07 YZ-450 piston pin breaking

[mxracer206]

Anyone had any problems with the upper piston pin on 07 YZ-450? Wiseco says it is a common problem as there is no oil mister going to the pin. I have not heard of any failures but they say that is why the wrist pin broke in half on my high comp piston.

[FreshDonutsCAN]

Will this happen for stock piston pins or is this uncommon

[grayracer513]

First I've heard of it.

There are a couple of things wrong here. KXF450's do have some reputation for shattering wrist pins, but not YZF's. Secondly, I do distinctly remember that one of the changes made with the the introduction of the '06 model was an increase in the amount of oil sprayed on the bottom of the piston crown to cool it, so not only is there a mister in your bike, it's bigger than the earlier models had. Besides, wrist pins usually get plenty of oil from that thrown off of the big end bearing, and the pin itself, should it seize, seems to me to be the least likely of the three parts involved to fail by breaking. Just my opinion.

[ThumperKid250F]

my wriste pin snaped in half on my 06 yz 450 on my last ride on the ice this year. it took out almost half of my motor:cry: i had a wiseco hi comp piston and there wristepin in it also. it also happen to one of my friends he use to ride for BSY Racing in the proclass and he just got a new 08 yz 250f and they put a wiseco hi comp piston in it and there wriste pin broke also ( there bike has 2.0 hours on it..\

heres my thread that i started when my wriste pin snaped https://www.thumpertalk.com/forum/showthread.php?t=612116

now i this note i had wiseco pitons in all my bikes and this is the first one that broke on me

[mike_dean]

Sounds to me like a Wiseco problem. Mike

[mxracer206]

You know as tough as the Yamaha motor is I have never worked much on the lower end, the YZ-450 definately has a mister but apparently one of the earlier 4-wheelers had this problem. The more I look at the pin the more I am sure it was defective. I will try and take some pics before I ship it off to Wiseco. I got lucky and only killed the rod and piston, maybe they will help.

[rickallen124]

You guys aren't the first ones I've heard of that had a wiseco piston or wristpin break. I'm sure there are tons of guys that have never had a problem but I haven't heard of any other manufactures, cp, pro-circuit, having these issues.

[642MX]

Sounds to me like a Wiseco problem. Mike

I agree.

[642MX]

Anyone had any problems with the upper piston pin on 07 YZ-450? Wiseco says it is a common problem as there is no oil mister going to the pin. I have not heard of any failures but they say that is why the wrist pin broke in half on my high comp piston.

Wiseco is a "not our fault" kind of company. Good luck getting any help from them.

[Bigcr]

Thumperkid...Please proof-read your posts. They are very hard to read when you abuse the English language like that.

[ThumperKid250F]

Thumperkid...Please proof-read your posts. They are very hard to read when you abuse the English language like that.

yea i just looked at it and your right will do next time.

[William1]

Sometimes, pin failures are attributable to the spacing between the piston wrist pin bosses and the rod. Some manufacturers of a non-stock design piston try to return it to the same weight as the stocker. They have to add material to achieve a particular function, like raising the crown slighly and therefore remove material from where they think they can get away with it. Thinner skirts, smaller pin bosses are the typical areas. Having a large gap between the pin boss and the con rod induces a lot of stress on the little wrist pin. The wider the gap, the more the stress.

[todds924]

my wriste pin snaped in half on my 06 yz 450 on my last ride on the ice this year. it took out almost half of my motor:cry: i had a wiseco hi comp piston and there wristepin in it also. it also happen to one of my friends he use to ride for BSY Racing in the proclass and he just got a new 08 yz 250f and they put a wiseco hi comp piston in it and there wriste pin broke also ( there bike has 2.0 hours on it..\

heres my thread that i started when my wriste pin snaped https://www.thumpertalk.com/forum/showthread.php?t=612116

now i this note i had wiseco pitons in all my bikes and this is the first one that broke on me

Definitely a Wiseco problem i think. Also what oil were you running in that thing????????????

[ThumperKid250F]

Definitely a Wiseco problem i think. Also what oil were you running in that thing????????????

rotella sny, changed it everyride, and i just changed the oil befor she blew too..

bike is prob not getting fixed till mid summer or late summer neather