Timing question ...

[TADracer]

Vacuum advance should be connected up when setting the ignition timing. It should be unconnected and #2 carb nipple plugged when checking the centrigugal advance timing.

Your cams do not look way out to me. The small dots on the cams will not necessarily line up perfectly with the cam cap arrows. If you are off by one cam tooth then your CAM will be out 11.25 degrees (23 degrees at the crank) which will be quite noticeable (and probably quite expensive).

If you are at true TDC in the picture (and I suspect you are not)then either your timing wheel is way off or your pointer is way bent or both. The stock timing wheel is not very accurate even when factory new. If you back off the center bolt and then just snug it back up then I bet you can move your wheel +/-5 degrees back and forth.

You need to confirm true TDC and the best way to do this is using a piston stop and a degree wheel. I gathered these items a long time ago when I installed slotted cam sprockets so I could tinker with cam timing. After seeing how much slop there is in the timing wheel I do not even rely on it anymore. It only takes ten minutes to pull the plugs, set up the degree wheel and find TDC so I even use it when I check my ignition timing.

If you are this unsure where your TDC is then I really suggest you invest in a degree wheel and piston stop. MotionPro makes a nice one and you can make your own piston stop and probably obtain both for under $30.00.

[thewiz]

A new day dawns ...

here in SoCal and just as soon as I get a bite to eat, I'm goin' out there to check a few more things. First of all thx to all the replys ...

Miti ... all timing components in good working condition

DenyP ... When Alanb suggested to pinch the vac advance, I did re-read all of the books, and it was as you said, none stated to disconnect it until checking the mechanical advance.

Tad ... I'm glad you weighed in too. And I have a couple more questions for you I had seen postings of yours relating to changing cam timing so I believe you're pretty tuned in to crank/cam timing issues. If both cams were advanced or retarded by a tooth, would the motor still run or are saying it would self destruct? My motor runs pretty good but peters out around 5500 rpm ... see my initial post. AND ... when you degreed the crank with the wheel, you had to turn the engine backwards and to find TDC, right? Is that OK? I could use a cruder method since we're dealin' with 11.5 cam degrees per tooth. That's about what it looks like I'm off .....

[thewiz]

guess I'm pisstoning ...

up a rope on this one. Just stuck a punch down #1 hole and felt the piston rise to what felt like its full height. Realizing that this isn't as accurate as a degree wheel or dial indicator but close, I then re-checked the cam dots. They were only a fraction off .... not anywhere near 11.5 degrees or one tooth. That very small difference between the hash marks and the dots is likely attributable to normal chain slack. Soooo .... bottom line is: seems that the cams and crank are in harmony I guess I'm glad ... didn't really feel like tearin' things apart anyway.

However to get the 'T' mark on the wheel and the pointer to align right, it does require the pointer to be slid most of the way toward the one side .... but I guess that's why they made it adjustable ... ??

[skids]

Re: guess I'm pisstoning ...

It seems like even with a brand new chain, the dots always line up like that...one right on and the other is off (in the direction to the right of that cam boss mark) by the width of a dot. If you try and adjust that intake cam more link to the left, you will find that it is way off.

[DiverRay]

I know I'm late, but I may have the question, or answer....
Check the TDC once again. If the pointer is off, you need to look at he advance system, ALL of it. Take everything off the left side of the engine, FLIP the pickup coil system 180 degrees, and reinstall it. You should then be able to line up all the pointers, but ONLY if someone didn't to a mix and match on the advance parts.....
Just a thought from someone with PMS...

[TADracer]

Re: A new day dawns ...

Originally posted by thewiz
here in SoCal and just as soon as I get a bite to eat, I'm goin' out there to check a few more things. First of all thx to all the replys ...

Miti ... all timing components in good working condition

DenyP ... When Alanb suggested to pinch the vac advance, I did re-read all of the books, and it was as you said, none stated to disconnect it until checking the mechanical advance.

Tad ... I'm glad you weighed in too. And I have a couple more questions for you I had seen postings of yours relating to changing cam timing so I believe you're pretty tuned in to crank/cam timing issues. If both cams were advanced or retarded by a tooth, would the motor still run or are saying it would self destruct? My motor runs pretty good but peters out around 5500 rpm ... see my initial post. AND ... when you degreed the crank with the wheel, you had to turn the engine backwards and to find TDC, right? Is that OK? I could use a cruder method since we're dealin' with 11.5 cam degrees per tooth. That's about what it looks like I'm off .....

Ray has a very good point in that if the timing mech. is installed backward then the pointer and wheel could be off like in your pic. That is the first thing I would check out too.

I think your cams are right. I suspect that if your cams are off advanced by one tooth there probably would be a collision between the piston and the intake valve since it is opening early and the piston is still rising in the cylinder toward TDC. If the cams are retarded by a tooth then it would be a late exhaust valve being chased up by the piston rising. If the motor still runs at all then it would run extreemly poor and your piston/valve clearance would be dangerously close.

If you decide to find TDC with a degree wheel and a stop you can do it like this. Put your finger over the spark plug hole and rotate the crank until you feel pressure coming out from the piston rising to the top on the compression stroke. If you have trouble rotating the crank on the ignition side of the motor then you can drop the alternator and use the big bolt on that side. Install the wheel and a wire pointer close to where you think TDC is then place the stop against the top of the piston and record the degrees. Then you rotate the crank in either direction until the piston comes back up and stops against the piston stop and record the degree reading. Subtract the lower number from the higher number and divide by two. Then move the POINTER to the degree that represents the answer to your math question. Then to check, you rotate the motor the opposite way until it hits the stop again and the pointer should be on the same degree on the opposite side of TDC. If it is then just remove the piston stop and turn the CRANK to where the pointer is on the TDC mark on the degree wheel and you are exactly there.

But to set the factory pointer after doing all this (which I have never had to do) you would need to carefully remove the degree wheel without moving the crank at all and then reinstall your timing wheel and adjust your factory pointer to the T mark.

[trbig]

I don't have an XS so I don't know, but that allen bolt on the timing plate... on the XJ, that bolt sits much deeper in the hole. Does it look normal to you guys?

There was a posting a while back where the timing plate slipped. If you take off all the vacuum stuff, make sure and check that there is a pin installed on the crank still... shown here...




This is what keeps all that stuff aligned.


Tod

[planedick]

I took off the cam cover on the Pathfinder once and noticed that the exhaust cam was just about 1/2 tooth late and decided to try to adjust it. After doing that I fount that the exhaust was now just a little early and it ran like you describe. I struggled with it trying everything and it would not run right. I had to go back in there and change it back. I never would have guessed it would make that much differance.

[thewiz]

Thanks ...

Skids, Tod, Mike, Dick and Ray ... Whew!!. Some really good stuff here. And I'm gonna' check it all out while I'm waitin for coils to get here.

Ray, I can't wait to check that one out too!! ... it is more likely that it's NOT the original timing stuff and very well could be flipped around b'kr'ds ... ooops, that coulda' been me that did that a year and a half ago I've been thrashing on this bike for nigh on to a year and a half and it still ain't right. I'm glad my others haven't been so un-cooperative. .... a definate mix and match on the timing guts though. I can look through the parts fiches, but are there differences that come to mind in the pre-81 stuff?

Will be tomorrow till I can get on it to check out all that stuff .... trying to coax Planedick to come over with his 'bag-o-shims' so I can adjust a couple of valve clearances in the interim too.

Draggin' my a$$ on getting wire .... found a 30' spool of Taylor solid core high tension lead at Summit Racing .... anyone interested in splitting it? Might even make three sets ??... dunno yet.

[egsols]

Hey planedick,

excuse my ignorance since I don't have much experience with cam timing but how do adjust for a 1/2 tooth? Was that causing your bike not to rev past 5500?

[TADracer]

Half a tooth

Dont want to jump over planedick but about the only way you can be half a tooth off is with slotted sprockets like this

[planedick]

Just jump

I don't know what you're trying to do besides call me a liar. I don't have the valve cover off so I can take pics now, but Pathfinder doesn't have slotted sprockets and the exhaust cam is just a half tooth late and no way to change it. I tried moving it as I thought it was a tooth late and after I did it was a half tooth ahead and it didn't run above 5000 rpm worth a s**t. It runs great late anyway. About the only way is an extreme stretched chain, which is not the case here.

[trbig]

Having had the cams out many many times, with many different motors, I know what you are talking about being half a tooth off. None of the cams I have run have been slotted either. The only thing I can think of the cause, is the chain stretching over time. I don't think it has to be a BADLY stretched chain as the adjuster has never been close to the limits when I have seen it. It may be a combination of wear on the cam and crank sprockets also.

If you try to adjust the half link off and move the cam sprocket a tooth on the chain, you go a half tooth off the other way as Planedick stated. Without a slotted cam, you can't adjust a half link... it's either a bit too far one way or the other, and you put it where it runs best.

I have seen many times where the dots don't quite line up for whatever the cause, and I have seen where they line up perfectly. So... I am going to have to disagree with Tadracer's statements in saying only slotted cams could cause this. I just wish I could definitively say what WAS the cause...

Tod

[egsols]

Wiz, planedick,

Is the 5000 limit in every gear or just the top ones?

trbig,

that's what I was wondering..... the cause.....only thing I could think of too would be the wear on the chain and sprokets, or if a sproket was slightly loose at one time and actually elongated the mounting hole.

[trbig]

I know in my case that none of the cam sprocket holes were elongated, but everything wears. Sprocket teeth, chain links where the sprockets are contacting them, and chains stretch. Having slotted cam sprockets may not be a bad idea if for any other reason than just to be able to keep it EXACTLY in time or slightly advanced.

I wishe someone were set up to where they could slot them economically to a maximum of 5 degrees in both directions, but I have noticed that over time, the cams only tend to retard, so being able to advance them a bit when needed when doing a shim check would be nice.


Tod