Update needed on cam mode

[RJB]

Math, I guess if a Canadian from Quebec can do it....

Just kidding - yeah, it sure is good to know that there is so much good info on this site. Saved my butt more than once. Don't know where I'd be without the internet and Thumpertalk.com (guess with my bike in the shop and a whole lot less money in my pocket )

[Math]

Math, I guess if a Canadian from Quebec can do it....

Yeah Yeah Yeah... ? .

By the way, I'm done. What about you? I send you good words and look at what I diserve! (Just kiddin )

Seriously, if I can help you with anything, post on man, I'll be happy to throw some input if I can.

OK, back to Sylvain's issue.

[Sylvain]

Math, I guess if a Canadian from Quebec can do it....

QUOTE]

We must be special Math. We attract a lot of attention. Muss bee hour haccent.

More seriously, with the last photo, my cam set up is exactly as pictured. I decided to put back the decomp rod, we never know for sure how things will be. Plus it's a good idea to have a way to flush the engine when flooded. I can put the plug back in when I feel there is no more need.

Thanks to everyone for the inputs on this. I will give you an update on how it changed my life .

[cowboyona426]

Sylvain, save yourself the trouble and just install the plug, trust me RJB, we are here if you need help man! Sent you a PM also

[Sylvain]

What does RJB mean ?

[Btwick]

Just finished my mod. Timed it without the tensioner and was ready to go, thinking I had matched the pictures from TT.. Put the tensioner on and it was one tooth off - not angled enough. Even the lobes looked symmetric from the right side. Had to remove the caps and move the cam over one tooth. Lesson: time it with the tensioner installed!!

Now my concern.. Ordered my TT plug and was waiting for it to arrive when I really wanted to start it up.. Put in the stock decompression rod, finger tightend the small bolt holding it in and fired it up, Did not attach the spring.. Felt great! Kicked over nice and easy and started on the second kick. SUCCESS!!

Well, as she's warming up, and I am now just getting some of the excess oil off my case with a rag and hit the decomp lever, pushing it down. It made a terrible, popping, clanking noise and dies... Realizing what I had just done, I am ready to DIE thinking I have bent a valve, f%$#@ up my piston, etc.. After all that work..

Anyway, it did start back up, seems to run fine (just a trip down the street), but seems to make a bit more noise in the engine. Or that might be my imagination. Does anyone know if that can ruin my motor, or if Yamaha was smart and designed it so that applying decompression on a running motor was not lethal to it? Seems that since the lever is up on the bars, it is plausible that a fall could push the lever in while the motor was still running, so Yamaha would have some reason to prevent a complete meltdown if that happend..

Thanks,

Brian

[grayracer513]

It made a terrible, popping, clanking noise and dies... Realizing what I had just done, I am ready to DIE thinking I have bent a valve, f%$#@ up my piston, etc.. After all that work..

Anyway, it did start back up, seems to run fine (just a trip down the street), but seems to make a bit more noise in the engine. Or that might be my imagination. Does anyone know if that can ruin my motor, or if Yamaha was smart and designed it so that applying decompression on a running motor was not lethal to it? Seems that since the lever is up on the bars, it is plausible that a fall could push the lever in while the motor was still running, so Yamaha would have some reason to prevent a complete meltdown if that happend..

The exhaust valve won't hit the piston ( it doesn't when you spin it over with the kickstarter, right?), so forget that. The noise is a combination of things. When you lift the exhaust valve with the decomp shaft, you increase valve clearance, so the cam strikes the lifter harder and makes the obvious noises. When the cam then lets the valve back down, instead of gracefully settling the valve onto its seat, the cam follower runs into the decomp shaft. More noise.

It's easy to understand that hugely excessive valve clearance is potentially damaging, and that it isn't beneficial to bounce the cam follower against the decomp shaft at the more than 10 times a second that would occur at idle. What is less obvious is that as the valve spring pushes the follower up against the decomp shaft, it creates a rocking force on the follower because the shaft is way off center from the valve stem. At a high enough speed, or done often enough, it seems to me that there could be a potential to bend or break the follower, and/or damage the bore in the head.

At cranking or bump starting speeds, when it was intended to be used, I doubt any problems would ever result. Your bike is probably fine, and I wouldn't worry about it. But I would plan to remove the manual decomp. You just don't need it anymore.

[cowboyona426]

What does RJB mean ?

RJB is another member that posted in this thread

[Blue ARC]

Do you find the '03 cam changes the power characteristic compared to the stock cam?

[Math]

Do you find the '03 cam changes the power characteristic compared to the stock cam?

Will probably change the feeling of Sylvain's 02WR because he bought a YZ cam so he must YZ time his WR now...

As for the YZs, I don't know if the 02 vs 03 cams are so different if we exclude the auto decomp

[cowboyona426]

The 450 cam smooths the power out a bit, and it seems to pull longer IMO.

[Satch0922]

Do you find the '03 cam changes the power characteristic compared to the stock cam?

Cowboy is right. It smooths out the powerband and the bike pulls forever. Also with less compression braking the bike is easier to ride.

[adrian]

Ok I have a question, I just bought a decomp plug so I need to remove the oil seal and the thing wont budge, is there an easy way to get it out?? I spent over 30 min trying to pry it out and all I kept getting were little chunks of rubber, so obviously I have destroyed the seal!! Any suggestions?? I loosened the rad to gain more clearance but still no luck??

[Satch0922]

Ok I have a question, I just bought a decomp plug so I need to remove the oil seal and the thing wont budge, is there an easy way to get it out?? I spent over 30 min trying to pry it out and all I kept getting were little chunks of rubber, so obviously I have destroyed the seal!! Any suggestions?? I loosened the rad to gain more clearance but still no luck??

DO NOT put the stock rubber plug in. Get the billet plug from the TT store and put it in. This requires that you leave the oil seal in and the plug goes right in place of your old decompression mechanism. If you pry the oil seal out and put the stock rubber plug in (like the new bikes) it may leak and or blow out (several TT members have had that happen on coverted 426's as well as newer 450s)

Go to the TT store, then go to "products by TT members" and you will see the decomp billet plug.

[Math]

Cowboy is right. It smooths out the powerband and the bike pulls forever. Also with less compression braking the bike is easier to ride.

Does it mean that the power of Sylvain's 426 is gonna be different from my 426 even if both are YZ timed and that because Sylvain's got the 03 cam? If so, this is cool I'm anxious to compare. .

What is the difference between 01-02 Yz cams compared to 01-02 WR cams if any?

[Sylvain]

ARE you feeling anxious young boy !!!!!

Pressure is getting to you ?

I should get the beast out tomorrow. I still have to install the rear wheel, chain, front sprocket, oil and coolant fill, etc... Go over everything once more and torque the last bolts here and there. I hope to try it out in the afternoon. I'll let you know how it feels .

A+

Seeya!

[Satch0922]

Does it mean that the power of Sylvain's 426 is gonna be different from my 426 even if both are YZ timed and that because Sylvain's got the 03 cam? If so, this is cool I'm anxious to compare. .

What is the difference between 01-02 Yz cams compared to 01-02 WR cams if any?

I believe the YZ and WR 01-02 have the same exhaust cames...the WR is just it's timing retarded one tooth.

[coulterk]

I have just had the cam fitted to my 01 426. At the time of fitting the cam timing was checked with a dial indicator. The inlety cam was out 3 degrees and the exhaust out 8 degrees. The cam gears where removed and put back on in the correct position. The bike starts either first or second kick and with not much effort. My mechanic told me that he has found that some exhaust cams have been up to 20 degrees out. This causes poor starting and also a loss of power. For those people that have complained about there 04 and 05 450 not having the power of a 03 450 get you cam timing checked.

[FFRacing79]

I have just had the cam fitted to my 01 426. At the time of fitting the cam timing was checked with a dial indicator. The inlety cam was out 3 degrees and the exhaust out 8 degrees.

These figures would hardly make that much difference. At what lift were they checked? Takes more than a dial indicator to correctly check cam timing. What were the lobe centers? There is approximately 20 degrees to one tooth on the cam sprockets. Tdub

__________________

[Sylvain]

Finally !

I test rode my bike today. First ride of the season. Nice difference. I was suspicious about the ease of starting, but it is unreal. It starts just like my son's IT 175 . But with a lot more brrrrraap .

Thanks to all for your help.