screw in vacuum line
 

okay i was checking over my bike again because the idle tends to fluctuate sometimes (ex. if i set the idle to 1700 it'll sometimes flutter to 1400) it feels like it'll stall out, i'm going to get the carb sync'd to see if that makes any difference.

anyway to the main point i was looking over my tubes and vacuum lines and came across what i believe is a carb breather line, the last owner seems to have blocked one line with a screw? what would be the purpose?

i found a second breather line and used my finger to plug the line for a second, it made the rpm slightly rise and made the engine sound like it was working faster. would it be harmful for me to remove the screw? or should i just leave it in there?

okay i took out the screw, and the exhaust sounded like it was a lot smoother. the engine carbs sounded like it was all firing in perfect order. the way the exhaust gases were coming out was very smooth, but i noticed the idle rpm was dipping a lot worse with the screw out and at one point dipped to 1200 rpm and backfired.

any input or help would be greatly appreciated.

Get you a service guide and check the hose routing.

I had to block a vacuum hose on my bike because the previous owner replaced the petcock with one from an F3, which does not use the vacuum hose. This left my hose lying around sucking in air to the engine, creating an intake leak and resulting in a lean running condition. The revs tended to hang around 3,000 when coming to a stop and it would backfire occasionally.

I blocked off my line with a screw to stop the leak. Sounds like you have a similar situation. Leave the screw in.

As for your rough idle, I'd clean the carbs first and make sure the fuel screws are all set to the same setting (stock setting is 2 1/8 turns out I believe for non-CA models). My idle varies by maybe 50rpm in either direction, and my engine is not the smoothest thing ever, since my bike used to be a trackbike.

thank you fuzzywuzzy!

i went back to look at all the lines, i do have a CA emissions bike. but what i discovered was the previous owner decided to chop out all the emissions parts and lines.

i found one of two lines (the one with the screw in it) had a sister line and it was also sucking in air creating a intake leak as you said. i simply plugged it up, the bike is running strong. no fluctuations in the lower rpm's at all.

thanks again for the advice, if you're ever in cali the beers on me :icon_beerchug:

You're officially the first person I helped! I just got my bike in February so I'm a rookie myself, but I happened to have the same problem you did. Glad it worked out for ya...