RB Head Mod Question

[risk74]

Is there any way, (other than comparing a stock and RB modded head side to side) to tell if a head has had the RB work done to it or not? Does he mark his stuff or will there be obvious signs? Thanks.

 

[Zrt1200]

Good question. You can check the squish gap and that would give you a very good idea if any one has worked on it or not.

 

[risk74]

Good question. You can check the squish gap and that would give you a very good idea if any one has worked on it or not.

Problem is, I do not have the head here to do it with. I am looking at purchasing a head that I believe has been modded by RB, seller is a salvage yard that has no idea, but I have verified the carb was done, so was hoping head too. I know when RB did the head for my KDX there was a tell tale machine mark from where it was held in place, was just wondering if anyone who had theirs done can tell me what to look for. Thanks.

 

[stabak]

even if the head was done, how can you be sure that the specs match your setup?

 

[Zman]

Head cutting is common practice so it will be difficult for you to differentiate who cut it. The stock heads have plated mating surfaces where the Orings seal. Head compression and squish mods regularly cut that mating surface so you can tell it has been modified because the plating will be cut away.

 

[cbutler]

If the head has been cut you would have to have the same jug and base gasket or it WILL be off

 

[Zman]

Do you have a photo of the cut head you are considering. If you get the precut head you can probably set the squish by adjusting the base gasket thickness. Alternatively, I think Eric Gorr will cut the head for squish for $50 (provided it is a center straight drilled plug).

 

[risk74]

If the head has been cut you would have to have the same jug and base gasket or it WILL be off

I don't mind setting the squish using base gaskets. I am trying to avoid sending my head out in the middle of race season and happened across this one for sale.

 

[risk74]

http://www.ebay.com/itm/2011-Gas-Gas-EC-300-Six-Days-Cylinder-Head-Top-End-NICE-w-Bolts-250-/322245589981?fits=Make%3AGAS+GAS&hash=item4b07557bdd:g:cOwAAOSwGtRXxYwk&vxp=mtr

This is the head in question. Looking to use it on my 04 300.

 

[Zman]

Yes that head appears to be cut to bring the compression closer and get rid of the huge stock squish. The combustion chamber still looks stock which is ok. It does not look to be cut too deep and the mating surface looks pretty smooth so I would not be afraid to use it. It should make a nice difference for you.

 

[risk74]

Yes that head appears to be cut to bring the compression closer and get rid of the huge stock squish. The combustion chamber still looks stock which is ok. It does not look to be cut too deep and the mating surface looks pretty smooth so I would not be afraid to use it. It should make a nice difference for you.

Awesome, thank you!

 

[(F5)]

Obviously you should check the squish with some solder when you put it on.
1mm will be safe minimum. It would be ideal to measure volume on the bike to see that compression ratio wasn't set for a larger squish than you have making comm higher.

Ahh she'll be right.

 

[Zman]

I fully agree and you should either run race gas or do some test runs with pump gas and check for detonation before you race.