Yamaha 1974 Dt 125 barrel will fit a 1974 DT 175 engine

[albrid-3]

Could someone inform me, 1974 Yamaha DT 125 BORE AND STROKE ARE THE SAME AS A 1974 DT 175, THE BORE on the 175 WOULD BE BIGGER, BUT IS THE STROKE THE SAME. I HAVE A DT 175 AND WOULD LIKE TO MAKE IT INTO A 125, OR BEABLE TO FIT A yz 125 a barrel, because the bottom ends are the all the same.

[Tim754]

The CT 175 and AT 125 both bolt on interchange, so it should be a goer for the 1974s too David cheers Tim

[Nathan S]

Yes. I've done the opposite, and it bolts straight on.
I wouldn't recommend the YZ barrel - a ported DT barrel is cheaper, easier to get rings for, and works better.
A 32mm carb from a YZ125D~F can be jammed into the standard intake boot. You can modify a MX airbox to take the larger carb, or just run a pod filter.
A YZ125X~E ignition goes straight on.
An MX or YZ pipe is a big help over a DT pipe, but both suck compared to a decent, modern design pipe.

Finding a gearset from an MX or YZ will make it a lot faster race bike. My 175 racer goes great (big carb, electronic ignition, modified YZ125A pipe, etc), but the standard DT gears mean that gear selection is absolutely critical.

[albrid-3]

thanks Nathan and Tim , you both have been a great help, Nathan what frame did you use., DT, MX, YZ
dav

[Nathan S]

Mine is based on a DT. Matching numbers bike that had been sitting out in the weather before I got it.

Here's a photo of it semi-finished, the first time:


Its significantly faster and easier to ride than my stock YZ125A. With the stock DT pipe, its well down on peak power compared to a proper MXer, but its stupidly easy to use and you can hold a really high corner speed because of this.

As it currently sits, mid rebuild:
DT donor bike.
YZ125A gearbox in DT cases. DT clutch and primary drive combined with the YZ gears, give it stupidly low gearing - even with a 15T front sprocket - it needs a much smaller rear sprocket.
Ported DT barrel.
32mm carby from YZ125E (E carb used because I had it).
CDI from the same 125E (for the same reason).
34mm forks from a DT250A, fitted with the stiffer springs from a DT250 monoshock.
Triple clamps from a YZ125C (same as YZ250A/B so are pre-75 legal).
YZ125A tank.
MX/YZ125A seat (needs frame mods).
MX/YZ125A airbox (needs frame mods + 2.25" exhaust pipe welded in to join airbox to 32mm carby).
YZ125D wheels - rear hub needs to be machined to fit, and apparently the 1K7 front hub isn't legal, but nobody has complained yet.
MX250A front brake.

Other pics that might be of interest:

http://i46.photobucket.com/albums/f128/annaandnathan/Bikestuff/Photo0008.jpg
http://i46.photobucket.com/albums/f128/annaandnathan/Bikestuff/Photo0009.jpg
http://i46.photobucket.com/albums/f128/annaandnathan/Bikestuff/Photo0010.jpg

Here's the DT175 racer. Same basic recipe, but this was just something fun to build and tinker with (as though I don't have enough projects.... ), so it was mostly built from 'left-over' parts. It also has a DT external rotor CDI, which really hurts its ability to rev quickly. Its an OK MX bike, but would be an awesome Vinduro bike if I could be bothered.