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Discussion Starter · #1 ·
I am just about to purchase a new 700xx and i just wanted to go over a few things about honda and their valves.
I currently own a 04-crf450r dirtbike and am hesitant to go with honda again because of all the valve problems they had with the 450's. anyone who has owned one knows what i am talking about. the valves need to be reshimmed every 10-20 hours due to the titanium intake valves stretching and creating zero tolerance on the valve lash. I understand that the 700 is not a racing engine so the cam and valves are prob different than the 450. I have heard of some catistrophic engine failure on a few of the 700s involving the valves but the cause seemed to be less experinced riders over reving the engine.
I would like to get a first hand view of people that own the 700 to see if anyone has noticed any problems.
Have the clearences changes at all since time of puchase??
thanks
 

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I am just about to purchase a new 700xx and i just wanted to go over a few things about honda and their valves.
I currently own a 04-crf450r dirtbike and am hesitant to go with honda again because of all the valve problems they had with the 450's. anyone who has owned one knows what i am talking about. the valves need to be reshimmed every 10-20 hours due to the titanium intake valves stretching and creating zero tolerance on the valve lash. I understand that the 700 is not a racing engine so the cam and valves are prob different than the 450. I have heard of some catistrophic engine failure on a few of the 700s involving the valves but the cause seemed to be less experinced riders over reving the engine.
I would like to get a first hand view of people that own the 700 to see if anyone has noticed any problems.
Have the clearences changes at all since time of puchase??
thanks
The bikes use Ti valves and the quads use SS so the valve issues just aren't there. I have never heard of a top end issue of any kind on the 700XX; the engine seems to be rock solid.
 

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Discussion Starter · #5 ·
Thats all I needed to hear!! If the 700xx is everything that people say it is on this site then its everything I've ever wanted in a quad! I do believe that when the press release test riders rode this quad they didnt get enough time in to really learn the characteristics and full potential of the machine. I believe that I will be satisfied with my decision and i'll let everyone know my overall thoughts on the outcome.
Thanks again
 

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:funny:

The 700xx is an awsome machine. So far it has been a rock solid machine that both the wife and I are enjoying (we each have one)!:hey:
 

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When you use high performance parts there is always an increase in attention to maintenance. The guys who had trouble with there 450's weren't checking valve lash as frequently as needed. The valve will stretch over a period of time, Not just suddenly that would catch you by surprise.
The XX doesn't have Ti valves so that is not an issue. The only valve failure I know of to date was on mine, This was from not double checking clearances on a piston install, not over revving. The XX has a limiter that is set well within over rev range.
The XX valve lash setting procedure is 100x easier then the 450 also, It uses a set screw and there are no shims required. Just out of curiousity, Where did you here of XX valve problems?
 

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Discussion Starter · #9 ·
When you use high performance parts there is always an increase in attention to maintenance. The guys who had trouble with there 450's weren't checking valve lash as frequently as needed. The valve will stretch over a period of time, Not just suddenly that would catch you by surprise.
The XX doesn't have Ti valves so that is not an issue. The only valve failure I know of to date was on mine, This was from not double checking clearances on a piston install, not over revving. The XX has a limiter that is set well within over rev range.
The XX valve lash setting procedure is 100x easier then the 450 also, It uses a set screw and there are no shims required. Just out of curiousity, Where did you here of XX valve problems?
based on all of the responses i got i am very confident about buying the xx now. I actually had just discovered the valve problems a few days ago on my 450 and assumed that all honda's were notorious for having valve problems, at least the high performance machines. I just felt that the xx being a 700 that i would fall into the high performance category.
I typed in google honda trx700xx engine problems and went through the first few pages that came up...... on was actually where the piston blew out of the side of the cylinder wall and all that was left was the wrist pin. they sent a field tech to inspect the warranty claim and the conclusion was lack of oil to the wrist pin. It must have been a one time thing or perhaps whoever it was didnt have enough oil or something freakish, the other was a guy was racing his friend and pulled way ahead of his buddy and parked by their truck to wait for his buddy to catch up and heard noise in the top end with no loss of power and his buddy said he saw him pull away and then all of a sudden saw smoke pouring out. it smoked the piston, valves, cam, etc. warranty tech said lack of maintenance and that the dust being pulled into engine it smoked the rings.
I guess with the valve problem i faced with my 450 being fresh in my mind I jumped to conclusions to fast and just needed to clear it up before the purchase. I hope i didnt startle any xx owners with my paranoia on this issue.
Im sure that the people that experienced thes problems probably didnt maintain their machines and that may have been the result
 

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The 450s are pretty much the only thing out there that had serious valve problems. That isn't just honda, it is across the board as they all Have Ti valves. The thing is, you have to check your valves. I think on the 700 is says every 100 hours in the manaul, if I am not mistaken (it actually may be more), but if you look at the 450's, it is every 10-20 depending on model (I have had two trx450r's, and I still have a 450X). If you add on aftermarket parts, then you should check your valves more often. I have only seen one 700xx that was bad, and I think it was smoooths if I am not mistaken on another thread. I have had mine pretty much since the release and the only problem I have had is a clutch that wore out too quickly IMO.
 

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Just as crwh said, Its a problem with all Ti valve engines, I've mostly heard of them sinking into the seats which cause the lash problem instead of the valve actually stretching. I've never had a Ti valve engine though, So that's just what i've read. The XX wasn't really built as a dedicated race machine so the benefits of Ti valve would have been minimal.

Go buy that XX, You'll love it
 

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The CRF valve problems were not caused by not checking valve clearances. I owned a 2003 CRF450R, so I have first had experience and did lots of research into the failures. The most common cause of valve problems in the CRF was dirt getting by the filter. Honda did not use hardened Ti valves; they used a hardened coating on the Ti valves. Once dirt made it by the filter, the dirt would wear off the coating, causing the valve to wear and “suck up” into the head. After owning my CRF for about 9 months, I had one ride wear I noticed a slight amount of dirt by the filter, and I mean slight. I checked the valve clearance and the one intake was already at zero clearance. I reshimmed and got maybe another 10 hours out of it before zero clearance again. I then pulled the head and replaced with SS valves. I ran those same valves for over three years and never once had to adjust the valves. I was also very religious about air filters after that.

That being said, dirt past the filter will kill any valve, just the original CRF Ti valves were real bad about it. Actually, I think the valves were alright, it was just the coating that was being used. A couple of years ago, I had dirt get by my TRX450R air filters, and even after 20 hours, the valve clearance only decreased by 0.002 in that time, and I noticed way more dirt then what got by my CRF. (At the time, I had Kibblewhite SS valves in the TRX.) I think Honda has pretty much fixed the valve problems in the later models. (I have not heard of many valve replacements in the newer CRF’s, but do not really follow them either anymore.) Around this same time (2003, 2004), Yamaha had Ti valves also in their 450 motors, and I never heard of any failures with them. I do remember one year around this time, KTM recalled a bunch of their four strokes as everyone was breaking Ti valves, I guess they used a Russian supplier for the Ti, and it turned out the Ti was junk.

The 700XX should not have any valve problems, as long as you check the clearances fairly often and keep the air filter well maintained. The problems in the CRF were caused by the type of Ti valve used, and the 700XX does not use Ti valves, is has SS valves. Also, the 700XX uses a totally different design for the valve train. The 700XX should be trouble free.

Doug
 

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Bergstrom, aren't you saying that it is actually caused by not checking the valve clearances like the rest of us. You are simply saying that dirt was getting by the filter and messing with the valves, which is more than I knew (I actually didn't know why the clearances would be off). However having a few crf's, I did have one have a valve train issue. After that, I checked the valves religuosly, and never had a problem again because I would check them sooner than later. Your post clears up why they would fail, the rest of us are just saying that if you didn't check your valves, they would fail on the 450's, and that the 700xx has a different valve setup completely, that should be very reliable. That's all.
 

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Bergstrom, aren't you saying that it is actually caused by not checking the valve clearances like the rest of us.
Not really. The valves never actually "failed". By failed I mean the valve does not break or anything, it just wears so bad that it goes to zero clearance. You actually did not even need to check the valves, it was pretty easy to determine something was wrong, the bike would have problems starting when hot. Once the clearance closed up enough and the motor would get hot, things would expand and the valve would actually stay open, the engine would loose compression, therefore was a pain to restart. That is actually how I figured out somthing was wrong. Went for a ride one day, shut the bike off to take a quick break, took forever to start back up. Once that happened, I knew what the problem was, as it was fairly common what the warning signs were. Even if someone ignored it, eventually the clearance would close up so much that the bike would probably not start at all, forcing someone to pull it apart to fix it.

Yeah, you can check them, but they would close up so fast you would need to almost check them after every ride. In all the research I did, I never found anyone who had a valve break, the bike would eventually just not start. I know when I adjusted mine the first time, I guessed about 10 hours on the bike before it had problems starting again, so it went from clearance in spec to nothing in a short time. In fact, I bet it was less then 10 hours, I know I only got a couple of rides out of it.

Again, I really do not here much about valve issues with the newer CRF450R's, so I think the problem has been fixed. Regardless, I think the 700XX should be just fine, I expect no problems with mine.

Doug
 

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He was saying like I was thinking, The dirt getting past the filter was not causing the valve issue. The valve problem is caused by the softer Ti valve hitting the hardened seat and it wearing a groove in it, This groove lets the valve come up higher closing in the valve lash. Letting the valve lash get bad enough to cause hard starts is the result of improper maintenance.
Any bike that comes factory with Ti valves is a race bike with a racing engine. It cannot be ridden like other bikes without lots of attention to maintenance before each ride.
 

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What happens in the pits stays in the pits
 

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LMAO. I understand what everyone is saying. Especially about the pits (I guess thats why I never end up having anyone in my pits :( ), however the problem with the Ti's can't really be solved, but it could be maintained (prevented) by checking the valves normally as we were saying. Which I am positive on the 450's it is every 10-12 or 15 hours, which is very frequent for any bike.
 

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Discussion Starter · #19 ·
from what I understand The 450 was designed as a high performance race bike therefor they used titanium valves. the reason that there are titanium valves is that it reduces reciprocal mass, hence more performance, i.e. it is lighter than steel, hence more performance. also, the cam was designed with fast opening and closing ramps and sets the valve down quik and when being over reved or heated excessivly the valve will bounce causing a peening action this causing the valve head to mushroom enough to cause zero clearance on the valve lash. The cam closing the valve quickly aslo causes that springs to wear quicker than normal there have been rumors of it being because of poor maintenance and dust contamination but I know for a fact that wasnt the case with mine, I changed and oiled the air filter after every ride. It is not something that can be prevented or maintained it is simply just the laws of physics that take place. you can only observe after it has happened. not saying that you should not be checking the valve clearances every 15 hours as recommended by honda.

But who knows...... I could be wrong
 
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