PROBLEM FOUND . .. .FINALLY!!!!!!!!!!!!!
Thanks to everyone for their thoughts and ideas. I had taken the bike into the dealer to have new tires put on and while it was there, the lead mechanic decided to take a run at the problem himself and went through the carburetor, the ignition, coils, etc. and couldn't find anything. He adjusted the
carb a little richer but said he thought it had not made a difference. I took it for a ride and it was no different and by the time I got home with it, it was even worse.
When placing my boot over the bottom exhaust tip, I could hold it there more firmly and the sound from the back cylinder of the open top exhaust had that characteristic heavy potato sound. But when I tried to close off the top exhaust, it kept knocking my boot away and the sound from the front cylinder of the open bottom pipe was extremely weak with no potato sound at all.
IT WAS TIME FOR THE ENGINE TO COME DOWN. I took down the front cylinder and removed the head. Went to the dealership and met with the mechanic. We worked like hell to get the valves out of it, one exhaust valve even appeared to be slightly bent, not to the eye but the manner necessary to remove it. We had to use a puller to yank the valve free from the head. The valve seats were holding but the valve action itself was so jammed that I likely had a piston strike on the suspicious exhaust valve at some point. Carbon was mounted all over the exhaust valves and the left forward intake even had carbon from back-pressure through to the intake on the other side. This was way beyond a sticky valve situtation. We had lost patency of the valve train almost entirely on the front cylinder.
This was definitely something that all the sea-foam in the world couldn't have resolved and it just goes to show that a standard compression test won't tell you whether everything is fine with the valve train. We had excellent compression on the test with no leak down, but that's because it was tested by just an engine-off rotation or two and NOT under running conditions. With the engine running, the failure of the valve train began to quickly diminish the compression performance of the front cylinder. The more it ran, the worse the valve problem became.
The repair????
Well, starting off with new 10:1 hi-comp pistons from Patrick Racing, new lifters and rods all the way around, stainless +2mm valves all the way around, recut the seats and port/polish the heads, competition dual valve springs with titanium keepers, Mikuni 42mm carb and a Patrick Racing ported intake manifold. We're going to leave the cam alone for now. The mechanic races bikes on the weekends and is an excellent tech on hi-performance parts. He's certain that we can steeply improve performance and compression, along with curing the valve problem, without the addition of the cam which will only add increased response at mid-range about 3200rpm or so and up. The new springs will add 20% or so increased pressure at the seats, the work to the heads, intake etc. will reduce carbon build-up and increase flow. It's already had
dyna coils and ignition added to round out the package.
Parts started arriving yesterday and by Tuesday, I'll be refitting it. He said when we're done with the improvements, it'll be a whole new riding experience.
So, I'll let you know how it all turns out, but that was the problem.
take it easy.
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