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78sharpshooter

01 426; do I need the 450 cam mod?

17 posts in this topic

I have a 2001 YZ426 with BK mod, SLP power pack, and JD jetting kit. The bike starts on the first kick after sitting a week or two so the benefit of easier starting with 450 cam mod doesn't matter to me. Yes, I have read the 450 cam mod post above but was left wondering exactly what the other benefits are to this mod (i.e. some say better low end, smoother power delivery etc.) What is the consensus on the enhancements with the 450 cam?

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you can still bump start it with out the mod. I do it with mine. all you do is pull the decomp lever in while you let the clutch out. very easy. :crazy:

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When I bump start mine I Pull the clutch and decomp start pushing the bike fast then jump on and i release the decomp just before the clutch. :crazy:

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I think you would only get the benifit of the auto decompress. Your cam timing is already set to yz. The wr guys sometimes want to get the yz cam for timing purpose.

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It doesn't sound like you want to do this mod and I don't know if I can convince you or not. My bike just behaves very differently. Much more smooth in the power but still the same power. I love the cam and am very glad I did it. I love it for kick starting it in difficult areas as I mainly trail ride. Don't tell me you can kick start it just as easy as that is a bunch of crap. It takes about 5-10X the pressure to kick start that thing with the stock cam. I can kick start it with my tennis shoes on over and over and it doesn't get me tired or anything. Has the feel of a 125 kick now. Doesn't flood as easily now as well. I remember trying to start the thing after it fell or stalled or something and I would have the kick the crap out of it or sit there and fry in my garb while it drained the gas so I could start it again. Not now. I loved my bike before the mod but love it even more now.

Also, you don't have to use the decomp lever to bump start your bike. Next time put it in 3rd and just pop the clutch. It will start the bike no problem. :crazy:

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I have an o1 426 and was going to do the cam mod but to be honest with you im glad i diddnt ive heard of to many problems with the timing issues and reliability afterwards. I have done a lot of checking though, and a YAMAHA 450 cam will just do away with the commpresion release they say if your gonna do it use a HOT CAMS so you at least gain performance, as in for starting belive it or not once you get the procedure down for your bike not just the 426 but your bike they all start different they are one of the easyiest starting four strokes in the world. no throttle and only use the hot start if you stall it and dont go to far past TDC when kicking it over.

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I have an o1 426 and was going to do the cam mod but to be honest with you im glad i diddnt ive heard of to many problems with the timing issues and reliability afterwards. I have done a lot of checking though, and a YAMAHA 450 cam will just do away with the commpresion release they say if your gonna do it use a HOT CAMS so you at least gain performance, as in for starting belive it or not once you get the procedure down for your bike not just the 426 but your bike they all start different they are one of the easyiest starting four strokes in the world. no throttle and only use the hot start if you stall it and dont go to far past TDC when kicking it over.

Could you elaborate more on what you've heard about reliability issues ? I haven't heard of ANY.

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Could you elaborate more on what you've heard about reliability issues ? I haven't heard of ANY.

I haven't heard of problems either. The locked thread above has numerous posts without one failure or complaint. I have talked to some who have had the cam in for 2-3 years now with no problems. Mine...no problems with timing or anything, in fact, the timing is better now than it was. :crazy:

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No problems here. I've had the auto-decomp cam for about 2 years. Its nice to kick the bike over without a starting drill. The 450 cam also broadens the power and takes some of the hit out.

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I have a 2001 YZ426 with BK mod, SLP power pack, and JD jetting kit. The bike starts on the first kick after sitting a week or two so the benefit of easier starting with 450 cam mod doesn't matter to me. Yes, I have read the 450 cam mod post above but was left wondering exactly what the other benefits are to this mod (i.e. some say better low end, smoother power delivery etc.) What is the consensus on the enhancements with the 450 cam?

It is definitely worth doing.I've been running one about 18 months,and would not change back.

It turns them into a completely different bike.It also reduces engine braking.

Not had any reliability problems, or heard of anyone else with problems.

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It's only a good idea if you like a bike that is rediculously easy to start and has a wider, smoother powerband than a stock 426...

Do the mod, it makes the 426 almost a completely different bike, you'll love it.

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I got a 01 426 late last year. I understood the start procedure and could start it given a few kicks. I had been in some gnarly stuff and it was hot last weekend. Given my abilities I was having to kick start the thing more then a few times. I had bought the cam from some guy on fleabay and got it for like 105 usd. I dug my heels in Tuesday evening and started figuring things out. I got my replacement shims yesterday afternoon and finished up the install after work yesterday.

I stomped on the kicker and holy crap it was a breeze to start. I am positive this will be great while on trails and in the sand.

I'm sure I'll get back to the dirt in a couple weekends, this one looks like a ton of rain and I'm scheduled for road racing. So I have to resort to playing in the backyard a little.

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I have an 02 426 and recently installed the Hot Cams cam. I had the starting drill down to a science, but not having to go through it is worth the money alone. Bike pulls like a tractor on steroids now too! :crazy:

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The 450 cam is a different grind than the 426, not simply a re-done 426 cam with an auto-decomp mechanism. This accounts for the performance differences.

The worries about reliability arose from the fact that the cam chains on the two engines technically each have a different pitch specification. However, as some owners have pointed out here, no one knows of anyone who has had any failure that could be even remotely traced to a mismatched pitch.

As to the question of starting, I know guys who can hop on most any 426 that's close to set up right and start it in one or two kicks. Even they cannot kick a stalled and flooded 426 with manual decomp 6 times as quickly as an old guy like me can kick an auto decomp engine 6 times. There is no drill, no set up, no pre-positioning, you just kick it.

I rode my first big British single in 1968, owned several, and rode hundreds more. I know all about bumping off bikes with the compression release, and any number of other tricks you can do with them. Before I bought the YZ450, I was looking for a 426, partly because of the fact that it had a manual decomp and the 450 did not. Now that I've owned the 450 for some time, I see no good reason to ever have the manual setup.

Bump starting is possible with the manual setup, but you have to be careful not to let off on the release too quickly, or risk the engine locking on compression. Auto decomp doesn't do that, and mine bumps off like an overweight 200cc two-stroke. One of the places this really shows up is when you stall the engine while moving, as when over-braking entering a corner. With a manual setup, you pull the clutch, pull the release, dump the clutch, and ease off the release, hoping that you're still actually moving. With AD, you simply flip the clutch to get the wheel to spin, and it lights back off, just like that.

People who have never used AD for any length of time, let me say this politely, don't know what they're talking about, frankly, when they say it's no big deal. They don't know what they're missing, either. No, you don't NEED it, but it sure is nice, and well worth the time and money.

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Auto decomp virtually eliminates stalling as well. Before the mod that thing would lock up like a beatch in the corners. Not a problem now. :crazy:

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Thanks for the input guys. I can definitely see where the auto decomp's easy starting would be invaluable during a race. I don't think I am going to jump up and do the mod but I will certainly consider it when I take it apart to check the valve clearances this summer.

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