Yes, but only on the inlet and outlet. Anything in between, no. The middle will collect sand in the muffler packing material.
I actually sand blasted my 1978 DT 400 (which is very similar to your 1978 DT 250). I wont be doing it again.

here is the thread.

www.yamaha-enduros.com/index.php/forum/r...rofest-2014?start=10

Thought I would give a status update. My father used the bike for Endurofest. He put, his engine, seat, tanks, air box, and skid plate on.

He currently has the bike and is riding it. I am glad it is being used. I am currently riding my 78 Dt 400.

* The oil pump mounting bolt was seized. The impact driver was not long enough, nor would vise grip pliers fit. I did not like the idea of cutting, drilling to get it out. Thinking of my options, I decided to use a torch. I am sure some of the heat radiated towards the oil pump.I figure it can't hurt to have my pump rebuilt. I will be sending the pump to Deet for a inspection and rebuild.

* The engine was ready to be leak tested and assembled. My father convinced me to replace all the seals. I think it's the smart choice. They don't make a seal kit reproduction And a NOS kit usually sells near $100. My father also told me the original yamaha crank seals were double lipped, The bike buzzard seal is only 1 lip. Its best not to cut corners for the cheap quality replacements. I will continue to buy the individual seals.

* They don't sell a reproduction gasket kit for my bike. They do make a reproduction 74 Dt 360 gasket kit. Most will fit the DT 250. I took it one step further and copied the gasket kit and made some spares out of some gasket material.

* tanks, seat pan, skid plate, exhaust are a work in progress.




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Devin . . . I included the correct OEM Yamaha crank seals in the package I'm about ready to ship out to you, so don't mistakenly throw them out with the packing materials . . . if you already have them, you can just give them back to me at Christmas,

Also, I'm going to bore the cylinder you left here, and give you a new piston & ring set . . . Merry Christmas!!

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What a nice dad. likey

cool . The Cylinder I left was for a 75/76 DT 250. is it the same as the 74 DT 250 Cylinder? I know the 75/76 cylinder head was a different design.

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As far as I can tell, it appears to be a 74 cylinder
1974 = 8 Fins and a heat sink pad that is cast into the top fin (on the exhaust side of the cylinder)
1975/6 = 7 fins, and no heat sink pad

It's currently a std. bore, so will probably be boring it to 1st over

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ok it sounds like a 74. I just recall the box it came in listed it as 74/75 or 75/76, but its common people don't know what they have.

EN, you are what I call "scary smart" when it comes to these old Yamahas! likey

The Yamaha oil pumps rarely fail, they are going strong over 30,000 miles on street bikes.

But what if your bike has been sitting for 10,20,30 or 40 years?
What if it has been exposed to extreme heat?
What if moisture got inside the cover?
Or what if you disabled your oil pump for fear of pump failure?

Not a problem. Sent it to DEET for a rebuild.

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"Better-than-new". DEET New!