Categories: all aviation bicycle gadgets misc motorcycle theater

Wed, 26 Mar 2008

Dyno time

After a slightly mad scramble to get myself and the CL175 down to Twinline, we arrived right on time. Jesse came with me, rolling his eyes when I said it'd probably take two hours. Little did he know.

Twinline is situated in an industrial district south of downtown Seattle, and occupies a small but well-organized space. Well, it's small for a workshop, perhaps 1500-2000 square feet. Ian (the head honcho, for lack of a better term) was out when we arrived, but we were instructed to roll the bike up onto the dyno, which was in the back of the shop.

The dyno itself is a big metal box with a substantial roller on one end. The bike is rolled up on top of the box so that the rear tire sits on the roller, and the front end is strapped down so it doesn't move. There's a computer attached to the roller, with a rat's nest of cables snaking around hooking various things into the system.

Ian's setup now includes an air/fuel mixture readout in addition to the spark pickups to determine RPM. We got the bike all strapped down and hooked up.

I'd asked Jesse to do some filming for me, but he was more interested in talking shop, and was uncomfortable jamming a camera into people's faces, so the footage I got is almost all tripod-mounted. Even then, I didn't film the majority of what happened, since I was too busy solving problems and working on the bike to operate the camera. The story of my life.

The first run was fine, but a little weird. The spark pickup just plain didn't work, so we had no indication of RPM, which is a fairly important part of the process. Still, we got a power curve out of it -- the engine produced a stunning 11.14 HP. (That's not very much.)

The second run was really exciting. Something was wrong with the engine, and it was producing thrilling gouts of flame out of the exhaust, running quite rough. Ian stopped the run, and we talked about what it could be. After a minute, we decided it was probably the coil, and set about testing: indeed, something was odd with the coil. Every once in a while it'd produce a big fat spark, but the rest of the time was producing really weak sparks. I also recalled that the right sparkplug cap seemed increasingly loose, so that it could be rattling around on the sparkplug, effectively moving the spark from the end of the plug to the cap. Not terribly useful, and it would certainly produce the flame-exhaust we were seeing.

The end effect of this was that I bought a new coil from Ian for way more than I would have normally paid. It's also a better coil than I would have gotten, so at least that's one thing I'll never have to think about again on this bike. It did sort out the rough running, though.

Of course, the new coil didn't fit where the old one did -- it was considerably larger, and had different mounting holes. So, we did what any good bodger does: ziptied it to the frame, to sort out later. Ian made up some cables for it out of the ridiculously expensive matching sparkplug wire, using his ridiculously expensive crimping tool. As an interesting aside, he mentioned that he's still at least a year away from actually being able to pay himself. Running a small independent motorcycle shop is no way to quick riches.

By this time, it was probably 10:30. Figuring out how to solve the coil problem took up at least half an hour, probably more. We'd wasted a lot of time trying to sort out the RPM-recording problems on the dyno. Ian got it second-hand, and I was actually his first paying customer for the dyno.

Finally, we were in the position to do what I'd showed up to do: get the jetting sorted out. The first real jetting run showed some wacky results, so we re-did it. It started making a bit more sense, and we were able to see: the engine was running too lean at high speed, which makes logical sense (finally!). We swapped out parts to fix that, going from #90 jets to #92 jets, basically up a size. That helped, but wasn't enough. There were no #94 jets in the shop, so Ian gently drilled out my #90 jets to approximately #94 size. This is not the best way to do it, since jets have a venturi-shaped cutout, but it was closer, and looked about right.

Unfortunately, doing the air-fuel mixture check on the second (right hand) cylinder showed that something extremely wacky was going on: it was all over the chart, literally describing a spastic sine-wave, like a rhythm-impaired earthquake. Some probing and prodding produced the conclusion that something was probably jammed up in the right hand carburetor, which was preventing it from filling properly sometimes, and overfilling it other times. Another thing to fix.

The final dyno run must have been around midnight. I think we did 14 runs in all. The best (ie, highest power) run we got was 11.81 HP. Not, in other words, very much. Still, between the first and the best run, we did manage to increase power by about .7 HP, which is a whopping 6% increase. More importantly, we were able to get the torque curve to look really good: flat from about 5k RPM nearly to redline, at around 7.5 lb-ft. It doesn't sound like much, but the bike and I will probably weigh under 450 lbs as we plod down the track.

It was nearly 12:30 by the time we left. Much later than I'd wanted to stay, but it was all worth doing. The one aspect I wasn't as fond of was that I was very aware that time was literally money. Ian charged me shop rate ($80/hour) for what we were doing, which was the special "first dyno customer" discount. Even so, it meant that pausing and deliberating on a problem cost a dollar thirty-three a minute. Thus I was inclined to do things quickly. This combined with the increasingly late hour to make mistakes more common than they should have been. Fortunately, there were no important mistakes, but it's definitely not my preferred way of working.

The night ended with me riding the Ninja 250 home (having dropped off the race bike at my house with a longing look at the front door, which I was still at least half an hour from entering) at about 1:15 in the morning, through pounding rain. I finally got to bed around 2, and spent a restless night once again trying to solve motorcycle problems in my dreams.

Tonight is dedicated to figuring out my coil and carburetor problems. Perhaps once I've got those solved, I'll sleep better.

Posted at 12:41 permanent link category: /motorcycle

Categories: all aviation gadgets misc motorcycle theater

Written by Ian Johnston. Software is Blosxom. Questions? Please mail me at reaper at obairlann dot net.