Carburetor Overhaul

11/25/12
Tore into a planned tuning job this weekend over Thanksgiving. The ninjette has been running oddly and since I had repaired the front end chatter problem a few weeks ago (check tightness of your engine mounting nuts and bolts!), it was time to tackle this one. The transition from low end to midend felt lean and the bike tended to sputter and/or hesitate momentarily off the start line or at the beginning of the drive out of a 30 mph turn in 3rd gear. After that, pulled to redline strong. Had the carburetor cleaned by a shop in the summer so it must be a cold weather tuning issue. I figured I would also recharge the forks and see how difficult it would be to replace the fork springs with those .70 Sonics I have been eyeing. Turns out Road Rider was having a sale so I bought some brake fluid for an anticipated brake fluid replacement due soon.

So on my list of things to do this weekend:
1. Remove airbox through rear of bike
2. Cut off battery box from airbox
3. Replace K&N air filter with stock and replace plastic retainer
4. Pull carburetor, drain any water from bowls, drill/check mixture settings, clean pilot passages, test to see if shimming the needle was necessary.
5. Change airbox to carburetor spring clamp to a more normal hose clamp using a screw.
6. Recharge forks and replace retaining ring with easier to remove 1.25" snap ring
7. Add fuel filter between petcock and carburetor
8. Shim needle with #4 washers if necessary.

Started on Wednesday. Tore into fender and rear fairing removal in order to yank the box out of the rear. Also removed rear wheel. Very messy to get to some of the bolts, but straight forward. Would have been cleaner if I had removed the wheel prior to getting to the underside bolts. Also removed the R/R and ignitor and loosened the junction box bracket to make room for the box to come out. Also yanked the tank and the front fairing. Box came out easily, just as the 250 faq advertised. Not a lot of sweat. Split open the air box and cut off the first half of the battery box. Should have started on the side with the screw and ignored the recessed area. 2nd half I wised up and the cut was much cleaner. Replaced air filter and plastic retainer. Yanked the carburetor. Sprayed the passages with carb cleaner which drained through quickly. Mixture screw blocker was already removed. It was set to 3 turns out. Left it there. Had difficulty with the hose clamp replacement during reinstall and went back to the spring clamp. Great, now the forks. Remember, safety glasses on and don't "look down the barrel," so to speak. Popped out the fork caps on bike. Used a 1/2" drive ratchet to push the cap down (thumb on socket attachment point) and then a small screwdriver to pry out the end. Then took needle nose pliers and popped it out. A third hand was helpful. The two jaw puller was completely unnecessary. Unloaded the spring carefully and pulled out cap and spacer and set aside. Pulled forks, dumped the fork oil (so little?), and cleaned with break cleaner and added 160mm of maxima 15w fork oil. Put everything back in and replaced the retaining clip with a snap ring or "circlip." Forgot to mark the bottom out point. Damn. I'll do that when the sonics go in later.

Test run was OK. The off the line hesitation was gone, but the roll on hesitation was still there. The forks felt great! Very confidence inspiring. Except when the engine hesitates during roll on. Not inspiring. Should be very easy to pop in the sonics later. Setting the sag by cutting the spacer will not be fun. Should put in a stainless steel snap ring at that time as well. The one I sourced from home depot will work for now.

Went back to it on Sunday. Work invested to remove the airbox and take off the battery box on Thursday was definitely worth it. I just scooted the airbox back and popped the carburetor out. Needed to undo the lower coolant bottle and the junction box bracket to make room for the scoot. Popped out the needle. Turns out a washer had already been added. Put in one more washer. Cut the fuel line and put in an inline filter. Checked to make sure stock filter was still there. Left both in for now. I don't the second filter will cause too much of a restriction. Dumped the stock clip clamps in favor of normal hose clamps.

Test ride was AWESOME! Ready for next mountain run and work commute.