Timing chain replacement - 03 450f

[JohnB]

2003 450f. I'm the original owner.

The valves just got checked after 2 1/2 years of riding. They are still in spec. Does the timing chain need to be replaced? What about the top end?

What have you guys seen as far as general maintenance and replacing parts when no wear is visible.

[642MX]

Its time to change the cam chain for sure. As the chain gets some wear in it, it starts to eat the bottom gear on the crank and could cause big problems. The top end should be fine, depending on your maintance practices and total hours on the motor. If its not using oil....its probably good to go. ?

Remember its blue, not red. ?

[grayracer513]

The timing chain is too cheap, too easy, and capable of causing too much trouble if left alone not to replace it. You should do so at least every two years, every year if it's your race bike and you're on it all the time. Simple cheap insurance.

While you have the cams out, you can take an inventory of what shims you have on which valves so that you can save down time if you find it needing an adjustment one day. ?

[Radbuster]

Thanks Gray for the heads-up.

I just ordered a new cam chain as you recommend to put in together with the new piston rings.

How far do you think the stock piston can go? I'm also the original owner, probably have about 100 hours on it, change the oil all the time, try to keep the air filter clean and ride like a wuss.

[old-n-sloow]

Thanks Gray for the heads-up.

I just ordered a new cam chain as you recommend to put in together with the new piston rings.

How far do you think the stock piston can go? I'm also the original owner, probably have about 100 hours on it, change the oil all the time, try to keep the air filter clean and ride like a wuss.

How long will the piston last? In Dec '98 my brother bought a '98 400 from an ex-pro motocrosser. My bro rode at least once a week, normally twice a week, 1 to 2 hour rides. In May of 2003 his oil pump went out, wasting the whole motor. He was religious about oil/air filter maintenence, otherwise nothing was done to that motor. He checked the valves, but they never went out of adjustment, never changed the piston, rings, camchain, nothing. If the oilpump had not gone bad he would probably still be riding that bike.

Off topic:

I think that the incredible durability of the first generation YZFs is largely responsible for the current popularity of 4 strokes. If the KXF/RMZ 250s had been first on the market, you couldn't give a new thumper away.

[Radbuster]

Thanks for the info.

It feels weird that the magazines barely ever give credit for reliability. If I'd me in the market for a new ride, the seat wouldn't be the tie-breaker, but rather the $2000 downside of an engine failure.

If something bad doesn't happen anytime soon, the cost per hour of this machine is next to nil. This one's a keeper and it'll get liberal amounts of any new spares it hints on needing.

Thank you Yamaha! (and ZipTy/Rekluse, etc, etc.)

?

[old-n-sloow]

I gotta agree with you on the magazine thing. I think they have a different perspective than regular buyers though, every year they get a warehouse full of new bikes. So if a bike breaks, no biggie, grab another. No dent in the personal budget. To me, longevity is the first consideration in looking at a new bike.

[MotoGoalie]

I gotta agree with you on the magazine thing. I think they have a different perspective than regular buyers though, every year they get a warehouse full of new bikes. So if a bike breaks, no biggie, grab another. No dent in the personal budget. To me, longevity is the first consideration in looking at a new bike.

Magazines are nothing more than Hype machines that rely on the bigger and better of tomorrow, aimed mostly at pubescent teens that ask thier daddies for money. Hey, that was me back in the day. They are money making ventures meant to sell advertising dollars. All thier little gimmicks and hyped aftermarket products are swell, there isn't a blem in the batch.

Bulletin boards are the real world. We have to pay for all this expensive crap and we bitch about it if it breaks.

The mags hold the YZF up as some horrible machine compared to the holy grail CRF. Fact of the matter is a 3 y/oCRF with as little maintenance as our bikes require will never happen. Yamaha has a nice design.

And BTW, I just absolutely hate the idea of the perimeter frame. I can get access to my carb and other things quite nicely. It looks like that 06 perimeter frame will be a PITA. Oh well, I'll be buying used 04 and 05 in 08 and 09 according to my current plans so I shouldn't have too many problems till then. ?

[642MX]

Off topic:

I think that the incredible durability of the first generation YZFs is largely responsible for the current popularity of 4 strokes. If the KXF/RMZ 250s had been first on the market, you couldn't give a new thumper away.

I couldn't agree more. The YZF is truely an amazing machine that seems to hold up 100 times better than the rest.

[760oldman]

Just putting the motor back together after a near catastrophic failure. Piston was getting ready to go sideways in my 03 450. Started making some odd noises on the lsat ride, and decided to tear it down for inspection. The piston was trying to stick at the front and back, and the cylinder was out of round by .003, bottom line, it was getting ready to go in a bad way. The oil was changed every other ride (4 or 5 gallons of fuel), always ran 91 octane, ect

Anyhow, question is putting the cams back in, maybe I am doing something wrong, but I can't seem to get the cam chain over both gears, and get them back in the head. Any suggestions to make this a simple thing?

[grayracer513]

...Anyhow, question is putting the cams back in, maybe I am doing something wrong, but I can't seem to get the cam chain over both gears, and get them back in the head. Any suggestions to make this a simple thing?

You need to check the chain as it runs under the crank to see if there is a looped link "hanging" from the crank sprocket. It's just barely possible for it to happen, but it can.

Also, with a new chain, the second cam has to be put into place between the cam saddles and rolled into its correct location in order for the chain to fit over them both.