Cont'd 02 CRF-450 valve problems ... suggestions?

[Nestrick]

This is the continuing saga described in the previous post of 08-09-2003 where I fully explained the problems I have encountered regarding the valves on my 02 CRF-450 and the subsequent alterations accomplished to remedy said problems.

Having had two sets of Titanium valves installed with several shim adjustments on each set, as previously described, the time interval between normal operating lash settings for the intakes and essentially complete closure had decreased to the vicinity of less than 25 hours. At that point I had my Honda dealer install a complete set of Kibblewhite stainless steel intake and exhaust valves along with the appropriate Kibblewhite valve spring kit components to hopefully end my valve closure problems. Following said installation I did encounter the 'increased kick start resistance' problem mentioned ... but this is of minor consequence at the moment.

I have now operatied the bike on Michigan trails, relatively easy running conditions, for exactly 11.0 hrs ... on checking the valves yesterday I found both exhausts and the right intake to have maintained factory spec settings of 0.011" and 0.006" respectively. However, the left intake is now down to 0.003" ... all with only 11 hours operating time on my new stainless steel valves!

I intend to order an appropriate shim to install to regain factory spec setting of 0.006" for the left intake on Tuesday after the holiday; but ... this doesn't jive with the many posts I have read about installing Kibblewhite stainless steel valves in CRF-450's ... especially the Offroad.com CRF-450 Project series posting on these valves. They have been quoted as the solution for such problems which most of the experts have noted to be a function of either the original Titanium valves or the original Honda valve springs. Since I no longer have either of these ... the only other possibility for the new valves to be closing up so quickly would seem to be the valve seats in the head? Perhaps they are not hardened properly?

My Honda dealer freshly cut each of the valve seats prior to installation of the new steel valves ... each valve was hand lapped to match the seat ... compression is supurb ... why is at least one of the intakes still going closed after such a short period of operation?

I can restate that the official "honda" solution for my problem was to purchase a new head and install new honda spec steel exhaust and titanium intake valves ... purhaps the head suggestion is more important than just properly matching to the new titanium valves which cannot be lapped?

Anyway ... I am now in a severe quandry. If I reshim the left exhaust and it still closes up after only a few hours operation I am guessing that the only step remaining is to buy a new head and have my current steel valves put in it? Unfortunately I am not sufficiently mechanical to do this and the cost for the head plus removal of the old parts and subsequent reinstallation will cost on the order of $650 ... after I have more than $1500 in the motor to date trying to resolve this valve problem since its beginning last year. This is very disappointing ... almost seems like my motor is a "lemon" and I should patch it up and sell it.

Suggestions ... advice ???

 

[gasgasman]

Sounds like you have valve seat recession.
The seats may not be properly heat treated.
Another area to check would be the cam bearing surface. The cam bearing may have excessive clearance allowing the cam to be off center.

Good luck.

 

[mike perry]

Nestrick-

I'm going to assume that you've got a tight air filter seal, so no abrassives are entering the intake tract and getting between the valve and seat. This can cause problems even with stainless parts. Not to mention what it will do to your rings.

Occasionally a valve and seat will take a set when first assembled. Sometimes it can be the result of a small piece of foriegn material being caught between the valve and seat when they are first adjusted. Remember you are talking about something with a cross section of few thousandths of an inch to get the change you've experienced.

Sometimes during the machining process chatter or a slight misalignment may occur, causing the valve and seat to "beat in" until the metal conforms to the direction it's being forced to go. This will cause a slight loss of clearance. This is not good for optimum performance, but it may not continue to deteriorate. The bummer is, if the problem was a misalignment, the valve will make room in the guide so it can go where it needs to, to find the seat. I'm not saying that's the case hear. I'm just throwing out some things I've seen.

Also if the guides have excessive wear they will allow the valves to hunt around and pound the seats out.

The seats that Honda uses are a type of powdered metal which work hardens as it is being run. I have seen some exhaust seats pounded out after several sessions run by a pro rider using every bit of rpm the engine would give. Most guys can't and don't run up there. We've been selling the kit for a year and a half and have lots of riders with lots of hours on these kits. I have not heard of any recession problems after the new pieces are installed.

Adjust the valves, and see if things stay put after that. I'm guessing they probably will.

Mike Perry
R&D Dept.
Kibblewhite Precision Machining

 

[Nestrick]

Thanks for the replies and advice. I have reshimed the errant exhaust valve back to 0.006" and have put about 6 hours operating time on the motor. Will wait until approximately 10 hours operation before checking the valve lash again. I am hoping that Mike Perry is right and my valves stabilize for an extended period of time. By the way, I have the full PC Racing seal kit on the bike including the neoprene foam gasket on the filter side ... the airway has never shown obvious particulate matter entering the system and I have maintained the Twin Air filter religiously. On both occasions of top end rebuilds so far, the cylinder wall and piston rings have been in excellent condition and did not show signs of excessive wear indicative of entering particulate matter in the air stream ... while not necessarily conclusive, particulates do not seem to be the culprit in my case?

Regarding valve guide considerations, Mike, the Honda techs informed me that the Kibblewhite folks explained I did not need to replace the original Honda guides since I was not changing the cam and they did not show obvious, visible signs of wear. Hence, my motor has all new Kibblewhite valves and associated Kibblewhite valve spring kit components, but retains the stock, original Honda valve guides.

Regardless, the motor is running about the best I can remember ... it starts well when either cold or hot, and the kick start resistance has begun to noticeably decrease with increasing run time on the motor. I will let you folks know what happens when I next check the valves.

Again, thanks to all for your kind help and considerations ... terry nestrick

 

[SFO]

Originally posted by Nestrick
. I am hoping that Mike Perry is right... terry nestrick

Me Too :worship:

 

I'd bet the farm on it...

 :thumb: