'86 VF500F lack of top-end

Your vacuum diaphragms have already failed then.

 

Say... would that mean that I could, as a temporary fix to get on the road, just connect a hose from the vacuum nipple to the vent nipple and go with turning the tap off when the bike's not running?
Sort of not sure of the internal routing.
A couple of searches for vacuum control delete haven't produced the actual instructional threads.

 

http://www.daughertymotorsports.com/howto/tankvalve/tankvalve.html

 

Was just about to dig that out for him.... lol

This mod is used more than maybe it should but does work perfectly.

 

There are a couple things that I regard in the same way as the human appendix: It had a use, but at some point it's just gonna fuck you in the middle of nowhere. And you don't really need it to continue on.

- Fuel Cut Relay (sure, keep it, but install a parallel toggle or have a jumper wire in your tank bag) See: 'middle of nowhere" above.
- Vacuum operated petcock (just get in the habit of turning your gas off)

Now obviously these are "Safety Features" and I get that. But it doesn't change the facts.

 

That is sure a nice bike you picked up....I wish mine would have been that nice. Good luck, and following your story!

 

Next issue...
It's running quite well now. To a point.
In light of the diaphragm failure and fuel drooling out of the vent nipple, I did install a short loop of hose connecting the petcock vacuum inlet and the diaphragm vent nipples. No fuel leaked onto the floor or into a cylinder.
Given the amount of fuel that had been coming from the vent nipple, I thought it could be enough to run the engine.
I just now took it for another test ride. After about 8 miles or so while running at good speed, about 70, it went into fuel starvation, slowly gagging down til it stopped altogether. I point out that it took a half-mile for the whole thing.
I pulled the gas cap, looked okay, as if that means anything, and got enough life to stagger home with one more stop to open the cap.
I have no idea how one would clear the cap vent system apart from compressed air, so that's what I did. A few small splotches of tarry, smelly goo spattered onto my hand.
I tried some forum-searching but I'm not hitting on the good search term.
Besides what I did, is there anything else in the way of cap vent cleaning?
Now, I do have petcock rebuild parts on the way and will do that, in case my hokey bypass isn't really a solution.
The Daugherty one is for the earlier petcock. I will have to see if it can apply directly to my '86.

 

Although the petcocks are different, the general design and parts are the same. The procedure is exactly the same. Did it to 2 86s.

The plastic center on the bottom of the cap incorporates the vent which vents up thru the key slot. Just make sure you don't damage it so it leaks out or lets water in. But I have blown them out before too, with no damage.

 

Time for an update. Pleased to report some successes.
I violated the diagnosing procedure rule of only doing one thing at a time an testing the results before going on to the next thing. I both blew out the tank cap vent as mentioned above and also installed a "petcock cover kit" from Partzilla ($62 with expedited delivery!).
It took a few tries to get the petcock kit oriented correctly so that the vacuum circuit functioned properly. I discovered that instead of going wet with the test procedure as in the book, I could remove the sediment cup- which was almost oddly quite clean- and watch the piston operate.
I then indulged in two test rides, a 30-miler with the Missus along for backup (and I am emphatically not getting on the back seat of her Ninja 400) at some moderate- to good speeds, then another of about 20 miles with large applications of the Gas Handle (as we have come to call it after watching too many Moto.it YouTube videos with the subtitle translations).
Both produced nary a bobble, with good, clean running, a steady idle even after some full-throttle pulls, and no signs of distress at all.
In one instance, after patiently waiting for a slow semi to clear his left turn into an industrial park on a 50mph road, I wrapped that Gas Handle all the way and zoomed to near redline in gears 1, 2, and 3. I have to tell you, I was actually startled by the acceleration the seemingly antique little 500 produced.
I did not have an opportunity to run above 75mph but even so, it all went quite well
In the next couple of days, Rich's Yamaha, Lockport, IL, will be levering on new Pirellis and I will get bolder.
The chain appears to be nearly new, clean and not kinky. The sideplate markings are "DID 50V3". That's an obsolete model, it seems, but given my past experience with D.I.D. V-series chains, that bodes well. My beloved Kawasaki ZX1100E had a D.I.D VX2 with 58,000 miles when I sold the bike and the chain was still barely within 20-link spec and showed no kinks. The answer to the immediate following question is: "PJ1 Blue Label every 400 miles".
So now I am on to the next things needing attention after the tires: the forks need an oil change at the minimum and I probably will go for Galfer stainless front brake lines to replace the soggy 35-year-olds that it has now.
The seat isn't really satisfactory as the foam is somewhat broken down and the shape not ideal anyway. The cover is a bit faded, so I am thinking of what direction if any to go with that.
I've replaced all the lighting apart from the instruments with LEDs so it's rather safer in modern evening traffic.
All in all, a nicer bike than I expected.
I have console Mr. McCulloch with the fact that I paid far more for this thing than he did for his: $450.
On the other hand, given my other projects around here, I doubt this bike will see anywhere near the depth of restoration he committed upon his.
Already the Missus is talking about selling and starting yet another project. Whoa, there, girl!

Edited to add a question: what is the real gasoline octane requirement? I've put in 87 without thinking, but did see somewhere, and I don't recall where, it needing 91. Is that so, in terms of ordinary American pump terminology?

 

Personally I'd answer that I think 87 ron will be fine as I'm fairly certain that that era of bikes were designed for it. However, as I don't own one, a better response may come from those that do.

 

Wow, you paid $450.00? You got a smoking deal on that. Especially since the engine had compression.

I never buy the same bike twice but I think I would pay $450 if that one like that showed up around here.

Regarding the gas, The octane is a good question. I have not been able to find an owner's manual on line so I have no idea what it needs.
I am going with the default non-ethanol premium which must be at least 91 ROM. I am going to see if the Buc'ees down here have the non-ethanol fuel available as that would increase my availability of fuel tremendously.

 

Neither the Factory Service manual nor Clymer manual specify the octane value. I just checked again (unless I'm missing it, but the word "octane" only shows up once in both, and I can't find it elsewhere).

However... page 78 of owner's manual states "91 octane". My assumption is that is 91 RON, so 87 ([R+M]/2) is essentially equivalent. I wish I could get ethanol free fuel where I'm at--it's not legal to sell it in my county.

 

Just to add- with a bit more mileage done, I have not detected any pinging, knocking, or other distress using the local "regular" grade 87.
There is a Speedway station just south of here that sells ethanol-free but somehow I'm never in that area when I need to gas up.

 

Thanks for finding that. First proof I have seen of the actual octane requirements.

 

Hey Capt.
Did you do the DMR VF Petcock Mod . Mine is totally gumbed up and by the sound of my research, I think modifying to non vac on - off is the way to go. Cooking it in the ultra sonic bath as I do this bit of research.
Thoughts?

Off to go pack some useless shit to put in storage with other useless shit while I wish I was riding.

Wavey

 

I have, it works as advertised. Might be a good time to rebuild the fuel valve itself too. You can get kits that you drill out the rivets and tap the holes to reassemble after installing the new guts.

https://www.ebay.com/itm/3621600857...xu7gEV8IWxBUVRLORUcQBFOA==|tkp:Bk9SR7jegqSXYg