Intake Cam Timing question

Just found this site a few days ago. There is alot of good info on here.

Heres the deal:
I have a 1980 xj650 maxim with pod filters and open exhaust. Runs great with plenty of power, but hard to start in the morning. Carbs have been cleaned, and recleaned, and I am gonna clean them again tonight.

When I set the timing, the exhaust valve lines up dead on at TDC, but the Intake Cam is right in between teeth on the sprocket. It is either just barely advanced, or just barely delayed. I have run the bike for 2500 miles with it delayed, and took the valve cover off last night while adjusting the cam chain tension, and thought about switching it to a little advanced to see what happens. Dead on would be in between teeth.

Any thoughts? Should I buy a new chain to help everything line up better? I would rather not have to deal with swapping out the chain, I can change the sprocket tooth by tooth, with the tensioner out, without taking the chain off.

Another Idea: Is it possible that if I take bolts out of the sprocket on the cam, and turn it 180 degrees that it would line up property? This wouldn't effect lining up the timing because the mark is on the shaft itself. I have not taken the sproket off before.

thanks in advance for any replys

 

Hmm I understood the timing was not adjustable so I'll let others more knowledgeable weigh in on that part.

Hard starting is almost always the enrichment jets. See this post to get them really clean...

http://www.xjbikes.com/Forums/viewtopic/t=8918.html

 

Cam timing is adjustable.... I bought the bike with the head off, the guy I bought if from broke a plug off, and took the head off to get it out. I guess he couldn't put it back together because I got the bike for $100 (It looked like a $100 bike too. Looks great now. About to upload some pictures in the Photo Gallery.

 

I'd be interested to know this too ....

 

Ok so now I see - You are rotating the cam itself. I should have read more carefully

The haynes manual says line up the timing dot then rotate the sprocket so the mounting holes line up. So it is possible you are correct about the sprocket alignment.

 

Thanks Bill, I'll give that a shot...

If it doesn't line up perfect what will be the effects of being a little advanced or a little delayed?

 

That I don't know. There are folks with more experience in this area - hopefully they will weigh in...

 

Hey Bill,
I just noticed you are from Raleigh,
I work in Wake Forest, and live in Wendell. Small world.

 

Cool check out the Raleigh riders post in the Eastern US section by MLEW. There are 3 or 4 of us that have started getting together for rides, lunch, help in fixing the bikes etc. We are always looking for new "gang" members....

Between us we have a lot of the tools. I have the YICS blocker (I don't think yours is YICS) and I have a colortune. I also have the tools to poke all the ports and jets including the TINY enrichment jet. We post rides and get togethers in the forum. If you need help just holler!

 

hard starter in the morn eh?
how are your mixtures?
usually a bit more richness makes it easier to start.
and with pods and and open exhaust i might assume ur runnin lean.

any thoughts turkey?

 

Honestly it doesn't seem to be running lean. I walk out in the morning, pull the choke, and it fires right up. Runs for 5 seconds, shuts off, and won't start again without starting fluid. First thought was not getting enough fuel from petock. Rebuilt petcock, no change. I can turn it to prime before I start it the first time, walk away for 20 minutes, come back and try it, and it does the same thing. One very small sqirt of either on each pod filter, and it fires right up, and runs like a champ for the rest of the day. I come out from work in the afternoon, pull the choke, and it fires right up with no problem. But let it sit over about 10 hours, and you can hang it up.

The reason I don't think the enrichment circut is stopped up is because I can tell an obvious diffrence between when it is pulled, and when it isn't.

That's why I am wondering if I get the timing set dead on, or better, if I will have this problem.

 

I'm wondering about the effects of slightly advanced timing as well, one of the things on the 'to-do-list' is a full custom exhaust and pods, then lots of tuning before i start cutting the frame up and doing my major mods.

 

The "Timing" of the Ignition on our XJ-Bikes is not a Mechanical Adjustment like you would have if there were a Distributer to rotate for an advanced or retarded spark.

The timing is done "Electro-magnetically" buy Pulse Width of an Interrupted Magnetic Field which sends the Magnetic Signal to the Igniter Box.
As the DURATION of the Pulse Width created by the face of the Crankshaft mounted Ignition Rotor, passing-over the Ignition Pick-up's, is lessened by increased RPM's ... the FREQUENCY of the Pulse Width INCREASES.

Integrated Circuitry, programmed to respond to the changes in the Pulse Width and Frequency ... alter the Ignition Timing in response to the changes in the Signal Strength and Frequency ... to Advance or Retard the Spark dependent on the information from the Magnetic Ignition Pick-up's.

Both the Pick-ups and the Rotor are mounted in a manner which does not allow for adjustments.
The Timing's Advance is Factory Preset to be within a Profile stamped on the Ignition Rotor.
The Profile stamped on the Rotor is considered to be the maximum amount of advance that the Engine can safely handle.

 

Thanks rick but I don't think you read the whole post. I am talking about lining up the intake camshaft timing marks.

 

yeah turkey i think he was answering me mostly there. =) From what I understand, the timing gears should unscrew from the cams to allow you to adjust it, then screw back down to rotate properly.

 

if you take the sprockets off the cams and change their position relative to where the holes line up you get a slight change. I found no science to it when I did it just kept trying different positions until it was dead on

 

Sounds good. I didn't really think about moving the sprockets until this morning when I got to work. My repair manual sucks and didn't say very much about this. It just says "line up the marks".... well no @#$!

 

Update:
Heres the deal. Intake cam shaft still does not line up direcly with the mark. I can take the sprocket off, readjust it, put it back on, still off. It lines up direcly in between links of the chain. I figure maybe my timing chain is stretched, but the exhaust cam lines up perfectly. I moved the intake cam from being a little bit delayed, to a little bit advanced, (and since I had the carbs off, I cleaned the enrichment circuts again). Now the Bike starts perfectly when it is cold. So I stand corrected, my carbs weren't as clean as I thought.

Back to the cam issue: By moving the cam sproket a link and making the intake cam a little advanced, I gained some low end power, but lost some power on top end. I also have alot more engine noise from the intake, but the bike runs great. I am gonna switch it back the way it was over the winter, may even try a new cam chain to see if that helps it line up dead on like it should be. Bike only has 14,000 miles, so i wouldn't think it would be streached by now, but who knows.

 

Maybe adjust (release) the tensioner? It would increase the 'play' in the chain, right?

 

The result of adjustment sounds exactly like what I'd expect. Porsche actually uses a variable tensioner between the sprockets to automate the adjustment you're doing: advance intake cam at lower RPM's and retard it at higher RPM's and get the best of both worlds.

 

The Timing Marks should line-up perfectly.
If they don't, you take the Chain off the Sprockets.
Put the Sprockets on the Cams and do a Chain Pull and Drop with all the Indicators precisely positioned.
There's no "Cheat" this way or that. That process is incorrect.

You should dismount and reset the Cam Chain Tensioner in order to for the Timing Process to be achieved without error.
The Crank and the Cam Timing Marks need to be Perfectly aligned.
The Slack in the Chain Removed.
The Engine put through two complete cycles -- (4 Revolutions)
The Marks lined-up for a Check after movement.
Marks are lined-up?
Yes.
Timing is correct.
Not lined-up?
Repeat the timing process until they are.

There's no "Off by a tooth or two"
There's ONLY ONE Standard in the Engine Timing.
All Timing Marks aligned "Dead-On" Indicators.

 

Rick is right. Anything else is a bent valve or worse. Double check your assembly you may have flipped a sprocket over?

 

I realize that this is a very old posting but I've run in to the exact same situation. No matter how many times I try it the marks will not line up. So what is the solution. Replace the chain? Try new sprockets? What.

 

The timing marks will be slightly off when you install the sprocket bolts. You will need to follow the manual and use a crescent wrench on the nut looking part of the cams to make the marks line up. Hope this helps.

 

Slot the cam sprockets and use a degree wheel to degree the cam's.

 

If the marks don't line up you've done something wrong. Replacing the chain and/or fitting new sprockets will give the same result if you refit them incorrectly as well. You need to follow RickCoMatic's instructions to the letter (above). Try again with one sprocket rotated 180 degrees if that's not right rotate the other. If that doesn't work try flipping each sprocket as bigfitz says (above). Try all permutations and eventually you'll get it right.



^^^
This is a photo showing my cams aligned correctly.

 

you can only adjust it by jumping it by one tooth either way. even if the marks aren't exact, the next tooth will make it very wrong.
i kind of remember checking the sprockets and they were symmetrical so flipping them over wouldn't make any difference.
make your final check with the guides and tensioner in place.
Thrasher, i thought about that but don't think it would work. i'd have to see a adjustable setup.

 

Does the TCI have a crank angle sensor ?

 

No, but the NSA knows the angle of everyones crank.......ho ho ha ha

 

This is the key. There is an actual sequence you need to follow that will produce the correct results. This is covered beginning on page 108 in the Haynes and in the factory book it is "Step 13" in the Engine Reassembly section; in my factory 650 book it begins on page 65.