mine or taken the covers off in a while, so I don't remember if I had any side play. I would assume, that a little play would be good since we are dealing with different expansion rates of steel and aluminum.

My problem was in the slop between the shaft and the cam. The steel pins in the aluminum disk that replaced the advance mechanism became sloppy and I could see the timing mark bouncing back and forth at idle. I also assume that at a constant speed that it was also bouncing back and forth. Overtightening was out of the question, so I epoxied the steel pin into the slot about a year ago. All has been good since. I'm sure that the little bit of epoxy will snap off if I need to take it apart.

Good luck!

very good, thank you for the reply. i don't think the issue has effected the function but we just happened to pick up on the other day. my helper also noticed some jumping in the timing so we'll check that as well.

 

[Marlin72xs]

Hint: I have found, through many people in this forum that are much smarter than me, that these bikes run better if the timing is set towards the retarded "F" mark. From there you can make carb changes and get better plug readings. There's a great article on spark plugs that explains a lot. Lost it and can't find it. Same as my marbles once in a while. Good luck!

The timing is gonna jump a little. It aint gonna be rock steady like a V8.

 

[Jan_P]

Hi
Assuming you have the stock advance unit with springs and weights
Side play ?
You are sitting on the bike is it side play transversely to the bike left right direction
which can be an adjustment / tightening / washer thing
Or is it play in the back front direction of the bike ..There is a Bushing inside the cam .
That can be lubricated and replaced if necessary I don't think is common .Need replacing
Some play is needed as mentioned for temperature and other variations. In both directions.
More play does not matter in the left right -- in the sideways direction .I believe
.It was long ago I had it .But the stock points setup had a cam about
10 mm long so a little movement would not affect that .
Not seen the Pamco setup but if we get the right description we can evaluate it
Any idea of how much it is.

 

[5twins]

Excess side to side or end play in the advance rod can make the timing marks bounce around some. I found that on my '78. On the advance side, if I pulled out on the advance rod and let go, it would snap back in with an audible "click". I thought this might be adding to the topend noise so I shimmed it out. As near as I could measure, I found about .015" of end play. I shimmed it down to about .006". This didn't make any difference in topend noise but it did smooth out the timing. See here .....

https://xs650temp.proboards.com/thread/1372?page=2

 

[jgimar]

Hi
Assuming you have the stock advance unit with sprigs and weights
Side play ?
You are sitting on the bike is it side play transversely to the bike left right direction
which can be an adjustment / tightening / washer thing
Or is it play in the back front direction of the bike ..There is a Bushing inside the cam .
That can be lubricated and replaced if necessary I don't think is common .Need replacing
Some play is needed as mentioned for temperature and other variations. In both directions.
More play does not matter in the left right -- in the sideways direction .I believe
.It was long ago I had it .But the stock points setup had a cam about
10 mm long so a little movement would not affect that .
Not seen the Pamco setup but if we get the right description we can evaluate it
Any idea of how much it is.

thanks for the reply. this would be, sitting on the bike, very minute play left to right but enough that we thought it may have a bearing on the flutter we're getting. the thread following yours is probably a good example. probably not more play than what he had. good info, thank you.

 

[jgimar]

Excess side to side or end play in the advance rod can make the timing marks bounce around some. I found that on my '78. On the advance side, if I pulled out on the advance rod and let go, it would snap back in with an audible "click". I thought this might be adding to the topend noise so I shimmed it out. As near as I could measure, I found about .015" of end play. I shimmed it down to about .006". This didn't make any difference in topend noise but it did smooth out the timing. See here .....

https://xs650temp.proboards.com/thread/1372?page=2

outstanding! i will check it out! thank you.

 

[Jan_P]

Hi again

it may have a bearing on the flutter we're getting

Perhaps you already know this but the mechanical advance unit ..Can give ignition problems ..Weak springs and non consistent
advancing and retarding..

 

[jgimar]

Hi again

it may have a bearing on the flutter we're getting

Perhaps you already know this but the mechanical advance unit ..Can give ignition problems ..Weak springs and non consistent
advancing and retarding..

I don’t care what i know, all assistance appreciated! Okay, rookie here! How do i determine weak springs? They seem to function properly for my amateur knowledge.

 

[650Skull]

I don’t care what i know, all assistance appreciated! Okay, rookie here! How do i determine weak springs? They seem to function properly for my amateur knowledge.

How dose one determine if the springs are week ???.........Use a bit of nouse......look at the weights, if they are not sitting correctly the springs may be weak. Use your finger to test the weights to see it they work as they should in an operating situation..........

 

[Jan_P]

Some reading
https://xs650forum.proboards.com/thread/1169/advance-unit-problem
https://xs650temp.proboards.com/thread/10738?page=1
https://xs650temp.proboards.com/thread/1372

 

[5twins]

Before condemning the springs, make sure your advance rod has been cleaned and greased where it runs through the cam. Although not mentioned in the manuals, this should be considered a maintenance item. You don't need to do it often, maybe every 5 years of so, but it needs doing. Most haven't been touched since the factory assembled them back in the '70's, so they're long overdue for this service. The springs may be fine on an advance unit that's sticking advanced and not snapping back smartly to the retarded position. No lube on the advance rod may be the cause.

After removing the advance rod, if you look in the ends of the cam, you'll see the I.D. of the bushing has grooves in it .....

These are for holding grease to keep the advance rod lubed. Chances are, you'll find little if any grease remaining in them after all these years, but clean out whatever is there and re-pack with fresh stuff .....

The shop manual recommends a grease with moly in it.

 

[jgimar]

How dose one determine if the springs are week ???.........Use a bit of nouse......look at the weights, if they are not sitting correctly the springs may be weak. Use your finger to test the weights to see it they work as they should in an operating situation..........

Great stuff, thank you

 

[jgimar]

Before condemning the springs, make sure your advance rod has been cleaned and greased where it runs through the cam. Although not mentioned in the manuals, this should be considered a maintenance item. You don't need to do it often, maybe every 5 years of so, but it needs doing. Most haven't been touched since the factory assembled them back in the '70's, so they're long overdue for this service. The springs may be fine on an advance unit that's sticking advanced and not snapping back smartly to the retarded position. No lube on the advance rod may be the cause.

After removing the advance rod, if you look in the ends of the cam, you'll see the I.D. of the bushing has grooves in it .....

These are for holding grease to keep the advance rod lubed. Chances are, you'll find little if any grease remaining in them after all these years, but clean out whatever is there and re-pack with fresh stuff .....

The shop manual recommends a grease with moly in it.

Will do, thanks so much.