Yamaha DT175; Smokes a ton and powerless

[blue175]

I have recently bought a 1975 Yamaha dt 175 with around 2000 miles on it and It has some issues running.
It smokes alot of white smoke out of the exhaust, oil spatters out the the exhaust and it is practically powerless.
I have a fresh right side crank seal in and it does run better than it used to. I am running premix of about 1:32.
I don't know if this is related but the clutch doesn't fully dissengage and It has 5 drive gears and no neutral. I think they were supposed to have 4 drive gears....
I would really like to know what's wrong and how to fix it.
Thanks in advance,
Blue175

[hmmmnz]

my guess is that your rings are poked or the barrel is scored,
whip the head off and have a look
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[blue175]

How would that cause it to smoke so much though?

[nathan k]

Are you sure it's not coolant? I.e head gasket failure.

[blue175]

It's just an old 1975 air cooled enduro.

[nathan k]

[blue175]

I don't have a tester. Do bike shops usually do that for free? Or how much could it cost?

[dansp1]

Crank seals lunched, sucking gearbox oil into the crankcase, sounds like it has ep90 in the gearbox too

[iooi]

[pdg]

[pdg]

Oh yeah, it should have a 5-speed gearbox too - practice finding neutral.
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[-]

If it's anything like my old DT-E125 twin shock motor, the crankcase halves mate vertically.

It's a doddle to remove the barrel on an air cooled bike, whip it off and if no damage to the piston or rings, then it's likely to be the crankcase leaking either through a seal of the actual sealing of the case surfaces where they join. This will requite a full on botton end strip down.

They should be sealed with something like Threebond ideally.

[blue175]

[blue175]

[bikenut]

you know of cmsnl for the exploded views etc.........you replaced crank seal very recently.........did the o ring go back in from memory and how much oil in the g/box...........maybe drawing in oil from there if gasket etc not good................oil pump still "rotating" with no oil in it........!?

clouds of smoke, maybe oil lying in the exhaust........being burnt off............you have a manual?? :karma:
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[blue175]

I didn't know of the exploded views. I actuallly replaced the crank seal yesterday, and by o ring do you mean the actuall crank seal or the really small ring?
And yikes I forgot to cut the electircs to the oil pump
I adjusted the throttle cable needle and that made some difference with the smoke. I do think alot of it is burning out of the exhaust becuase when the exhaust heats up, even if I turn off the bike there is still some smoke trickling out.
Somthing else for you, The bike isn't powerless, it just cant get into the higher RPMs. The gauge reads 4000 as the highest it will go, and any lower than 2000 It will die. It just wont rev any higher and will not idle at all.
Oil litteraly drips from the exhaust.

[stickybackbob]

As it's an old two stroke, it should be blowing blue smoke out of the back although not too much.

Before you mess about with any more carb settings, was there still oil in the lines/pump. If the engine is getting a double dose of oil, then it will be running very lean.

If it was meant to run with an oil pump, then it should be running one. Pre-mix is a 'get you home' job. Not sure on your particular bike but is there a pipe running from the oil pump to the carb? If so, this needs to be blanked off to run pre-mix as it'll be pulling extra oil or air in the mix.

If it's just a cable to sort out the pump, then splash out on a cable or at worst, one of those emergency repair cable kits.

As you appear to have done a fair amount of work, there could be any number of 'adjustments' that have been made during the re-build so we'll just have to try and eliminate them one by one

[m3-paul]

What colour is the spark plug electrode?
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[-]

[blue175]

So plug the oil lines so the engine doesn't suck in extra air? The spark plug is new and after running the bike for a halfhour its still shiny steel with just a little clean oil on it. Again the bike is just sputtering and coughing like it's running rich but I cant seem to fix that... IT's not getting a double dose of oil, I made sure.

[stickybackbob]

Yep, block the oil lines from the pump if they're not providing oil to the engine and do something to stop the pump turning too or that'll need replacing if it's dry run.

I noticed you only changed the right crank seal....any particular reason you didn't change both seals?

[blue175]

Replaced right because that was what I thought the problem was and because money is tight

[-]

Seriously, how much is an oil pump cable?

We're messing about and causing other damage to a classic 2 stroke over £20 here aren't we?

A set of powevalve cables is no more from Yamaha.

[blue175]

Okay, I plugged the oil lines and am working on shutting off the pump.
It is lagging so bad its not even funny, The smoke is so thick you could see it from 2000 miles away and if I hold it at full throttle it chokes out and dies. Im really thinking about aborting the mission and maybe reselling. I would love to get it riding but I have no idea whats wrong.
Im feeling very discouraged...

[blue175]