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Most common cause of a broken valve spring and bent valve?

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Hi guys I got a 2003 honda crf450r with: the MaxRPM Ice Cube 498 big bore kit, high compression Wiseco piston, full Yoshimura exhaust, 2006 head with APE stainless steal valves and APE springs, stock porting, 2006 40mm carb with JD jetting and Boyeson Powershot, running a #168 main jet and #40 pilot jet... I recently revved up the engine about an hour into a trail ride and it broke a valve spring and got a bent valve... I've been a CR250 2 stroke rider for the past 8 years and have no idea what would cause this to happen... Can anyone help?

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Not sure if you want to know why yours failed?

I would say fatigue (work hardening) if the spring is old.

You didn't mention the cam you are using. If the lift is to high for the spring it will cause the spring to coil bind and weaken or break.

If the installed height is not right with the spring you can float a valve or coil bind the spring and it will break.

Your jetting is way off with a JD jet kit. You should be about 185 mainjet.

Which valve spring broke intake or exhaust?

Edited by Rocksalt
typo

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if you installed the heavier valves without stronger matched keepers, the keepers wont hold up to the heavier valves, they'll prematurely fatigue and youll drop a valve. seen this happen time and time again.

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Thanks for the replies guys. The head was ordered COMPLETE from APE with the SS valves and heavy duty springs. So unless they are not a reputable company I don't see why the clearances would be off or the keepers being to weak to support the valves. The spring that broke is an intake valve spring. Since I have a 498 big bore kit I have been told that if anything you want to go down in main jet size... not up... Why would I want to put such a large main jet? The bike ran 100% fine and like a raped ape before the spring broke. Instant throttle response, easy to start, etc... I totally appreciate the input guys please elaborate.

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Thanks for the replies guys. The head was ordered COMPLETE from APE with the SS valves and heavy duty springs. So unless they are not a reputable company I don't see why the clearances would be off or the keepers being to weak to support the valves. The spring that broke is an intake valve spring. Since I have a 498 big bore kit I have been told that if anything you want to go down in main jet size... not up... Why would I want to put such a large main jet? The bike ran 100% fine and like a raped ape before the spring broke. Instant throttle response, easy to start, etc... I totally appreciate the input guys please elaborate.

The JD needle is fatter and requires a larger MJ to achieve the same A/F ratio. Example: 03 MJ stock is 168. JD needle: MJ is a 185 or 180 depending on the needle position. That jetting is fine if you have the stock needle.

Unless the spring height was wrong I don't think it was anyone's fault. Just bad luck or poor quality valve spring.

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Cool man that makes sense to me. The carb work was done by the guy I got the bike from so I'm not sure if he went with a JD needle or a stock one... Is there any way to know if the needle is a JD needle or a stock one?

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The JD jet kit is composed of a MJ and a needle.. that's it. The JD needle has a red or blue dot on the end of the needle where the clip is. A factory needle will have a 4 letter code on the side of the needle at the top.

Hopefully just the spring broke and the valve dropped and bent. Simple replace the valve and install new springs. Then again, this could have happened:

Fatigued spring or poor quality. This was the single spring variety from Ferrea. Since then I switched to Kibble White with no other changes and it has worked flawless.

rhchead.jpg

cylinder.jpg

Edited by Rocksalt
added info

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Wow that IS nasty... Thanks for the assistance Rocksalt. I got lucky and had a clean break. The spring shattered into 4 pieces and the valve itself bent ever so slightly and did ZERO damage to any other valves nor did it reach down and cause any damage to the piston or cylinder.

My problem now is trying to figure out if I can just call APE and get a single replacement valve, spring, and other components that go along with it or if I'm gonna have to go with another brand and get 2 intake valves and springs.

What do you think about leaving the 2 exhaust valves and springs alone and just getting 2 Kibblewhite intake valves and springs?

This bike is pushing 60 hp and I want to keep it reliable but at the same time don't want to spend an arm and a leg on stuff I don't necessarily need...

Here are some pics... Not sure how to upload them on this forum:

http://frombroketorich.com/crf450headandcylinder

Edited by CRF498RBigBore

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I think the answer is obvious. Replace the springs, all of them. Look at the valves for cupping and if the coating is removed. Measure the installed spring height and compare against the max lift value. Then meausure the lobe lift to see if you are in specification.

That head that was damaged cost me 550.00 to repair (new valves, new springs, bronze seats, new guides, new keepers, new retainers, welded head). Went with Kibblewhite black diamond. I found a complete KibbleWhite kit on ebay with everything for 200. The cylinder was another 230 and piston 200. Replaced the crank 275(OEM), bearings, timing chain... That valve "fix" alone was 980.

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Did you know you can get a complete 2006 head including valves and springs from APE for under $700?

The expensive part is the porting...If my head was stock I would have thrown it away and found another.

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I would give APE a call. I installed one of their heads and on my first ride, one of the pins that holds the wheels on the carb slide came out and got sucked into the engine, it bent and exhaust valve. Nobody's fault, just really shitty luck. I called APE and told them what happened, I was going to order a valve and have a local shop install it for me. They ended up giving me a free valve and fixed it for free, I just had to pay shipping.

Awesome customer service!

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Thanks joman I called APE and they were great. They offered to look at the head and fix it up for a killer deal but I'm in a crunch for time so I just ordered a new SS valve and spring. Pat provides awesome customer service and they really stand behind their product. In fact this is the first time he's even heard of one of their valve springs breaking on any of their 450 heads.

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Thanks joman I called APE and they were great. They offered to look at the head and fix it up for a killer deal but I'm in a crunch for time so I just ordered a new SS valve and spring. Pat provides awesome customer service and they really stand behind their product. In fact this is the first time he's even heard of one of their valve springs breaking on any of their 450 heads.

yea they are awesome! before i tore apart my engine i thought that maybe i had dropped a valve because a keeper or something broke because my valve bent just off idle and after about 2 hours of riding. i called them on my way home and they told me they have never heard of anyone having a failure like that and to rip into it and see what i could find. when i found it wasnt their fault i figured i would call them and let them know and wanted to order a valve and they took care of me big time :smashpc:

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i am in need of some valve springs so i can install a megacycle x1 cam does anyone know what is the better of the two spring kits ape are 100 dollars or kibble white at 185 dollars.i know the kb are dual springs and i have heard if one spring breaks most of the time there is no damage.i would think dual springs would be better also but i am not too sure any thoughts on this

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Did you know you can get a complete 2006 head including valves and springs from APE for under $700?

did you know you can get an old 06 head for 150 and have it rebuilt at Pro-1 for 200! valve train for another 195.

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