hi all on my 125mx i noticed when i came to strip it has a 6 hole head gasket and 6 studs.everywhere i look should be 4 hole even on 175.its a basket case so before i try to repair the barrel i want it standard if poss.its the right size got 123cc on side of it.were these an upgrade or aftermarket.
cheers ogre 

just had a proper look its got 2A8 on the barrel and 2A7 on the head with the yamaha logo so presume genuine yammy

2A7 is a DT175 head which has 6 studs holding it on.

When you get to the monoshock generation, only the 125 had 4 studs holding on the head.

My guess is someone has doctored a 175 cylinder marking to say 123...  Since you're calling it an "MX"  which means "monoshock" in other parts of the world I'll guess you're not in the USA? 

Anyway, I've heard that some countries had licensing age and displacement restrictions so there could have been an incentive to forge the displacement and model markings on the barrel. 

If bore is around 56mm, cylinder is a 125.  If bore is 66mm or more, then cylinder is a 175.  That's a 10mm difference so should be easy to tell.

hi no im in the uk and your probably right they have stamped there own i think cos i measured the bore and it is 66mm bore not 56mm so dt175 hopefully pics will upload thanks.