87 VFR 700F2AC – My 50th Birthday Present to Myself

OK gotcha.....

 

Yes, I believe I found all of them on the carbs including the oddly placed one. I did find one vacuum port that the previous owner must of put a screw in. It looks suspect, so I'll take it out and redo it. As for the airbox emissions, its spigot is capped well too.

I took off the steel lines off from the front of heads (next to radiator) and cut the metal flange off about 3/4" long. I then took out my tap/die set and threaded both flanges to accept steel plugs. I doped them up with thread sealer tightened them into the flanges, and then mounted the flanges back to the heads.

I'll try carb cleaner tonight and look for the leak. Otherwise, I guess I'll be ordering a set of diaphragms.

Repairs are sometimes needed, and it is not until you fix one problem that another presents itself. But, damn I just want to ride the bike! Thank you everyone for all the advise! I do appreciate the help, and this old girl WILL be back on the road soon!

 

Yeah, sorry. I abbreviated the regulator / rectifier. The battery would charge, but immediately discharge within minutes. Both the battery and the regulator / rectifier were swapped out. I went back with a Mosfet.

Yes, I did rebuild the clutch master cylinder, purge the line, and blead the clutch slave cylinder. I've verified with the engine not running that it does disengage the drivetrain, so I'm good there.

The brakes were functional, so I have not spent any time on them other than check fluid levels. For this bike to have been stored so long, I'm surprised that so many of its systems are functional and no leaks. I should probably knock on wood, but overall the bike is in pretty damn good shape. Now, if I can just get to drive it.

 

Sounds like you did a good job on the de-Cal.

Don't just blindly order diaphragms. Pop the air box off and check their action.

Did you install new insulators? I don't think that's the issue, just wondering.

 

Yep, new insulators.
Quick question, do the carbs need to come back off the bike to properly inspect the diaphragms? I re-read your post on checking them, and I think I understand. But, is there any benefit to pull them off the bike and visually inspect each one?

 

Not if you get the action you should expect. If they are pinched or torn, it is obvious. Plus I don't think all 4 would be bad, or improperly installed, so one bad one should stand out.

I really wouldn't expect the bike to run and rev (no load) as good as you say if they were.

 

Another dumb question from me.....

Are you trying to run the bike in 1st gear while on pavement (ground) - or on a rear paddock stand?

Would be interested in what would happen if engine running while bike on a rear paddock stand, in neutral, pull clutch lever, then let out in 1st - or any other gear.

And.....you are able to roll the bike around in neutral engine off, right? She rolls very easily...no resistance?

 

Bike on ground, engine running, in 1st gear, letting the clutch out slowly will kill the engine.
Yes, the bike will roll both in neutral and in 1st with clutch pulled in (engine or or off - same result/no resistance).

 

if the new needles and seats were not correct for your bike or if the float heights were incorrectly adjusted, it could cause your problem. your poor running might be due to low fuel level in the bowls, caused by wrong float setting, anything much more than about 9mm. seems like your carbs may be going lean in the main jet circuit.

vfrs usually run sub-par without air filter and box in place.

 

I don't think that's my problem. I ordered Honda OEM parts, and measured/adjusted each float as I put the carbs back together.
From what I've read, the floats for an '86 are supposed to be set at 9mm and the '87 at 7mm. I split the difference and went with 8mm.

 

that should work unless your measuring is wrong. did you need to change any adjustment tabs ?

 

Okay, I did a little test tonight to see how the diaphragms behaved. I put a minimal amount of air to each one, and they opened up. However, it appears they are closing very fast. I would expect them to close slower. Does this look right to you all?

https://www.youtube.com/shorts/8jKrYFvFS1M

 

^^ yes, best way to check.

you could measure the springs to see that the length is similar. possibly, the return rates could be adjusted a little by working on the springs by stretching.



>>>>>>>>>>>>>

the front/rear mismatch may not affect anything noticable in everyday riding, but it does seem irregular and needs further research.

 

Today, I took off the carbs to inspect each diaphragm individually. I did find one that had a small rip in it, and I'm hoping this is the cause of my problems. The other 3 all looked fine. Question, would 1 bad/torn out of 4 diaphragms be enough to cause the bike to die under load? Plus, what is all this rust colored shit on the diaphragm?

IMG_1432 by mcpmartin posted Mar 8, 2024 at 5:34 PM

 

If had one that was torn, I would replace them all. They are all probably very fatigued and likely close to failing the same way.

Sure looks like your fuel supply is (was) tainted if those were clean when you put it together.

 

is the red a sticky dried sealer stuff or powdery dry dust ?

red rust-dust is common at the bottom of float bowls on some bikes and could only get on the diaphragm if carbs had some fuel in them when they were set upside-down on a bench for some time. only a guess, but finding red dust right there is something ive never seen before on any carbs. how it got there is the question.

could be a sealer too, lab tests required. any sealer on the rubber that reduces flexibly might change its operation.

 

The color sure looks like the fine red rust type shit you find caked in the bottom of float bowls.

 

Yeah, it's a dust like substance. I neglected to check these diaphragms when I took out the float needles, seats, etc last weekend. Question, do I need to do any special cleaning inside these diaphragm areas? There are a few tiny passages under the diaphragms that I have not seen until today. Is there any special way to clean them?

Also, can anyone recommend a place to find replacement diaphragms? All the usual parts places are out of stock.

 

I found some on eBay....$98 each....ouch!

HONDA VFR700 750 INTERCEPTOR DIAPHRAGM CARBURETOR VACUUM SLIDE 16111-ML7-004 NEW

I'm sure others here can offer you some other options........

Push come to shove, you can contact Joe at V4 Dreams......he rebuilds them and also sells sets......

https://v4dreams.com/index.html

 

cheaper to buy just the diaphragms without the slide.