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just did a valve job, but what`s really the deal....."update"

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Ok i did change the intake shims from(left side 170mm, right side 172mm) to L 145 and R 147.

What makes a biks that has less than 25 hours riding time to be that off, i`m thinking engine problems here you guys.

I now have 0,16 and 0,28, but what can cause a big jump in shim size?

btw, the exhaust was fine,maybe 0,27 to 0,29

thanks

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thats lack of maintanence! You were .009 inches out of spec on the both sides...no way that happened between one valve check interval! valve check interval and oil change interval should be the same...

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I "think" I had 40 hours on my 02 when things went bad. Regular checks up till then were fine.

Strange you got so much movement at 25 hours----------but I do remember Bikewriter talking about some 04's he knew of recessing intakes within a couple months of rolling off the showroom floor. RR.

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good be set of weak valves, the titanium is soft and it dishes in on the seats pretty easy when you really building a fier in there. Causes the valve stems to get longer in essence. Making it go out of tolerances. I never checked my tolerances for 2 years and all was great. One day it just wouldnt start, pulled the cover, yeah the left intake valve was out, adjusted and was good to go for another six months or so. The lower end came apart, so i decided to do an entire rebuild. i got all the valves out and looked, they all had small dishes on the seats of the valves, letting them go farther up to the cam. Looked at replacement valves that had teh perfect 45 cut on it, pretty big difference, but basically thats what you are doing, the valves seat more and due wear, so you compensate by adjustting to thinner shims

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valve check interval and oil change interval should be the same...

That's a joke 😢. Right ?

I hope you not correct and that is a joke! - 25hrs and the valves are that out of spec....I have a red 05 on reserve and this is scaring the piss out of me....... 😢

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It seems to me after reading these valve issue posts regarding the CRF450 for the past few months that the CRF450 has an automatic valve checking process. It seems you know automatically when to check your valves when the bike gets hard to start. It also seems if they are out of spec that shimming them is only a short term solution, shortly after you reshim it seems the vast majority of people that have posted here state they go out of spec and then you are looking at replacing the valves and seats and usually going with the SS solution.

To suggest to check your valves every time you change your oil is just ridiculous. I change my oil after every ride plus clean the air filter, and I have never checked my valves, reason being, it starts first or second kick all the time!

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GA426Owner,

I have an '04 w/35 hours on it and the valves are still w/in spec. (knock-on-wood!) I change the air filter (Twin-Air) every ride & engine oil every 3 rides (Stainless Scotts Filter cleaned every other oil change). This is my fist Honda ever after many years of Yamaha 250 2 strokes and a '03 250F. I really think that the bikes that have problems are not serviced correctly or that they are over revved. I'm an old VetB guy who luggs!

Hope that gives you some peice of mind.

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It amazes me that all these 4-stroke owners think they need less maintenance then a 2-stoke. There are more moving parts on the 450F and the bike is designed to race at maximum performance.

My suggestion to you is; if you want reliability of a trail bike, buy a trial bike.

Yes these bikes need to be looked after. Failure to do so will result in dents in your wallet and your head.

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Once your clearances change, re-shimming is a band-aid, if its out of tolerance, time to replace the valves, and springs. If you catch the problem soon enough, you wont have to get the valve seats recut, just lap in the new ones and go. I now have a hour meter, and I will check the clearances every 10 hours.

the spoiler is, mine went out in less that 40 hours, whether I had checked them or not is a mute point, once they go, they go, period, reshimming does not fix the problem.

Also, I changed my oil every two rides, air cleaner every ride. Some people never have trouble, some people have trouble quickly.

Dave, the bike is worth the valve maintenance, no way in the world would I not get another one, consider it just like doing a top-end, with slightly more labor involved.

GO GET THAT 05', you'll love it. 😢

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I really think that the bikes that have problems are not serviced correctly or that they are over revved.

I know in my own case it wasn't lack of service or an excess of revs, and a lot of our customers fall into the same boat.

My valves started losing clearance after about 30-35 gallons of fuel had run through the engine.

The rpm range was normally very close to the plots below I took from the data acquisition system over a 15 minute run on a tight SX track. In spite of having to change the OEM valve gear for Kibblewhite parts it's still the best bike I've owned.

crf__otn_histo_15min.jpg

crf_otn_plot_15min.jpg

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Ok guys thanks for the respond, first i want to say that i have raced 4-strokes since my first husaberg in 97,several yzf`s and finaly my 2004 crf, and i can honestly say that i do a lot of work on my bikes, oilchange after every 2 hour riding and filter every time, and i consider myselves to be a good mechanic. But how can you over rev a engine witch has a rev limiter ,and the exhaust valves was not out of specs, but after i put on the pro-circuit lowboy titanium system the starting issue got worse and worse, maybe this has something to do with the intake valve problem, i have 14 friends who ride the crf, one who raced the mx des nations, and he pushes the rev limiter almost for 40 minutes in a race, and has never even measured his valves, and no starting issues

And why does this only happens to a few bikes, makes me wonder.

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I'm dredging this one back up because of a quick question.

A potential fix to this valve issue would be to lower the Rev limiter, right? I think I read that in one of the other 60 threads on this topic. When you add an aftermarket exhaust, aren't you freeing up the topend and allowing the bike to rev out a little farther? Isn't this what is meant by people saying "it'll pull forever now"? If that's the case, wouldn't you be exacerbating the problem by adding an aftermarket exhaust? If that is the case, wouldn't technically be a little "safer" sticking with your stock exhaust (since it seems to choke the bike a little on overrevs)?

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Update...

I pulled the head off and found nothing, did measurements every possible place, all was in of specs, shimed it, put the bike together, (last time before i pulled it into pieces, i had to tow start it behind my car.)

Turned the gas knob( the bike had not been started since the cartowing episode), one kick, just one kick and the bike fired right up, did a 45 min practice yesterday and the bike runs so smooth that it feels like a differnt bike.

I`a happy camper 😢

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You're having the "Cold Start" problem. I had a post a few months back (over the winter) entitled "I'm hating my 450" where I was running into the same issue. For some odd reason, the bike just REFUSED to start. I checked valves, hot start clearance, new plug, and everything else, but it just absolutely refused to start. Then, one day, out of the blue, it started on my first attempt! No explanation...the only constant was that it was cold outside (40-50 degrees).

If you just encountered this problem, then you'll definitely encounter it again unless someone comes along with a true fix. Good luck!

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I am now forced to add something. If Rich Rohrich says it is the best bike he has ever owned --> I picked the right bike!

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I also need to ask a question that I keep going over in my mind. If my valves go out of spec. Can I JUST put in new valve and springs pin it back up and call it good, or do I (should I)have to do more.

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I also need to ask a question that I keep going over in my mind. If my valves go out of spec. Can I JUST put in new valve and springs pin it back up and call it good, or do I (should I)have to do more.

Strick - Any time you replace the valves you should re-cut the seats even if it's only a light touch up. It's the only way to ensure a good seal and a concentric seat that's running square with the valve guide.

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u also have to re shim it too. Every bike that rolls out of production has different shims from the next one, thats why ther is no such thing as a stock set. Any time you change valves, or do anything with the valves, you should check the lash to make sure you are in spec. Mainly just so the thing will run smooth and easy. If you change cams too, you should check tolerances. Each one is different. Just a little. 😢

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