timing a viper

I checked out your link and I have no problem with the piston stop method of finding TDC, but you cant figure the 5 degrees of advance anywhere near correctly with a cloth tape. You see when you have a degree wheel on the crank end and a dial indicator on the piston top, you can corelate the differance of movement of .001- whatever" to a degree of crankshaft movement,you cant hardly read anywhere near that fine on a tape, you could do it using a protractor method, but would need to convert mm to inchs and then only again be so close, the human eye/error isnt that good! The differance between 3,to4,to 5 or whatever is only in .XXX" thousandths of an inch.
By moving the piston lets say .003"-.005" you may have changed the timing by as much as a few degrees.

A better way for the backyard mecahnic without getting into tools youll never use again is to use a timing light with a advance dial on it, simply use your piston stop and make your 2 marks on your flywheel , once spinning the engine over left hand till stop, then rotating it to thr right till stops, you are then going to divide the distance by 2 and make your tdc mark, fire it up and turn the dial on light till your mark comes back to the zero in center, theres your advance at idle! the method that you had the link to is to most commonly used to check to see if the ring on the harmonic balancer has spun on the hub, by finding the tdc you can then see if the balancer mark lines up with the timing cover tab, and we unfortuantely dont have a timing mark on the flywheel of these engines! your not seeing one because there isnt one on the newer systems!
 
upper dash area of the harness has not been inspected yet, I'll look at that next...

they were the 1/4 second flashes (i think) and I think there were the 7
which is what led me into the whole PV/ CDI thing


what would really piss me off is if I can't tell the difference between a 1/2 and a quarter second flash and there were 8 not 7 and the damn thing has just been trying to tell me all along it had a bad fuel gauge (which I just fixed, had a dead spot) although I don't remember the fuel light blinking along with the warning light (fogged LCD makes reading such things difficult) #$%&*

Dead spot in the pickup would also explain the pull though and it only happening under acceleration conditions (fuel slosh pulling it to the dead spot)

Guess I'll inspect dash wiring it put it back together and run it on the lake and see what happens now
 
ok, hey let me know would like to see ya whip this problem!! pm me when ya get the info.
 
same here, been following along would like to hear about the resolution. great stuff mrviper (as usual). dont let it beat you up erik, you'll get it.
 
Using a MAC TL 200 advance timing light (borrowed from a buddy) indicates that I've either got 7.5 or 15 degrees advance depending on which set of numbers on the dial applies. Both are wrong for base timing on a Viper.

Research is being done as I type as to which set of numbers applies in this case. More Later
 
And.....
Intermitently under load it still throws a 7 flash code.
Although now it's even more intermitent than before.

What we know.

The base timing is off. (Yamaha either has sloppy tolerances or something is up with the box)

It throws a YPVS code sometimes under load. ( There is something up with the wiring or the box is going bad, it didn't do this before the rebuild so I suspect the box is the problem)

I need to go throught he harness with a very fine comb. (eliminating the wiring is free)

Gosh this is fun.
 
what cylinder are you basing the timing off of??

Again, there is no flashing sequence for ign timing from the diagnostic system, and a couple degrees is nothing you could ever tell or feel. It wouldnt show up in the engine running as low power, unless it was massive amount. You are still chasing your tail with this timing thing, its not the problem. Like your dealer told you theres no test for the cdi box, they usually either work or they dont. I have found the problem with the 98-99 srx having a weak signal output for the servo, but the sled will run absolutely perfect until the 7000 ish rpm point then just nose over and not gain rpm and become very flat. Only 1 newer srx to have this go bad, but theres no guarantee on electrical items, so I would venture to guess if you cant find a wiring chaff on the harness you need to replace the cdi box.

the 7 flash is the servo code as you know, and if the servo works then you can eliminate that, still back to the chaffed wiring going to it or the signal from the cdi box.

if ya cant find a chaffed wire your gonna have to belly up for a used box.
 
mrviper700 said:
what cylinder are you basing the timing off of??

Again, there is no flashing sequence for ign timing from the diagnostic system, and a couple degrees is nothing you could ever tell or feel. It wouldnt show up in the engine running as low power, unless it was massive amount. You are still chasing your tail with this timing thing, its not the problem. Like your dealer told you theres no test for the cdi box, they usually either work or they dont. I have found the problem with the 98-99 srx having a weak signal output for the servo, but the sled will run absolutely perfect until the 7000 ish rpm point then just nose over and not gain rpm and become very flat. Only 1 newer srx to have this go bad, but theres no guarantee on electrical items, so I would venture to guess if you cant find a wiring chaff on the harness you need to replace the cdi box.

the 7 flash is the servo code as you know, and if the servo works then you can eliminate that, still back to the chaffed wiring going to it or the signal from the cdi box.

if ya cant find a chaffed wire your gonna have to belly up for a used box.
Click to expand...



I'm not doing anything more with the timing just making an observation that the base timing is wrong which would probably be the box since I imagine Yamahas tolerances are better than that.
 
And teh winna is.....
The electrical problem was not electrical. We now know that tight powervalves can cause a YPVS code to flash. I would have sworn on my life that I had adjusted them, apparently I did with the motor in a different spot than it should be.

Base timing is still wrong though. I may or may not pursue fixing it.

Thanks for all the input and good suggestions.
 
You must log in or register to reply here.


Back
Top