Peer Pressure 1986 VFR700

You're pretty spot on with your "head" to PSI numbers, especially the factoring in of the specific gravity of gasoline. This is also based upon a 1" diameter coulmn of water. A 1" column of fuel, 3' high, is just shy of 1 PSI. So figure you are using a 1/4" diameter column of fuel...well, you can extrapolate the rest....

This is a subject that comes into play doing calculations required to do some of my job tasks, people always get googly eyed when you tell them that a 3' high, 1", column of fuel will exert the same amount of pressure at the bottom of the tube, as a 120' diameter AST will exert on the tank bottom with 3' of fuel in it.

 

Just out of curiosity and because the 700 is about thirteen times easier to hook up the throttle linkage than the 500... I dropped in the carburetors and fed it some fuel. Fired right up. I know it's all coming right back off but it was encouraging to hear it roar up! Sounds awesome.



There's coolant leaks and a bunch of other stuff I need to address. But that was encouraging to hear. And very fun. I don't know how it's even running with how bad carb #1's throttle plate is messed up.

 

That's very cool, but I had zero concern that the bike would start and run.... It's an 86 VFR. If it doesn't look like it's been parked out side, or in a pond, with the plugs out, they are usually good to go.

And of course those carbs would let it run, but I don't think you'd ever get a balance and a properly smooth idle out of them... But you never know. It did sound pretty fucking good. Hell yes! It was awesome when you just got enough revs for that exhaust to bark a little.

If (when) you're ready to buy carbs, hit me first. I will make you a very good deal.

 

I think I'll be messaging you about those carbs in the next few days. I wanted to make sure this was a project I really wanted to get into first. Hearing the bike run and rev to about 7k.. man, that's a cool noise. Probably shouldn't have shelled out for those metal fuel tubes, but oh well.

I ran into an issue just now that I need to investigate a lot further and I expect will involve some more purchasing. I wanted to run the bike to hot to check for leaks and other issues. Was much harder to start with the air filter on and took a lot of messing with the idle adjustment to keep it running. Died fairly often. It ran better with the filter off.

I checked the running voltage and it was a steady 16.6-16.7V. Non-running about 13V. Which, idk what it's supposed to be, but I'm pretty damn sure it shouldn't be that high while running. So in the interest of not frying my battery and other components, I shut it down. I've been going back and forth with a track friend on some advice to check the stator since he thinks that's the most likely culprit. I do have a spare R/R for the VF I bought that I could probably test. I should probably do all the work for the wiring harness swap first though.

Anyway, I get what all of you guys are on about now. VFR's sound really, really awesome.

 

^^ a stator in failure mode provides less voltage, never more.

 

CD, Ideally you would expect ~ 14.0 volts at idle and mid-14's with revs. 16.6V looks like it could be rectified, but NON-REGULATED output from the R/R - the regulator functions by limiting the output voltage, max. voltage should be ~15V. hth.

 

Thanks for the information Phil. That explanation makes sense. I'm reading through some of the really long threads here about R/R and stator tests, and I'm going to give some of those a shot. I ordered some new connectors as well. Sounds like I'll get to use that "Diode" test setting you introduced me to on the multimeter again, hah.

 

> I'm reading about R/R and stator tests, and I'm going to give some of those a shot.

The overvoltage you've measured is consistent with a failed voltage regulator, not a stator failure or a rectifier failure. I'd expect the stator and all 6 rectifier diodes to test ok. You mentioned that you had a spare R/R - swap it in and Bob's your uncle.

 

Turns out the 1987 harness has some differences from the 1986--at least as far as I can tell. It's very similar but not quite the same based on what I'm seeing when I lay them next to each other. I bought a kit so I can replace some of the 4 and 6 pin connectors, and I'm going to just put in my cheap spare R/R before deciding later if it makes sense to spend a lot more on one of the Rick's or other variants.

Staring and inspecting these things for quite a while... it seemed like the better idea would be to actually just try to repair the existing '86 harness. I knew that everything "worked" on it, and the connectors were actually in better condition. The major issue was the wires coming from the clutch diode which were for some reason way worse than anything else. idk what all that was about.






Not pretty but, eh, it's better than it was before. The damaged wires are gone and copper isn't exposed anymore. Judging by how the rear fairing piece came off in pieces, nothing's going to be particularly aesthetic about this machine for a while.


If someone needs a spare 1987 harness--tell me where to ship it.

 

Yeah, the harness is one of those things that needs to be the correct year to make it easy. One of the things that really highlights the differences between years. The ignition system changed from 86 (analog) to 87 (digital), and the cam sensor got eliminated.

 

Lmao, this was the exact moment I went back to the eBay posting to double check what year harness I bought. I'm staring at the 87 harness trying to figure out where the cam sensor plug is considering there was absolutely no indication that it had been removed.

Thanks for the clarification. I'm actually a bit relieved knowing I wasn't going crazy and they weren't actually the same.

 

> If someone needs a spare 1987 harness--tell me where to ship it.

Might want to ask V4D Joe

 

Not a bad idea. I'll shoot him an email and see if he can use it for anything. Thanks Phil.

 

Learning curve! Keep after it.

 

Any tire recommendations or deviations from stock profile to consider? 110/90-16 and 130/80-18 is what I'm seeing as stock sizes.

If the 160/60-18 that's on it now didn't look like such a dangerous profile, I'd probably hold off on buying tires until I had the bike running well.

I'm probably going to go with the Bridgestone BT46s. They're getting pretty damn expensive though. Metzeler Lasertec and Pirelli Sport Demons are two others I'm looking at.

Just figured I would ask first.

 

I installed BT45 on the 1986 VFR750F "Rain Bike". They are/were great bias tires, and the BT46 are as well.

120/80-16 (V)
140/70-18 (H)



110/90 look stupid to me. The VF1000F/R came with 120/80-16 from the factory with the same size rim. 130/70 on the rear is also a solid choice.

I like to keep the profile lower on the rear 18" so it's not a fucking wagon wheel outer diameter, so I go with the H rated tires to get into 70 series profiles, I'm not doing sustained +130 mph on this bike. No idea why they don't offer them in V, it's usually the other way around.

If I were doing it again on the stock rims, I would go 130/70-18. It's right in the rim width sweet spot of what the tire was designed for (3.00-4.00). It will put that 70 series at a sweet sporty profile and the bike will be nice an nimble. I will always put 12/80-16 on the front 2.50-16. The 140/70-18 H is designed for a 3.50-4.50 rim, so acceptable, but "pinches" it slightly. Never had an issue though, plenty of good contact patch. It doesn't look "pinched", but will highlight the flat spot that develops as you burn more miles. Ironically, the 130/70 will probably "look" bigger on that rim than the 140/70.

Now this is ALL personal preference, but I've been playing around with bias tire sizes for years, and sold them for 12+ years. YMMV.

 

Thank you for the detailed response Captain. The 110/90 looks odd to me as well which is partially why I wanted to ask. It looks like a bit of a balloon on there. I know you and (I think) a few others also pointed me in the direction of a 120/80 rear for the VF500F as opposed to stock.

It looks like both of your preferred tire sizes are available for the BT-46 and in stock. I think that's probably what I'm going to end up doing based on that suggestion, thanks! Bridgestone usually runs a $50 rebate in the spring/fall, but I'm not sure if I missed it or if it's just not happening this year.

 

Here's the 140/70-18 after a fair bit of miles. Looks really good. 130 or 140 are both good, rim width appropriate sizes.

 

I couldn't really get an exact comparison because I don't have the kickstand on now and there's a pole in the way, but that 120/80 looks so much better than a 110/90.



I laughed a bit when I realized your picture wasn't the result of two opposed mirrors and was actually one big party of similar looking Hondas!

I guess one last question regarding tires that I was going to ask you in a few months anyway... are bias ply track tires similar to modern radials in setting pressure for track use? I was just going to start at 32F/30R if everything goes right with the VF this year. I can't find any information about this--was going to shoot an email to Bridgestone. I won't be pushing any speed boundaries--that's what the SV is for (well, "speed boundaries" for me, anyway).

 

When I raced the 500 and had Avon Race Sprint Compound AM23/22 (best bias ply tires ever to me), I found the percentage for increased tire pressure after warmed up was real similar to the Michelin Radials on the CBR-F2 race bike. I think I hovered around 29-32 cold (either tire) depending on what I saw that day after a few practice laps when re-checked.