Changing valve springs without removing cylinder head?

Anyone ever managed this? I want to check free length of (reportedly frail)
VF500 valve springs but I don't want to remove cylinder heads if I can
avoid it. Using a magnetic collet catcher and filling the cylinder with
string is something I have heard about but never tried.

--
Jeremy
Ireland
FJR1300ABS
GSX-R750K7
VF500F2F

 

How the hell would you compress the spring in the first place?

 

An inverted magnetic collet pusher and a cable tie ?

 

There's lots of stuff about using compressed air in the cylinder to
hold the valve shut, but I don't know anybody who's actually done it

 

Depending on how accessible the valves are, it's not really all that difficult.
My question is, why do you want to check the valve springs' free length?

 

I tried it once on a diesel engine (replacing the stem oil seals), but
failed. If you can be sure the piston's at TDC it will hold it up. I
think I managed *most* of the valves but I got it wrong on one cylinder
and a valve dropped down. I ended up taking the head off.

 

It's straightforward to make sure each piston is a TDC and to lock the
crankshaft firmly in place. If it has a central spark plug I suggest you
could get a big syringe, fill the cylinder head with a really heavyweight
oil and screw an old plug back in, creating a nice hydraulic lock. Remove
the springs then suck most of the oil back out through the plug'ole and pump
the remainder out by turning it over quickly a few times.

 

I assume you push as much string in as you can and then rotate to TDC.

Apparently (Vfrworld forum) the springs are underengineered and can cause
valve float which then leads to a hammer action on the valves which in turn
causes the valve to fatigue, fracture and drop into engine. I assume over
time if engine is thrashed, the valves take a permanent set which will make
them more prone to float.

 

How much time have you spent hammering the piss out of your VF500F? On a bike
used for racing you *might* have a problem, but in normal street riding I
really doubt you'll ever experience any problems with the valves.

If the top of valve stems aren't visibly deformed from this hammering action
I'm sure you have nothing to worry about.

I owned an '84 VF500F for a couple of years until I gave it to my son, and I
am still responsible for the maintenance of anything more complex than oil
changes. Fun bike but even after rodding out the radiator it tends to run
hot.

 

Could work. This assumes I have an engine in reasonable condition tho.I can
imagine the oil gradually leaking away.
The string idea is similar without the leakage issue.


--
Jeremy
Ireland
FJR1300ABS
GSX-R750K7
VF500F2F

 

The bike is new to me. No idea of history. I bought it cos the engine
reportedly gives trouble. I WANT to fiddle with it.
--
Jeremy
Ireland
FJR1300ABS
GSX-R750K7
VF500F2F

 

I've done it on a car with compressed air. I replaced valve seals on a
Ford XR2. I drilled the centre out of an old spark plug & brazed in a
tyre valve. Turn engine to TDC on compression, squirt some oil into
cylinder to help seal it & apply compressor. I even used one of those
compressors that runs off the battery & it gave enough compression. I
used a long piece of angle iron with a bit welded on like the end of a
valve spring compressor, secured one end to something solid then pressed
down on valve collar. Having given valve collar a tap with hammer first
to help release it.

I had doubts but friend who is a car mechanic told me it would work & it
did.

 

OK, I can understand that. Mind you, I've never heard of valves falling
into the cylinders, not saying it hasn't happened, just that I've never
heard of it. As far as I know the only knock against the VF500 was a
few early engines broke their cranks but that issue was quickly fixed.

I used to own a really nice '82 GPz550 that I bought from the original
owner. After buying the bike, he went to the parts counter and bought a
cylinder head gasket for it. The parts guy asked why, and my friend
told him he wanted to look at the combustion chambers when he got home.

 

Filthy pervert

 

Cheers. This sounds like the best option. I have a compressor too. I knew
someone would have tried it.


--
Jeremy
Ireland
FJR1300ABS
GSX-R750K7
VF500F2F

 

It does happen. I read most of the 1st gen VF forum on vfrworld and there
are quite a few incients of it happening on there. Some guy posted picture
too if you want them.



--
Jeremy
Ireland
FJR1300ABS
GSX-R750K7
VF500F2F

 

Then take the head off and clean the ports,valve faces and combustion
chambers at the same time

 

Undoubtedly I will, but I want to eke it out.


--
Jeremy
Ireland
FJR1300ABS
GSX-R750K7
VF500F2F

 

And polish out the piston tops to a flawless mirror, then back it off to a
4200 grit finish. That will keep you busy for a day.
Obviously it will also "release more power and reliability"

 

It works, but I've never tried it on a bike engine, just car lumps. No
reason in principle why it shouldn't do the job.