Using TRX450 ATV valves in a CRF450

Rich Rohrich · Apr 21, 2004

I answered the following question on TT so I figured I would pass the info along here at the home base :)

I was told that I can go ahead and put in the intake valves and springs from the new quad and save quite a bit of money in comparison to the kibblewhite and get the same benefits...no more valve issues.

Is this true? What else do I need to replace while doing the valves and springs?

Nope won't work. The spring won't handle the additional weight of the steel valve. If you use the steel ATV valves in a CRF you'll still need an updated spring kit like the Kibblewhite pieces . The Honda ATV valves are only about $35 less than the much higher quality Kibblewhite stainless valves so there doesn't seem to be much point really.

We were discussing this a few weeks ago and Mike Perry was kind enough to send me the following notes from his research:

For the ATV Honda has:

-Gone to a steel intake valve but left the spring pressure the same as the ti valved bike head. Valve head diameter and overall length same as the bike.

-Gone from a 5.0mm stem exhaust valve to a 5.5mm stem.

-Dropped the head diameter on the exhaust valve from 31.0mm to 30.0mm. Dropping the head diameter has compensated for the weight increase that the larger stemmed valve would normally bring to the combination. The weights of the exhaust valves are the same. Spring pressure on the exhaust side is the same for the bike and the ATV.

-Retainer to seal travel is only .390" on the intake side. less .040" for a safety margin. No snap ring on the guide so you could conceivably push it down in the head to get a little more room. About .410" on the exhaust side.

-Guide lengths are different.

-Seat OD's are the same, so O/S valves can be fitted.

-According to Laurie the cam is quite a bit milder on the ATV. I would hope so. Lest they have serious spring issues due to the weight of that intake valve. I imagine the ignition box is also set up with a much lower rpm ceiling.

DEANSFASTWAY · Apr 26, 2004

thats funny Rich cuz on the quads weve been putting the Ti valves in a few of them.030 washer under exh spring baseSort of reverse strategy but these are race intent. Were trying CRF pistons too. CRF cams Also trying to add an extra clutch disc but that dopesnt look like it will pan out .I think maybe the CRF could benefit from a bit more oil reserve like the ATV has. An E start 450 would sell to the seniors although theyre really not hard to start IMO.Ive heard Tell of the AtVs cracking the kickstarter parts real bad on starting , I guess some people dont know the drill.

hamilcrf · Aug 27, 2006

Ordered the TRX 450 valves springs and upper retainer they have different part # thinking I can safly use this intake vavle parts in my CRF450 any insight hate to ruin the motor

Rich Rohrich · Aug 27, 2006

You can't use the TRX valves without using a much heavier spring like the Kibblewhite kits use. The CRF has a valve spring designed for the weight of a titanium valve and a very radical cam. The TRX steel valve is MUCH heavier and the cam in the TRX is much less radical. It's more like an XR cam.

TRX valves with CRF stock springs is a disaster looking for a place to happen.

hamilcrf · Aug 27, 2006

I haveordered the trx springs and TRX upper retainer to use with the TRX valves still a disaster?

Rich Rohrich · Aug 27, 2006

The TRX valve spring is designed to work with the TRX cam and is much too light to work with the CRF cam. The TRX stock intake spring and the CRF stock intake spring were identical in the past. Honda was able to get away with this because the TRX cam was so mild.

What you are trying to do doesn't work, period.

If you want to run steel intake valves in a CRF you have to buy good aftermarket springs and lightweight upper retainers. There is no cut-rate way around this.

hamilcrf · Aug 27, 2006

thanks for the insight Ritch I saw the upper retainer and springs have different part # for the trx vs the CRF so I naturaly thought they were desighned differently to compansate for the weight.Seems some Honda REp told a honda tec that this would work yet the story I got was the valves would work yet you must change the springs the confusion is for me did the rep mean the kibblewhites or the TRX springs.I know alot of folks say this is a dead horse yet it is new to me I had an 02 CRF 450 and now the 05 my son has the 05 also and I have done new stock valves once in my 05 twice in the 02 and my sons left intake is running .002 with the 120 shim so I am investigating options thank you for your insight and patience,Kenny

Rich Rohrich · Aug 27, 2006

It's worth the money to buy the full Kibblewhite kit so you get the good valves, the race spec dual springs, and the titanium retainers. The Kibblewhite valves are made from a high grade stainless while the TRX valve is a lower grade steel that isn't stainless. The TRX valve was designed to be built at a much lower unit cost compared to the Kibblewhite or Ferrea stainless valves. In other words the TRX valve is just a cheap steel valve. Material spec and valve head shape is far superior on the Kibblewhite CRF valve.

On a CRF450 the Kibblewhite setup is a good investment that really pays off in long term reliability.

Don't forget to change the cam chain tensioner every season while you are in there and make sure you get the valve seats machined so the new valves seal properly. ;)

hamilcrf · Sep 15, 2006

Got the TRX 450 intake valves and TRX 450 intake valve springs in the 05 CRF 450 6hrs on the set up no ill effect have wraped to the rev limiter more than occasionaly seems fine !Kenny

Rich Rohrich · Sep 15, 2006

Congratulations, you built yourself a timebomb. :coocoo:

adam728 · Sep 15, 2006

Don't you love it when people ask for advice, then chose to ignore it?

Rich Rohrich · Sep 15, 2006

It's a free country. Everyone is entitled to build their engines whatever way they think is best.

chris82785 · Sep 18, 2006

it's also good to hit the rev limmiter - really treats internals nicely :coocoo:

hamilcrf · Sep 22, 2006

very long fuse anouther 10 hrs on the the set up valve clearances staying at .006 no sighns of unusual camshaft wear.Been a mechanic my whole life shop owner for 18 years Graduated AMI top of class in 1975.As you can see not afraid to tinker.Have no Idea what your credentials are seems you have a good pen and attitude of infalability I will let you know the progress on this 450 seems fine to me

MikeS · Sep 22, 2006

Funny this post has come up. I have 2 customers, they say they do not know each other but that is not the issue.
One has put the ATV Int valves in his bike with the slacked out oem springs. He found some funky shims and put .060" under the intake springs. He raved that it worked so good for 2 months of riding the trails etc etc. Last weekend he did a harescramble 30 minutes into the race the motor locked up.... End of that story.

I got another call that a guys is ready to put those same valves in his bike but he said : wow they feel heavy, so he called for some springs. Kibble springs could not be found anywhere at my sources so we opted for the Ferrea kit. He still said the dealer and a few guys said just get 2 oem intake springs and shim them... Atleast they said to use NEW springs. Note the dealer is the same dealer that has the first guys bike.

I declined to work on that first rats nest since I suggested a complete new bullet proofed top end, head, cylinder and piston, since it is an 05 with alot of time, just to start with. This bike has had 3 sets of valves, never cut the seats, never had a piston replaced.... He figures it should be under a grand from the dealer or he will just trade it on a new YZ because they run forever..???????

hamilcrf, I wish you luck but the time is ticking.....

hamilcrf · Sep 22, 2006

Mike S please give me some detail as to the failure of this locked up motor what failed was it the piston contacting the intake valve at high rpm the head of the valve droping off the cam shaft snapping can you confirm the atv valves were the culprit I would like to know some details instead of just "end of story" This forum is to learn and discuss I did cut the seats before installation tell me what failed I may need to get them out of there thanks,and for the one who seems to think asking for input and then going forward albeit possibly in the wrong direction have a good one,Kenny

MikeS · Sep 22, 2006

I am on one foot and not driving from surgery to my leg but I will make some calls and see what I can find out. I suspect the piston tagged a valve and then exploded into the bottom end.. In talking to him he said the bike was hard to start the night before the race so he did a quick shim, stating they were not bad. It then started fine and at the race. I would suspect that the springs are too weak and the valves started to hammer the faces that caused them to tighten up in a few weekend rides.

The other guy was in today to get his Ferrea springs for his new valves and he seemed very happy he waited. I asked if he new the guy but he didnot. He said the dealer sold him the ATV valves as the best fix.... He only saved $30 from Ferrea or KW steel valves with those ATV valves. The dang springs are 2 bills+...

I will post back and maybe some photos...

hamilcrf · Sep 23, 2006

Hey Mike thanks yea its the 200 for the springs I ordered the ti valves today and will go back to them it is not such a big deal to install just time.As for the rev limiter hits well I hill climb a little unortodox in my tecnique I find it is better to slam her down a gear early to keep it pulling strong before you would think I should resulting in hitting the limmiter if you think it don"t work come to Grand Junction Colorado and check out the climbs cool fun this is something I don"t need to do with the 500 2 stroke considering building my own AF any one with a late model crf with a lunched motor give me a call I will buy your bike for the rolling chasis,yea I know I can buy one from service honda.

Vic · Sep 23, 2006

I'll keep you in mind in case I lunch my motor. :)

MikeS · Sep 28, 2006

Well as an update on the CRF450 that made it to the dealer. Seems the valve floated, the piston twistesd in the bore and the skirt in turn tagged the crank. Cases are gouged up but useable. It needs a head, cylinder, crank, piston and valves.... the owner was in and ordered some bling for his NEW yz450... He did not elaborate on what deal he made. the dealer wants 2500 for the bike as is, I declined as I can get a running 05 CRF450 for 3300-3500 around here...

mafols · Sep 29, 2006

Seems the valve floated, the piston twistesd in the bore and the skirt in turn tagged the crank.

Is there a correlation between the valve floating and the piston twisting? Unless you mean...the valve struck the piston and sheared the wrist pin and it turned, I'm not sure I understand... :whoa:

Could you please elaborate....Thanks

Matt

MikeS · Oct 1, 2006

mafols said:
Is there a correlation between the valve floating and the piston twisting? Unless you mean...the valve struck the piston and sheared the wrist pin and it turned, I'm not sure I understand... :whoa:

Could you please elaborate....Thanks

Matt

Twisted was a bad word a guess. When it hit the valve, the valve bent and mashed itself into the head. It did not break. The piston hit it again and again I would guess. The piston was found jambed in the bore. Locked up. It was tough to get out. The rod was also bent. The mechanic made a bigger mess by hammering it out. The rear side (intake) of the piston was pushed into the bore more than the exhaust side hence my use of the word twisted. :ohmy:

hamilcrf · Oct 6, 2006

OK so here is where my 450 with the trx valves is at I went to the dealer HONDA dealer that is the one that cut the seats and asked the service manager a freind I ride with that cut the seats for a set of ti vaves he looks at me and says your preaty paranoid about them trx valves so I tell him about this chat he says they put the H1R I think thats the term Hondas raceing kit for the trx any how he claims the cam in the kit is every bit as radical as the crf cam and they use the stock trx valves and springs, so I leave the trx intake valves and springs in the 05 put 4 more full days of rideing on it,will take it to Caneville Utah for 3 days this weekend every thing is still fine with this motor have yet to have to adjust the clearence time will tell,Kenny

SFO · Oct 6, 2006

I am glad everything works for you.
Having your dealer install it and stand behind it is very valuable.

Muroc · Oct 6, 2006

hamilcrf said:
Been a mechanic my whole life shop owner for 18 years Graduated AMI top of class in 1975.As you can see not afraid to tinker.Have no Idea what your credentials are seems you have a good pen and attitude of infalability

Rich is the four-stroke engine builder for Eric Gorr's company Forward Motion Racing, and he does all their four-stroke race engine porting and builds the cylinder heads.

His credentials are pretty well spelled out in this thread from a while back ==>> (I can't post live links so you have to cut and paste the link) dirtrider.net/forums3/showthread.php?t=40126

He's not an AMI grad like you but far from a newbie so the advice certainly has merit.

Our local Honda shop used to recommend the same thing yours did when the trx stuff first was available. They stopped doing it when they had to start covering the repairs from broken engines and po'ed customers. I hope you have better luck.

The dirt trackers I know who have tried it all ended up with engines like Mike S described above. Seems like a big risk to save a few bucks.

Using TRX450 ATV valves in a CRF450

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