Z-Start Installed Yea!!!
Posted March 15, 2003 - 10:20 AM
Posted March 15, 2003 - 01:49 PM
I did a 40+ mile ride today on a YZF450 with the z-Start. For the most part I loved it, I think I could get used to the YZF, well in fact I did get used to it and when I hopped on my CRF, I didn't like it as much but more on that later.
My big concern with the YZF is chattering. When I did the initial driveway tests (I have a very long driveway) everything was smooth. When I got out on the trail, there were a few conditions where I could get it to chatter. Basically, in first gear, crawling very slowly up hill, just before the clutch would lock up, it would chatter sometimes. Also, if I had been idling for a while and just pulled away slowly in first gear, it would chatter a little bit. Not a harmonic spring bouncy kind of chatter but a high frequency squeal kind of chatter. I could get it to go away by just going through a couple of stop/start cycles. It was most noticeable after idling for a while or after being on the throttle hard for a while and then coming quickly into a slow section.
I believe the chattering is caused by not enough oil getting to the clutch plates. We pulled it apart on the trail when we first heard it and the inner clutch and plates were very dry. It's not that bad, I think for MX you probably wouldn't notice it because you tend to be on or off the throttle pretty hard. Tight woods, you definitely hear it but it really doesn't affect enagagement very much.
I'm going to read up a bit here on what people have done to get more oil to the plates (I assume open up the holes in the center clutch) and probably try that to see if I can get it to go completely away.
This was my first time on the YZF450. I must say that I am very impressed. I thought I'd hate the 4-speed tranny, first gear actually feels lower than the CRF and 4th seems about the same as the CRF 5th! The only thing I didn't like wass the gap between 2nd and 3rd, I thought it was just a bit too much.
At first I thought the steering felt pretty slow but I just turned the GPR damper down to 1 and it felt great. I did no setup of the suspension and felt the forks were better but the shock not as good as the CRF. The YZF felt more stable to me.
Fun motor, it's the first four stroke that I thought could actually use a flywheel on the slick hardpack. When I first rode a 426F after riding my CRF I thought the 426F felt like an XR600 motor. After switching from the 450F back to the CRF, I thought the CRF felt like the 426F (in terms of flywheel effect). The CRF felt more forgiving and tractable, the 450F felt snappy.
We dragged the 450F against the CRF a couple of times. It was on a road with a bit of moisture, just about ideal traction. 2nd gear roll-on starts on the 450F I couldn't keep the front-end down. With 3rd gear roll-on starts, there was too much traction and it bogged a little. The CRF was launching perfect in 3rd gear (slighlty lower gearing) and beat the YZF out of the hole every time. If I had more time and changed out the z-Start external adjuster spring on the YZF for a little more slip, I think the YZF would have got the CRF. The YZF feels faster.
All in all a real fun day. I will work on the center clutch and see what I can do to get rid of the chatter.
Posted March 15, 2003 - 01:59 PM
Posted March 15, 2003 - 03:54 PM
Thanks and let me know how it goes tomorrow.
Posted March 15, 2003 - 08:14 PM
Glad to hear you got your auto clutch installed! Al installed mine last night and I was able to put about three hours on it today. I had them tune it fairly agressively and I discovered that it was probably too agressive. In Al's LONG driveway it felt good but in the dirt it acted a bit differently. The only issue I'm having with the clutch is that I can easily get it to stall the motor by locking up the rear wheel. Not sure what kind of tuning needs to be done but I'll get with Al and see what he recommends. Overall I am very pleased with it and glad I made the decision to go with the Z-start. The external adjuster made it a snap to adjust on the trail. Al and Danny at Rekluse Motor Sports were very good to work with. Highly recommended!
Posted March 16, 2003 - 03:45 AM
Posted March 16, 2003 - 04:41 AM
I was headed that way until the recession hit.
Posted March 16, 2003 - 09:16 AM
We tested the YZ426 for over a month and got no chatter, smooth engagement and no stalling. I'm going to pull both clutch bosses and see if the oil holes are different. For the 450s it may be necessary to have the oil holes drilled out or the Yamaha bulletin fix (putting in the '02 plates) to get the z-Start to work smoothly.
Posted March 16, 2003 - 01:43 PM
Just came back from the track and this is what I found. I still have heard no chatter since I put the z-start in. I also found the strongest spring worked the best and I used a set of calipers to measure the length of the spring coils when they are preloaded. The length I have now is .85 which is not much more than the spring length at a rest but it was what I found worked the best. The other springs really had little affect on the engagement. It probably is due to the short area on the YZ450F. As it is now it engages just above an idle and all it took was 1 turn on the adjuster to make a lot of difference from the .85 setting. The YZ450F absolutely needs a flywheel weight as I could still stall it with a blip of the throttle at the wrong time. Power slides into corners worked great as it never stalled once I had the right spring setting and I think the z-start broke in more as I used it. Also the bike kept running after I dumped it which was pretty cool. The z-start is great it just is going to take me awhile to get used to that big empty area on the Handlebars. I do not know how many times I reached for the clutch and came up empty and felt a feeling of panic due to the empty reach. I am going to order the Dr. D 6 oz tomorrow and I think with this I will be set. I also found the riding a gear higher than I normally do worked the best for me now, with the slipping of the clutch I had no worries anywhere on the track in 2nd. Once I put it in 2nd it never came out and this is a very tight indoor track which is very gear sensitive. Great work! This product is highly recommended to anyone.
Posted March 16, 2003 - 02:15 PM
I know what you mean about reaching for that clutch lever! It was a strange feeling not having it there because it's just second nature. I'll be speaking to Al this evening about tuning for my stalling issue. Other than that I love the new clutch!
For those that are interested, I have posted photos on www.wr450.com of the installation into my WR450.
Posted March 16, 2003 - 02:23 PM
Posted March 16, 2003 - 03:45 PM
I don't think you'd be going wrong with the 6oz flywheel, I think the 450 could use it, it is a bit explosive down low. However, you shouldn't need it to prevent stalling, especially if you increase your z-Start stall speed a bit.
Posted March 16, 2003 - 04:15 PM
Posted March 16, 2003 - 04:48 PM
That being said, lots of other things can cause stalling. If you stalled in the air from chopping the throttle, that does seem a bit weird and could be lack of flywheel inertia.
With a high z-Start stall speed, the clutch is fully disengaged early enough that decelleration of the engine slows quite a bit before you hit idle and the motor can generally recover without stalling. The lower the stall speed, the faster that decelleration is into idle and the more likely you are to stall.
Flywheel inertia definitely helps keep the motor going in these situations. But everybody seems to like a low stall speed, especially now that we have the external adjuster and you can dial it in to exactly where you want it. One real nice thing about dial'ing in a low stall speed is that you can keep your engine braking down hill. At one point on yesterday's ride, I stopped at the top of a steep hill while in first gear and began rolling down the hill with the clutch disengaged. By the time I hit 10-15mph, the clutch had re-engaged with compression braking without me blipping the throttle.
If you're racing, I recommend turning your stall speed up at least 250 RPMs above idle and make sure your jetting is spot-on to avoid a stall at any cost. If you're just out trail riding and you like a real low stall speed, just turn the stall speed down to where you like it or until stalling becomes an issue.
Posted March 17, 2003 - 10:22 AM
Posted March 17, 2003 - 07:35 PM
Al took my bike tonight and went through the clutch. When he installed it Friday he mentioned that we were pretty tight on the clearances between the pressure plate and the first clutch plate. He added one extra layer of shims and this fixed the stalling problems. I know this has helped them with R&D and I hope they provide this level of service to all their customers. They have been really great to work with!
Posted March 18, 2003 - 01:26 AM