bigjohnsd wrote: ↑Fri Jul 19, 2019 9:27 pm
We fixed that Sumbitch!
On our recent trip to Prudhoe Bay, Festar's ManStrom got atrocious fuel mileage 30-33mpg was the best he saw.
The bike was obviously running rich and would emit some brown smoke from the tailpipes when under WOT conditions.
We knew that one of the previous owners had screwed with the ECU using a "Yosh Box".
The Yosh Box is a scarce item made by Yoshimura in the early days of motorcycle EFI to enable their Pipe selling dealers to make tuning adjustments to early EFI bikes to solve lean issues after pipe installation. Much research and searching on the VStrom Forums and ADVrider, as well as some emails, led us to believe that we needed to "Un-Yosh" the ECU and get back to ground zero on the EFI tuning as well as establish a baseline of engine setup. In our diagnostic checks, we discovered that the rear cylinder exhaust temp was running hundreds of degrees cooler than the front and as we got to Spearfish the bike had begun to really miss, especially at low speeds.
We replaced the sparkplugs and cleaned the air filter, performed a leak down check on the engine and discovered that the rear cylinder was leaking past the intake valves, Hmmmm.
We pulled all the plastic and went to work to check the valves. Both sets of intake valves were tight and the rear cylinder Intake valves had no to negative clearance. Exhausts were marginally in spec.
Alex, of BH Moto fame, had a brand new shim kit at his house which he was kind enough to let us use.
We reshimmed the valves so all were at the loose end of the spec.
As we reassembled the rear cylinder Festar and I discovered that something didn't look right. As we had taken it apart the Compression release was on the Intake valve rather than the Exhaust valve. Upon further investigation, the Cams have Cast INT and EXH right in them and the Cam Gears are labeled E and I, the last person to assemble the head (previous owner we surmise) had put the cams in the wrong side of the rear cylinder head. It is a wonder the bike even ran!
We put it together correctly, verified our valve clearances, and made a few more adjustments, reassembled and fired it up.
The FestarStrom ran much better, a quick Throttle Body balance and she was quite smooth. Festar did a little Vanocker Canyon test run and was much happier with the smoothness but was still depressed about the crappy Fuel mileage.
However, "Help was on the way," On Sunday I noticed in a VStrom for sale ad that a guy in Iowa had an elusive "Yosh Box" to go with his bike. I reached out to him and promised my first and second grandchild if he would loan it, rent it, sell it to us. Just like the typical FJR Forumite, he said, of course, you can use it, please cover my postage costs. He put it in the mail and it arrived on Thursday at noon.
We immediately hooked up the box and performed the simple 10-minute procedure to return the FestarStrom back to stock. A quick Idle adjustment later and we each went for a test ride. Both of us thought the bike ran much smoother and noticed no flat spots or lean surge.
Yesterday evening we made a 160-mile loop through the Black Hills, Spearfish Canyon, Highway 85 South to Newcastle, over to Upton, then Sundance and back to Spearfish on I-90. Speed from mid 50's to '80s.
When we fueled after the run Brian got 39.25 MPG! By George, I think we've got it!