Carb overflows after sync

[stanG]

I’m looking for some help with a carburetor issue on my 83 VR. The carbs have been off, completely cleaned, jet blocks removed and cleaned, float levels set to factory specs and the low speed jets set to 2.5 turns. I have also installed the needle shim kit from Skydoc_17. Prior to the shim kit the mileage was about 38-39 mpg. The bike was running fine with no issues but the carbs had not yet been synced. Using a Morgan Carbtune, the initial setting showed the #2 carb (rear left) significantly higher than the rest. After adjustment, I was able to balance everything out using the proper procedure. Initial test ride indicated good performance with no issues.

 

A couple days later I rode the bike to work allowing it to warm up only a short time with the choke cracked about 25%. When I took off from the house I left the choke on for about a half mile then shut it off. Within the next half mile the bike appear to be flooding out and dumping some gas out of the overflow on one of the left side carbs. After the engine warmed up completely the flooding seemed to diminish. At lower rpms in 5^th you could smell some gas but it was not coming out of the overflow.

 

When I got home I pulled the side covers and put the Carbtune back on to check sync and it was OK. I noticed that there was a slight amount of gas on the top of the #1 and #2 carbs that looked like it was coming out of the air cleaner boot. I then reset the sync to the original setting where the #2 carb was reading higher vacuum and took another test ride. No issues and the gas on the top of the carbs was gone.

 

One thing that I have not done is replace the slider diaphragms. Could this be a contributing factor to this problem or is there something else I should be taking a look at?

[Yammer Dan]

Sea-Foam? Sounds like you could have got some dirty gas.Don't take much to keep them from shutting off the way they are supposed to. Piece of dirt could have gone right on thru after causing all that. Check drains to make sure they are flowing the way they should and catch gas in something to see if any dirt comes out of carbs that are acting up.

[stanG]

Don't think so. Remember, the problem goes away when the carbs are unbalanced and I have put over a 1,000 miles on it since all the major carb work.

[skydoc_17]

Hey Stan,

By returning the Carb. Sync to it's original position, (one cylinder pulling high vacuum) you are Band-Aid fixing a leaky Slider Diaphragm. I would bite the bullet, and replace those Diaphragms, and readjust the Sync again. Here is the link for the Sirius site where we get the VR.ORG discount. Be sure you mention you are a VR.ORG member:

http://www.siriusconinc.com/

My guess is, (because I haven't actually laid my hands on your bike) that raw gas is leaking past the pin holes in that Diaphragm. When you increase the vacuum in that one cylinder, it is sucking the gas into the intake. You could also have a sticking float bowl needle. (did you replace them when you had the Carbs. off?)

I am also assuming that you didn't do something crazy like ADD the Needle Shim Mod shim to the shim that was already on the Main Jet Needle, instead of removing the old shim and replacing it with the new shim. (no insult intended, just trying to think of all the reasons that your bike is flooding) Without the new slider Diaphragms, you really don't have a good base line for the condition of the Carbs.

Earl

[stanG]

Hey Stan,

By returning the Carb. Sync to it's original position, (one cylinder pulling high vacuum) you are Band-Aid fixing a leaky Slider Diaphragm. I would bite the bullet, and replace those Diaphragms, and readjust the Sync again. Here is the link for the Sirius site where we get the VR.ORG discount. Be sure you mention you are a VR.ORG member:

http://www.siriusconinc.com/

My guess is, (because I haven't actually laid my hands on your bike) that raw gas is leaking past the pin holes in that Diaphragm. When you increase the vacuum in that one cylinder, it is sucking the gas into the intake. You could also have a sticking float bowl needle. (did you replace them when you had the Carbs. off?)

I am also assuming that you didn't do something crazy like ADD the Needle Shim Mod shim to the shim that was already on the Main Jet Needle, instead of removing the old shim and replacing it with the new shim. (no insult intended, just trying to think of all the reasons that your bike is flooding) Without the new slider Diaphragms, you really don't have a good base line for the condition of the Carbs.

Earl

 

 

Float bowl needles are good and no... I didn't add the needle shim ;-). I have already sent an email out for the diaphragms to Sirius. I think you are confirming what I already suspected.

[stanG]

Following up on this... I have replaced the diaphragms and re-synced the carbs. The bike running very well now and the overflow problem is gone. Fuel mileage has increased to 42-43 mpg.