I'm looking at a low mileage 79 DT250. All original but needs a fair amount of work due to inactivity. I have a question about the fresh air hose that circulates into the exhaust port. Is this a problem? can it be eliminated? What is the typical method of dealing with it? Just leave it be?
Anything I should be aware of with this year. Thanks in advance.

That's soimething we never had down my end of the world. I feel deprived lol.
I'll do some research but i had something similar on a chinese 4 stroke kids atv & just blocked it off. Had a reed valve involved somewhere--i guess so it only draws into the exhaust & doesn't feed hot gas back.

Can see the items here, not that i understand how it works. An air filter feeding fresh air into the exhaust, how trick is that. Wonder if it helps the emission as it's meant to.
www.partzilla.com/catalog/yamaha/motorcycle/1979/dt250f/intake
www.partzilla.com/catalog/yamaha/motorcy...linder-head-cylinder

hello Jimmy Carter, where's the air pump!

Made me wonder about jetting and other ways to clean the air at the expense of fun, so I went to partzilla to compare jetting between a 79' 250 to a 71' 250

pilot/main
'71 80/160
'79 50/150

edit ps. I would plug the after burner line

I am sure there are other differences but perhaps there was a limit that bike needed to meet?

Rare beast. If it's low mile original I'd leave it that way.

This bike has just over 1800 miles. Pretty dirty, is in a barn. I just know they were loosing favor by this year. Not the best looking trim package of the DT line, but a good price. I hope for a good running around bike. I seldom hear or see anything about the 77-79 bikes.