1975 DT 175 Project

[Loydee]

Hi there, just got a really beat up DT 175 1975 that's been used as a field bike. I cleaned carb and fires up no problem.However it doesn't want to idle, revs vary by itself and it runs on choke when hot (better!).Tried another carb on it with similar results.
It's running pre-mix as oil lines are disconnected.There's some top end noise but nothing horrendous. I'm thinking air-leak and probably crankcase seals. Seeing as engine looks similar to my TY175 I assume the seals can be done from outside without splitting cases? Am I on right track with all this...!

[vandy010]

i've never done seals from the outside so i'm unsure as to wether it's possible or not but to my way of thinking, if you're doing seals, then do the bearings and be sure. grab the flywheel and check it for up/down/sideways movement, if it's got some of that, then do the bearings and be sure. has the oil feed line from the autolube to the carby {or barrel, i can't remember?} been blocked of properly? plug ok? reed block rubber not cracked?

[Nathan S]

What Vandy said.

They're about the easiest engine in the world to freshen up, and the main bearings and seals are available from your local bearing place - it'd be the best $30 you'd be able to spend on the thing, I reckon.

I've got all of the bearing and seal numbers, if you want to order the bits before pulling your bike apart.

[Loydee]

Thanks for all the help with this. I've just checked the flywheel for movement and you can feel & hear the play . Rather than split engine I have a really good spare  TY175 engine on the shelf (minus covers and stator/flywheel). Would the DT flywheel and stator fit the TY engine??

[mx250]

Would the DT flywheel and stator fit the TY engine??

I would guess 'yes'. In the 250/360 series the taper stays the same and all the ign swap  .

[vandy010]

hey Loydee,
the flywheel and stator plate should just swap straight over no hassles but if you don't have the stator engine cover for the TY motor, i doubt the DT one will fit as i'm pretty sure they are different.

[Loydee]

Been thinking I should overhaul the bike's original engine. Could I have those part numbers please Nathan S? Thanks a lot.

[Nathan S]

No worries.

Edit 2...

Main bearings:
6205 C3
6304 C3

Gearbox behind clutch:
6304Z

Gearbox behind front sprocket:
6304

For a paddock bike, you can get away with 'non-C3' main bearings.
The bearing behind the clutch usually/should have one dust shield removed (the one on the gearbox side). I don't understand why this is so, but when in Rome... Alternatively, a non-sealed bearing will work fine too - if you can't easily get your hands on a 6304Z, then a 6304 will do the job just fine.

I haven't been able to find a non-genuine source for the needle roller bearings on the 'other' ends of the gearbox shafts, so the part numbers are useless - just go and visit your local Yamaha dealer (although they're usually in re-usable condition as they take much less load than the 6304s).

It's just occurred to me that the seal numbers I have are for the YZ125C engine, and I'm pretty sure some of them are different to the twin-shock DT engine's seals (some of the bearings are different, but I've given you the correct numbers for the DT bearings).
Let me investigate the seals and I'll post the correct info.

[subanator]

hey Loydee,
the flywheel and stator plate should just swap straight over no hassles but if you don't have the stator engine cover for the TY motor, i doubt the DT one will fit as i'm pretty sure they are different.

No I know they dont swap over, I have a '76 DT175 for parts for my TY175, and found the taper is different on the flywheels, the coils backing plate and that all will bolt in, but with the wrong flywheel and cover - nothing is going to fit without changing the LHS cover etc.
Just do up the old girl, it will be easier, and besides, whats the use of the TY low range box?

Infact I might get the DT back into some sort of shape one day looking at it recently, it has all the road going gear too.