Last Sunday I the alarm went off at 3:30A to head off on the bike to provide spare wheel support for a 106 mile onroad/offroad bicycle race, but it never happened. The weekend before I put about 350 miles on the bike and it ran like a top-didn't miss a beat. Fast forward to Saturday, I washed it and started it before turning in for the night. Then on Sunday morning I started it up, settled right down to a normal idle, suited up and pulled out-putting down to the end of the street. When I gave her some throttle she totally choked out with any throttle when the revs got to 2.5 to 3k rpms. I let the carb drain for a few minutes and started her up again and still was doing the same thing. I pushed it back to the house and confirmed again fuel flow, checked the main, the jet needle, and the needle jet for any obstructions. All was clear. I realize the idle jet controls up to 1/8th throttle opening and the needle jet taper controls the next portion of the throttle opening. This is why I checked the jet needle and needle jet. Sitting in the driveway at 5A on a Sunday morning holding a flashlight in my teeth wasn't the way I wanted to start the day. I'm stumped. I've got an inline automotive fuel filter upstream, so the gas should be free from debris. All passages are free which control this portion of the throttle opening, yet the bike bogs to the point of dying with any throttle input. Gonna pull the carb this weekend to play inspector Clouseau and try to figure this thing out...or I might finally install that FCR that's been in the bottom drawer of the toolbox. Any other ideas from the collective? The tach has had an intermittant short for the last 600 miles. I can't imagine this would have any effect. Any ideas or suggestions? The '03 I had demonstrated a similar problem (not wanting to rev out) but after a whole lot of head scratching I found one of the wobble heads on the valve adjusters had broken off. Surely this hasn't happened....again at only 13k miles. Dirty
The first thing that popped into my head was a leaky diaphram on top of the carb slide. If these leak on a BMW airhead, the bike will not rev past about 4000 rpm. You might just have the same problem here, although the bike started acting up after you washed it, so maybe water intruded somewhere?? Good luck.
The slide diaphram is fine. I pulled it to get to the jet needle and needle jet. It won't rev out in neutral. Thanks for the input guys. Dirty
A couple of things to check, try running a fuel hose direct from the petcock to the carb bypassing the fuel pump and any filters... Check your fuel cap for proper venting... If your tach has been shorting out, I would go over your wiring, do a full inspection including the underside of the cluster strapped to the dash support bar... Try snipping 1/4" off your spark plug lead and screwing the cap back on... Check the wires inside your ignition switch... Check the cluster going into the CDI... Lets hope it is something simple,you may just discover something lodged in the carb internals when you tear it down...
Make sure the ignition is sound. Double check spark plug cap, and coil connections. Check to see if the inline fuel filter is clear, its a tiny filter inserted into the steel line of the carb. If the carb has been worked on, it may be missing. daryl
Been up to my eyeballs with Work, Life, Scouts, and the Fam. Gonna get into it this weekend. If the 640A problem isn't enough, Tiny D and I went riding this past Saturday. Me on the YZ450, Tiny D on his '09 259SXF. He always suits up and manages to head out before I do just to make a few passes back and forth within sight of the parking area. Well, he was gone for about 10 mins. and by this time I peeled off to go find him so we could get the first ride in. I rounded the corner and there he was pushing his brand new to us (but used) bike back to the car. We never could get it started again. Fuel, and spark were both good, but it wouldn't even fire. Fingers crossed though that we don't have some sort of catastrophic failure on our hands. Arrrrrrggggghhhh! He spent the day tooling around on my 450 which makes him smile even bigger than his 250. It would have been a lonng ride home if he hadn't gotten in ANY seat time. We get home only to find that my next door neighbors ORANGE lawnmower crapped out on him. Superstitious? Nah. Dirty
Dirty, Check the idle jet and blow the passages out(if completely plugged the running goes way off), check for fuel flow above the float needle and the float system after you bipass like Gunner suggests. bill
Ahhh. Mental therapy today out in the shop. Mental days are good for the soul....provided you have a good set of tools and some Motorhead on the hi-fi. The on-again off-again tach was partially disconnected. I reconnected it and loosely zip tied it together for good measure. All four wobbleheads on the valve adjustment screws were intact. So this potential culprit was scratched. I went ahead and adjusted the valves just for kicks. Spark Plug was fine. I pulled the inlet filter of my Holy BST. Fine. Then pulled the carb and had good intentions on going through it from stem to stern. I've been putting off installing the FCR39 I pulled off of the '03 for some time now, so I went ahead and pulled the trigger. I went through this thing, checking everything. It all checked out just fine and the AP still squirted across the shop. It fired right up! It's all good in the hood. Man, I wished I mounted up that FCR 10,000 miles ago. The thing lofts the front end now like my YZ450 does. Thanks for everyone's concerns and input. Dirty
