Beware of Auto decomp damage

Frost,

now that you have the cam installed how does the e-start work? A friend of mine has a 07 and it is showing the same signs. Also, if you have it handy, can you send me the part # for the bucket?

Frost,

now that you have the cam installed how does the e-start work? A friend of mine has a 07 and it is showing the same signs. Also, if you have it handy, can you send me the part # for the bucket?

Hey Max

The buckets are officially called “valve lifters” and the part number is Y 3FV-12153-10-00. They’re a tad pricey, I paid $49.99 each.

The 06 YZ cam # is Y 5TA-12180-10-00, $256 for that.

I haven’t installed the parts yet. I had friends visiting last week, and the weather has been beautiful so I’ve been getting some practice on my trials bike. When I get it together I’ll let you know how the starting is.

Hey Max

The buckets are officially called “valve lifters” and the part number is Y 3FV-12153-10-00. They’re a tad pricey, I paid $49.99 each.

The 06 YZ cam # is Y 5TA-12180-10-00, $256 for that.

I haven’t installed the parts yet. I had friends visiting last week, and the weather has been beautiful so I’ve been getting some practice on my trials bike. When I get it together I’ll let you know how the starting is.

I just thought I would share my experience with the e-start and the 06 cams combination. The e-start is somewhat finicky now with the cams, but it does work, it just takes some figuring out. Almost like a carefully planned ritual. Here's what I've found with my bike:

Starting the bike cold - Choke on & give it a twist of gas - fires right up every time.

Starting hot after a short break to wait for other riders, take pictures, drink water - Small twist of gas and hotstart lever - starts right up 99.99% of the time.

Starting warm after being turned off for a few minutes, (this is the tricky one) - No gas and no hotstart lever, works most of the time, occasionally it might refuse to start, then I kickstart it.

What I've also noticed is that if it doesn't start within the first 3 attempts with the button, the battery loses power and doesn't spin the engine fast enough to start anymore.

I took a die grinder to my decomp pin to make it more rounded. Then I polished it up with some emery cloth. It was difficult because the pin can twist back and forth about 40 degrees and you are working very close to the cam lobe. I can't take as good closeups as Frost. it came out okay, but I would have liked the sides to be more symetrical. We'll see if it works.

3442552236_301c1d8334_o.jpg

I took a die grinder to my decomp pin to make it more rounded. Then I polished it up with some emery cloth. It was difficult because the pin can twist back and forth about 40 degrees and you are working very close to the cam lobe. I can't take as good closeups as Frost. it came out okay, but I would have liked the sides to be more symetrical. We'll see if it works.

The fact that the pin can ONLY rotate a limited amount can be turned to your advantage in that it means you need only chamfer one side of the pin, and don't really have to address the edge adjacent to the cam lobe. Round over the leading edge in a slightly curved fashion so it doesn't matter if you grind it totally square with the lifter, and leave it at that.

Hey Frost,

Thanks for those #'s. I found them since I posted last. Do you or any others out there know the difference between the 06YZ and 07 YZ cams. They have different part #s as well as the intake cams. Erick, Thanks for the starting info.That is exactly what I need to hear. What year cams are in your bike, what year bike, and any performance gain? Thanks all.

The fact that the pin can ONLY rotate a limited amount can be turned to your advantage in that it means you need only chamfer one side of the pin, and don't really have to address the edge adjacent to the cam lobe. Round over the leading edge in a slightly curved fashion so it doesn't matter if you grind it totally square with the lifter, and leave it at that.

I ground the leading and the trailing edge. My guess is only the leading edge is doing the damage, but chamfering the trailing ede won't hurt either.

Do you guys think the pin is causing all of the damage or is it from a general lack of lubrication and the cam and maybe the pin are doing this?

Do you guys think the pin is causing all of the damage or is it from a general lack of lubrication and the cam and maybe the pin are doing this?

The damage is only showing up on the bucket that the pin contacts. All other buckets are fine. Maybe it's the pin and a lack of lubrication, but it's definitly the pin. But I don't think lubrication is causing it. It seems like everyone who looks close enough at their bucket sees the same thing.

I ground the leading and the trailing edge. My guess is only the leading edge is doing the damage, but chamfering the trailing ede won't hurt either.
You have a point about the trailing edge. Either way, though working the sides of the pin is unnecessary.
Do you guys think the pin is causing all of the damage or is it from a general lack of lubrication and the cam and maybe the pin are doing this?
There's no lube problem with the design.
I just thought I would share my experience with the e-start and the 06 cams combination. The e-start is somewhat finicky now with the cams, but it does work, it just takes some figuring out.

Thanks for the info Erick. The first time I fire up will also be running the new Athena jug and piston, so I’m sure that I’ll also be fine tuning my starting procedure. I’m very accustomed to revising startup techniques. When I installed my new block heater, I also changed the jetting for colder weather. The bike was nearly impossible to start, but ran great once it did fire up, so I thought maybe my starter jet was too lean. Turns out the block heater works a lot better than I expected. At -30C, I plug the heater in for less than 5 minutes, and the engine is too warm to start with the choke. Now I plug in and fire up – no choke – and it starts perfectly.

I took a die grinder to my decomp pin to make it more rounded. Then I polished it up with some emery cloth. It was difficult because the pin can twist back and forth about 40 degrees and you are working very close to the cam lobe. I can't take as good closeups as Frost. it came out okay, but I would have liked the sides to be more symmetrical. We'll see if it works.[/img]

You’re a brave man Pablo, nice to see some experimenting. For the close ups, most digital cameras have a macro setting that let’s you focus very close to the cam, and switching to manual focus helps too. When you’re up close, the auto focus seems to jump around to different points. It seemed to like the lobe and the shaft more than the pin. I shot my pics through a lighted loupe. I pushed the camera lens right into the eyepiece and the autofocus worked fine through the magnifying glass. The light helps too, and I get great detail when I blow the images up to full resolution.

Hey Frost,

Thanks for those #'s. I found them since I posted last. Do you or any others out there know the difference between the 06YZ and 07 YZ cams. They have different part #s as well as the intake cams.

Do you guys think the pin is causing all of the damage or is it from a general lack of lubrication and the cam and maybe the pin are doing this?

Hey Max, I don’t know the difference between the 06YZ and 07 YZ cams, but the 06 YZ exhaust cam lobes are taller and wider than the 07 WR lobes.

I think the pin is the cause of the damage, but I’m wondering when the damage is being caused. I’m pretty sure it’s happening at startup, since once the engine is running I can’t imagine something causing the counterweight to move to the pin out position. The question is - is it at normal startup, or is the pin sticking a bit at startup and staying out longer than it should, or is the pin sticking and smacking the bucket for a good while during the beginning of a ride.

I tend to start my engine and let it idle to warm up. It seems to me now that it may be a good idea to rev it a bit right away, to make sure the decomp counterweight is flung out and the pin retracted. You’d think that the high idle with the choke on would do the trick if the pin was sticking, but as I mentioned, I don’t use my choke for winter morning start-ups, so my engine doesn’t go through that – start off cold, then rev up as it warms and flick the choke off- routine. Also, when you start your bike when the engine is warm, you don’t get the high idle revving, (which may help to retract the pin, if it is sticking).

Now that I read what I’ve written here, I’m thinking that warm engine starts may be more likely to cause damage than cold engine starts, which was my initial thought. Of course, as always, I could be wrong.

I have a new valve cover gasket, and I’m thinking about modifying the half moon puck beside the exhaust cam, so I can see the decomp counterweight while the engine is running. Maybe I’ll grind out the metal cap and set in a piece of lexan. Even if the engine is spinning too fast to clearly see the gear, the digital camera should be able to stop the action at low RPM. This may also let me see if frost is forming on the weight and causing it to stick. I have seen frost under the valve cover when I remove it while working outside, so for me, it makes sense that ice could be one of my problems, although that goes against my “warm engine startup damage” theory. Time will tell.

Hey Max, I don’t know the difference between the 06YZ and 07 YZ cams, but the 06 YZ exhaust cam lobes are taller and wider than the 07 WR lobes.

The difference in the '06 and '07, or for that matter, '03-5 cams is timing. The '03 set has closer lobe center spacing than the '06, which is closer than the '07. Running wider lobe centering gives a bias toward top end power at the expense of low end power. Other than that, I believe these 3 different YZ450 cams are all of the same lobe profile. The '08 and up use a more aggressive profile.
The difference in the '06 and '07, or for that matter, '03-5 cams is timing. The '03 set has closer lobe center spacing than the '06, which is closer than the '07. Running wider lobe centering gives a bias toward top end power at the expense of low end power. Other than that, I believe these 3 different YZ450 cams are all of the same lobe profile. The '08 and up use a more aggressive profile.

Grayracer, the lobes on my 06YZ exhaust cam are 1mm taller and noticeably wider (the lobe itself, not lobe center spacing) than the good lobe on my 07WR exhaust cam.

lobediff1.jpg

Frost,

I was speaking only of the comparison between the various YZ450 cam sets. If you were on a different subject, I missed that.

There's no question that the later WR has a much less aggressive cam grind than any of the YZ's did.

Frost,

I was speaking only of the comparison between the various YZ450 cam sets. If you were on a different subject, I missed that.

There's no question that the later WR has a much less aggressive cam grind than any of the YZ's did.

My bad Grayracer. Max had asked about YZ to YZ, and I noted that I was comparing the YZ to the WR. I see now that you were responding to the YZ/YZ question.

While on the subject, do you think there is a possibility of my exhaust valves banging off of the piston with the higher lift YZ cam? I'm wondering if the YZ piston has deeper fly cuts to accomodate the extra mm.

My bad Grayracer. Max had asked about YZ to YZ, and I noted that I was comparing the YZ to the WR. I see now that you were responding to the YZ/YZ question.

While on the subject, do you think there is a possibility of my exhaust valves banging off of the piston with the higher lift YZ cam? I'm wondering if the YZ piston has deeper fly cuts to accomodate the extra mm.

I know you asked gray to answer, but I'll tell you from personal experience that the valves seem to be OK, and there's no indication that they hit the piston. I might be talking out of my behind:moon: , but doesn't the wr use the same piston some yz's use or used in the past? I'm sure gray can answer that one.

The pistons are different, but I don't think there will be a problem. The cam has only .030" more lift, and the point at which the valve is closest to the piston is not at the moment of peak lift.

The pistons are different, but I don't think there will be a problem. The cam has only .030" more lift, and the point at which the valve is closest to the piston is not at the moment of peak lift.

I checked the part#s and I recall that the 07wr and the 06 YZ were the same. I may be wrong though. Obviously it would be a good idea to spin the engine over by hand before starting the first time.

Yup part #s are the same.07wr and 06yz

Oops. I checked an '06 WR, which uses the same 5TJ-11631-00-00 as the next few earlier models. The '07 uses the same 2S2-11631-10-00 as the '06 YZF.

My bad. That should settle the clearance question though.

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