Carb Air Tube Connects to What on the Bike

Uh, I am putting carbs back on VF500 (86) that have been off for a yeare and I don't recall where this is connected. See Image. Right now there is just a tube that turns down from between carbs 1 and 3. I don't understand the dynamics of the air tubes and carbs. If someone can explain I would appreciate it. Service Manual doesn't mention anything that I can find. If this tube is positive air like a vent, and blows out, then maybe there is nothing on the bike to connect to??

 

Nothing (On non-CA bikes). It just points down, venting to atmosphere. It won't necessarily "blow", it just allows the carbs to work properly, like a gas cap vent.

There is usually a little bracket mounted to a diaphragm cap screw with a hole for the tube, keeping it pointing down.

A tell tale when reassembling bikes is looking for clamp marks in a tube, like what style and what clocking. Or none.

 

Ah...California. Where the beer flows like wine! Had to get my reference in for the day. I was suspicious of this definitely no clamp marks. Thanks again for the information. .

WD

 

Thanks for getting all of the connections cleared up for me ! I am back at the bike today after first start in nine years yesterday (link below)

In the shop again today. It's cold and snowy outside and I have to leave the rollup door open. I opted to mix up a very small amount of Liqui Moly into the half gallon jug that is feeding the bike to let it idle for awhile with that mix. With the choke full, the bike idled at 500 rpm, so I began to nudge the idle speed up slightly to work toward 1300. Once I started doing this the engine began to lope/ocilliate between 1300 and 3500 rpm. At this point I started to nudge the choke off everytime the engine ocillated up to higher rpm. I got to the point where the ocillations were les drastic and the choke was about half off. I am wondering if the fuel line I am using from the gallon jug may not be letting sufficient fuel volume into the carbs? The bike sounds like it is running out of gas continuosly, however the bike will rev and run smooth when you back off the choke, but it won't idle with it all of the way off. Maybe I should go ahead and put the tank on? I was kind of holding off until I got the bike to start and run consistently.

I did have these carbs all the way off cleaned, then re-assembled. Ultrasonic bath, and replaced most of the rubber components.. No signs of any gas leaks at the carbs.

 

I have very low confidence it is a fuel supply issue if you can rev it out at all.

 

Any suggestions or ideas?

 

Yes, but you're gonna hate it.

Re-check your work and carb clean, verifying all passageways are clear. Thoroughly inspect the vacuum diaphragms and installation.

The symptoms (and audio) sound like dirty carbs. Possibly combined with a bench synch that is way off.

But I am often wrong when diagnosing across state lines, so install the tank and run it, so you can let that go.

 

I am with you on the part where it wouldn't rev if it was fuel supply. I concur with your dagnosis with the passage ways still having some crud. I think I will idle a little more Liqui Moly through her. It is improving it will idle with the choke only at about a third now, and isn't ocillating as much. I am also in agreement with the balance being way off. Kinda needs to idle at temp better than it is now to start that up does it not.? I am not far from taking them back off to go over them again. (I did not ultra sound the complete carb bodies, but did all the small parts. Replaced all of the diaphrams and other rubber. Mostly with your good guidance. I followed Squirrelmans how to about cleaning and checking the pilot passages. I don't think it is that? But.... I will run a little more tomorrow and get back to you.

Just ordered fork seal kits for my front end...puddle on the floor now.

By the way I never see enough of your bikes and shop. I need to check out your gallery if you have one!

WaveyDavey

 

Holy Shit! I did look at your gallery! I am not worthy.

 

Good plan and it is refreshing to see you are open to going back in and not discounting that. You have been very thorough and asking the right questions. You'll get it.

My photos are all over the place, I don't have just one collection gallery. That is part of the reason I am showing what bikes I rode this Summer and just to create some content and spark conversations.

 

Good plan regarding sparks and conversation. I certainly enjoy that.
Regards....

Here is a spark. I resurected this piece from the grave... I had a 69 Cortina that was a much better car than this all around. The Opels looked cooler though. It wasn't worth much after I jammed a V6 Buick GN engine into it.

 

Always loved those things... much to my Father's chagrin.

"It kinda looks like a mini Corvette!"

"But it's not a Corvette."

{balloon pop / fart noise / sad trombone}

 

davey, try removing the mixture screws again and shooting carb cleaner through the hole, followed by compressed air. how did u do your bench synch ?

note that our bikes dont run best without the air filter in place. in the video we see alot of unusual smoke from pipes. maybe test compression on all cylinders.

 

for a decent bench synch u should be lining up the throttle plate with the first progression hole starting w #1 carb. the big hole u circled isnt part of synch, ignore it.

 

SM,
Good idea to take the pilots back out and cleaning again. I did blow gumout through them and and compressed air as well as your wire tip!
Bench balancing was me measuring the the distance between the butterfly valve and port shown with micrometer at various fixed throttle openings. I have Hondaline vacuum gauges but haven't used them for a loonng time. You cant balance them while the bike is choked i don't think.
Smoke could be that it was only about 35F in my garage. Also could be 35 ml of liqui moly in 3/5 gallon of gas running through bike??
I do have the air filter installed. Oh and I dont have a compression testor at my disposal. I did change the plugs before start up. The old ones had no oil fowling, but did have some substantial carbon build up.

Thanks again. Keep it coming! I will report back after pilot screw cleaning.

 

What is the first progression hole? I think you told me this last year? Sorry need a refresh.

 

look on the side opposite the big hole for 3 or 4 very small holes. line up the #1 reference carb throttle plate to just begin to expose the first hole. match the others, and further refine by moving the idle speed screw in and out to check again. snap the throttle a few times after u move any synch screw.

some ppl like using a slip of paper (about .004" thick) to set synch by matching the drag when pulling if past the plate, too inaccurate imo.

best final step needs a proper synch with gauges unless ur pleased with how its running as-is.

 

Ah yes ... my mind is like a steel sieve. Similar to Cheech! I did do that when you suggested it last year! Can you believe that ? A year and I am still working on it!

WD

 

let some carb cleaner spray drain down through all the progression holes.......repetedly. followed with compressed air.

 

This is done with the carbs back off the bike I am assuming? Or ???