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top end rebuilds?

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so how often do you have to do it? i know with 2ts its usually around/between 40-50 riding hours depending on how hard you ride i but how about 4 strokes? say an 06 or newer 4 stroke 450. and how much does it cost? ive always been and always will be a 2 stroke lover but eventually they will be gone :worthy::ride:

i know 2ts cost between 100 and 300 for new top ends but how about 4 stroke 450s?

Thanks and happy riding 👍

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crf 450 top end rebuild - $1500. have around 100 hours on the SS intakes with no movement yet. I am going to check them just in case soon though. I figure I will be able to get 300+ hours from the top end. my crank already has 170 hours on it. seems to be strong still!

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I wish i could say the same for my old crf 450. That thing always ate intake valves. then one day the rod went through the cases and that was my last day on a 4 stroke.

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I replace my piston rings in my '09 yz450f every 50 or 60 hours, and replace the piston every 100/110 hours. The cost to replace the piston/rings is around $140 (shipped, OEM parts) including all of the gaskets/pin/c-clips etc. If I'm just replacing the rings it costs me $63 shipped. A cylinder for my bike, if needed is $265 shipped.

I had 7 Honda's before this Yamaha, I lived the Honda valve issue and that's one of the main reasons I bought my YZ. I put 70 hours on my last crf450r before I had to spend $500 replacing the valves (did the work myself) with aftermarket stainless ones. That $500 was a complete waste of money IMO and until I know that Honda has fixed the problem, I won't buy another one. Yamaha's are about as reliable as you can get, although every brand has it's issues...

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Last fall I spent $1400(parts and labor) for: CW 270 big bore kit($400), head ported, Hot cams($250), and new OEM valve kit($254). So far, I've put 110 hrs on the set-up and to date, only one valve has needed adjusted one shim size. That adjustment wasn't needed until the 100 hr mark. I plan to do a new Vertex piston($165) this winter and by then the top end likely have 150 hrs. I'm hoping to go 100hrs past that before I do new valves again.

IMO that's pretty damn good for a highly modded XC race bike.

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put stainless steel intakes on a crf450 and you are good to go any day of the week. yz450f has 3 intake valves as far as I know.. unless theyve changed that. that helps a lot with longevity.

I will admit, the TI intakes in the crfs and the seat materials isnt the greatest.. but once you fix that simple problem via SS intakes, you are bulletproof!

otherwise the yamaha has 2 cams, 2 cam chains, etc.. double everything in the cam assembly compared to the honda. thats a lot of rotating mass. rotating mass in the engine.. thats never good.

I am also not a fan of the clutch oil and engine oil all being used as one big 1.7L mess in the yfzs. I like hondas separate 800-1000ml per side in the engine and clutch respectively.

sad to hear you guys had so many problems with your crfs. mine has been pretty good once I put the bigborethumpers SS intake head onto it. but then again.. now that I think of it, the bike is literally 80% aftermarket/upgraded parts. I honestly cant think of too many things on the bike that are OEM honda. maybe its not even a crf anymore?!

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put stainless steel intakes on a crf450 and you are good to go any day of the week. yz450f has 3 intake valves as far as I know.. unless theyve changed that. that helps a lot with longevity.

I will admit, the TI intakes in the crfs and the seat materials isnt the greatest.. but once you fix that simple problem via SS intakes, you are bulletproof!

otherwise the yamaha has 2 cams, 2 cam chains, etc.. double everything in the cam assembly compared to the honda. thats a lot of rotating mass. rotating mass in the engine.. thats never good.

I am also not a fan of the clutch oil and engine oil all being used as one big 1.7L mess in the yfzs. I like hondas separate 800-1000ml per side in the engine and clutch respectively.

sad to hear you guys had so many problems with your crfs. mine has been pretty good once I put the bigborethumpers SS intake head onto it. but then again.. now that I think of it, the bike is literally 80% aftermarket/upgraded parts. I honestly cant think of too many things on the bike that are OEM honda. maybe its not even a crf anymore?!

The new generation YZ's have a 4 valve head, so far I haven't heard of any big valve life issues. And yes, to the mechanically inclined it is a relatively simple fix to replace the valves in the Honda but... chances are I won't have to do that/waste my $$ with my YZ.

Uhh, 2 cam chains in the YZ ?? Actually the only "double" part that the Yamaha has is an exhaust cam, whereas the honda has their Unicam int./ex cam in one. I doubt that any of us here could tell the difference in rotating mass and the overall effect one more cam would have on any given bike. So no, the rotating mass in the Honda Vs Yamaha is pretty much a non-issue.

I do like the seperate clutch/engine oil reservoirs in the Honda, now with the YZ I change my engine oil 2 hours sooner (runtime) than I did in my Honda's.

It's not that I had "so many" issues with my Honda's, the biggest/most expensive issue was having to put new valves in it. In 2010 when I was looking for a new '09 I went with the Yamaha for a few different reasons. they were :

#1) Valves

#2) The '09 Honda had the worst suspension stock, whereas the Yamaha's was the best out of the box (out of the big 4).

#3) The 4 spring clutch in the Honda, still don't know why they decided to create an issue where there wasn't one before ?

#4) Flameout issues with the Honda

I'm not so brand loyal that I will buy what I consider to be an inferior product just to stay with that particular brand. To tell you the truth, I'm not real crazy about the new Yamaha.. but my preference is to run either Honda or Yamaha. Guess I'll ride my '09 for another year..

Sorry, didn't mean to hi-jack this thread.....

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The new generation YZ's have a 4 valve head, so far I haven't heard of any big valve life issues. And yes, to the mechanically inclined it is a relatively simple fix to replace the valves in the Honda but... chances are I won't have to do that/waste my $$ with my YZ.

Uhh, 2 cam chains in the YZ ?? Actually the only "double" part that the Yamaha has is an exhaust cam, whereas the honda has their Unicam int./ex cam in one. I doubt that any of us here could tell the difference in rotating mass and the overall effect one more cam would have on any given bike. So no, the rotating mass in the Honda Vs Yamaha is pretty much a non-issue.

I do like the seperate clutch/engine oil reservoirs in the Honda, now with the YZ I change my engine oil 2 hours sooner (runtime) than I did in my Honda's.

It's not that I had "so many" issues with my Honda's, the biggest/most expensive issue was having to put new valves in it. In 2010 when I was looking for a new '09 I went with the Yamaha for a few different reasons. they were :

#1) Valves

#2) The '09 Honda had the worst suspension stock, whereas the Yamaha's was the best out of the box (out of the big 4).

#3) The 4 spring clutch in the Honda, still don't know why they decided to create an issue where there wasn't one before ?

#4) Flameout issues with the Honda

I'm not so brand loyal that I will buy what I consider to be an inferior product just to stay with that particular brand. To tell you the truth, I'm not real crazy about the new Yamaha.. but my preference is to run either Honda or Yamaha. Guess I'll ride my '09 for another year..

Sorry, didn't mean to hi-jack this thread.....

sorry, I dont know what I was thinking when I said 2 cam chains... its bee a while since I was in the dirtbike world! 👍

its not that its an issue that people can tell the loss of power due to the 2 cams, more rotating mass, etc.... its just that it seems way more complicated/expensive to work on. 2 cams, harder to find timing, etc... the honda top end is very simple and easy to work on. I have never worked on a yzf head firsthand though. but have friends who have, it looked a lot more tedious than my crf heads.

otherwise you are completely right about the newer crfs... ive been out of the loop for almost 2 years now. I forgot about the 4 spring clutches in the new crfs.. what a horrible move. as for the suspension... well im not fast enough and dont have enough time to worry about that! if were talking about the whole bike in general.. then I would say the yamaha is probably a better bike (it kills me to say that). but if were talking about the engines/heads.. I still personally think honda has the best with the unicam and separate clutch/engine oil, and once you put SS intakes it becomes very hard to beat IMO.

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