killer454
11-14-2010, 11:45 PM
as you guys may know i bought my first 400ex 2000 4-stroke awhile back and it was blownup with a bad piston.I have put a new 11-1 and it had a stage 1 cam,i whent riding for the first time yesterday and about 4 hours into the ride it started poping throught the exhaust on deceleration and reving in neutral.but ran fantastic
so i took it apart today checked the valves for adjustment,they where set right on.so then i noticed that the intake was hanging on the head at an angle,so i pulled the black part of the intake off and it seems to have a couple little cracks in it.is the intake suppose to be able to come apart in 2 peices?
1. the alluminum spacer 3-bolts to the head
2. the black round part that the carb bolts to
is this suppose to come apart?
anyway im thinking it was sucking air from around the intake causing it to run lean.i think the only thing that saved my engine was that im running a 175 main jet on the new build.i put the engine together with the 175 jet and it was rich,rich on the new plug when i first got it firedup,and after the ride yesterday i took the plug out and it actually leaned the moter out enough to change the plug to a tan color which is right.
im thinking if i set the jet up right from the start this 7 hour poping thing would have done my new engine in.
by the way it was also backfiring through the carb i noticed that today,but i didnt on the trails.
i hope this is the problem and i will repost here to let everybody know the outcome on this problem.
im posting this because it might help other people with the same problem on their 400ex.and can anyone tell me about the intake question,i have seen them for sale but dont know if they come apart in two peices.
thanks for reading
killer454
so i took it apart today checked the valves for adjustment,they where set right on.so then i noticed that the intake was hanging on the head at an angle,so i pulled the black part of the intake off and it seems to have a couple little cracks in it.is the intake suppose to be able to come apart in 2 peices?
1. the alluminum spacer 3-bolts to the head
2. the black round part that the carb bolts to
is this suppose to come apart?
anyway im thinking it was sucking air from around the intake causing it to run lean.i think the only thing that saved my engine was that im running a 175 main jet on the new build.i put the engine together with the 175 jet and it was rich,rich on the new plug when i first got it firedup,and after the ride yesterday i took the plug out and it actually leaned the moter out enough to change the plug to a tan color which is right.
im thinking if i set the jet up right from the start this 7 hour poping thing would have done my new engine in.
by the way it was also backfiring through the carb i noticed that today,but i didnt on the trails.
i hope this is the problem and i will repost here to let everybody know the outcome on this problem.
im posting this because it might help other people with the same problem on their 400ex.and can anyone tell me about the intake question,i have seen them for sale but dont know if they come apart in two peices.
thanks for reading
killer454