Monthly Archives: January 2009

Early last week I was invited to race with a team at the 12th annual 3 hour ice race on Fox Lake, about 1 hour north of here.  I’ve ridden on the ice but never raced but I have raced Supermoto and I just spent a summer having to learn how to navigate high-speed corn fields at GNCC races so I was up for the challenge.

There’s a group of local dirt track racers that I loosely know and that’s how my name was tossed into the ring as an available rider.  I negotiated time away from family and make contact with the guys organizing the team.  Over the course of our discussions I learned of an second team that was looking for a fill in rider.  It was suggested I could ride for both teams if we coordinated well enough.

I put every bit of warm clothing I own in my biggest gear back and headed north.  It was forecast to get up to 7 degrees F at 3pm but when I arrived it was -4.  And there’s little shelter on  a frozen lake so factor in the wind and you see why I brought every bit of my warm clothing.  It was damn cold.

They say the ice was 18" thick where we were parked. Good thing because that's a lot of hardware to support.

I got hooked up with the initial team organizer – Thomas Baker – right away and we drove a lap of the course in his car.  I was shocked at how long the lap was (3.4 miles) and at how many turns there were.  The ice was super hard because of the low humidity and low temperatures but that would turn out to be a good thing.  the bummer was that there wasn’t much ice showing.  Blowing snow and that the pick-up truck plows couldn’t scape all the snow off made it so that about 80% of the loop had more than a dusting on the ice.  Normally that would be a good thing – snow has to have more grip than ice, you’d think, but the heavily studded tires don’t grip on snow.  But they bite with heroic grip on ice.

Thomas introduced me to the other riders and to the bike.  It was a 2005 YZ125 that was bone stock except for the 18″ rear wheel, fenders and ice tires. I was stoked to get time on a 125 since I’ve been working so much on Project 144.  My teammates were super cool and laid back; it was going to be a fun time.

The troubled 125

Then I made my way down to the other team’s camp.  It was polar opposite of Thomas’ crew.  The second team had a heated 24′ trailer, D16 championship riders and a very, very heavily modified motorcycle. I stepped into the trailer but got the impression that the only way I would be on the ice with these guys was if proved to be fast rider.  Fair enough; they are obviously serious and the bike is worth something and they might be here to win.  The bike was a YZ250 that had been punched out to a 285 but that’s only the beginning of the mods this bike had.

The 3.4 mile course was so big you couldn't see the far side. Practice looked like complete chaos with bikes going every direction.

Practice started and I got two laps in on the 125.  It was very difficult to change from naturally avoiding hard and shiny surfaces to actually aiming for them.  The glare blue ice had Velcro-like grip and the “fluff” had nothing.  And there are no course markers out there on the ice – you just stay between the snow banks.  The 125 was a handful for me.  The ergonomics were fine and my hands were relatively warm but the suspension was pretty stiff and I was concerned about how choppy the ice would become.  I didn’t look forward to the battering the race would deliver.  My practice laps were fine other than finding the limit of traction once and low-siding at low speed.

I walked back down to the Trim Tex sponsored “factory” team for my chance to earn a spot as  a guest rider.  I was warm from just doing laps on the 125 and I understood the whole ice=grip thing now so I hoped to get in a clean lap or two.  I was drawn to the bike and wanted to spend time on it.  Over the course of the day I met a guy named Diesel Joe.  He’d obviously been involved with motorsports in the WI area for some time and knew about the team and the bike I was about to mount.  He suggested the bike was the best ice weapon at the race that day.  At first I was skeptical of those high praises but I would later learn that he might have been right.

Here’s a vid clip of the bike when it was a 250:

Hey! The grips are heated on the 285! Actually, the whole handlebar is heated.  The engine’s coolant is routed through the bar and your hands slip into tidy sleeves mounted on brake and clutch perches.  Fantastic.  I ended up racing in my Moose XCR gloves (even tho it was just above zero degrees F). Next, the bike as a Rekluse clutch.  I knew how this thing worked in theory but never put time on one.  It was pure magic.  The bike was running in gear when mounted.  All I did from then on was move the shifter with my foot and twist the heated throttle with my hand.

Handlebar plumbing.

The ride on the 285 was nearly as harsh as the 125 but my speed was up now so the bike skittered across the bumps rather than deflect off every one.  And the power delivery was much more friendly becuase of a broad and meaty power band, as opposed to the light switch characteristics of the 125.  Plus the auto clutch made it easy to recover from bad gear choices.  Just roll on the gas and point it in the right direction.

In the two laps on the 285 and only fell once – same as before with a mistake in the soft stuff at slow speed.  The course was quickly becoming one, narrow fast line with everything else just fluff and totally without grip.  Being somewhat precise and staying on line was the difference between a fast lap and falling down.  It also made it impossible to pass or be passed.  I did manage to get in a good enough time to impress the bike’s owner and they asked me to check back after my stint on the 125.  A good lap time for me was sub 6 minutes.

I drew the short straw for the start and brought her around to the start line.  I was chilled  but excited to get things rolling.  There might have been 60 bikes on the line and more than 100 rider being that most teams were relays.  My start sucked because I was on a 125 and totally uncomfortable in a field of dirt trackers armed with viciously studded tires.  I slowly lost positions on those opening laps because 1) I prefer to to keep the wheels in line with each other, 2) the ice dust was intense.  Those dirt track guys can really back it in and still maintain speed.  Really cool to be tailing someone into a turn and watch them drop the bike on its side, spraying a huge roost of ice.  But the ice dust killed my confidence and it stung on my cold face.

We planned on me doing 6-7 laps to open the race.  That would be about 45 minutes worth of racing before the next guy would take over.  I got a few spots back after the field spread out but for sure I was at the back end of the field.  As I passed the pit before my pit-in lap I signaled to the crew and put my head down for one last lap.  About 2/3rds around that last lap the bike bogged then died, rear wheel locked up and skidded me to a stop.  I didn’t even try to kick it because I feared I had just seized the bike and therefore ended the race for us all.

A rescue trailer was nearby so we loaded the bike and headed for the pits.  When I was on the trailer I got curious and kicked the bike just to see.  It started but sounded like the engine was full of gumballs.  Rattled something horrible.  Bummer.  I appologied profusely and made it clear that I’d pay for whatever it takes to put it back together.  Those guys were so nice about but I felt rotten.

Still, I had the other bike to ride if I could get over feeling bad about the 125.  I made my way down to the heated trailer to check in.  Within a few minutes it was my turn and I headed out.  I was back on song and catching riders every so often.  I only got passed a handful of times so I guessed that my pace wasn’t all that bad.

At home in the "fluff"

The ice was super choppy by mid race and had a few spots that had whooped out to the point of rattling your teeth out if you weren’t careful.  Good thing the bike had a steering damper.  I later asked the owner about the suspension settings and he preferred the front of the bike stay up high under braking.  I guess this is to keep the geometry sound for backing the bike into turns.  Perhaps if I were willing or able to ride tailend out I would have liked it more.  But the way I saw it was softer = control and with a high-speed course that was bound to deteriorate, several clicks backed out on the compression damping would have helped.  However, not my bike, and I’m happy to be invited and thrilled to be riding on the ice.

I had a few slow speed falls that were more frustrating than anything else.  It was difficult to tell what had grip and what didnt’ after the course fell apart.  I did manage one big get off that happened slow enough for me to process the events as they unfolded.  I hooked the front end on the edge of an ice rut and that knocked me off balance on the bike.  I was hard on the gas and the rear end let loose and ducked out from under me.  My left foot was sliding on the ice and started to put lateral loads on my knee.  That was about the time I jumped off.  The bike pirouetted off into the snow on the side of the course and I slid along beside it hoping no one was going to hit me from behind.  A deadman switch is required for AMA ice races so the bike was dead when I got back to it.  I remounted, kicked it to life and rolled on the gas.  It was in 3rd or 4th gear but it didn’t matter because of the Rekluse clutch.  Cool.

Cutting back across the course after the race. If my face wasn't so frozen you could probably see the smile. That as fun!

We finished 8th in the middleweight relay class.  I never intended to have great results but I’m happy with how it turned out.  Saddened that the 125 died under me and as a result of the bike breaking that team didn’t finish.  I think I raced for about 2 hours if I added up the time I spent on both bikes.  I’m pretty sore and tired today, the day after.

Good times and the experience makes me want to build up a bike and do it again next year.  How about it, Mark?

Vesrah Suzuki’s Mark Junge helped me dyno my RM144 project bike this afternoon. I’m trying to get more mid-range power out of an engine that’s designed to make power at high rpms. Why more mid-range? So it’s better in the woods. The challenge might be insurmountable but it’s been fun trying to change the way the engine performs, none the less.

Test Protocol: carbs, venturi splitters, jets, pipes and wishful thinking

We had time for 6 test runs.  I was playing hooky from work and I could only stand so much guilt before I had to bug out.  We ran a baseline that gave us a decent looking power curve and 27.5 peak horsepower but as we suspected, all the power was above 10,000rpm.  It’s impossible for me to ride this thing in the woods in that range.  That’s why we’re here; move that usable power down in the rpm range!

The engine’s displacement has been punched out to 144cc from 125 and the porting had been massaged but the compression ratio and carb are stock. I’ve put an FMF SST pipe on to eek more power across the range and that seems to be working, based on the limited ride time I have on the bike so far.

Mark had to calibrate the rpms the bike was making with the dyno and then get the computer set up to collect data. When it was time to start the bike, Mark grabbed the kickstarter with his hand and gave it a push. It started. I laughed because who would have though you could do that but I was also very embarrassed; why am I trying to make a beast out of this teddy bear?

After the baseline we inserted a Power Now venturi splitter.  It’s said to increase low- and mid-range power by increasing air velocity and decreasing turbulence in the bell opening of the carb.  With the splitter in place we fired it up and got ready to take data. The bike revved up to 9,000 rpm or so then totally died. I immediately jumped to the conclusion that we’d blown it up. False alarm – it was out of gas.

Here’s a video of what a few test runs look and sound like:

The Power Now slip-in splitter

After fueling up, the Power Now splitter made some unfortunate results. It did nothing but decrease both mid-range and peak power.  Bummer – I had high hopes for that thing!

Carburator swap

Mark called the helpful people at Sudco for some carb options. They sent us a 36mm Keihin carb that bolts right onto this bike. The stock carb is a 38mm Mikuni. Our thinking was that the smaller venturi would have a higher intake velocity and give more mid-range power. This is similar to what the Power Now splitter was supposed to do.

One of the best things about single, two-stroke engines (other than you can start them with your hand) is their relatively simply design. The Keihin bolted right into place and used all the same hardware as the Mikuni – same throttle cable and reed block and air box boots. But ultimately the best thing was that the bike started first kick after the carb swap!

The dyno / repair stand

Then the head scratching started. The smaller carb didn’t enhance the midrange at all but it carried the peak horsepower about 500 rpm farther down the line. It didn’t make more HP but it made it for longer. That wasn’t supposed to happen.

This got us going down the jetting road. Tony Pogue is Mark’s full-time mechanic. Tony has been doing race bikes forever and had lots of two-stroke knowledge to share with us. We pulled the plug on my bike and got Tony to “read” it. It was a lovely golden brown but, according to Tony, we could lean it out a little. He took a long look at the thing and pointed out that where the colors were and what the colors were was indicative of both jetting and timing.

Tony (right) reads the plug

Looks perfect to me but Tony says, "lean 'er out!"

Chasing jetting can take forever. I was going to run out of time, if I didn’t run out of premix first. We did change the main and raised the needle and got more peak power out of it but still didn’t increase the mid-range.

Mark called a friend about the jetting issue and why the smaller carb didn’t help the mid-range more. He learned that the stock carb has a throttle position sensor that we had bypassed. That might have been hindering the timing somehow so we plugged the electric solenoid from the stock carb into the wiring harness but ran the bike with the smaller aftermarket carb. Still no increase in midrange.

Singing along at 67mph and 12,000rpm

So what did we learn?  First off, there’s something the smaller carb doesn’t account for in the electronics.  The solenoid influences the throttle position somehow which in turn affects the ignition timing.  Second, there’s lots of performance to be had in the jetting.  This isn’t really new to me, just a reminder that the more you know, the more there is to know.  Thirdly, Suzuki has the thing pretty dialed with that stock 38mm Mikuni carb.  It’s going to be difficult to improve on how the bike is out of the box.

In the end, it might take some trail riding to get the best combination of parts and jetting. Have to wait until St Joe in late February for those experiments. I think there’s more to learn by fiddling with the jetting and I also think an adjustment to the timing could be good. I also think that becuase we were doing wide-open throttle runs the benefits of the splitter and smaller carb aren’t as obvious as they might be at 1/3rd or 1/2 throttle.  Riding the bike in the woods is the only way to know for sure.

It was a fun day of trial and error for me, although I didn’t walk away with a better performing engine. I haven’t lost hope and think there’s still a lot to benefit from with the lighter RM125 chassis. Next stop: St Joe Recreation Area in St Louis, MO.