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xs650 > > Motorcycle Systems > > Engine > > Valve lash: gotta knuckle down...


Valve lash: gotta knuckle down...
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TeeCat
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PostPosted: October 13, 2009, 8:08 am    Post subject: Valve lash: gotta knuckle down...

Guys...

I have had the best intentions, for some time now, of checking my valve lash for the first time, and adjusting if necessary, but I'm really timid about it. Have to learn how to do it, though. I had printed out 5twins' guide, but can't find it anywhere, and was wondering if anyone has a suitably detailed procedure. Thank you.

Part of the reason I'm doing this is because I hope it might be part of the solution to my erratic idle when hot, with occasional stammering and almost shutting of, as well as some occasional kickback. I'm not sure if the latter is a timing issue - I set the timing when I put the Pamco in several months ago - or just my occasional failure to kick at the right point, or all the way through.

Again, the bike is just an absolute kick in the pants above idle and off-idle, but displays some odd idle behavior when hot. The carbs have been cleaned several times, screws 3/4 turns out, choke seems to work (though I have no way of assuring that it's utterly tight when it's off), carbs synched with the dead cyl method, dual throttle cables replaced and dialed in with no binding, floats set to spec, replaced needle valves/seats.

This is one of my last remaining really annoying issues with this bike, so I'm hellbent on sorting it. When hot, the bike "hunts" a little, will stammer unexpectedly, nearly shutting off, and then recover, usually. Also, when I crack the throttle hot, the rpms do not return as quickly as when cool or cold.

I have adjusted the timing chain to a very slight bobble - you can feel it with your finger more than see it - but I want to check the valve lash and re-do the timing, as I'm hoping that it will help or cure this. Alternatively, I am temped to get another set of 38s to try, wondering if there is some "ghost" in these carbs.

I have valve cover gaskets so I can replace the existing ones. Now I need instructions and my nerve.

Also, would it be worth it to replace my carb holders? If so, which ones can I use, as Mike's does not appear to have anything for the '73, though there are #48-7479 for the BS38s?

otivated... getting closer...

TC
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yamaman
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PostPosted: October 13, 2009, 8:39 am    Post subject: Re: Valve lash: gotta knuckle down...

TC, this about covers it:

answers.yahoo.com/ques...412AAD9rkB

Remember, too loose is better than too tight, go for around .004" inlet & .006" exhaust. If you can't hear them now, but after your done you hear a bit of noise from them DON'T WORRY, loud valves save lives!

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TeeCat
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PostPosted: October 13, 2009, 9:30 am    Post subject: Re: Valve lash: gotta knuckle down...

Thank you, sir!

y valves seem pretty quiet now... little bit of tapping from what seems to be one... not sure which. Btw... wouldn't valve misadjstment make itself apparent at speed, too?

Would it be worthwhile to replace my auto-advance mech? I had help servicing the rod once before, but replaced the springs with new ones from Mike's, and still had to take a coil out to get them to return with a "snap". Might that cause this issue, and is the replacement fairly easy?

Thanks, much!

Edit: After reading this thread:

www.650rider.com/index...hlight=ATU

... me is thinking that a new ATU would eliminate one possible variable in my effort to sort this idle issue, and I can't see how it could hurt if I can replace it properly. Agree?

Edit: ATU on the way... I see it as one more step toward a solution, and one less worry or unaddressed variable.

TC
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yamaman
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PostPosted: October 13, 2009, 2:35 pm    Post subject: Re: Valve lash: gotta knuckle down...

You might enjoy this piece TC

dansmc.com/valveclearence.htm

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xjwmx
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PostPosted: October 13, 2009, 4:42 pm    Post subject: Re: Valve lash: gotta knuckle down...

TeeCat wrote:
wouldn't valve misadjstment make itself apparent at speed, too?

I had a bike that idled like it had an air leak, but ran fine "at speed."

There was no significant air leak that I could find. It turned out that the exhaust valve had no clearance. Adjusting it fixed the idle problem (a severe idle problem). My theory is that the e. valve was so out that it was slightly open during the intake stroke, in effect causing an air leak. From now on I do the valves first.
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TeeCat
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PostPosted: October 13, 2009, 6:08 pm    Post subject: Re: Valve lash: gotta knuckle down...

yam, thanks for that article! Smile

Quote::
There was no significant air leak that I could find. It turned out that the exhaust valve had no clearance. Adjusting it fixed the idle problem (a severe idle problem). My theory is that the e. valve was so out that it was slightly open during the intake stroke, in effect causing an air leak. From now on I do the valves first.

xj, wow! That's actually pretty encouraging! Maybe I'll find something obvious when I look at my valves.

I'm glad I decided to replace the ATU, though. Should have it later this week. Since the ATU is the "hard link" between the throttle and the timing across the band, I see it as smart to replace it, especially since I had to put new, shortened springs on it; there may be other wear-related issues with it as well, so I'll just eliminate that variable.

TC
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pumps
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PostPosted: October 13, 2009, 11:07 pm    Post subject: Re: Valve lash: gotta knuckle down...

TeeCat wrote:


Would it be worthwhile to replace my auto-advance mech? I had help servicing the rod once before, but replaced the springs with new ones from Mike's, and still had to take a coil out to get them to return with a "snap". Might that cause this issue, and is the replacement fairly easy?

... me is thinking that a new ATU would eliminate one possible variable in my effort to sort this idle issue, and I can't see how it could hurt if I can replace it properly. Agree?
TC

I am far from an expert but to me, if the advance springs "snap back" ok , at idle is when they would be under the least stress , therefore should not cause a problem as you describe at idle....does that make sense?
TC the valve adjustment is not a huge deal. Mine has/had leaky O rings on the covers that I was able to get at my local hardware store. The little tool to actually adjust with I got for $10 at a local mom and pop mc place. I think its Motion Pro. The tool kit one was not there.
I get a little tap tap when it is cold. Not a big deal.
An air leak is certainly possible. Met a GS1100 builder who said to use a propane torch UNLIT and pass it around the boots to see if the idle changed. That would indicate a leak. Hope some of this makes sense and helps.

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TeeCat
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PostPosted: October 14, 2009, 7:02 am    Post subject: Re: Valve lash: gotta knuckle down...

pumps, it does make sense, thanks.

One of the reasons I am replacing the ATU first, though, is because I have had trouble with it in the past. One of the local guys, Chris, came over last year to help me with a no-start issue and some other misbehavior, and we learned that the weights were not returning to rest. We serviced the rod and I replaced the springs, but still had to remove a coil from each. I recall that Chris seemed to think that the posts and/or pivot holes were worn.

The weights return, but I still think that a potentially kloogy ATU is potentially part of the problem... a link in a chain... so for 60 clams, I'm going to eliminate that variable right out of the gate. From there, I'll move to the valves.

Glad you told me I needed a tool! I thought I could use open-end wrenches! Sad

As to the potential air leak, I want to replace the boots just in case, but still am unclear as to which boots to get for a '73, as Mike's does not appear to have them. Can I use Part #48-7479 with vac plugs to block the vac port?

So... you just blow the gas at the boot?? Risk of odd spark or static would creep me out...
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pumps
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PostPosted: October 14, 2009, 2:10 pm    Post subject: Re: Valve lash: gotta knuckle down...

"you just blow the gas at the boot"
Some guys say to spray starting fluid around the boots..I would say run the torch close around them.

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mtc57
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PostPosted: October 14, 2009, 3:32 pm    Post subject: Re: Valve lash: gotta knuckle down...

Tee: The valve adjustment is a piece of cake. You'll do fine. This is a 360 degree engine, with just two valves per, so nothing to worry about. Just read the instructions, and once you're in there, it will all make sense. I'm guessing your idle issue is more likely an air leak around the carb boots, but valve adjustment is a good thing to do anyway. It's getting cold for much riding, but come springtime we should meet up for an XS ride in the eastern panhandle of WV.
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TeeCat
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PostPosted: October 14, 2009, 3:56 pm    Post subject: Re: Valve lash: gotta knuckle down...

mt... I just noticed... you're maybe an hour down the road. I'm in Ellicott City. Smile Yup... we'll have to meet up. I'll feel better about that as my bike gets more reliable.

I'm feeling better about the adjustment now that I have instructions... I just worry about having a bonehead moment and hosing something up. But it seems pretty straightforward.

I'm inclined to agree with you guys about the boots, but I might end up trying Permatex Copper around the inside and outside of them, because I can't seem to get an answer on replacements for the'73. I see them for '74s, but I don't know what the difference is. Waiting for an e-mail from Old Bike Barn.

ATU should arrive tomorrow... I think I can manage that okay.

Hey... for another way to test the boots... how 'bout a wet cloth wrapped around each boot like a tourniquet? Seems dumb, but might be easy and safe.

TC
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xjwmx
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PostPosted: October 14, 2009, 4:01 pm    Post subject: Re: Valve lash: gotta knuckle down...

I don't worry much about the "feel of the drag on the gauge" like one of the links was talking about. What I do instead is after the lock nut is tightened back down, check to make sure the gauge still goes in, and then check to see that the next larger size doesn't. very easy to do.

Do that before you loosen the lock nut in fact, and you might find they're adjusted fine already, and save yourself some work. The intake valves are probably both ok really. Maybe the exhausts too.
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Joseph
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PostPosted: October 14, 2009, 4:54 pm    Post subject: Re: Valve lash: gotta knuckle down...

Tc seeing as you are very thourough in yopur research I'll tell you what hapened to me. You can use, and I do, a 4mm wrench to hold the square valve adjuster while you loosen the lock nut with I think 10mm. Twice my little wrench 4mm or 5mm broke while adjusting. I found the peice both times but will be more carefull for now. I would have hate to think about that litttle peice of wrench caught in a spring or something.
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TeeCat
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PostPosted: October 14, 2009, 5:07 pm    Post subject: Re: Valve lash: gotta knuckle down...

xj and Joseph... thanks for the extra info! I appreciate it. I'm going to get the ATU out of the way first, and try to get it all done sometime this coming weekend.

ight go down the road to the local MC dealer to see if they have a valve adjustment tool. Worth checking.

TC
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xjwmx
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PostPosted: October 14, 2009, 5:23 pm    Post subject: Re: Valve lash: gotta knuckle down...

There isn't any valve adjustment tool that I know of. Just a feeler gauge for $5 at Harbor Freight, and a wrench. I only use one wrench, on the lock nut. 12mm I think. The adjuster doesn't seem to want to turn with the lock nut on mine, so one wrench is okay. You can turn the adjuster itself with your fingers once the lock nut is backed off. The time consumed is 20 min removing covers and putting them back, 1 min turning the crank, and 3 min doing the adjustments.

Just make sure the timing mark is lined up and you're working on the correct side. When the timing mark is lined up and an exhaust valve spring is compressed, the other side is the correct side to adjust. Then turn the crank until the timing mark is lined up again and the other exhaust is compressed and do the other side.
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pumps
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PostPosted: October 14, 2009, 6:10 pm    Post subject: Re: Valve lash: gotta knuckle down...

4 and 3 mm ends.


Seems like the stock tool kit has one in it.

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TeeCat
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PostPosted: October 14, 2009, 6:15 pm    Post subject: Re: Valve lash: gotta knuckle down...

xjwmx wrote:
There isn't any valve adjustment tool that I know of. Just a feeler gauge for $5 at Harbor Freight, and a wrench. I only use one wrench, on the lock nut. 12mm I think. The adjuster doesn't seem to want to turn with the lock nut on mine, so one wrench is okay. You can turn the adjuster itself with your fingers once the lock nut is backed off. The time consumed is 20 min removing covers and putting them back, 1 min turning the crank, and 3 min doing the adjustments.

Just make sure the timing mark is lined up and you're working on the correct side. When the timing mark is lined up and an exhaust valve spring is compressed, the other side is the correct side to adjust. Then turn the crank until the timing mark is lined up again and the other exhaust is compressed and do the other side.

Okay, very good then.

Now, I have seen those timing marks a LOT on this bike in my crank seal replacement adventure, and so on... but if memory serves me, is there a specific corresponding mark on the rotor and stator that indicated TDC? I seem to recall that there is a "range" for timing purposes, and then a clear TDC mark within that. Just been a bit since I've been in there.

TC
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xjwmx
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PostPosted: October 14, 2009, 6:28 pm    Post subject: Re: Valve lash: gotta knuckle down...

On mine there's a rectangular notch or etched place about 1/16" wide and a pointer on the housing to line it up with, if memory serves.

y crank oil seal, I didn't have to replace yet, but had to tighten the nut down to fix a leak (which I'd assumed was coming from the push rod since that's the one everyone talks about).

Thing is that nut was scary loose, like somebody here said they're usually loose. Don't know what would immediately happen if that sprocket came off.

Would like to see some mention of the commonly loose drive sprocket nut and how to fix it, in the Vault.


Last edited by xjwmx on October 14, 2009, 6:38 pm; edited 1 time in total
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xsjohn
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PostPosted: October 14, 2009, 6:36 pm    Post subject: Re: Valve lash: gotta knuckle down...

Front Sprocket (extra safety) so it won't come loose..........

Just clean the sprocket nut and shaft with brake cleaner and use a drop or 2 of "blue" loctite....and use the safety washer also......

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TeeCat
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PostPosted: October 14, 2009, 6:39 pm    Post subject: Re: Valve lash: gotta knuckle down...

pumps, thanks for that! I can approximate, I think.

"My crank oil seal, I didn't have to replace it yet, but had to tighten the nut down to fix a leak (which I'd assumed was coming from the push rod since that's the one everyone talks about)."

Oh, you mean the countershaft seal. Yup.. I replaced mine, and the crankshaft seal as well, behind the rotor. That wold be a good Vault article too... I posted my procedure with some piccies. If memory serves, I may be the first or only person here as yet to have replaced a crank seal in situ, that is, without splitting the cases. So maybe I can help if you ever have to do it. Mine was not leaking last I checked it, but oil seemed to be coming from a nearby case joint; I hope to have mitigated that with a reed breather valve. *crosses fingers*

TC
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xjwmx
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PostPosted: October 14, 2009, 6:54 pm    Post subject: Re: Valve lash: gotta knuckle down...

Sorry, I'd quit thinking for a bit.
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gordo
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PostPosted: October 14, 2009, 7:57 pm    Post subject: Re: Valve lash: gotta knuckle down...

Way back, I was taught by an oldtimer how a perfect clearence "feel" should feel.What he did was grab a micrometer, with known variable's( his was a good one, came with the .500 standard).Set the mike to ANY specification, let's say .003",and run a clean, lightly oiled .003" feeler guage through it. That is what a proper clearence should feel like. Once you get a good handle on what/ how much tug the feeler guage has, it's something you'll never forget. Good luck TeeCat, you'll be fine. Your worrying too much about a simple, straight forward proceedure. Also, the tappet screw & adjuster nut that Mike's sell's for $7.50 each are a good investment. They have a 4 mm allen head instead of the square that Yamaha uses. Make's it allot easier to hold when tightening the lock nut. I got them, and really like that feature.,,,Gordo
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yamaman
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PostPosted: October 14, 2009, 8:24 pm    Post subject: Re: Valve lash: gotta knuckle down...

Cool Gordo, simple & totaly effective, I like it!
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PostPosted: October 15, 2009, 11:14 am    Post subject: Re: Valve lash: gotta knuckle down...

No word from Old Bike Barn, btw. I'd still love to know what peeps with pre-74s are doing for replacement carb holders.

TC
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