Timing or something else....so lost

ok so i had to replace the head on my 82 xj650 maxim. my father in law says it doesnt sond like its firing. i checked the plugs and there is spark. im thinking the timing might be off so i checked cylinder 1 at TDC the mark on the reluctor was right on the T. so does that mean timing is good? thanks in advance this is driving me crazy

 

Might need a little more info

The bike isn't starting? If you had the head off, that would have been the perfect opportunity to make sure your valve clearances are in spec.

The timing is right. There's not much room for error on the XJ timing. It's either right on or way off. And if you're at TDC and the timing mark on the pickup coil is lined up, then you should be good.

What happened to the previous head? Maybe there is another issue that is contributing to this one.

Put in new spark plugs. After trying to start it, are they wet?

 

yea bike is not starting. i had to replace it with a used head because the carb boot screws were rusted beyond reason when i got it so the snapped off and i couldnt get them backed out. ill try the new plugs and no their not wet. could the valves be in a different position from the original head and this cause the issue?

 

Bad cam timing is a very dangerous thing, as I'm pretty sure these are interference engines. You should carefully recheck the cam alignment procedures in the manual to make sure you installed them properly timed.

However, why not back up a step (or 10), and tell us the history of this bike... when you got it, how you got to this point, whether it was ever running since you've owned it, etc.

 

They are interference engines; and just because a cylinder is on TDC when the crankshaft pointer is at TDC doesn't mean that you have the cams timed correctly.

If they're "out" in the wrong direction(s) you could very well bend some valves trying to start it (if you haven't already.)

STOP. Double-check the CAM timing. Once you're 100% sure of that, then check your valve clearances and do a compression test.

 

ok well i got the bike about a month ago and it ran but it wouldnt idol with or wothout the choke, cold or hot itd die out. one morning i went out to start it and the throttle was very slow to respond and it wouldnt stay running. then it gave a backfire and the crankcase filled with gas.i quick drained the oil and took off the carbs to clean em/rebuild em. one of the bolts that hold the carb boot on was broken half in the head so i soaked it in some penetrating oil and couldnt get it out. tried drilling it out and nothing, there went the head. so i got one off ebay and here i am..lost. i have the haynes manual for the bike but all i can find on timing is TDC for the pistons.

 

not the haynes manual the yamaha workshop man

 

I have the yamaha manual on PDF. PM me with your email and Ill send it to you

 

I don't think not having the manual is the issue. I think the issue is that he's not finding the section on how to install the cams so that they're timed properly to each other and to the crank.

 

ok i found it in there and got it set like it says..once the battery is charged cross your fingers

 

Don't try to start it yet. Check the valve clearances and do a compression test FIRST, let's be sure you haven't bent a valve already.

Once the valves are in spec, if it makes decent compression numbers, THEN try to fire it. No sense taking a chance on ruining the motor.

 

Fitz knows what he's talking about bro, if it was my bike that is I would do.
If there is a problem find it now before it gets worse, a little while longer is better than not at all

 

They are Interference Engines.
Part of the Timing Check is to Jog the Mill over by hand through 2 Complete Cycles and check >>> ALL -- 3 <<< TIMING Indicators.

With the Crank at TOP Dead, ...
BOTH (Arrows, Dots or Bullseye Detents) MUST be Perfectly Lined-up with the Timing Markers for the Camshafts.

First you deal with putting N0.-1 at TDC, ...
Then, ... you follow TIMING Procedure to the Letter.


If, ... after you Install the Cams and Manually Turn the Crank through 2 Complete Cycles -- (4 revolutions ) without binding, ...you L@@K at the Marks.
If they are NOT >>> Perfectly aligned!!!

Start from scratch.

 

Awesome info! Well everything is lined up and clearances are good. I charged up the batt and tried to fire it this morning and it wanted to fire with starter fluid and gave a few pops but that was it. I swapped spark plugs and still nothing..

 

AND THE RESULTS OF THE COMPRESSION TEST WERE:

 

I have no idea my father in law did it since he knows how to do that

 

If you're cams were out of time, you may well have bent one or more valves. I bought my GPz with bent intake valve (probably from over-revving); all four were bent, but #3 was bent much more than the others. The symptoms were: needed a bit of gas to start, wouldn't idle low (had to keep idle at like 1800 RPM), not much power, and would pop a lot, especially once warmed up.

A compression test is very easy to do: thread the gauge into the spark plug hole, remove the ignition fuse, crank for a few seconds with the throttle wide open. For a good, warm, engine at sea level, you should get 120PSI or more for each cylinder. The GPz was showing 30PSI. I'm at 6000 feet elevation. That will reduce the max PSI of a good reading... but not by that much.

I suppose the good news is that, since you still have the old head (I hope), if you have bent valves you could save money by reusing the valves from the old head - assuming they're OK.

One other thing I'll throw out there was that, when I had the valves out of the head, I chucked them up in a lathe and could easily see the bend by looking at the wobble of the seal edge when spinning them slowly. A drill would probably work about as well to see whether a removed valve is bent.