When hanging around the track last night for the firt time this year I was listening to a few guys talking about how they waited longest on getting the heads decked this winter. I was just wondering exactly what you do, how much it would cost, and IS IT WORTH HAVING IT DONE??????????

 

Decking/shaving the head increases compression. Thumpers have a timing chain...so you would'nt wanna deck the head on your 400ex.

 

When a machine is rebuilt the head should be checked for warping. If it is not perfectly flat the machinist can take a very small amount of material off the bottom of the head so it is perfectly flat and makes a good mating surface for the gasket to cylinder junction. This can also be done to raise compression ratio, but should only be done by someone whe really knows what they are doing. When a head is decked, the amount of material is so small it would never affect timing chain operation, there is a chain tensioner that takes care of this.

 

This appears to be different on quads than. When you deck a V-8, you are milling the block so that the piston is flush at TDC. When the piston is at TDC there should be none sticking up beyond the block. This is of course if you are using a dished piston.

It's what I thought.

Smitty

 

Not 100% on this, but as far as I have heard the term used, "decking" refers to taking material off of the cylinder to true it up, and raise compression.

When the head is modified, it is called "shaving".

"Decking" the cylinder, or "shaving" the head.

Never heard the two term interdispersed before.

 

kciH is correct. I think I'm going to have to have my head/cyl. decked. [img]i/expressions/face-icon-small-sad.gif[/img]

 

Decking, shaving, it's just removing material. You're usually better off decking (shaving) the cylinder than the head. This will accomplish 2 things- raise the compression ratio, and bring the piston closer to the head, decreasing the "squish" area. Squish is the area around the outer edge of the piston in relation to the head. By keeping this distance down to around .050 (stock is about .090), it will increase turbulance in the combustion chamber, which inceases power and decreases the chance of detonation. Just shaving (decking) the head increases compression due to a smaller combustion chamber volume, but does not affect squish.

It's not expensive, usually $50 or so.

A really cheap way to do the same is to run Hondabond for a base gasket and a thinner head gasket, just make sure the case centers don't have a ridge where they meet. Plus make sure you still have enough piston to head (and valve) clearance.

 

There's a really good post on this topic at exriders.com. There's something like 75 responses on it, those guys really got into it. Its worth checking out.

 

Yep, and it's not done yet. [img]i/expressions/face-icon-small-happy.gif[/img]