1973 TX650 Valve Clearances - WTF Should They Be? All sources inconsistent.

OakBehringer

OakBehringer

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Intake/Exhaust

MikesXS and 650Central: .006 / .012
Various posts on this form: .003 / .006
My Clymer: (don't remember, I think it lists the same for both, though!)
Other sites on the Internet: a myriad of different values

I just noticed these varying specs. Anyone have the correct answer with a reliable reason? I'm inclined to go with .006/.012 to be safe.
 
Those models aren't really clear. I'm assuming row two is supposed to be XS2-TX650... but then the next row should be TX650A (1974) - ???
 
Checked my Clymer, it actually does say .006" and .012"

Really, doesn't make much sense why they would be double for that year, though.
 
According to the Yamaha service data sheets I have, your model is listed as .003/.006". The only model listed as 6 and 12 is the 1st year, the original XS1. You can try the 6 and 12 but I'll bet it clatters like hell with those settings.
 
I've run it with 6 and 12 for the past year and a half, so the chatter wouldn't be anything new :)

It lists those figures (6/12) on 650central, MikesXS, and my clymer, not that the latter is known for it's reliability. But I have seen 3 and 6, as well. I just looked at the cmsnl parts fiches for the XS1, XSB, XS2, and TX650, the part numbers are the same for the head, cam, valves, sleeves, rockers, crank, pistons, and connecting rods, which is all that would really change, necesetating a clearance change for mechanical reasons. So it looks like they were changing the gap by year as a response to how they'd seen the motors responding to years of running. Something must have happened in '72 to make them double the gap :)

Anyway, the only potential adverse affect I can think of from tightening my valves to 3/6 would be the rockers running hotter b/c they're in contact with the hot valves longer. And since everyone with an XSB is doing fine, with the same parts, I should too. I should also get a slight, unnoticeable performance boost, as well as a quieter top end.

- Adam
 

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If you wanna wear a bald spot on the other side of your head from scratching, research fork oil amounts for the 34mm forks, lol.
 
Fork oil comment is so accurate I laughed.

Realise it's been 9 years, but I've been running my TX650A on the 3/6 without realising it wasn't right (According to the book), I'll see what I put it to most recently though. I think I always did 3/6 (.076/.015 in Metric), I'll try both and see how it goes. Only used my feeler gauges for this bike so I'll probably be obvious which ones I've been using.
 
In general....all engines,,,, .002" is too tight, especially on exhaust valves, over .006" is too sloppy. .004" to .006" should work with almost any engine.

I just love doing the valve adjustments on engines that use the 25mm shims. I have a secret source for those shims, $4 each. Whenever I go to get two or three of these shims I'm asked, almost begged, if I will take referrals to do the shops valve/shim adjustments. WTF, these guys went to school to learn their trade!!!!!

Scott
 
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Once I installed the VW elephant foot adjuster screws (which run quieter), I experimented with larger clearances. I found no performance increase or benefit, just more noise, even with those quieter adjuster screws. Yes, you can get the elephant foot screws to clatter if you go too big on the clearances. I can (and do) run slightly larger clearances than I could before with the stock adjuster screws. But like I said, just slightly bigger. I use 4 or 5 for my intakes, 6 or 7 for the exhausts. With the original screws, I had to use 3 on my intakes or they ticked like crazy, even though 4 was the factory spec for my '78 model. To me, the biggest benefit of slightly larger clearances is to let more oil in between the parts. I think the exhausts do fine already in that respect with .006" clearance. It's those .002" to .003" intakes I worry about.
 
This thread got me thinking about the 1978 I'm slowly working on.

Decided to pop off covers and see where the valves are right now.

Both intakes are about midway between 0.004 and 0.005 inches
Exhausts are, left side, midway between 0.005 and 0.006 inches
Right side right at 0.010 inch!

Have not decided on where I will be setting them.
 
It's become accepted practice to use 3 and 6 on all models. I wouldn't use 2 and 4, too tight for oiling purposes in my opinion. 4 would be better than 3 on the intakes, again for oiling purposes, but in my case it just ticked too much. Bottom line I think is use the biggest clearance you can without inducing excess noise. That value will probably vary from bike to bike depending on the condition of the valve stem tops and the adjusting screw tips. The adjusting screw tips in particular get all beat up over time (dimpled and pitted). You can replace them but the same thing will eventually happen to the new screws too. I think it's just a poor design. That's why I do the elephant foot screw mod to most of the heads I work on. That eliminates this wear issue.
 
My bike got real hot today, and with the 3/6 adjustment it was louder than it's ever been, only on the intakes though, I'm starting to think that maybe I did always do the 2/4 adjustment or I adjusted them warm, it was making me concerned because the longer I rode the louder it got, when I stopped everything was in spec though.
 
If you're running the 15-40 diesel oil like many like to do, you will get more top end clatter. I tried it but went back to the 20-50 because of that extra noise.
 
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