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Adjust Valve Clearances On Work Bench

  • Thread starter Thread starter Suzuki_Don
  • Start date Start date
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Suzuki_Don

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Can those people that are in the know answer this question for me? Is it possible to adjust the valve clearances on an 8 valve motor on the workbench. This would be done by installing the valves, springs, etc and then the buckets, shims and finally the camshafts and torquing them down as per the manual. This of course would only be done when rebuilding the head. The object of the task would be that it might be easier to do it on the bench than on the bike. I don't know if this would work. I'm just throwing it out there to see what others think. And if noone knows I might be the guinea pig that gives it a go to see if it works and if it is practical.
 
Sounds a bit like a bench sync for the carbs. Might get you close, but fine-tuning will still be necessary.

Let us know how it works. 8-[


.
 
I can't say for sure, but I don't see any reason why it wouldn't work fine.
 
Yep it would get you close. If you plan on doing it that way ? set them on the loose side.. Run it for 500 miles & re adjust
 
You can acheive exactly the same outcome as doing it in place on the bike.
 
are you talking of rebuilding the head only? cos, it might be difficult to turn the cams without the camchain...
if you have the whole engine on the bench then i see no reason why it wouldn't work (and be easier to fiddle with the shims)
 
psyguy said:
are you talking of rebuilding the head only? cos, it might be difficult to turn the cams without the camchain...
if you have the whole engine on the bench then i see no reason why it wouldn't work (and be easier to fiddle with the shims)
Click to expand...

Yes PSYGUY that was the only problem that I could see with it. It could be difficult to turn the cams against the valve spring pressure. I thought vice grips would probably be the only way to turn the cam through the full cycle.
 
Using a screwdriver to lever off the top of the head (with something between s/d and head to protect surface) onto the teeth of the sprockets or even using polygrips on the cam sprockets, makes turning them a fairly straight forward process.
 
I thought of a good way to move the cams. If you can set the head up two boards with a gap where the cams are, you could use an old timing chain and just pull the chain to rotate the cams. I've got one of those old steel Craftsman work tables with an adjustable wooden top that would work great for something like this.
 
Suzuki_Don said:
Yes PSYGUY that was the only problem that I could see with it. It could be difficult to turn the cams against the valve spring pressure. I thought vice grips would probably be the only way to turn the cam through the full cycle.
Click to expand...

i thought of doing it that way myself when i rebuilt the engine but gave up the idea for another reason - i thought that bolting down the cams twice (as you need to take them off to put the camchain through later on) would place unnecessary stress on the threads in the alu head (i had to helicoil most of them anyway) + i thought that i wouldn't get exactly the same shim gap readings after removing / replacing the cams for the second time, so why bother?
 
Yeah I'd thought of the same thing myself after having initially started the post. I'm also in the process of checking out the cam bearing bolt holes as 3 of the 4 holes over cyl 4 are stripped and one of these looks like it has pulled out a Recoil that had been inserted previously. Not sure what to do about this one as the hole is too large to take the standard 6mm Recoil (Helicoil). It really needs to be drilled out quite a bit larger and be tapped to take a larger bolt (stud) maybe 8 0r 10mm, but I dont know if there is enough room to do this. Still trying to get my head around this issue. Any suggestions greatfully received. Might try and get a pic later tonight if I can, in between watching Australia and Sri Lanka in the One Dayer.
Cheers Don
 
Last edited:
Suzuki_Don said:
... as 3 of the 4 holes over cyl 4 are stripped and one of these looks like it has pulled out a Recoil that had been inserted previously. Not sure what to do about this one as the hole is too large to take the standard 6mm Recoil (Helicoil). It really needs to be drilled out quite a bit larger and be tapped to take a larger bolt (stud) maybe 8 0r 10mm, but I dont know if there is enough room to do this. Still trying to get my head around this issue. Any suggestions greatfully received.
Cheers Don
Click to expand...

Don,
I have not done this myself, but know of someone who just had the stripped holes drilled out quite large and tapped and filled completely by screwing a threaded aluminium rod into it with threadlocking compound and smoothed off. Then he just redrilled and tapped with the original sizes. No helicoils were required. Maybe this will work for you, just work back from a standard size aluminium rod to get your drill die and tap sizes required. Otherwise aluminum weld and do the same.
 
Thanks Matchless. As you can see by the hole, there is not much room between the hole and the camshaft bearing surface. Don't know how I will go for room. still some investigation to go. See ya.
 
I was just having a closer look at the holes and think you will have to approach an engineering concern to retap. I would first go to an automotive head rebuilder for an opinion.
It does not seem like something one will be able to do at home with ordinary tools. It should be repairable, but is going to open your wallet!
 
I can't see any benefit whatsoever to adjusting valve clearances on the bench. It would be pointless and possibly inaccurate. It could also be damaging -- as noted, the cam cap bolts are rather delicate, so the fewer stress cycles of taking them out and putting them in, the better.


Adjusting valve clearances is quite easy in the bike, since a motorcycle makes a very nice custom-fitted engine holder. There's plenty of room to work. So what's the point in the first place?
 
bwringer said:
I can't see any benefit whatsoever to adjusting valve clearances on the bench. It would be pointless and possibly inaccurate. It could also be damaging -- as noted, the cam cap bolts are rather delicate, so the fewer stress cycles of taking them out and putting them in, the better.
Click to expand...

I agree with this post :-D its a pointless exersise trying to do it with the head off, i just set the valves as i'm rebuilding the engine then throw the completed engine in & dont worry about it till the next service :-D
 
regards re-tapping the bolt hole - as matchless has suggested OR - there are inserts made from mild steel that fit one into another - you drill (with a special tap) for 8mm insert that then takes a 6mm insert.
 
Matchless said:
I was just having a closer look at the holes and think you will have to approach an engineering concern to retap. I would first go to an automotive head rebuilder for an opinion.
It does not seem like something one will be able to do at home with ordinary tools. It should be repairable, but is going to open your wallet!
Click to expand...

I was have arranged to take the head to a place in Sydney that does race car heads to have the valve seats recut, so they should be able to do whatever repairs are required. I will get a quote off them anyhow. Don't want to stuff the head up and be up for more money. I could normally do this myself, but the inserts that were put in before have been ripped out and left a mess.
Thanks Matchless
 
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