Rich, 250F questions
- Thread starter Chili
- Start date
Ol'89r
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- Jan 27, 2000
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Rich Rohrich said:
Excellent read Rich. :cool:
Chili.
I don't have much experience with the KX's but I have set up several CRF 250's and 450's with the combination Rich suggested. The Kibblewhite SS valves and torque cam is a excellent combination and most riders can't tell the difference between the SS valves and the ti valves. The torque cam makes the bike easier to ride from corner-to-corner and brings the revs down a little bit. Hence, a longer life. I would have to agree with Rich, if the guy only has one bike, that would be the way to go.
- Thread starter
- #30
Terry by Torque cam are you referring to the Stage 1 Hot Cam? As far as difference between the stainless and Ti valves, if the rider could tell, what differences would he be noticing? Also are we changing both intake and exhaust cams or just the intake in these kinds of setups?
I've seen many posts that the Kibblewhite stuff is good for 300+ hours, should the other parts (guides, springs, retainers etc) be replaced on a much shorter schedule? The reason I ask is this same rider put the Kibblewhite stuff in his 04 RMZ and while the valves lasted without issue a spring retainer let go leading to a very difficult diagnosis process but thankfully no valve train damage. Not a knock as the retainer likely had well north of 100 hours when it wore through.
I've seen many posts that the Kibblewhite stuff is good for 300+ hours, should the other parts (guides, springs, retainers etc) be replaced on a much shorter schedule? The reason I ask is this same rider put the Kibblewhite stuff in his 04 RMZ and while the valves lasted without issue a spring retainer let go leading to a very difficult diagnosis process but thankfully no valve train damage. Not a knock as the retainer likely had well north of 100 hours when it wore through.
Ol'89r
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Doug.
Yes, the stage one hot cam is a good one. It can be installed without any mod's to the piston although the clearances should be checked. I also use WebCams torque grind. They come as a set and both cams should be changed,
The difference between the ti valves and the SS valves is a slight drop in top end rpm. For an Intermediate rider he would never know the difference. Also, setting the bike up for torque instead of top end will make it much easier to ride and allows for better traction on shorter tracks.
If the bike is ridden hard, the springs will lose their tension before the valves go bad. I usually check the springs with a spring tester and replace them if they test low. Have never had a problem with any broken springs or retainers with the Kibblewhite setup. The guides in these engines seem to last for a long time. Since the cam pushes directly down on the valve cups, it keeps the valve from rocking in the guide like they do in a rocker arm type of engine. Therefore, there is less wear stress on the guides.
Of course, all of this stuff should be checked at regular intervals when he re-rings the bike.
Yes, the stage one hot cam is a good one. It can be installed without any mod's to the piston although the clearances should be checked. I also use WebCams torque grind. They come as a set and both cams should be changed,
The difference between the ti valves and the SS valves is a slight drop in top end rpm. For an Intermediate rider he would never know the difference. Also, setting the bike up for torque instead of top end will make it much easier to ride and allows for better traction on shorter tracks.
If the bike is ridden hard, the springs will lose their tension before the valves go bad. I usually check the springs with a spring tester and replace them if they test low. Have never had a problem with any broken springs or retainers with the Kibblewhite setup. The guides in these engines seem to last for a long time. Since the cam pushes directly down on the valve cups, it keeps the valve from rocking in the guide like they do in a rocker arm type of engine. Therefore, there is less wear stress on the guides.
Of course, all of this stuff should be checked at regular intervals when he re-rings the bike.
Ol'89r
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Also, I have used both the stage 1 and stage 2 cams with excellent results. The stage 2 cam runs a little higher rpm and is a little more aggressive than the stage 1. Neither cam is really that radical. With the stage 2 cam you would have to make sure to clearance everything where as the stage 1 is a bolt-in. Although, it is still a good idea to degree and clearance the cams regardless of which one you use.
Of course, the more radical the cam the more stress on the valve train and the harder the bike is to ride. It would all depend on the rider. That would be your call.
Of course, the more radical the cam the more stress on the valve train and the harder the bike is to ride. It would all depend on the rider. That would be your call.
Chili, keep us posted what mods your friend is going with. From your first post, I would bet he does not like what you are going to tell him! The magazine said so, or I know a guy are tough ideas to break. I did not know the 08 suffered the same ap adjuster issue that the 06's have, and require the wire or o-ring mod. There is a company that makes a solid ap adjuster, no floating or lag. I have heard nothing about the adjustable leak jet bowl. It is almost as finicky as the mixture screw. Unless he has a team green support truck at his access, jetting and suspension, and keep up better with rebuilds, for sure! Heaven would truly be a new set of tires at every race!
- Thread starter
- #34
Actually I think the Dad is very pleased with all the advice he's received here, although I think he's avoided mentioning the practice bike suggestion to his son :laugh:
First mod happens next week when I take the suspension to Jeremy Wilkey.
First mod happens next week when I take the suspension to Jeremy Wilkey.
That was an interesting read :cool:
From what it sounds like it would be ideal to vary the IVC timing compared to RPMs, then the port size would be less important, Stronger Power throughout... :think:
But Anyways..
Merge Racing makes a stiffer AP spring, so your Jimmy-rigged Orings don't fall off.
From what it sounds like it would be ideal to vary the IVC timing compared to RPMs, then the port size would be less important, Stronger Power throughout... :think:
But Anyways..
Merge Racing makes a stiffer AP spring, so your Jimmy-rigged Orings don't fall off.
- May 27, 2007
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Im actually glad I read this post, can't quite comprehend all of the information here, but that exhaust i have been thinking about will be on the back burner and a cheaper cam will come first and some new valves.
We never tried the stage 1, we liked the stage 2. It is hard for a mx guy coming off a 2 stroke and get them to short shift. Trails, fine, need plenty of torque. Long outdoor track, stage 2 and at the time, we got talked out of the ti valves. Not that big of a difference off the top. A dyno shows it. I would be surprised if a blind rider could tell the difference. The guy we sold our modded 450 to, took everything off except Eric's head, it still screams on the top end, like a 2 stroke, and scares the hell out of the old rider! Replace the valves with the ss kibbles, and eliminate the head job every piston change. A retainer letting go on an rmz450, crap happens. Could have been defective? Chili is going to SEE Jeremy? Check out some of Brandon's handy work, he is modding heads! He does have the gift, and the right people behind him. I would use him for valve work, except I have access to one Danny Mitchell in my back yard. The ap, http://www.readyracing.com/pdf/rapidresponse-productsheet.pdf, end of issues and I really like these guys! Anything to increase oil flow and keep it cooler always seems a good idea also.