Pamco all the way retard, still too far advanced?

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RCGRT

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Well I've finally got it all buttoned up and got it to fire a few times. Looks like my PMA regulator isn't working. I'm getting about 18vdc. But Hugh said he'd send me another one. When i degreed the cam i was getting about 3 degrees advanced. I got the cam from Mr.Riggs, and i did the crank. Well from what I can tell that would advance my pamco with it. I noticed immediately a consistent kick back as I was trying to kick it. Once I finally got it started and the timing light on it, it was at or past advance at or around idle.... I've already adjusted the pamco plate as far as it will go (counter clockwise as you face the pamco), and tried taking the slop out of the pin at the mechanical advance that drives the pamco rotor... Is it possible that cam is so far advanced that I will not be able to get the timing right? The cam only rotates half of the crank, so seems like it would have to be way out to have to adjust it that much?
Is it possible i could have something installed wrong and yet close enough to still run? Seems like the pamco install is either right or wrong, and wrong as in it will NOT start. But I could be wrong.... I'm all ears....
 
RCGRT,

Well, you are right about the cam only turning half as much as the crank, but what that means is that for every 1 degree on the cam equals 2 degrees on the crank.

Whatever your problem is, I would not recommend any extensive riding until you get it sorted out and start using 93 Octane gas.

The ignition timing can be way out and the engine will still start and run. The first thing to do is to verify the position of the PMA rotor.
 
just had same problem, check hughs flywheel make sure to get a woodruff key in there to keep timming marks in check...... make sure tdc mark is dead on check it twenty times just be sure. next advance..... the big ugly nut that holds it to the cam(underthe weights) get that slop out........none of this helped me just do it for fun........is your cam in time with the crank..........if you run out of options and are sure mechanically everything is in time and spec........ pm me and ill tell you how i fixed my 277 with the same problem
 
pamcopete said:
RCGRT,

Well, you are right about the cam only turning half as much as the crank, but what that means is that for every 1 degree on the cam equals 2 degrees on the crank.

Whatever your problem is, I would not recommend any extensive riding until you get it sorted out and start using 93 Octane gas.

The ignition timing can be way out and the engine will still start and run. The first thing to do is to verify the position of the PMA rotor.
Click to expand...

Pete,
Thanks again for the quick response.
Yes checking the rotor mark to TDC is first on my check list, the male and female taper were clean and dry when I installed it, so I doubt it moved, but I won't just dismiss it, it will be checked.
At this point my suspect is the cam, it was the first time I have ever degreed one, but I did check it several times, and it averaged out to about 3° advanced (I even checked both cylinders).
Now if I were off by ONE tooth on the cam... 36 teeth, that's 10° per tooth, 10° on the cam would mean I would have been off by at least 20° at the crank...
Seems like I would have noticed that, or valve interference, or it would not have even started... I'm not sure.
I did have fresh 93 octane in it.
 
GRIMM-BEAVER said:
just had same problem, check hughs flywheel make sure to get a woodruff key in there to keep timming marks in check...... make sure tdc mark is dead on check it twenty times just be sure. next advance..... the big ugly nut that holds it to the cam(underthe weights) get that slop out........none of this helped me just do it for fun........is your cam in time with the crank..........if you run out of options and are sure mechanically everything is in time and spec........ pm me and ill tell you how i fixed my 277 with the same problem
Click to expand...

GrimmBeaver,

Thanks for the info. Last night I did disassemble the advance unit and push the slop out of the pin/slot in a counterclockwise direction in order to try and gain as much retard as possible. The plate is pushed all the way until the notches are hitting the screws, and it still seems advanced. My suspect at this point is my cam, take a look at my reply to Pete if you don't mind.

So in your case your cam is degreed in good, and you still couldn't adjust the pamco enough to get the timing correct with out doing some sort of mod? The reason I keep referencing to the cam, is well the pamco rotor is essentially located and driven by the pin on the right side of the cam.
 
sounds like you're off a tooth in lining up your cam. i have went through the exact same thing. the bike will run but the timing too far advanced. a quick way to check is to get to tdc and open the right side cam cover. pull the advance and take a look how the pin on the cam lines up. however with yours being a rephased cam it may be different.

this is what a stock cam looks like when you are off a tooth. correctly installed the pin should be at 12 o'clock with the pistons at tdc.

C1164E54_zpsb14576f0.jpg
 
GRIMM-BEAVER said:
just had same problem, check hughs flywheel make sure to get a woodruff key in there to keep timming marks in check...... make sure tdc mark is dead on check it twenty times just be sure. next advance..... the big ugly nut that holds it to the cam(underthe weights) get that slop out........none of this helped me just do it for fun........is your cam in time with the crank..........if you run out of options and are sure mechanically everything is in time and spec........ pm me and ill tell you how i fixed my 277 with the same problem
Click to expand...

I could be wrong, but i don't think you use a woodriff key with HHB PMA....
Maybe someone else with more knowledge can verify this?
 
Rush2112 said:
I could be wrong, but i don't think you use a woodriff key with HHB PMA....
Maybe someone else with more knowledge can verify this?
Click to expand...

Rush,

The key is not absolutely necessary with Hughs PMA, however after installing the new PMA, you will have a timing TDC reference mark on the rotor, so without a key installed, it is possible that the shaft can spin inside of the rotor. Once that happens your timing mark is no longer valid. The rotor fits the shaft on a male/female taper, if they are clean and dry, and the proper torque is used, I would agree it should not slip. If someone wanted to be 100% certain it cannot slip, a key can be fitted and used.

Hope that helps.
 
:doh:
deadchef said:
sounds like you're off a tooth in lining up your cam. i have went through the exact same thing. the bike will run but the timing too far advanced. a quick way to check is to get to tdc and open the right side cam cover. pull the advance and take a look how the pin on the cam lines up. however with yours being a rephased cam it may be different.

this is what a stock cam looks like when you are off a tooth. correctly installed the pin should be at 12 o'clock with the pistons at tdc.

C1164E54_zpsb14576f0.jpg
Click to expand...

Thanks for the input.
I'm really leaning towards the same thing. It's crazy to think that it will run 20 degrees out though. The only thing is I degreed the cam, and checked like 3 times. I checked the lobe centers for "intake 100 deg after top dead center" and "exhaust 99.5 before top dead center" My 3 different checks averaged out to about 3 degrees advanced. Again I lean towards the cam because we all know the pamco is located and driven from the pin in cam...
If you've got any other ideas I'm all ears
Thanks again
 
here is my '81 last year before i fixed the cam timing. got it from the po like this. it would run but once the ignition would start advancing it would just stumble.

 
Here is a picture of my right side cam where the advance unit goes. From what I have read the locating pin should be vertical when the right side cylinder is at TDC. So I pulled the plugs and gave a quick eyeball to put the piston at TDC. The pin does appear to be vertical. I really don't think it's off 10 degrees, this would also comply with the numbers I got when I degreed it, 3 degrees advanced.
When I did the crank, I rotated the right side advanced. I'm pretty sure the cam I got from Mr.Riggs was rotated the same way. I told him how the crank was done when I bought it from him. It's actually a 256 cam with a late model 36 tooth sprocket. And I did check both cylinders when I degreed it.
 

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The two red dots on the pamco rotor are where to two magnets are. As you can see the trailing magnet is right about where the hall effect sensor is.... while that cylinder (right side) is at TDC
 
I just got done installing a 277* Pamco and there are 2 slots in the rotor where it engages on the advance shaft. Are you sure you used the correct slot? I am assuming the red dots correspond to the magnets. Hugh did a great write up on how to install the 277* pamco here. You may want to take a look at it and double check what you have.
 
ippytattoo said:
I just got done installing a 277* Pamco and there are 2 slots in the rotor where it engages on the advance shaft. Are you sure you used the correct slot? I am assuming the red dots correspond to the magnets. Hugh did a great write up on how to install the 277* pamco here. You may want to take a look at it and double check what you have.
Click to expand...

Yep, here is a picture of the two red dots while cylinder #1 at TDC. As Hugh describes in the write up, they should be horizontal, as you can see in the picture (and I did notice this when I first installed it) they are not perfectly horizontal. Just a tad advanced, I was thinking that maybe since the cam was a little advanced then that is why they are. But really if the cam is 3 crank degrees advanced, that means the cam is actually only rotated 1.5 degrees. The two red dots seem to be rotated more than 1.5 degrees from horizontal.
I don't know, the only thing I can come up with at this point is maybe I totally goofed the degree process and the cam is more than 3 degrees out. Even so, I would still think there would be enough room in the pamco plate to compensate. I'm not sure how many degrees Pete designed the plate to be able to move one way or the other.
But again, moving that pamco plate 5 degrees....would advance the timing 10 degrees, so seems like that cam would have to be way out for there not to be enough adjustment in the pamco plate to compensate.
Possibility that the pamco rotor slots are not orientated to the two magnets? Sure I can see that they are machined from two different sides of the part. But I'm sure Pete has a good quality vendor. I guess the next thing to do is re check the cam degree....
 
Forgot to attach that last picture
 

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That certainly looks to be about the right amount for being off by a tooth on the cam. Another way to set cam timing on these with a cam from Mr Riggs is to put the right cylinder a tdc and align the dot on the cam with the surface of the head instead of trying to eyeball the notch. I would have to say that it appears to me that you are off by a tooth there.
 
Ok. I re-checked the cam degree. Here are my findings.

Cylinder left side #1
Intake - 26 deg BTDC @ .05" lift / 33.5 deg ABDC @ .05" lift =
26+33.5+180= 239.5/2=119.75-26= 93.75
from what I was told by Mr.Riggs it should be 100, not 93.75.
If watch the indicator as the valve reaches max lift and stop right as the indicator begins to move the other direction. The reading at the crank is about 97 / 98 ATDC depending on where I stop it. My valve valve clearance is set at .003

In the book for XS1 the spec says
intake BTDC 47 deg open / ABDC 67 deg close
when they say "open", well how open? if i watch my indicator and stop as soon as I see less than .001 movement, the crank reading is like 80 deg BTDC, if I roll it around to 47 deg BTDC like the book says I've got about .008" lift
I'm not sure what to do...
If my thinking is right, well if I move the cam "back" one tooth (10 degrees), that would put me at 103.75 just a little retarded, but closer to spec than 93.75
 
Hey, RCGRT. Cross-checking your numbers with my notes, looks like you're advanced 1 tooth.
If the intake has the clearance, you could take a compression reading before re-timing, another after.
We used factory valve lash when cross-checking service manual prints. The racers and custom cam grinders used other values for builds (like @.040" lift for example), was a more accurate system, but for everyday shop mechanics, the factory preferred to not confuse us.
Right now, you're reporting 80° BTDC for initial travel on intake set for .003". Very advanced. If you backed-off by 1 tooth, that would be 10° at the cam, but 20° at the crank, getting you to 60° BTDC, still advanced by just looking at intake. However, the XS1s used a flat front guide. You've probably got one of those newer 'arched' front guides that will advance the cam a little. Kinda of a double-whammy here. But, if a flat front guide was in there, that 60° BTDC intake would be closer to that 47° BTDC book spec.

Just food for thought. Hope mrriggs jumps in here to straighten this out...
 
TwoManyXS1Bs said:
Hey, RCGRT. Cross-checking your numbers with my notes, looks like you're advanced 1 tooth.
If the intake has the clearance, you could take a compression reading before re-timing, another after.
We used factory valve lash when cross-checking service manual prints. The racers and custom cam grinders used other values for builds (like @.040" lift for example), was a more accurate system, but for everyday shop mechanics, the factory preferred to not confuse us.
Right now, you're reporting 80° BTDC for initial travel on intake set for .003". Very advanced. If you backed-off by 1 tooth, that would be 10° at the cam, but 20° at the crank, getting you to 60° BTDC, still advanced by just looking at intake. However, the XS1s used a flat front guide. You've probably got one of those newer 'arched' front guides that will advance the cam a little. Kinda of a double-whammy here. But, if a flat front guide was in there, that 60° BTDC intake would be closer to that 47° BTDC book spec.

Just food for thought. Hope mrriggs jumps in here to straighten this out...
Click to expand...

Hey thanks for the info. Ok you just stated something that I was having a hard determining yesterday. 10 degrees at cam 20 at the crank. I understand that per the fact it's a 2:1 ratio. So initially I was thinking, well I'm off by 6 or so degrees at my .05 lift check. So I couldn't see how moving one tooth would work as I thought that would throw me way!! Off. However everything else except my very first degree checks pointed towards one tooth advanced. Included a few that commented on this thread. So I thought again... The cam is just following the crank... So I thought about it like this if I were to have done the same excersize (degreeing it) and position the crank at the cam lobe center I found (advanced) and then theoretically moved the cam back one tooth, well I'd be exactly 10 retarded from where I was. I think there is a little more math and geometry going on here than I can wrap my brain around. But everything pointed to one tooth advanced. Solid facts being, consistent kickback every kick, pamco fully adjusted retard while timing light showed past advance at idle, and finally the two pamco magnets that should have been horizontal and were not as you can see in the picture. All of which pointed to moving the cam back one tooth as a fix.
 
RCGRT,

Did I miss something here or have you already pulled the PMA rotor to see if it slipped?
 
Last edited:

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