400exbiggun
10-03-2005, 06:41 PM
Long story short, i got a warrior and a blaster on a trade for my 400ex about a year or 2 ago. When i got the warrior it ran like crap, always has and seems to always will. So at that time i had no idea what i was doing topend wise and took it to a place in NJ called C&G atv or something like that. While it was in there i sold it to my sister for $1800...pretty damn cheap it seemed since i shelled out $450 for this new topend. It "got" a new timing chain, valve seals, and bored .030 with wiseco piston.
Took it home and it ran pretty decent. I only rode it around the yard a couple times since she never rode it. Then one day i took it to jack frost, after a few easy laps i saw oil leaking from right above the exhaust port :eek2: :eek2:. It sat for a while after that (meanwhile this motor had about 5hrs on it). We rode it somewhat then during the winter until it starting to get alot worse. Then one day in the spring i took it for a ride. It near died on me about ever 200 ft on the trail. Smoked like a ***** on startup, bogged every gear. Ill go 1/4 throttle, crack it to 1/2 throttle and hold it for about 10 sec then it would bog, backfire, sputter. It sat like this until about 3 weeks ago.
So I pulled it apart and the cylinder still looks good. Only one line in it, but its not really leaking from there. After I pulled it apart I knoticed a chip in the valve seat. Sent it out and got the intake valve reseated and a new seal put in. Installed with a new head gasket today. I can't stand working on a motor in a tight area, so I pulled the motor from the chassis. After I got it all in at TDC, cam all lined up, head tightened I turned it over by hand and again I hear a PSSSSSSSS comming from the intake valve on the compression stroke . Again it seems to have ****ty compression, as it takes no effort really to crank it over. Can I just slap the starter back in, hook it to the battery and crank it over out of the frame for a comp check?
I dont really want to put it all back in only to pull it back out for a complete topend.
Im still set on that the cylinder is good. It has no marks really.
Its pretty frusterating, i just want this beast to run right. It had a larger mikuni carb, supertrapp exhaust and k&N, after i got it running right i was going back 100% stock so i could run stock jets and not worry about jetting. But i cant get it to seem right.
Took it home and it ran pretty decent. I only rode it around the yard a couple times since she never rode it. Then one day i took it to jack frost, after a few easy laps i saw oil leaking from right above the exhaust port :eek2: :eek2:. It sat for a while after that (meanwhile this motor had about 5hrs on it). We rode it somewhat then during the winter until it starting to get alot worse. Then one day in the spring i took it for a ride. It near died on me about ever 200 ft on the trail. Smoked like a ***** on startup, bogged every gear. Ill go 1/4 throttle, crack it to 1/2 throttle and hold it for about 10 sec then it would bog, backfire, sputter. It sat like this until about 3 weeks ago.
So I pulled it apart and the cylinder still looks good. Only one line in it, but its not really leaking from there. After I pulled it apart I knoticed a chip in the valve seat. Sent it out and got the intake valve reseated and a new seal put in. Installed with a new head gasket today. I can't stand working on a motor in a tight area, so I pulled the motor from the chassis. After I got it all in at TDC, cam all lined up, head tightened I turned it over by hand and again I hear a PSSSSSSSS comming from the intake valve on the compression stroke . Again it seems to have ****ty compression, as it takes no effort really to crank it over. Can I just slap the starter back in, hook it to the battery and crank it over out of the frame for a comp check?
I dont really want to put it all back in only to pull it back out for a complete topend.
Im still set on that the cylinder is good. It has no marks really.
Its pretty frusterating, i just want this beast to run right. It had a larger mikuni carb, supertrapp exhaust and k&N, after i got it running right i was going back 100% stock so i could run stock jets and not worry about jetting. But i cant get it to seem right.