-
Enjoy XS650.com? Consider making a donation to help support the site.
XS650.com receives a small share of sales from some links on this page, but direct donations have a much greater impact on keeping this site going.
us custom 650 1981 bike tappet settings
- Thread starter Frankyboy
- Start date
in inches .003" and .006" are the general consensus "best" settings, some variation from those hasn't resulted in blown motors that I know of. The thing is; XS650 motors relentlessly hammer their tappet ends and valve stems. They are seldom perfectly smooth so the clearance actually continuously varies as the motor runs. Try to measure these rough surfaces with your perfectly flat feeler gauge and fun follows. I like to think I am close to ideal if the tappets are easy to hear when the motor is cold and quiet once its's well oiled and warm.
Last edited:
They will at THOSE settings.
A little more coffee, and maybe the missing zeros will appear...
Last edited by a moderator:
BWHAHAHA let's pour another cup and see.
I don't see nothing wrong..... 
Must have been the extra coffee.
I don't see nothing wrong.....
Well, that confirms it. I must be having a stroke.
Or nutritional deficiency.
Not swallerin' enuff bugs during my rides...
That's some pretty powerful coffee. Seems to fix everything. I could use some of that...
Last edited:
When you think about it 0.003" is a ridiculously small setting to try and achieve consistently and its so small that once the motor heats up you are likely to have problems with the exhaust valve not seating properly or for long enough
yamaha recommended much looser settings for their earlier models XS-1 and XS2 . Inlet 0.006" and Exhaust 0.012"
I read that Yamaha recommended tighter settings for later bikes to reduce tappet noise .
I was reading some Yamaha service bulletins the other day and it appears that Yamaha were changing their recommendations literally year by year !
1977 -78 inlet 0.05mm -0.10mm Exh 0.15mm
1979 inlet 0.10mm Exh 0.15mm
Apologies for the metric measurements but to be fair the whole bike was constructed with metric dims
A well known X650 Engineer Howard of Smedspeed recommends much looser valve settings and gives a very instructive explanation which he has extracted from some pretty exhaustive testing . Howard recommends 0.006" Inlet and 0.012" Exhaust which he claims saves power and compression and significantly improves heat transfer from the exhaust valve to the head .
This is a good read when you have a free moment and a coffee and donut
http://www.smedspeed.co.uk/tech.html
yamaha recommended much looser settings for their earlier models XS-1 and XS2 . Inlet 0.006" and Exhaust 0.012"
I read that Yamaha recommended tighter settings for later bikes to reduce tappet noise .
I was reading some Yamaha service bulletins the other day and it appears that Yamaha were changing their recommendations literally year by year !
1977 -78 inlet 0.05mm -0.10mm Exh 0.15mm
1979 inlet 0.10mm Exh 0.15mm
Apologies for the metric measurements but to be fair the whole bike was constructed with metric dims
A well known X650 Engineer Howard of Smedspeed recommends much looser valve settings and gives a very instructive explanation which he has extracted from some pretty exhaustive testing . Howard recommends 0.006" Inlet and 0.012" Exhaust which he claims saves power and compression and significantly improves heat transfer from the exhaust valve to the head .
This is a good read when you have a free moment and a coffee and donut
http://www.smedspeed.co.uk/tech.html
Last edited:
Wut the peanut gallery sez...... If you can stand the clatter.
P.S. .003" is the intake, exhaust is .006"
Noon; switching to coke.
P.S. .003" is the intake, exhaust is .006"
Noon; switching to coke.
I have to confess I've not tried these settings myself yet
I've just started sorted out some of the problems I have on my bike for the MOT test but i will definitely be resetting the valves and cam chain tension etc so i'll do some experimenting and report back on my hearing
...yamaha recommended much looser settings for their earlier models XS-1 and XS2 . Inlet 0.006" and Exhaust 0.12"
I read that Yamaha recommended tighter settings for later bikes to reduce tappet noise .
A well known X650 Engineer Howard of Smedspeed recommends much looser valve settings and gives a very instructive explanation which he has extracted from some pretty exhaustive testing . Howard recommends 0.006" Inlet and 0.12" Exhaust...
...I have to confess I've not tried these settings myself yet
There's that missing zero again. Weak tea???
I've run variations at both ends of the fence.
Ran at 0.005" in, 0.010" ex, for a long time.
Feels a little pepperier mid-range when loose. But, sounds like a well-broke-in racing Husqvarna.
I know that the early cams had a long/lazy entrance ramp. Best to use the looser setting.
Don't know about the entrance ramps on the later cams.
Apologies for the metric measurements but to be fair the whole bike was constructed with metric dims
Now, THERE's a fun challenge.
I'll start: Wheel/tire diameters of 16", 18", 19"...
I think they call it a senior moment .
Difficult to believe sometimes that I attended a private school and 2x Universities .
Today I picked up some shopping .Her indoors asked me where her crisps were .
Couldn't find them anywhere.Found them later in the fridge !?...............she said they tasted ok chilled lol
Haha, peanut. You've just invented a new breakfast cereal.
Frosted Crisps
Friend of mine did a similar thing. Misplaced her can of Pledge.
Found it hours later. In the freezer.
I'll never forget that time when I prepared my morning coffee,
and proceeded to pour it into my ashtray...
Frosted Crisps
Friend of mine did a similar thing. Misplaced her can of Pledge.
Found it hours later. In the freezer.
I'll never forget that time when I prepared my morning coffee,
and proceeded to pour it into my ashtray...
Interesting read on the wider clearances, I have been running mine at 0.1mm and 0.15mm for years as that is what Halco recommended...... Wouldn't running a larger clearance give the tappet and the tip of the valve a harder time??? I am up for more power though...... Frankyboy, is this bike a bit top end noisy?? I would check the cam chain adjustment as well, Just fixed my friends XS for the summer and it sounded dreadful and the tappets were not as loose as I was expecting but the I had to wind the cam chain tensioner in loads, it sounds sweet now!! take the plugs out and turn it round to TDC and the plunger should be flush with the adjuster, I do mine nearly flush as too tight is bad as well, don't want a broken chain!!!
are you a brit Blim ?....
I never met Tony Hall I got back into bikes just after he died . Such a shame and a loss for the XS650 fraternity. There is a excellent interview with him on youtube somewhere. He was only just down the road from me too ....
Good call about the camchain tension. I shall be checking and readjusting mine shortly after I have first checked my clutch basket clearance. I think the po fitted an extra shim to gain more clearance to the crankcase which could account for the washer I had left over after rebuilding the engine !
These old engines really do respond to careful and meticulous setting up .
I don't think I would be all that concerned about potential wear to the cam followers myself. My engine has just 18,000 miles on it from new with no appreciable wear. I doubt I'll put another 18,000 on it in my lifetime. I just keep thinking about how long those exhaust valves are open and how hot that is making the engine.
With a smaller valve setting the followers will be in contact for less time with the cam. The ramps are gentle and long so presumably there could potentially be less wear ?
Yes I am brit, er your clutch, in my engine there is a thin shim on to the bearing then a plate then the outer basket then the baring plate and then the roller bearing then another plate then the inner basket and finally a flat washer a belled spring washer and the nut.... I have just checked the manual and my memory is correct.... is a lot of shims and plates in there.... I think I had to check the exploded diagram one time to make sure as it confused me the number of bits and the order etc. just saying that extra shim might be correct....
I am going to try the wider valve clearances and I will let you know if it makes any difference to performance and heat, I am running an XS1 cam so may well notice the difference as the wider clearances were the spec for the early motors, I got my local machine shop to press the sprocket off and swap it for one off a 447 cam, did notice a difference with the cam, stronger mid range pull... I hear what your saying about the ramps, also running tight can cause wear so maybe loose is the way, if it sounds like death I may compromise with my settings lol.... could go 0.15 and 0.25 or something, I did an SV1000 a while ago where I was working and that was fairly big clearances more than I was expecting, think that was supposed to be between 0.19-0.25 on exhaust.... I hear the theory on it as not a lot good is happening if the valve is slightly open for a period of time, either shut or wide open, a little open is not letting much through in the way of flow and is loosing compression.... Whats the deal with the aftermarket cams, should you still run big clearances on say a megacycle cam???
I am going to try the wider valve clearances and I will let you know if it makes any difference to performance and heat, I am running an XS1 cam so may well notice the difference as the wider clearances were the spec for the early motors, I got my local machine shop to press the sprocket off and swap it for one off a 447 cam, did notice a difference with the cam, stronger mid range pull... I hear what your saying about the ramps, also running tight can cause wear so maybe loose is the way, if it sounds like death I may compromise with my settings lol.... could go 0.15 and 0.25 or something, I did an SV1000 a while ago where I was working and that was fairly big clearances more than I was expecting, think that was supposed to be between 0.19-0.25 on exhaust.... I hear the theory on it as not a lot good is happening if the valve is slightly open for a period of time, either shut or wide open, a little open is not letting much through in the way of flow and is loosing compression.... Whats the deal with the aftermarket cams, should you still run big clearances on say a megacycle cam???
This can get extremely complicated. But, to oversimplify, there's a 'sweet spot' in the camshaft's entrance ramp lift profile that keeps initial lift accelleration (and jerk) to reasonable levels. That 'sweet spot' is supposed to match the cam grinder's published clearances. The XS1-XS650s cams went thru numerous iterations, and I haven't found any detailed info on their entrance ramp profiles. What this means is that this subject isn't as simple as it looks, since the factory published initial clearance values, followed by (I suspect) marketing's attempts to appease the customers.
If you want to see how deep the rabbit hole is, WebSearch on "camshaft acceleration ramp profile".
Be sure to have 3 gallons of coffee at the ready...
If you want to see how deep the rabbit hole is, WebSearch on "camshaft acceleration ramp profile".
Be sure to have 3 gallons of coffee at the ready...
I don't think you really need to go to that much detail for these agricultural engines 2M .
The ramps are so long and slow that the cam followers are in contact with the valves practically the whole time .
This must have been intended by Yamaha to reduce valve train noise I guess.
Howard states that the camshaft itself has a runout tolerance of 0.002" which really makes nonsense of the 0.002" inlet valve setting
Have you read Howards notes on this yet ? he discusses the xs650 cam profiles and makes a good case for looser tappets .
quote
© Copyright 2015 by smedspeed.co.uk
'If the inlet valve tappet clearance is set at 0.002 the overall inlet cam timing event is 93+180+122 = 395 degrees, if the tappet clearance is opened up to just 0.006 then the inlet cam event total is 49+180+77 = 306 degrees.
The late XS650 stock cam holds the valve off its seat for nearly 45 degrees before it actually lifts more than 0.005; this is just wasting power, and compression.
Setting the intake valve clearance at .006" versus .002" means you have lost 89 degrees of the valve opening event. (44 degrees on the intake opening side and 45 degrees on the intake closing side) It won’t lose you any flow or power however, as the valve was only a couple of thousandths of its seat.
The intake valve is just loitering off the valve seat but is still open when it could have opened 44 degrees later, and closed 45 degrees earlier, allowing for greater dynamic compression, and more time for the valve to lose its heat through the valve seat. There is no flow advantage with the slow opening and closing rates that leaves the valves open for 89 degrees a few thousandths off the seat except burned valves, lost mixture and compression.
The early Yamaha XS650 ( XS1, XS2 etc) had tappet clearances of 006" and .012" for the intake and exhaust respectively. It’s one of the reasons the earlier engines perform better, they do have a slightly wilder camshaft (not much) but most of the increase in compression comes from just keeping the valves shut longer .
Setting valve clearances to the LATE stock cam specs just contributes to reversion and lost compression with these antique slow cam lobe opening and closing rates.
The design of the cam echoes the “cooking model” cams of the British bike industry, but as Yamaha engineers had no previous four stroke experience what else could they copy err…. benchmark.
I have checked stock and performance cams from the opening to the closing in thousandths per degree every 10° of crank rotation, just to check cam profiles. Most of the newer design (non symmetrical) cams open the valves faster than they close them, but both rates are very much faster than the old style cam designs of the past. Computer modelling cam profiles helps in this area.
The late XS650 cams set at .002" intake tappet setting is ridiculous. I can’t think of another OHC engine with valves this size that has such small clearances, the camshaft has a run-out of over 0.002 in many cases and setting the tappets to this small clearance will allow the valve to stay open perpetually. It is an effort by Yamaha to reduce engine noise, but this is not the way to do it.
I set all the tappet clearance at the early settings of 0.006 and 0.012. It allows in more oil, and allows for a generous growth in the metal parts, remember….. A loose tappet is a happy tappet.'
© Copyright 2015 by smedspeed.co.uk | Design by Free CSS Templates - Thanks to Web Design Dubai
The ramps are so long and slow that the cam followers are in contact with the valves practically the whole time .
This must have been intended by Yamaha to reduce valve train noise I guess.
Howard states that the camshaft itself has a runout tolerance of 0.002" which really makes nonsense of the 0.002" inlet valve setting
Have you read Howards notes on this yet ? he discusses the xs650 cam profiles and makes a good case for looser tappets .
quote
© Copyright 2015 by smedspeed.co.uk
'If the inlet valve tappet clearance is set at 0.002 the overall inlet cam timing event is 93+180+122 = 395 degrees, if the tappet clearance is opened up to just 0.006 then the inlet cam event total is 49+180+77 = 306 degrees.
The late XS650 stock cam holds the valve off its seat for nearly 45 degrees before it actually lifts more than 0.005; this is just wasting power, and compression.
Setting the intake valve clearance at .006" versus .002" means you have lost 89 degrees of the valve opening event. (44 degrees on the intake opening side and 45 degrees on the intake closing side) It won’t lose you any flow or power however, as the valve was only a couple of thousandths of its seat.
The intake valve is just loitering off the valve seat but is still open when it could have opened 44 degrees later, and closed 45 degrees earlier, allowing for greater dynamic compression, and more time for the valve to lose its heat through the valve seat. There is no flow advantage with the slow opening and closing rates that leaves the valves open for 89 degrees a few thousandths off the seat except burned valves, lost mixture and compression.
The early Yamaha XS650 ( XS1, XS2 etc) had tappet clearances of 006" and .012" for the intake and exhaust respectively. It’s one of the reasons the earlier engines perform better, they do have a slightly wilder camshaft (not much) but most of the increase in compression comes from just keeping the valves shut longer .
Setting valve clearances to the LATE stock cam specs just contributes to reversion and lost compression with these antique slow cam lobe opening and closing rates.
The design of the cam echoes the “cooking model” cams of the British bike industry, but as Yamaha engineers had no previous four stroke experience what else could they copy err…. benchmark.
I have checked stock and performance cams from the opening to the closing in thousandths per degree every 10° of crank rotation, just to check cam profiles. Most of the newer design (non symmetrical) cams open the valves faster than they close them, but both rates are very much faster than the old style cam designs of the past. Computer modelling cam profiles helps in this area.
The late XS650 cams set at .002" intake tappet setting is ridiculous. I can’t think of another OHC engine with valves this size that has such small clearances, the camshaft has a run-out of over 0.002 in many cases and setting the tappets to this small clearance will allow the valve to stay open perpetually. It is an effort by Yamaha to reduce engine noise, but this is not the way to do it.
I set all the tappet clearance at the early settings of 0.006 and 0.012. It allows in more oil, and allows for a generous growth in the metal parts, remember….. A loose tappet is a happy tappet.'
© Copyright 2015 by smedspeed.co.uk | Design by Free CSS Templates - Thanks to Web Design Dubai
Last edited:
yes the shim that frequently gets left out at clutch rebuild time is the 1mm thick large shim ( shim 5 in my image) that is placed against the needle race . its due to the fact that Yamaha workshop manuals left the washer out of their drawings and countless owners have also been leaving it out over the decades.
The left over washer that I had was a small washer 35 x 25mm which is the very first shim against the bearing.( shim 1 in my image)
Heres a handy clutch rebuild sequence I constructed a couple of years ago when rebuilding my engine. I bought the engine dissassembled in boxes so I had no knowledge of its rebuild sequence .
