64 falcon/rev800
New member
hi there hope someone can help me its my sons sled if you try to give it say around half throttle it falls on its face starts breaking up new fuel pump ,new coil, cleaned the carbs a few times now fresh fuel looks to have good spark ? all line are new when you take the air box off it runs fine put the are box back on runs like crape again air box is clean not plug sled ran fine and then started to run like crap have had the sled for 9 years compression is 130 psi on both could it be not enough power to the coil ?? stater ?? this is my 10 year old son sled so its not riding hard thanks for looking and your help 
Bam94
Member
Did you ajust the air screw on the carbs.
64 falcon/rev800
New member
need help
its right in the same spot checked and double checked that a few times thats what i thoughtBam94 said:
PZ 1
Member
- Joined
- Mar 12, 2005
- Messages
- 987
The change with the removal of the airbox points to too much fuel or not enough air.
Incorrect float height. Holding the carb upside down, the float should be parallel with the float bowl mounting surface or flange.
Incorrect enrichener (choke) cable adjustment. The cables should have a slight amount of up and down free play at the carb fitting with the choke lever down. The enrichener plunger(s) could also be sticking or blocked.
Leaking carb inlet valve. Dirt in valve, worn or damaged.
The new fuel pump should eliminate that as a problem.
Make sure the rubber plugs inside the float chambers are in the right holes. Do a search here for the location.
The adjusting screws on the carbs are fuel screws. Turn in to lean the mixture, out to richen. Because the problem happened without anything being changed (or was something changed?), the setting should not be the problem, but the setting should be checked. The adjustment should be checked at least once a year anyway. Also, different weather conditions will change the optimum setting. The spec given for the setting is just a starting point - the screws should be adjusted with the sled running (at the specified idle speed) and the proper setting may be at some point other than the specified starting point number of turns. If the sled still has a bog, open the screws slightly in steps until it is eliminated. The normal recommendation on a system like this is to have both screws turned out the same amount.
Plugged muffler. Mouse nest inside, loose baffle blocking the exit etc.
Incorrect float height. Holding the carb upside down, the float should be parallel with the float bowl mounting surface or flange.
Incorrect enrichener (choke) cable adjustment. The cables should have a slight amount of up and down free play at the carb fitting with the choke lever down. The enrichener plunger(s) could also be sticking or blocked.
Leaking carb inlet valve. Dirt in valve, worn or damaged.
The new fuel pump should eliminate that as a problem.
Make sure the rubber plugs inside the float chambers are in the right holes. Do a search here for the location.
The adjusting screws on the carbs are fuel screws. Turn in to lean the mixture, out to richen. Because the problem happened without anything being changed (or was something changed?), the setting should not be the problem, but the setting should be checked. The adjustment should be checked at least once a year anyway. Also, different weather conditions will change the optimum setting. The spec given for the setting is just a starting point - the screws should be adjusted with the sled running (at the specified idle speed) and the proper setting may be at some point other than the specified starting point number of turns. If the sled still has a bog, open the screws slightly in steps until it is eliminated. The normal recommendation on a system like this is to have both screws turned out the same amount.
Plugged muffler. Mouse nest inside, loose baffle blocking the exit etc.
64 falcon/rev800
New member
just took the carbs off my buddys sled and we are going to try them they are the same year and sled and his runs fine going to try that and go from there