Posted: 4/28/2008 5:14:58 PM EDT
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Ok, So I picked up this 83 CM 250... 305 miles thing is practically new... Went over the whole thing today, spent 13 hours wrenchin and got some progress... However there is a problem... The bike will start on FULL choke, and revs fine... I push it down to half choke and the engine revs up and quits... It seems like its starving for gas.... I have cleaned the carb 20 times and I am sure its debris free... Gas is coing out of the tank at a strong dribble... Should it be a pretty good stream? I am at a loss on what to check, Float is fine, both jets are clean... The only other thing is the air screw adjustment. Any ideas on where to start on that? I can get it to barely fire on no choke when I mess with it, but as soon as I give it throttle it dies... Any ideas? Thanks! |
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Inspect the intake boots between the carbs and the cylinder head make sure all vacumn lines and plugs are intact and connected. If the rubber adapters are old and petrified they may be leaking. Spritz a little carb cleaner on the rubber adapter and see if you get a large increase in rpm. It sounds like it sat for a long time. The carburetors may need to be completely disassembled and soaked in real carburetor cleaner. The carb cleaner in the aerosol can won't get completely in the carburetor passages. Some auto parts stores have Berryman carburetor cleaner in a one gallon can with a little basket. It works well but stinks to high heaven. It really reeks!  Don't do it near the house. It will stink you and the garage up. Do not get in on bare skin either it will burn. Wear eye protection!!!!!!!Find a service manual and dissassemble the carburetors completely. The brass nozzles that the mixture needles go into will need to be removed if possible. Remove the pilot jets so the cleaner can get into the small passages. Make sure you get all rubber and plastic bits off. The ones you can't remove will have to soak so only leave it in the cleaner for 2-3 hours. Remove from the cleaner and rinse in very hot water. Use Eye Protection. Blow all the passages out with air. Then use your carburetor cleaner in a can to spray out the passages. Put the spray tube in the pilot jet holes and see if fluid comes out of the holes next to the throttle plate. You may need to hold the throttle plates open by hand. Eye protection is manditory! |
Does your bike have a vacuum activated tank petcock? Did you hook the vacuum line up correctly? Is the vacuum line cracked? If you did then see if your petcock has a prime position and turn the selector valve to that position, then try it again. If all else fails then remove the float bowl drains and see if you get fuel coming out of all 4 float bowls in an equal amount. As was pointed out, check the intake boots for cracks by spraying carb cleaner or Gun Scrubber in and around the boots to check for air leaks. |
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Yup! Got her going... I overlooked some holes in the carb.... Got it going now great... Bike has 305 miles! Got it for free, got under a 100 into it! Pics are here! |