Posted: Mon May 25, 2009 3:48 pm
Well here is the deal, had this ATK 450 from Jeff Stoess. Quad ran when we got it but smoked and knocked. It supposedly didn't have many hours on it after being rebuilt. Tore it down, knocking was a broken cam cap bolt and so every revolution the cam would pop up and hit the valve cover, pretty strange. No big deal had a brand new ported head from Timbo with good cams in it, I'll just run that. Upon further inspection the piston and sleeve were pretty scarred up, not sure why. After removing the piston the oil ring was most definitely installed wrong and was over lapping, causing the burning oil problem I'm sure.
So I put a brand new Asso stock piston kit in it. along with this ported head. Put it all back together fired right up and ran pretty good, I broke it in a bit and began to tune it. At first it ran good, but after a while it developed a hiccup and would stumble pretty bad in the mid range. I figured it had to be the tuning, so I started tuning it more and EcuDiag failed when sending a map, that sucks, it messed up the Hex code and no I'll have to send it to someone to reflash. No biggie though got plenty of ECUs on the bench. Swapped one in loaded the settings. Stumbling got progressively worse, to the point where you had to go idle, or all out, no in between because it would stumble and miss so bad. Tuned it for hours and the weird thing was none of it would help the stumbling. It seemed like it was starving for fuel but after pulling the plug it was black so definitely not.
We switched out a bunch of things, coil, voltage regulator, and still it was doing this. After loading another map I took off on it and bam it just dies in my driveway and wont fire what so ever, something is definitely wrong. Spun flywheel I thought, or sheared key, nope not at all. Checked the compression and it read zero compression. All that I could think was that I didn't tighten the tensioner all the way or something ridiculous and it jumped time. Yanked the motor out, everything looks good. Not sure where to go with it. Lots of black soot on the exhaust ports. Piston is covered in fuel it seems, hopefully not oil? It is also pretty dark and dirty already.
Any help would be greatly appreciated. This is a downer for me being that its the first piston kit I've installed and I was so happy to hear it run good at first and now I'm just disappointed as ****.
So I put a brand new Asso stock piston kit in it. along with this ported head. Put it all back together fired right up and ran pretty good, I broke it in a bit and began to tune it. At first it ran good, but after a while it developed a hiccup and would stumble pretty bad in the mid range. I figured it had to be the tuning, so I started tuning it more and EcuDiag failed when sending a map, that sucks, it messed up the Hex code and no I'll have to send it to someone to reflash. No biggie though got plenty of ECUs on the bench. Swapped one in loaded the settings. Stumbling got progressively worse, to the point where you had to go idle, or all out, no in between because it would stumble and miss so bad. Tuned it for hours and the weird thing was none of it would help the stumbling. It seemed like it was starving for fuel but after pulling the plug it was black so definitely not.
We switched out a bunch of things, coil, voltage regulator, and still it was doing this. After loading another map I took off on it and bam it just dies in my driveway and wont fire what so ever, something is definitely wrong. Spun flywheel I thought, or sheared key, nope not at all. Checked the compression and it read zero compression. All that I could think was that I didn't tighten the tensioner all the way or something ridiculous and it jumped time. Yanked the motor out, everything looks good. Not sure where to go with it. Lots of black soot on the exhaust ports. Piston is covered in fuel it seems, hopefully not oil? It is also pretty dark and dirty already.
Any help would be greatly appreciated. This is a downer for me being that its the first piston kit I've installed and I was so happy to hear it run good at first and now I'm just disappointed as ****.