How many hours will a 450 go before rebuild

Trying to estimate when and how much it will cost?

LOOOOOOOOOOOOOONG time. But fairly expensive

My cousins 01 YZ 250f was rebuilt about 2 years ago because the original owner neglected the bike big time, The head, all 5 valves/springs/retainers, piston rings, cam chain, and crank were all replaced (the crank was fine, the sprocket for the cam chain was shot). The parts bill would have been about $1500-1800 at retail. The big motors will last significantly longer. I know of 400s and 426s that have never had a shim touched and still start on the first kick.

Billions of hours...

They may never need rebuilt if you take care of them.

Billions of hours...

They may never need rebuilt if you take care of them.

I hope you are right cos I am on my second piston and cylinder but then I didn't keep my oil drain plug tight enough once (that is all it took)..

Be real careful with the oil drain plug..

I think you are probably right about them lasting if you take care..

it is important to check and make sure you allways have a gasket or gramet on all your fill plug and others as well just for engine safety

I have had just over 200 hours on my CRF 450, when the mechanics tore it down they said it was as close to letting go as they have ever seen. They suggest at least a piston and rings about every 100 hours. That part sucks, I ride enduros and I can put that many hours on in less than six months. I do all the recommended maintence, the last rebuilt set me back $800, and it included new valves, springs, seats, piston, rings, gaskets, minor head work including having seats recut. I think next go around I will go with stainless valves instead of the titanium stock valves. I started running Amsoil in the tranny and motor after the last rebuild and am real happy with it.

How can you tell when you need to rebuild a 450? Mine is an '03 and I know the guy that had it before me raced, and now I am starting to go to the tracks. It will still start first kick if it hasnt been sitting for more than a day or two and it has plenty of power. How do you tell? I have no idea as to how many hours I have on the bike.

Only way to tell is to tear it down, but check your valve clearances first. That might give the mechanic an idea. Fix it before it blows and you'll save a ton of cash.

When you tear it down what are you looking for? What are the tell-tale signs that it needs to be rebuilt?

Make sure that the valve clearences are right and then do a pressure/leak down test.

Is is a Yamaha or Honda? It pains me to say it (I'm a Honda Guy) that the Yamahas will go longer between rebuilds and valve adjustments than Hondas CRF's.

Is is a Yamaha or Honda? It pains me to say it (I'm a Honda Guy) that the Yamahas will go longer between rebuilds and valve adjustments than Hondas CRF's.

The truth hurts sometimes don't it...:thumbsup:

The truth hurts sometimes don't it...:thumbsup:

Yes, right in the pocket book, ouch!

OK. I'm not having any problems with my 426. I just want to get a figure for number of hours to rebuild. I log all of my hours - anal I know - and want to see the bike at 1/2 life or so. Then it's time to get something newer and lighter.

Dirt Bike magazine a month or two ago had an article that compared the cost of owning a 4 stroke and a 2. In the end the two stroke came out a little cheaper, but obviously a pain in the ass concerning the pre-mix and a simpler, but more frequent rebuild schedule. The best news was that the usual simple maintainance goes a long way as do watching your RPMs. The article pointed to the fact that a rev happy 20 year old A rider will need to rebuild far earlier than a "slower" 35 year old :thumbsup: like me !!

I was thinking that you could do a lot of 100.00 top ends in a 2 stroke for the cost of a top end rebuild in a 4 stroke.

How can you tell when you need to rebuild a 450? Mine is an '03 and I know the guy that had it before me raced, and now I am starting to go to the tracks. It will still start first kick if it hasnt been sitting for more than a day or two and it has plenty of power. How do you tell? I have no idea as to how many hours I have on the bike.

Take note of the compression and listen for funny noises. I don't think my 98 yz 400 has ever been rebuilt, but it still runs perfect, starts first kick, and has tons of compression. In my opinion if these bikes are well maintained they can run for years without a rebuild. :thumbsup:

My 99' 400 was raced by the previous owner, he never adjusted the valves since it was new, and they are still well within spec!!!

I checked the valves once at the beginning of july, and I'm going to check them again as soon as i tear down to drop this hotcam in there. So farr they have not been adjusted once since new off the showroom floor.

usually when a four stoke gets hard to start then that usually means its time for valve adjustment.

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