Valve Adjustment Question

[anvil]

It's valve adjustment time for my VF500F. The bike has 28k and has never had a valve adjustment. I've been doing lots of research before I jumped in and being this i my first time attempting a valve adjustment I didn't want to F it up. Two feeler guages, clymer manual and special tool in hand, I gave it a first shot last night.

Following the clymer manual, there are two TDC positions, front and rear on the flywheel, adjusting to a 1,4,3,2 cylinder order. Instructions state the intake and exhaust valves can be adjusted at the same time. I was finding I couldn't get a feeler under all valves, I adjusted the exhaust valves on 1, 4 and intakes on 3 and nothing on 2. So my question is do valves need to be loosened? Can they tighten over time? And can a tight valve be considered out? Thanks.

[YoshiHNS]

YES!

There is a high and low limit on the valves. Your valve gap should be between those values. So if your intake gap spec is 0.005"-0.007", you should be able to get a 0.005" shim in, but not a 0.008" shim. If you can't get any shim in there, you need to loosen it. Adjusting the valves on the VF500 is a piece of cake, so get them all where they need to go.

[anvil]

Perfect YoshiHNS, thanks for the info and pep talk. This was driving me crazy with very little data out there inquiring about tight valves.

[Guest]

I hope nobody minds me jumping in with a little primer. I've had too many of these and other engines apart not to have discovered long ago that there are precious few that after 40K are near spec.

So here goes, for those who are interested.

Engines are very carefully engineered to operate within very specific tolerances. Well duh.

In engineer-speak, mechanical components that are put in motion at a cost of energy without doing work equals waste/loss of power.

Where this pertains to valves is that “theoretically perfect” use of energy means that the instant the rocker moves the valves will respond. Engines are indeed designed to conform to the theoretically perfect model, but with the understanding that practical application is by definition imperfect.

You got a whole lotta metals that are expanding and contracting at varying rates so some fudge room simply has to be present. It's all about limiting it to the most efficient (and therefore longest lived) compromise.

That being the case, we get as close as we can realistically manage to zero lash at operating temperature---which logically dictates a practical value that at the very least won't lead to valves not closing all the way. Hence the “cold valve lash” spec. If only we could set it and forget it.

In real life, as the valves “bed” themselves in, they “rise” in relation to the rockers (and the rest of the cylinder head) thus lash goes away.

I used to be head of tech support for a power equipment mfr and I had the devil's own time with service centers whose “experts” habitually and against my advice set lash too close, with the predictable result (to me anyway) that large (20+ kW) generators when hot failed to produce full power.

So, I wrote a service bulletin.

Very simple, I “trapped” a cold valve in my caliper and heated it.

The stem grew in length by exactly .006 in. No surprise there but it sure got the bosses' attention.

It becomes just this obvious: If your lash is .004 in. cold and the stem lengthens by .006, since it has nowhere to go at the rocker a .001 gap appears at the valve face and seat (not bad math---we're accounting for expansion of the cylinder head as a whole). This, in terms of engine dynamics, is the grand canyon.

We do carbs, only carbs, all day every day. All makes, all models, all vintages. So naturally I talk to a whole lot of guys who are resurrecting a long-abandoned project or fixing one up that's lost performance over the years and thus have a bucket of unknowns to cope with---many of which they never bothered to think about.

Consequently I preach every day that we should sort out compression and valve clearances before you hand me a bunch of money. For sure old carbs need to be seen to and I'm happy to take the cash but let's make sure they solve the problem instead of reveal others.

Real life moral to the story:

I picked up a 1986 VF500 Interceptor in near perf condition except that it sounded like a tractor. Supposedly the carbs were all boggered up. Not really but I did them anyway.

One valve job (and 15K later)...I like it better than the VF1000.

So here's my overall thrust: If there's one thing Honda did back in the day it was spend lavishly on R&D so the engineers had as many engines as they wanted to perform destructive testing on. Imagine playing myth-busters every day and getting paid for it. LOL. Point is I tend not to argue with their specs unless there's a documented misprint.

For a simple measure of how robust all early generation Hondas are, just imagine what's going to have become of your Ninja 650 after 35 years of sitting in the rain. Thought so.

On the practical side, I favor lash a TEENSY bit on the fat side. I'll take some minor ticking (if any) all day long before I'll put up with trouble climbing a hill when I'm pushing hard through the turns.

On the fun side, (if you're in the SF bay area that is) Pescadero Rd from the beach (0' elev.) to Macdonald Park (900') will tell you if you have valve or compression problems. At the crest, shut down and immediately restart. If you encounter trouble at least you're on top of a steep hill.

OSC

[anvil]

That was a book. Thanks for the details but I'm trying to single out the advice here? Keep the lash on the fatter? The tight valves are a sign of age?

[Guest]

Yes to both but don't overdo on lash. Late valves are their own troubles especially on intake so merely nudge the upper limit. Actually my long-windedness is the result of someone asking me some time back to write a blurb for my website, which is where you'll see this someday soon.

I rarely log onto forums but chance intersected with opportunity in a way I couldn't pass up..

I owe you one for spurring me to action.

Orings throughout for your carbs are yours for the asking. The fuel joints on the 500's take orings that aren't standard across the other V4's---fatter. There's that word again. LOL.

OSC

http://www.oldschoolcarbs.com

[anvil]

Ok, thank you for the tips. Very appreciated.

[Charlies]

Lots of ansewers to questions I had and hadn't thought of! Thanks OSC!

I was always a afraid a little tick meant a big hammer, so would stay to the tight side...

[Guest]

Let's put a slightly finer point on the issue.

For one, as V4 engines wear and compression begins to drop, operating temps go up thus expansion of the valve stem drifts toward max.

Warmer than optimal conditions are also helped along from slow speed circuits in the carbs leaning out with time, which began life lean enough thank you owing to the EPA.

And on top of all of this, the water jackets around the cylinders tend to load up with accumulated crud---especially when you run water-only in the cooling system. There are dielectric forces between water, which is mildly acidic, and aluminum that lead to odd crystal-like particles forming and collecting in low places when the bike sits. Such as the bottoms of the forward water jackets.

This is why I always tell folks that I'll take care of jetting you a little richer (and thus cooler), and while you've got the carbs off let's flush pressurized water through the jackets and have a peek inside the water pump to ensure that if you've got metal impellers they're not eroded---by the same dielectric imbalance that loads the jackets. And which can also clog the radiator. An ounce of prevention...

Sooo, this is why I favor the upper range of spec.

The odo on one of my Vf1000's made a brief horrible noise and gave out about four years ago, at 89 thousand miles. Just sayin...

OSC

http://www.oldschoolcarbs.com

[Guest]

valve spec are on the frame-??/- thats what honda wants thats what honda gets--go with specs