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Top head Hole


dwb5151
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Hi I am currently doing up my 2011 sherco when looking around it i found a hole on the top head. It looks like a small bit of the top head has came off. Is this normal i could post a picture of it, if it would help. Any advice would be appreciated many thanks Dw.

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Looks like you have corrosion happening from the inside out. 

You might be able to patch it with some JB Weld or simalar epoxy, but first you should find out what is causing it

The head is aluminum and the bolts are steel. Looking at your picture their appears that rust is forming on the bolts. Their is probably electrolysis happening between the dissimilar metals (steel, aluminum) Usually antifreeze contains inhibitors to help control this but if water or weak antifreeze solution has been in the motor this could be what is aiding the reaction.

You should remove the head and find out the what the damages are.

Also, you should take a look at your water pump impeller/housing. If you are getting this type of problem corrosion it is likely that their may be problems with that too.

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Ok I just looked at the Sherco manual. Definately not the stock bolts. Here's the problem, by not using stock bolts which may be stainless steel or at least a better grade of corrosion resistant steel you may have caused corrosion in your water jacket. Using tap water or non-premixed coolant will accelerate corrosion. Sorry to say this but you might want to pull the engine out of the frame for a proper tear down. Radiator flush is probably in order too.  

Good call Beta_Blocker

Edited by dan williams
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Just looks like a small casting flaw/ void from manufacturer that the paint or thin bit of aluminum may have chipped off of by looking at your pic. As long as there is not coolant leaking out of it, I would not get bent out of shape worrying about it, same with the head bolt material, its not a big deal ...just use oem recommended coolant and get out and ride  

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Do not use stainless steel into aluminium thread (where galvanic corrosion have conditions to happen). It will corrode aluminium much more than zinc plated steel (like OEM are)

There are more galvanic potential between stailess steel to aluminium than zinc or steel to aluminium.

tip: If you put a multimeter tip into radiator water and another into you frame and see a reading of few mV. It's it. Change water and put antifreeze. 

Edited by cascao
foregin language issues
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Old bolts lost their zinc plated and become prone to galvanic "welding". So, inspect and discart these bolts if you feel that the are becoming stick sometimes. This happen on cars spark plug when people used to clean it with sand blast or wire brush.

On enduro motorcycĺes brake calliper bolts (yellow plated) is where I see it most. All of them seems like lost their beautiful yellow cover

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