Rephased Cam Question, Advance pin position?

lidirtrider

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I think I may be a tooth off on the cam. Cam was rephased by Hugh. I have the threads on the right hand side of the engine. Advance Unit mounts just fine, all checks done on advance unit and PAMCO check out OK.

I've been searching on here for days but I can't seem to find anything to come to any hard conclusions. If you've seen my other thread on the "White Trash Bobber" you know I've been through some, lets call them "issues" with this bike.

The issue now is that its SUPER difficult to start. Not in that it won't fire up, but that it takes everything in my being to kick it over, and the starter struggles to turn it over, and it kicks back like a bastard. But it will start and run if the PAMCO plate is as far retarded as I can get it. All the symptoms of cam being off a tooth or 2 off. I can turn it over with a wrench on the alternator nut, and everything moves freely, no valves hitting pistons or anything like that, but it's still very hard to get passed the compression stoke on either side. When I installed the cam I made sure the notch was vertical and the punch mark was dead center to the head. What I realize NOW is that I didn't install the cam chain tensioner until after I closed up the engine and reinstalled it in the bike, so I didn't confirm its position. I also see the when I check the location of the pin on the right side of the cam, under the advance unit, with the left cylinder at TDC on Compression, that pin is at about 7 O'clock.

Everything I read on here says that the pin should be "vertical" and most posts say it should be at 12 O'clock. But I haven't seen anything posted specifically to a rephased cam. If everything is the same as for a stock cam, and "vertical being EITHER 6 or 12 O'clock, then my position of 7 O'clock seems to mean that at least a tooth off. Pic below is the right side of the cam.
IMG_6353.JPG
 

5twins

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Yes, it looks like you're off a tooth with the chain. I take it the chain isn't new? That looks like quite a bit of chain stretch there.
 

5twins

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But I'm not real familiar with re-phases. I'm not sure which cylinder you use to time the cam. How's the pin location look with the right cylinder at TDC? Edit - scratch that. I just Googled it and re-phase timing is done on the left cylinder, with it set at TDC.
 

lidirtrider

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Cam chain was brand new when I originally installed it, and had only maybe 15 minutes of run time before I tore the engine back down to replace a botched (by me) piston ring installation, and maybe 5 minutes of running since I got it all back together.

My thoughts are that if the pin position on a stock cam should be at 12 O'clock, then on a 277 rephase, if the right half of crank and cam is rotated 277 FORWARD, then the pin position should be at roughly 9 O'clock or just passed? Or does cam go 544 degrees forward (2:1 ratio), which would put it between 6 and 7 O'clock?

I don't want to, but Ultimately I still just may have to pull the engine and open the top to DEFINITIVLY verify the cam position.
 

5twins

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Now that you mention it, you're right, with the right side of the cam relocated, that pin hole isn't going to point straight up or down at left cylinder TDC anymore. It probably will at right cylinder TDC though. Why don't you check that. To check for proper cam timing with the left cylinder, you'd have to have the top cover off so you could see and use the marks on the cam sprocket.
 

lidirtrider

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Now that you mention it, you're right, with the right side of the cam relocated, that pin hole isn't going to point straight up or down at left cylinder TDC anymore. It probably will at right cylinder TDC though. Why don't you check that. To check for proper cam timing with the left cylinder, you'd have to have the top cover off so you could see and use the marks on the cam sprocket.
Ah, good call. I'll check that when have time. Like I said, Notch on cam was straight up at TDC (compression) on Left cylinder, but without cam chain tensioner, so could be off because of that. Maybe I'm just over thinking the whole right of the cam, and that pin position.
 

5twins

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Yes, new chains are tight during install but loosen up pretty quickly once you run the engine. We went into my buddy's topend because of a bad cam bearing. It had been done already probably 5 or 6K miles before. We replaced the cam chain at that time but didn't this second time because it was still relatively new. We had to apply the tensioner when timing the cam. We set it initially without the tensioner applied but once we tightened the tensioner, it threw the cam timing off and we had to re-set it (move the chain over another tooth).
 

lidirtrider

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I have been going crazy trying to figure all this out, and it "seems" like my is installed correctly. I went back thru a bunch of pictures I took as I was reassembling the top end. Unfortunately I didn't take any pics of the cam after I put the bearings back on, and I didn't take any clear photos that show the cam notch at 12 O'clock and the punch bisecting the head that also show the right side of the cam with the advance pin. However there are 1 or 2 pics where I can just see the pin on the edge of the photo, and it looks like relative to the notch that pin is about 1 O'clock. SO...when I bring the LH piston at TDC on COMPRESSION, that pins lands at about 1 O'clock. Now I just have to make sure that the 2 pins on the advance rod are indexed to the pin in the cam, and I THINK that should be what I need to get this thing firing right.

2M, reading through that thread you posted, it seems like with a Hughs rephased cam, with all other things being correct, that right side (advance unit side) pin should land at about 1 O'clock.

I also think that may be something Hugh left out of his 277 PAMCO install guide. He mentions bringing that pin to 12 O'clock for ease of installation, nowhere have I seen and mention of the location of that pin when the cam installed properly with LH piston at TDC. I think would help a lot of people here iin the future. I feel dumb, but I only thought of reaching out to him just now to see if he has insight for that.

I also just reread my first post on this thread and I said that the pin is 7 O'clock with LH piston at TDC, but the other pic I mentioned show it at about 1 O'clock, so I might have misspoke and that pic above might be with RH piston at TDC.

Again, I plan to check all possibilities this weekend, and may still in fact have to pull the motor to ensure everything.

So the plan now is to get in the garage on Friday when I'm off and have look see. If you look at my "Whit Trash Bobber Resurrection" thread you'll see that I had it running last weekend, so I know I was close. I just want it right.
 
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Ratranger

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The clymer manual has directions on how to degree the cam. You find TDC on the left cylinder, then with valve lash set at a number I can't remember rotate engine counter clockwise and the intake valve should open 110* before TDC. So it can be checked without disassembly. Look up the directions as I'm going off memory and probably have something wrong.
 

lidirtrider

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The clymer manual has directions on how to degree the cam. You find TDC on the left cylinder, then with valve lash set at a number I can't remember rotate engine counter clockwise and the intake valve should open 110* before TDC. So it can be checked without disassembly. Look up the directions as I'm going off memory and probably have something wrong.

I plan on doing all the visual and physical inspections I can before I pull the motor out. And yep, degree the cam is on the list. But thank you.

I really do mean it when I say that everyone here is helpful. Theres no way I could have learned what I have, and actually got this thing running without this place.
 

lidirtrider

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So based on those videos you can hear some popping n the exhaust. So far seems like cam install is correct, timing chain, and valve adjustment seems ok. Having a little issue with the PAMCO, like I ran out of adjustment. plate is retarded as far as it can go, and still doesn't seem quite right. Could also be some carb issues too. Had them redone by Rick at Oldskool, but still possible they could be plugged up somewhere, or not setup properly.. Next step is to check for air leaks in all the usual spots. Somewhere on here I read about the exhaust not being sealed all the way at the flange. Running the Pandemonium Yo Mama's and have tried tightening the nuts down but seems like the flange is starting to bend a little and I'm also afraid of stripping the exhaust stud or just tearing it out of the head.

The last time I tried to running the bike it was erratic at best, and was popping very loudly, like GUNSHOT loud, with a flash of blue/orange flame, out of the exhaust, while it was idling. I could also see occasional puffs of vapor from the carbs. I stared playing with the sync while it was idling, then it went of like canon and died. Was able to get it started and idling again, but still backfiring/popping, and puffing out carbs.

Also, since I'm pretty sure the advance unit was from MikesXS, I decided to spring for NOS one I found. Hugh has mentioned that those Mikes units can cause some issues with how it fits/lines up, and that the springs on them are somewhat weak. So better to help eliminate all potential problems.

Next day off I plan on :

- Double, NO, TRIPLE CHECK TDC and marks on PMA rotor.
- Adjust Cam Chain
- Valve Adjustment
- Remove Carbs - Bench Sync, Inspect/Clean all orifices, Check float heights, verify correct (factory) jets and settings
- Check/Adjust Ignition timing at Idle with Timing light

Any other thoughts/recommendations? or a different order to do things?

Hopefully the new advance unit gets here before the weekend.
 
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TwoManyXS1Bs

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...The last time I tried to running the bike it was erratic at best, and was popping very loudly, like GUNSHOT loud, with a flash of blue/orange flame, out of the exhaust, while it was idling. I could also see occasional puffs of vapor from the carbs. I stared playing with the sync while it was idling, then it went of like canon and died. Was able to get it started and idling again, but still backfiring/popping, and puffing out carbs...

With a "wasted spark" ignition, diagnostics can be tricky. Sounds like the unburned mixture is being ignited on that side, during the overlap stage, when both valves are slightly open. With traditional dual ignitions, it'd be easier to diagnose that side.

Maybe swap plug wires?

Another member here had a mysterious non-symetrical ignition, timing on one side was several degrees different from the other. Fixed with a replacement ignition rotor. There were a couple of reports of rotors with a magnet put in backwards, wrong polarity.

Could try,
Pull left plug, leave plugwire connected, plug grounded,
Start engine on right cylinder.
Adjust idle up so it stays running.

Then, reverse,
Put left plug back in,
Remove right plug, plugwire connected, plug grounded,
Try to start engine on left cylinder.

Report the results...
 
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lidirtrider

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With a "wasted spark" ignition, diagnostics can be tricky. Sounds like the unburned mixture is being ignited on that side, during the overlap stage, when both valves are slightly open. With traditional dual ignitions, it'd be easier to diagnose that side.

Maybe swap plug wires?

Another member here had a mysterious non-symetrical ignition, timing on one side was several degrees different from the other. Fixed with a replacement ignition rotor. There were a couple of reports of rotors with a magnet put in backwards, wrong polarity.

Could try,
Pull left plug, leave plugwire connected, plug grounded,
Start engine on right cylinder.
Adjust idle up so it stays running.

Then, reverse,
Put left plug back in,
Remove right plug, plugwire connected, plug grounded,
Try to start engine on left cylinder.

Report the results...


yeah I thought about that, the "dead cylinder" method. and just swapping the wires on the plugs. Kinda bummed cause I know Pete isnt around much anymore, and this unit is several years old even though it really got installed recently. Through all the digging around on here it seems that a few folks with PAMCOs for rephased engines have had similar issues, and a few folks had to either trim the PAMCO plate or remachine the rotor to achieve the proper timing. I'm not saying MY PAMCO is not correct, or that Pete is at fault, but mistakes do happen. It's just one more variable is all. And another variable could be wheter or not it's genuine PAMCO or one of the Mikes knock offs. I honestly cant remeber how/where/when I ordered. I have a vague memory of getting from Mikes tho.
 
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