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melted crank stuffers ideas

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Hi, looking for some ideas....09 YZ250 just had a guy replace the crank, bike ran great for about 20 hours....this weekend it seized, i pulled the cylinder, it was fine, the top ring is seized in the ring grove no other damge to the piston. The crank stuffers are melted bad and the brass shim in the crank rod bearing tore apart and gouged up the crank cases pretty good.

Bike has a 180 mJ, running motul 800 32:1, checked the plug 2 weeks ago and it was not lean at all, rich maybe.

so what condtion would cause this damage? air leak? cooling system...

throw all the ideas out there...thanks!

oh and it was first practice at mini O's, I have one bummed son:(

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Check post for weisco pistons, there was something about some pistons having a ring pin in the wrong place.

But this would not explain the melted stuffers.

Was the crank split and the rod replaced? Maybe the clearance was too tight and caused a lot of heat.

Was the cases forced back togather putting pressure on the crank? Not so likely the cause.

Even if the crank seals where installed incorectly, i dont think the heat generated would melt the stuffers.

I would be looking into the lower rod bearing closely. Unless the melting came from rubbing,"screws that hold the stuffers in place", came loose.

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your sure the stuffers are melted? i could see something getting past the rings and bouncin around but ive never heard of badly melted crank pieces

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Melted crank stuffers happens all the time. Your big end seized which built up a lot of heat melting the stuffers.

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The big end bearing failed and melted the stuffers. Was it a weisco crank or what kind of crank? Your lucky it didnt damage more than it did.

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The big end bearing failed and melted the stuffers. Was it a weisco crank or what kind of crank? Your lucky it didnt damage more than it did.

it is a hot rod crank....yeah the big end bearing is toast, crazy that the brass shim got tore up and came loose....

so....what are the conditions that can cause the bearing to seize?

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defective crank id say. I run oem cranks now. I get 300+ hours out of oem cranks. I put oil the crank up good before I install the top end. I wouldnt beat yourself up on the cause. If it were me id put a oem crank in there and ride hard. Ive lost faith in weisco and hodrod cranks after hearing all the problems. I ran weisco cranks for a while and my stuffer screws kept coming loose. Weisco cranks are 5 degrees off on timing also. What kind of cheap crap is that. I have a brand new weisco crank kit on my shelf that is a paper weight now. I used the gasket kit out of it. It blows it happened to you.

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Over use. Those bearings have a lifespan. Dirt coming through the carb also contributes to shorten that span.

By what he said he replaced everything 20 hours ago. Even if your dumping dirt in there it should last 20 hours.

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I've seen a crank seize in 30 minutes in dusty conditions from an air filter coming loose. It takes *very* little time to ruin a perfectly good crank due to sucking dirt.

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i know theres lots of aftermarket crank company horror stories but stay the he11 away from wiseco! there junk!

ive had real good luck with hotrods cranks though...the 85 my cousin races gets a full season outta the same crank. i change the air filter after every ride EVEN IF WE RODE FOR 10 MINUTES! lotsa stories r from guys who cant do maintenance and then pooof!

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OEM Crank is the only way to go. It could have been worse, look what happened when my crank stuffer melted (I assume). It was a weisco crank, no idea the hours, was in it when I bought it. I run weisco pistons, always have.

IMG00022-20101107-1826.jpg

IMG00021-20101107-1826.jpg

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I run Hot Rods cranks all of the time. No problems! As one customer said to me "you mean I have to oil the filter"! Who knows what happens with these people. I have ran HR cranks for years in many different bikes without ever an issue.

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OEM cranks are the only way to go in my opinion.

No matter what crank you run, the stuffers will melt when the big end bearing fails.

If it was caused by dust/dirt (poor air filter maintenance) you would see the telltale signs on the piston skirt, rings and cylinder walls. It would look like hundreds of minor scratches and scuffs and with an uneven dull finish on the piston skirt.

Is it possible that someone forgot to add premix to the fuel? That is the fastest way to trash a big end bearing.

I grabbed the wrong gas can once and caused a similar failure in my 2002. Caused almost no visible damage anywhere else, but I replaced the entire crank and top end to be on the safe side.

I use red oil in a blue fuel. That results in a brownish color when mixed.

After my failure I drained the tank, out came a gallon of tell-tale blue fuel.

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OEM cranks are the only way to go in my opinion.

No matter what crank you run, the stuffers will melt when the big end bearing fails.

If it was caused by dust/dirt (poor air filter maintenance) you would see the telltale signs on the piston skirt, rings and cylinder walls. It would look like hundreds of minor scratches and scuffs and with an uneven dull finish on the piston skirt.

Is it possible that someone forgot to add premix to the fuel? That is the fastest way to trash a big end bearing.

I grabbed the wrong gas can once and caused a similar failure in my 2002. Caused almost no visible damage anywhere else, but I replaced the entire crank and top end to be on the safe side.

I use red oil in a blue fuel. That results in a brownish color when mixed.

After my failure I drained the tank, out came a gallon of tell-tale blue fuel.

to be honest, after inspecting everything and the lack of damage else where, thats what I'm thinking, I checked the gas tank and it is red...Motul 800.....but my son "said" he put 12 oz for the 3 gallons...32:1...he had a nasty get off at Mini O's so I'll give him the benefit of the doubt....just orderd every thing with new seals and some misc etc.....$432....so much for new boots this XMAS:)

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A little off topic but what performance gain does Crank Stuffers bring. I imagine they reduce the volume of air in the motor but are they worth it? Any risk (with a quality OEM crank) with the right material? What is best to use?

Thanks!

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A little off topic but what performance gain does Crank Stuffers bring. I imagine they reduce the volume of air in the motor but are they worth it? Any risk (with a quality OEM crank) with the right material? What is best to use?

Thanks!

The Yamaha OEM cranks have the stuffers installed. Both Wiseco and Hot-Rods use crank stuffers that appear identical to the OEM parts. The aftermarket cranks are not performance upgrades for the YZ, they are simply lower cost replacement parts.

Regardless of the brand, if the big end bearing seizes, the heat will melt the stuffers. Even the OEM cranks will do this if the big end bearing goes out.

The danger of running a lesser crank would be connecting rod failure. Take a look at JCMINIS photos a few posts back. That broken rod will usually destroy the cylinder and the center cases. Basically it's game over for your whole engine if the rod breaks in half.

The fear shared by many of us is that the quality of metals and the forging process for the connecting rods with the cranks made in places like China and Tiawan will not be as high as a rod forged in the USA or Japan.

I am running a Wiseco crank and top end in my 2002 and I haven't had a single problem with it. The timing is a little off on the Wiseco, but you can correct that when you set your timing. The part that worries me is simply the metallurgy of the connecting rods. For that reason alone I'll spend the extra money on an OEM crank assembly to replace the Wiseco. I assumed the Wiseco cranks were made in the USA (like the pistons) when I bought the kit. They are not, but I was told that the pistons still are.

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Th.

The danger of running a lesser crank would be connecting rod failure. Take a look at JCMINIS photos a few posts back. That broken rod will usually destroy the cylinder and the center cases. Basically it's game over for your whole engine if the rod breaks in half.

Correct, look closely at the cylinder pics you can see both skirts cracked.Also busted both cases. I bought new cases and bearings, welded up the skirts and machined back down and its currently out to Derek @ HP bikes for a 265 kit. I installed a OEM crank, I do not blame weisco for the failure as stated, I have no idea how many hours was on it.

It could have been less damage I suppose, if I was somewhere with off or light throttle, BUT I was skimming whoops wide open and boom.

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I do not blame weisco for the failure as stated, I have no idea how many hours was on it.

It could have been less damage I suppose, if I was somewhere with off or light throttle, BUT I was skimming whoops wide open and boom.

Yeah, I haven't heard of or seen any failures that could be attributed to bad workmanship on their cranks, I hope I didn't sound like I was. I have had no issues with my Wiseco bottom end. I just want the OEM Japanese parts for piece of mind.

BTW, Skimming whoops? That's a really bad time/place to have a boom of any kind.

I was lucky, mine gave out near the end of a fast straight.

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