Just a Different Carb Question '86 750

Playing with the carbs yesterday on the 1986 750. I noticed the choke inlets next to the butterfly valve situated the same in three of the carbs.


In #1 carb the outlet sits higher up.


#2 - 3 & 4 measure out at 22/32 from bottom of hole to lip of casing.


And yet mysteriously carb #1 measures out at 24/32


The vent holes measure the same diameter.
The carbs have been bench synced so it's not that the butterfly is a different positions.

WHY??? What is the purpose???
Doesn't this change the air/fuel mixture in that carb???
Is this on all your carbs???
Am I just being anal retentive???
Why??? Why??? Why is it like that??? :grief:

 

Have you tried to sync them on the bike?

 

You might even have that AR gene--but that's good sleuthing to notice it.

1. The carb bodies are just a casting and as such the lip is not a precision reference surface from which to make measurements.

2. The choke outlet is just a port to dump the enrichment mixture and allow air to by-pass the butterfly throttle valve. It is a dumb port that requires no precision in location to function as long as it is downstream of the butterfly.

3. Not a problem to worry about, won't affect synch or any other aspect of carb operation.

Take a look at this porn to see more circuits: http://vfrworld.com/forums/1st-2nd-...tor-fuel-air-circuit-identification-porn.html

 

Yes I have but that has brought on a whole new headache. Like I thought it would be a 5 min job. :nerd:

I bought used boots off E-Bay. I know better than to try to save money when it comes to such things. Wrong ones. I need to order some from the dealer in town today or the ones off of Partzilla.
With the used boots the rear cylinders were not firing. I could use fuel or a squirt of starting fluid to get them to fire. I found a bunch of leaks around the seals of the used boots so I put the original old cracked up ones back on. I could get fire in all cylinders when the original ones were first put on. Once they heated up a few times & hardened up again #1 cylinder stopped again. I have been using a temp gun on the exhaust pipes to check the fire.

To answer your question: have I tried to sync on bike?. Yes, had it tuned in at one point, but now I get instant high readings on two front cylinders and the no fire on #1. I have pulled the carbs a few times checking & rechecking my work. Bench sync with home made plastic feeler & rechecked with drill bit trick & checked again. I have floats checked with slide ruler and gauge (.35 +/-) also using the clear tube on the drain plug. Air mixture screws at 2 1/2 turns. Compression in between 150 to 170. It has a 2.4 needle jet, 122 main jets & 38 for a slow jet.

I also need to get a new battery this one is only putting out 42% of its ability (@ 165cca I'm only getting 70 amps on my test) This I'm sure could be a problem. Am I right on this or not as far as bad fire due to weak battery. I have been using a good car battery next to it as a jumper.

Any input from any and all helps. I know I have the boot and battery thing to remedy prior to knocking my head to hard.
My baby ran great prior to letting it sit for a bit.
Here it is beating my 87 GSX750 off the line. Just for the record there was no back brake pedal on the VFR so I had to shut it down sooner.

https://www.facebook.com/photo.php?v=487711057933063&set=vb.100000825194276&type=2&theater

Hope one of these links works

https://fbcdn-video-a.akamaihd.net/..._=1395940786_93c76dc8d6c9cccdc478cb29e9c644cd

 

Thanks for the info and the porn.

 

That don't mean shit ! :witless: so some guy wuz drinkin saki at the carb factory that day. arty2:

Keep comparing your plug colors until they're the same.........

 

Since you said it set for a bit-- might need to check and clean any clogged pilot jets, mixture screw ports or transition ports. Of course if you have a big ole air leak around the boots then no air is flowing thru the carb-- and the fuel circuits won't work without airflow. Good luck on getting it sorted out sounds like you are close.

 

The carbs will be on hold for a week or so. Partszilla sent me an E-Mail saying the boots will be sent on Tuesday the 1st.
So now it's off to bodywork & paint.

Squirrlman: I'll keep an eye on the plugs. Have you ever heard of or used these colortune plugs??

http://www.gunson.co.uk/item.aspx?code=G4074

Kennybobby: Thanks for the input. Yes it has been sitting for a bit. I pulled the carbs just for that reason, to clean out the fuel system. Had every thing out of the carbs....cleaned....poked.....blew [ :bootyshake2: I love when that happens ] .....pulled it apart again to recheck & triple check. Like ya said and I'm at that "Air Leak". I just don't think it's the carbs besides the fine tuning.