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zStart Clutch in the dunes and production update

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After 2+ months of recovery from a broken ankle and lots of overtime hours developing my zStart autoclutch, I finally got out this past weekend for a fun ride on my CRF with the zStart. Over the past two months I've put in lots of testing time on my 300' driveway (over 15 miles!), at the local flat track and in the Boise foothills (fire roads). I've watched friends test it at the MX track while I watched from the sidelines and sent it off with my riding buddies to trail ride while I stayed home and nursed my ankle. Finally it was my turn!

I slapped on a massive 5.60 10 paddle tire and headed to St Anthony sand dunes with my brother and two other friends. We did a quick 20 mile warm-up ride in the morning, gassed up and headed out for the long ride.

The CRF is awesome in the sand, especially with the big 10 paddle tire. At first I thought it wasn't steering too well, then I realized it was because the front tire was in the air all the time! It steered alot better with a neutral or trailing the throttle. The tire just hooked up incredibly well and got me up and floating on the sand in a hurry.

The automatic clutch also worked great in the sand. Although not the drastic improvemnt the autoclutch brings to tight technical trails, stops and starts are smooth and those little low-speed recovery moves are a breeze.

Things were going great until we hit 50 mile mark of our second ride. One of the XR400s went to reserve and we were still a good 15 miles from camp. Then my brother on the Husaberg went to reserve and I started hearing a little clicking noise as my clutch engaged, hmmm...

When we stopped again, the zStart failed to disengage. Now I was starting to worry (we were still 7+ miles from our camp and about 2 miles from the nearest camp). I started racking my brain for what could possibly go wrong that would cause this.

I thought back to that 5 minutes I had to get the zStart back in my bike after work while my friends waited impatiently for me to load my bike in the truck (I use the original proto alot as a visual aide while building the new pieces). Then it hit me, I cinched the zStart down to the inner hub with my electric screwdriver, got interrupted and never went back and torqued the bolts.

At that point I knew the zStart had worked its way loose and suspected that one side of it had jumped out of the basket fingers, levering the other side into the friction plates (causing engagement). I let everyone know my prediciment (I couldn't stop!) and decided I best head to the nearest camp. I pushed my self down a little hill and with a clunk got myself going. About a half mile from the nearest camp one of the XRs ran out of gas. I reluctantly stopped and donated a few cups of my gas to the cause.

This time, when I rolled down the little hill and clicked it into gear I heard a snap instead of a clunk. The shock of dropping into gear with loose inner hub bolts sheared the inner hub bolts stand-offs.

The zStart itself survived the incident unharmed (it's pretty tough) and a new inner hub is on its way. Like any engine part, the zStart is not very tolerant of improper torque values. I'll be sure to highlight that in the manual.

As far as production goes... I am down to tooling for the last part (of the five parts in the clutch). Every part has presented its own little challenges to hold down while being machined. Until I'm done I can't promise anything but I'm hoping to have it all sorted out, tested and ready to sell very soon.


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Here's the latest update...

All of the production tooling is finished, finally! However, to speed up the test/debug cycle time on the production fixtures, we did all the parts in 6061 (4 of the 5 parts are actually 4130 but 6061 machines about 5-10 times faster than 4130). So now we're going back and making everything in the appropriate material, making sure we can make 10 of each all within tolerances and finally back to testing to make sure we didn't mess anything up along the way.

We can definitely see the light at the end of the tunnel now. Hang in there and look for the TT banner ad soon...


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Hey Mike, on what basis do plan on comparing the three systems?

Scientifically or Seat-o-Pants?

Are you planning on doing any long-term testing?

Who all's gonna be doing the testing?

On a different subject, how did your most recent group ride turn out? I hope to ride with you next summer.


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The ride went well, although not as well as the first one. We got nailed by an early snowstorm and so drove down to Hartmans Rocks, a high desert area. Rode some good singletrack there, but I still like the high alpine stuff better.

I am afraid the comparison wont be too scientific, I am not a magazine and had to pay for these things. The main flaw in this comparison is that the Revloc is on a CRF and the EFM is on a 250F. If there is someone in the Denver area that had a CRF with a EFM or a 250F with a Revloc I would love to include them.

I have already started the comparison over on the 250F side, if you want to go there and read it. To summarize, the Revloc is far easier to install than the EFM. But there is no core replacement issue. When set up to MFG recommendations, the Revloc engages far more smoothly (but there may be something a little off with the EFM, it pulses when it engages, and another TTer says his doesn't). The Revloc is cleaner in that no 3/8 inch spacer is required.

I think reliability is a big concern for people. I will keep track of hours on both and report any problems. I will let you know how much the clutch plates wear.

I am going to get three friends and go to an MX track and a technical enduro area and swap bikes. These friends have stock CRFs and 250Fs so there will be a direct bike to bike opinion comparison from these people as to how much the devices help. The skill level of these people varies quite a bit.

What I think we will see is that these devices aren't near as big a deal on the MX track as they are in technical enduro sections. I also think that the more inexperienced the rider, the more he will like these devices (but I will not put words in someone elses mouth).

I have my first HS race of the season tomorrow, and will use the CRF with the Revloc. I will post my impressions next week.

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I don't have any beta testers setup for the denver area but I'll try to hook you up with someone there if I get a buyer in that area.

I could also provide you with some technical information about the z-Start and at least some about the revloc (I have a very early revloc for the CRF, don't know if they've changed). Things like ramp angle, force generation curves, stall speed adjustment range, etc.

I have not seen an EFM clutch so I can't comment directly on that but for the most part, these things should behave fairly similar when setup the same way.

As far as installation goes, I think I have the other two beat easily with the zStart. Remove the clutch cover, remove the six pressure plate bolts and bolt on the z-Start pressure plate. I can do it in 5 minutes (although it helps to remember to torque the bolts, see previous post).

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Cool, Al. I really love these devices. People who ride mine love it and want one. I will point some business your way. Sorry I couldn't wait, I wanted one for my HS yesterday.

The ease of taking yours on and off is a good selling feature. If I had to do it over, all things being equal, I would buy yours because I have a WR and YZ 250F, and swapping back and forth would be so easy.

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