Yamaha MX175a 1974 cylinder porting and mods dt at ct

Video #2 of my clean up / race prep of a 1974 Yamaha MX175a. These principals apply to any 2 stroke cylinder porting.

[@DIYPhil]

Hi. I am working on a similar Yamaha DT175 bike. My next task is porting the ports on the cylinder and found your videos extremely helpful.

[@lifebehindbarz60]

Good deal, glad it helps!

[@onemantwohands5224]

Good vid mate, I like your approach to not going overboard with timing but flowing along with the boysen reeds . Good all round combo !

[@lifebehindbarz60]

Hello, if you look at the port specs in the manual they are not based on installed piston height, they show actual measurements from the top deck. These specs are often off due to manufacturing practices. That is what I'm correcting in this video. Now, if you want to get into high performance mods, port enlargement and reshaping, then yes, knowing where the piston is in the bore at tdc and bdc is important. Extra base gaskets, while modifying the port timing, lower your compression ratio, another important factor of a high performance engine.

[@lapistola28]

Hey buddy , good job . Your piston will never go below the the bottom of the transfers so intake width is not dictated by pin boss position but it is by piston skirt width .

[@hugieflhr03]

Nice tips and warnings. That’s something many youtubers miss. I have a DT250 1979 that’s getting a little sluggish on the top end. I’m thinking my cylinder should be pretty close to your MT or I hope it is.

[@MX-fo2nu]

Nice Video; i woul recommend to check full open transvers at BTC and e.g to add Spacer below Cyl and mill the same away from the top of cyl or mill the head an let the brun room contour fully move into the cylinder to reach the squitsch to spec. ;and if wanted extend lower width INlet area because at BTC the ring end is some mm away from that deeper area.

[@pauldean8638]

What you should of done before modifying the exhaust port is put extra base gaskets in . Yeah put the piston on and put barrel on and you’ll notice it sits different height when pistons in the barrel on the bench

[@lifebehindbarz60]

Thank you!

[@jamesbowers259]

Can you do anything with a ct1 without killing the bottom end ?

[@NortheastVintage]

Great video. How much of a difference does all this work make in the end?

[@lifebehindbarz60]

Honestly, a 1-2 bike length gain to the first corner is what I would estimate. For the serious racer that is well worth doing as it may put you several spots closer to the front of the pack.

[@moto922]

Just got a 74 MX175 fixing to start restore to racing shape. What manual you showing in your video. I watched your other MX175 video's and you did a very good job. Thanks

[@user-ig3ui9tk9v]

Эх на восход бы этот цилиндр