A few days ago after an afternoon ride, temp at 27 deg C (81 deg F) with the sun shinning gas was spewing out the air filter after I turned off the bike. I'd forgotten to turn the fuel valve off and a lot of pressure was released when I unscrewed a gas cap (gas was boiling in there). The bike started up ok but like a flooded bike. Anyway, is it possible that the back pressure in the tank could have damaged the carb somehow? (new CV carb installed about a month ago)

Today, the bike just stalled out on my way to a meeting. Gas was again spilling out the air filter, but this time it's early evening and quite cool outside. No back pressure in the gas tank when I opened a cap. Wiped up the gas, waited a few minutes and all was well after a hard start (flooded condition).

I have a new tank and an old tank. The old tank had a lot of fine particle debris in it so I installed an in-line external glass sided fuel filter and I clean it whenever I see debris in there. I don't know anythin about the HD CV carbs, is it likely that I damaged the float bowl mechanism on that first occurence, or by something getting past the filter?

The bike ran fine later on this evening, about an hour later after the community meeting. It's a 1988 Heritage Softail.

Pat

 

Why did the CV carb get replaced? This to me sounds like a carb tuning issue more than a damaged carb, but I am by no means the expert. Hopefully somebody with more fuel/air experience will chime in here

 

The bike had an S&S shorty on it when I bought it. Me, or the dealer's shop could not get that thing working right so it was replaced with a new CV, installed and tuned at the HD shop.

Pat

 

A few things here, first the cap should have vented the tank so there would not be pressure in there, replace the cap, second is that if pressure build up was present in the tank, about the only problem is that it would have flodded the engine by pushing past the needle and seat in the float bowl. I seriously doubt that any damage could have happened to the carb. You might check the oil to see if it was diluted by gas overflow from the carb. If you can smell gas in the oil, change it. With the junk in the old tank, it's a possibility you have some residuals in the carb now, it might pay to clean it out and start new again with a new filter also.

 

you might want to pull off the float bowl and check for crap in the bowl

 

Thanks TC

I have replaced the cap, so something else is going on there. My service manual does not show me how to take this carb apart to clean it - the one shown in the manual is totally different. Do you have a link that would show me how? I've googled but can't seem to find the right kind of page. I've checked the oil for contamination - no problem there. The fuel filter element was changed last night when I got home.

Pat

 

Pat, take a look here until I can come up with something better http://www.nightrider.com/biketech/hd_cv_mods.htm

And here http://www3.telus.net/dougsimpson/CVcarb.html
This isn't exactly your carb, but it will give you an idea of the parts in it.

[IMG]local://upfiles/2318/B4F9A2DA990C48E7BB54AE257B74676B.jpg[/IMG]

 

Pat

Basically, it's just the lower float bowl that needs to come off. 4 screw at the 4 corners, but you run into a snag with the accelerator pump rod. It's got to go back together the same way it comes off, it's simple just look on the foward side of the carb and you will see it and it's easy to see where it goes. You remove the float bowl and you will see the main jet hanging down the lowest and the slow jet is up in the well next to it. Unscrew them both and clean them and also up in the wells where they came out of with some gum out carb cleaner in the spray can. Don't get it all over the bike now. You'll see the float hanging there too, take the pin out that it hinges on and the needle will drop out with the little metal clip attached to the top. Note how that hooks on to the float for reassembly. Do the same clean out here and maybe even flow a bit of gas from the tank out there also to further clean it out. When you feel that you have done all you can to assure it's clean , reverse the order to re assemble it again. You might want to capture the drippings on a clean white paper towel so you will see any crud in there. Also check the openings in the jets themselves and clean them out to make sure they are not partially blocked. More than likely you will find debris in the needle and seat assembly when you remove it, that's what it sounds like to me. It's not allowing the fuel to completely shut off my the float assembly and flooding the engine.

When you have the jets out , clean out these and the air bleed jet that you will see on the intake opening of the carb with the carb cleaner.

You might also want to uncap the idle mixture screw and remove that also and do the cleanout there also, just don't replace it and screw it in HARD. Just LIGHTLY seat it and open it up about 2 1/2 turns open, warm up the bike and set the screw to the highest and steadiest mixture you can get out of it.

 

I can't add a lot from what's been said except I had the same thing happen to my flstf.
It indeed was the float seat and needle. Cleaned out the little bit of trash and I mean little and
no problems since.

 

Definitly some particals are hanging up the float. All you can do is completely take it apart and clean it.