Between late last night and this morning, I disassembled, dipped, cleaned, and rebuilt Luna’s carburetor.
Luna is a 2006 Yamaha Virago 250 XV250. We recently purchased her as a gift for my girlfriend, Sherrie.
She (Luna) had sat off and on for 2 or so years and so she came with an interesting issue – during the first half-hour or so of engine run time (from cold), the first 1/4″ or so of the throttle would bog down the engine to the point of failure. Pumping the throttle and then moving into the 30%+ throttle range would do the trick, but even in the high RPM range, the bike seriously lacked power (even for a 250).
I surmised that it was likely a carburetion issue, but I like to tackle easy stuff first, so I checked / replaced the following:
- Checked fuel strainers on the main and reserve fuel lines, inside the gas tank, for debris, gumming, and corrosion. Fuel strainers were both clean, undamaged, and devoid of debris.
- Replaced main fuel line with clear hose and flushed reserve line.
- Replaced inline fuel filter on main fuel hose.
- Emptied gas tank of suspected degraded Regular grade fuel (in actuality, the fuel looked and smelled brand new) and replaced with Premium grade fuel.
- Mixed carb cleaner in with fuel and ran half a tank through the bike.
Slight improvement in the bike’s behavior was noted after a significant portion of the carb cleaner had been run through the carb, but only slight…like, so slight that the “improvement” may have been just my optimism and not any actual improvement…
Since the bike had recently been serviced (received new plugs, wires, and some other stuff) I surmised that the carburetor itself was simply so dirty and/or gummed up that to fix the problem, it would have to be removed, disassembled, and soaked in carburetor dip.
Friday, Jan 28…evening. Sherrie and I mount up to head to Woodstock so I can attempt the carb rebuild. Upon warming Luna up, Sherrie notices fuel leaking from the carb. I determine that the fuel leak is coming from where the float bowl seals to the carburetor body. Not encouraging, but luckily enough I had already thought to order and pick up a new O-ring. We top Luna’s gas tank off and hope she makes it the 35 miles or so before the gas leaks out. Thankfully, we were successful.
Friday, Jan 28…night. Drawing on some of my father’s motorcycle wisdom, I disassemble the top half of Luna and remove the carburetor.
Removing the carb body from the bike was tricky – the carb is mounted sideways from the “usual”, and it is attached to the air-intake on top and the carb’s outlet (the cylinder intake manifold) on the bottom. To remove the carb body, I removed the four bolts that secure the intake manifold between the cylinders. This allowed me to rotate the carb body out of the bike, detaching it from both air-intake and intake manifold.
Using a cupcake tin for the small parts (jets, etc.) and a metal flower pot for the main body of the carburetor, I mix a solution a 1 part Yamalube Carb Dip to 2 parts tap water. Jets, float assembly, pilot screw, and everything else I could take off the carburetor is removed. The main body of the carb is submerged in the flower pot and the rest of the parts are submerged in the cupcake tin. Completed disassembly / submersion around midnight. Left carb soaking overnight.
Saturday, Jan 29…morning. Carburetor parts are CAHLEAN…and I mean KUH LEAN! It’s amazing – they look brand spanking new. Removed carb parts from the dip solution. Cleaned the flower pot and filled with clean tap water…submerged carburetor parts and agitated to remove excess dip solution. Used WD-40 liberally to remove water and used compressed air to dry the carb body enough to commence reassembly. Inserted float assembly and follower. Used compressed air to blast out both low and high speed jets and double check for debris (aka “sunlight” test). Inserted both jets and attached float bowl and idle screw assembly.
Thoroughly cleaned sides of vacuum slide. Used a small amount of Vaseline to seal the diaphragm to the top of where the slide slips into the carb. Attached metal cover over the vacuum slide, along with the throttle cable mount. Inserted wire attachment points after thoroughly drying.
Reinserted pilot screw assembly. Tightened all the way in (NOTE: Be sure not to over-tighten when adjusting the pilot screw) and backed out 2-1/2 turns.
Attached carb to intake manifold, then rotated and finagled the air intake attachment until the carb was reattached and in position. Secured the carb to the intake manifold and air intake and secured the intake manifold to the cylinders using the four bolts I had removed yesterday. Reattached fuel supply lines and wires to appropriate places. Using needle nose pliers and a bit of tenacity, reattached throttle push and pull cables to throttle assembly.
Double checked to make sure there weren’t any spare parts, got the key, prayed, and cranked her up. It took a little bit for the engine to draw enough fuel into the carb to start up, but after 3 or 4 start attempts, she fired up and idled beautifully…ice cold with NO CHOKE. Muuuuch better… =) After a few minutes to warm up, tried the throttle. The “dead zone” in the power curve was gone, and she revved up beautifully and without hesitation. Fiddled with the pilot screw setting (ended up coming right back to 2-1/2 turns…good guess) and the idle screw to get “optimum” settings.
Also adjusted clutch lever ‘cuz it was WAY outside useful range.
Went for a test ride with Sherrie. She reports that Luna is running BEAUTIFULLY and has more power than she ever had before.
1x Yamalube Carburetor Dip – Purchased from Motions / Mountain Motorsports on Hwy 41 / Cobb Pkwy in Marietta, GA for about $10. Have about 1/2 of the bottle remaining.
1x O-ring for 2006 Yamaha XV250 – Also purchased from Motions for about $15.
1x Metal flower pot – Found lying around my parent’s house…no idea, but can’t be more than a few bucks.
1x Cupcake tin – About $5 at a grocery store in the bakeware section.