Sorry for the confusion. Lou, I wasn't only following your advice I just started doing engine diagnostics with your suggestion first (checking the timing). About the timing, I was simply following the manuals instructions on checking the timing (not changing it) dynamically using a stroboscobe. Basically you "plug" in the stroboscope to a spark plug wire and when the spark plug fires the stroboscope flashes. Using the timing marks on the alternator (same ones used for adjusting the valves) the stroboscope will flash when the marks (either the LF or apparently the RF) pass by. On the stroboscope I bought you can turn a knob to adjust when the flash will flash (advanced timing) and by turning that knob until the marks line up (either LF or RF) I can tell how many degrees off the timing is. Now that I concluded that my timing is off I am asking you guys how I can diagnose which system is failing like is there any way to test the TCI Box (maybe by checking resistance)?
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OneRider, which light light did you get? I am 1/2 interested in getting one, (perhaps by next spring I will be fullly interested 
No problem, I was joking about not taking ALL the advice ALL at once.
Believe me, it would be a while before I'd be pouring old oil through a paper towel looking for pieces of the inside of the engine. LOL. But I would eventually get to that if all else failed.
I don't know how to adjust the timing or where it should be adjusted to. I have to assume the repair manual will outline that in detail.
I guess it is best to first assume that the timing is simply mal-adjusted - rather than to first assume that the chain has jumped a tooth. If the latter, then taking part of the engine off to get at it is in your future.
Also, there is a counterbalance shaft in the dohc. Is it possible for the chain, (or whatever) that drives it, to jump a cog resulting in a balance shaft which creates a new vibration instead of dampening the the regular ones?
@arfstrom here is the one I got seems to be a nice one for a pretty good price. Nice bright light with the advanced timing control I have no real qualms about it. http://www.harborfreight.com/timing-light-with-advance-40963.html
@lou ranger yeh i'm with you on the that. Paper towel sifting = last resort
As for the counter-balance does the SOHC have one? the 1980 xs400g model that I have does not have adjustable timing, i'm trying to find the broken part. I started at the ignition coils and they ohm-ed out within spec. Now I want to test the TCI module unfortunately I don't really know how to go about that. I am assuming I have to check its resistance but i cant find any specs for that in the manual.
@lou ranger yeh i'm with you on the that. Paper towel sifting = last resort
As for the counter-balance does the SOHC have one? the 1980 xs400g model that I have does not have adjustable timing, i'm trying to find the broken part. I started at the ignition coils and they ohm-ed out within spec. Now I want to test the TCI module unfortunately I don't really know how to go about that. I am assuming I have to check its resistance but i cant find any specs for that in the manual.
Re: the TCI, Dave is the only one I know of who figured that thing out. Maybe he will chime in.
As to whether there's a balance shaft on the sohc - I don't know, wasn't able to find an engine cross-section.
Re: the timing - the manual says if its out, the only cause would be a loose rotor bolt:
Attachments
Interesting info (I will take a better look at it) but it seems that I forgot to mention that at 1200RPM it is lined up with the LF mark its when I rev it between 2K-3K that its off, for the manual says it should have a 36-40 degree advance but it needs 53 degrees saying that the timing is off by about 13 degrees. This makes the engine spark later then it should which I hope to be the source of my vibration, if that makes sense.
Leave it to the japanese to make things easier by making it more cryptic,
"Loose Spark Unit Rotor bolt"
Ya One, I think we are with you, You have me hooked cause I am looking for my lack of fuel economy, and this is one of the thoughts I had. Keep us ontop of this. There have been ebay specific shop manuals for our bikes, I have been almost ready to pop for. One expired today, right after church, I was half watching it.
Good luck
"Loose Spark Unit Rotor bolt"
Ya One, I think we are with you, You have me hooked cause I am looking for my lack of fuel economy, and this is one of the thoughts I had. Keep us ontop of this. There have been ebay specific shop manuals for our bikes, I have been almost ready to pop for. One expired today, right after church, I was half watching it.
Good luck
Is the pick up coil connected to the spark unit rotor bolt?
If not, why spend time there when, according to the engineers who made it, the only possible explanation is the rotor bolt?
Certainly, if a bolt were loose instead of tight, it could allow a 36 degree advance to wobble up to 53 degrees.
If not, why spend time there when, according to the engineers who made it, the only possible explanation is the rotor bolt?
Certainly, if a bolt were loose instead of tight, it could allow a 36 degree advance to wobble up to 53 degrees.
If I'm understanding what you've written, your HF timing light says your timing is on the mark at idle and 53 degrees advanced at 3000 RPM (spec is 36-40). Have you verified that the TCI module you have is the correct one? There are a number of other bikes that used similar modules with different advance curves. The PO could have replaced it with one from a different Yamaha or even a Honda to get it running...
Check the model number? For example, TID12-07 is the European/Canadian module for DOHC engines. As best as i can tell, the 12 is the module code, and the -07 is the version. 
The US spec module for the same engine is a TID12-08 and its advance curve is wimpy.
The only Yamaha module that I know of that even comes close to the advance you are reporting is the TID14-35 from a mid '80's XJ700X, and I don't know if it has the right connector on it...
The US spec module for the same engine is a TID12-08 and its advance curve is wimpy.The only Yamaha module that I know of that even comes close to the advance you are reporting is the TID14-35 from a mid '80's XJ700X, and I don't know if it has the right connector on it...
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@Lou, That is the bottom most line of your gif image, I just find it really cryptic. I have pulled the case apart, but never did anything with the Head, pistons to crankshaft. So Bow to your knowledge, 
@onerider - it could be, I just don't know. But if it's a question for me I figured it might be for you and hoped if someone has the answer they will chime in.
@Dave - how on earth do you know all this stuff?
@Tobie - do I have a gif image - what is it? .. If you mean then yes, that pretty much sums up my knowledge - mostly second-hand.
The first hand knowledge which I have (like where to get an oil filter cover welded or how to fix a nubbin) mostly come as a result of self-inflicted maintenance opportunities which I create for myself.
@Dave - how on earth do you know all this stuff?
@Tobie - do I have a gif image - what is it? .. If you mean
then yes, that pretty much sums up my knowledge - mostly second-hand.The first hand knowledge which I have (like where to get an oil filter cover welded or how to fix a nubbin) mostly come as a result of self-inflicted maintenance opportunities which I create for myself.
@Arfstrom - "Loose Spark Unit Rotor bolt" makes perfect sense if you think about it. The "Spark Unit" is the ignition pickup sensors, and they use a rotor to trigger the sensors. The rotor is mounted with a bolt, which would have to be loose to cause changes to the ignition timing - assuming no other problems or changes... I've noticed a marked improvement in fuel economy and performance since I replaced my failing TCI module. I wish I'd spent less time with jetting changes and more on troubleshooting the ignition. Having spark doesn't prove the TCI is good, just that it hasn't completely failed...
@Lou - WAY too much time spent reading the service manual and searching online...
@Lou - WAY too much time spent reading the service manual and searching online...
Yes, true, but isn't that what old guys are allowed to use rainy days for?
PS - - how on earth do you know all this stuff?
Rainy days, early mornings, late nights, lunch breaks... I don't memorize it, I read it and remember that I've read it. I record valuable info in Evernote or download files to my computer. Finding the exact info doesn't take long when one knows what they are looking for.
@VGTIDave I will check my tci module today but I think I'm just gonna buy one and return it if it doesn't help. I see a nice one one ebay for a 1981 but I have a 1980. Their ID #s are 12-02 (1980) and 12-02C (1981). Whats the deal with the "C"?
Quick little update: I decided that I would just recheck all the ignition system components just to be extra sure. I started off by checking the ignition coils. The ignition coils' resistance came up well within spec so I went on to check the pickup coil. I first checked the pickup coils resistance and that was well within spec so I took off the cover and checked for the Loose Spark Unit Rotor bolt but it was tight. Just to be safe though I unscrewed it then torqued it back to spec. I then as VGTIDave instructed checked my TCI module and after a bit of research found that it is indeed the right one for my bike and year (12-02). In conclusion I am just going to get a new TCI module and see if that fixes all my problems. Which brings me back to my previous question can I use a 1981 TCI box with the 1980 model?
I just did a quick search and it appears that TID12-02 will work on 1980 - 1982 models.
I have to wonder if there is another member in your area who would be willing to let you try their module to see if it cures your vibration and timing problems? Before you go spending $100+...
I have to wonder if there is another member in your area who would be willing to let you try their module to see if it cures your vibration and timing problems? Before you go spending $100+...
