yzf 450 valves and over heating??


12 replies to this topic
  • x2468

Posted April 16, 2008 - 03:36 AM

#1

Hey guys, i'm looking at getting a used 5-speed 450 for trails, free riding, and off-road racing. I've been looking at the yz450 and the crf450. I've spent a bit of time in the crf forum trying to get info on that bike. seems like the two main issues are valve problems (may or may not be a problem for me because i lug a gear high, but very $$$) and overheating issues on slow trails (could be a big pain for me!).

How is the YZ in these two issues?

From what I understand the only issue i might have with an 06 YZ would be the leak jet. how much are the zip ty units that are so popular?

Is the 2003 yz450 a 5-speed? just curious, i thought they were all 4-speed until 06 but someone told me the 03 was a 5-speed.

  • Windseeker

Posted April 16, 2008 - 03:54 AM

#2

Overheating - yes. But. I am fresh off WR450 so have yet got not used to higher gearing/speeds needed to ride YZ450 properly. Last weekend on a 6 hour forest ride I boiled YZ once and overheated clutch couple of times to the extent in stopped disenganging. :thumbsup:

Our group had another rider on YZ who rode it for one season already - he was slower that our fastest WR on a slippery trails but no overheating or clutch issues.... He had them last year :confused:


:thumbsup:

  • SRT426

Posted April 16, 2008 - 04:10 AM

#3

03 and 04 are 4 speeds, I believe they went back to a 5-speed in 05. As far as valves, it's a Yamaha not a Honda. Early Hondas have developed a reputation for valve issues while any search in this forum will commonly yield a result of "I haven't touched a valve in 3 years". As far as overheating, run a quality coolant like Engine Ice or Maxima's Coolanol and you'll be fine. I run 426 on mainly single track with both brands depending on what I buy at the time and it will overheat if I'm putting slow and dogging it but for the most part if you've got airflow across the radiators it will stay cool enough.

  • x2468

Posted April 16, 2008 - 04:54 AM

#4

Overheating - yes. But. I am fresh off WR450 so have yet got not used to higher gearing/speeds needed to ride YZ450 properly. Last weekend on a 6 hour forest ride I boiled YZ once and overheated clutch couple of times to the extent in stopped disenganging. :thumbsup:

Our group had another rider on YZ who rode it for one season already - he was slower that our fastest WR on a slippery trails but no overheating or clutch issues.... He had them last year :rant:


:ride:


wow, well 6 hours is a pretty tough test. so i'd accept that.

i'd suggest a rekluse clutch for you. and if it's possible, maybe the WR radiator fans (can they bolt up to YZ radiators?). not to side line my own thread lol.

  • x2468

Posted April 16, 2008 - 04:55 AM

#5

03 and 04 are 4 speeds, I believe they went back to a 5-speed in 05. As far as valves, it's a Yamaha not a Honda. Early Hondas have developed a reputation for valve issues while any search in this forum will commonly yield a result of "I haven't touched a valve in 3 years". As far as overheating, run a quality coolant like Engine Ice or Maxima's Coolanol and you'll be fine. I run 426 on mainly single track with both brands depending on what I buy at the time and it will overheat if I'm putting slow and dogging it but for the most part if you've got airflow across the radiators it will stay cool enough.


im 99% sure they went back to 5-speed in 06.

  • grayracer513

Posted April 16, 2008 - 06:08 AM

#6

I'm 100% sure; the '06 was the aluminum frame and the 5 speed, and is night and day a better bike than the '03-'05. All '03-'05 were 4 speeds.

There are no valve issues with the YZF. It's to the point that it seems impossible sometimes.

As far as leak jets and AP mods and all that, IMO, the importance of these is rather overrated. I've done nothing but rejet both of mine and they run quite well.

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  • x2468

Posted April 16, 2008 - 07:05 AM

#7

well now i know why yzf's used are more money than Crfs.... this information must be built into the price.... and the price of a head and valves must be discounted into the price of crfs.

  • x2468

Posted April 16, 2008 - 07:08 AM

#8

what about the power between the too? from what i've read the YZF is a bit more mellow and the CRF has more brawn. can anyone elaborate? do the mags kinda over exaggerate the difference?

  • grayracer513

Posted April 16, 2008 - 09:03 AM

#9

There was a lot made of the difference in power delivery when the '06 YZ450 first came out. You may recall that the same magazines universally ragged the '03 and '04 as being so fierce they were unmanageable by mere mortals. Their peak power was never any more than that of a comparable CRF, but the way it was delivered off idle in one big, hard edged chunk was reminiscent of the power of a late sixties muscle car; if you went near the throttle, it would accelerate HARD. It took a lot of energy to manage the thing, and while it was a lot of fun in its own way, most people weren't faster on one.

The '06 was different. All the mags came out and said the bike had "soft" low end power. They loved the rest of the bike, and MXA put it in a tie for first in their shoot out that year, saying that if it had a more aggressive engine, it would have won. The odd thing was that in a great number of cases, the test crews turned significantly lower lap times on the YZF. Maybe they didn't notice that.

The so called soft bottom end of the '06 YZ450 is one of the world's great illusions. Everyone who rode an '03-'04 and an '06 in the dirt would say the '04 was more powerful than the '06. But running the two on pavement side by side gave one a different look at it. The two bikes would run dead even up into upper third/lower fourth gear. After that, the '06, which actually has 2-3 more HP than the '03, pulls away.

If you ride a CRF, you'll think the same thing. It will feel stronger, not explosive, like the older YZ450's but still more of a brute than the current YZ450. But if you ride the YZ against a CRF, you'll find that the red bike can't just walk away, either, and that the YZ won't give up anything to it pulling off corners or down straights. You will also find that the way the YZ delivers its power allows you spend much less time worrying about throttle control, and lets you just sort of rip into it a little like you'd ride a 250F.

What's funny is that after all of that, some are now saying that the '06 has so much more bottom end than the '07 does, and such. Oh well...:thumbsup:

  • sacfelix

Posted April 16, 2008 - 06:52 PM

#10

I ride a 06 yz450 and only ride single track and technical trails through out the National Forest system in California. I am the original owner of the bike and have never had any issues with the bike over heating. The only thing I done to the bike was go up on the main jet, pilot jet, raise the needle to the 4th position, reroute the breather tube, install gytr H.D clutch springs and install an adjustable air screw. I stay on top of my maintance and am still on the original clutch. I went on a 5hr trail ride from Middlecreek to Goat Mountain and riding mainly black diamond trails. My buddy rides a 06 CRF450X and has never spilled any fluid. The only thing he has done to his bike was adjust the valves after 2700 miles of trail riding and one back rim from wear and tear.

  • x2468

Posted April 17, 2008 - 04:10 AM

#11

I ride a 06 yz450 and only ride single track and technical trails through out the National Forest system in California. I am the original owner of the bike and have never had any issues with the bike over heating. The only thing I done to the bike was go up on the main jet, pilot jet, raise the needle to the 4th position, reroute the breather tube, install gytr H.D clutch springs and install an adjustable air screw. I stay on top of my maintance and am still on the original clutch. I went on a 5hr trail ride from Middlecreek to Goat Mountain and riding mainly black diamond trails. My buddy rides a 06 CRF450X and has never spilled any fluid. The only thing he has done to his bike was adjust the valves after 2700 miles of trail riding and one back rim from wear and tear.


thanks for the info. from what i've read the 450x handles slow trails no problem, but the 450R needs higher speeds and more airflow.

  • cliff1818

Posted April 17, 2009 - 04:54 PM

#12

the wr 450 and the yz 450 are almost the same bike. the wr only has a battery and sits a little lower due to more weight. their should not be a diffrence in boiling between the two.

  • cliff1818

Posted April 19, 2009 - 11:08 AM

#13

the yz is almost the same as the wr so it must be a half way good trail bike.





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