1979 DT175 smoking - Off-Road Forums & Discussion Groups
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post #1 of (permalink) Old 07-20-2005, 07:08 PM
Evmo
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1979 DT175 smoking

Hello everybody!

I'm brand new here and i was hopeing you could help me with a little problem i'm having.

I just picked up a 1979 DT175 from a co-worker He gave it to me for free so i figured what the hell. This is my first motorcycle. It wasn't running when I got it but after about 100 bucks i got it to start up.

What i did:

Replaced Pipe with one from identical bike that was crashed.

Bought a carb kit and rebuilt the carb.

New air filter and spark plug.

New fuel filter.

Now my problem. When the thing is running i have quite a bit of grayish smoke coming out the tail pipe. I know these bikes have weeper systems and i filled up the oil tank with the proper oil. Could the oil pump be pumping in to much oil? Other than that everything seems to be in order.

Any help would be appreciated. If the problem is a real obvious one please bear with me as i'm a newbie.
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post #2 of (permalink) Old 07-21-2005, 08:22 AM
Evmo
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Re: 1979 DT175 smoking

Anyone?
post #3 of (permalink) Old 07-21-2005, 03:49 PM
YoungVintageRide
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Re: 1979 DT175 smoking

Isn't it a 2-stroke engine(Do you have to mix the gas)?
If it isn't then try checking/replacing the piston rings.
But if it is a 2-stroke then it should have some gray smoke.
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post #4 of (permalink) Old 07-21-2005, 06:28 PM
Yamaguy
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Re: 1979 DT175 smoking

I would be surprised if it didn't smoke. If you run it enough to get it nice and hot, and do a few sustained full throttle runs, it will be less for a while, as you have blown all the residual oil out of the lower end; but unless it is making clouds of smoke, so much that you can't see, then that's what it is supposed to do. that's why no new two strokes are street legal anymore, and about not to be off road legal; too bad, they still pollute less than any diesel truck. But I guess that they are ok...

If you switch to Bel-Ray Si7 synthetic injector oil, you will find that it does smke a bit less, and no carbon build up as well. Drain all of the petrol based stuff out first if you switch.

There is a small bleed screw on the oil pump, usually a small phillips head witha red or black fiber washer under it as a gasket. run the engine, remove this screw, push the pully looking thing at the front of the pump with the cable attached to it from the throttle all the way in towards the pump body. look for air bubbles to come out of the hole. It should pulse as the pump plunger moves in and out, but no air bubbles. If (or when) good, replace screw, make sure it is tight. with throttle closed, a small pin or screw on the body of the pump should line up with a mark on that pulley. If not, adjust cable until it does. pump operates two ways: more pumps per minute as engine speed increases, and more of a stroke each pump as throttle is opened. That way you use what you need, not too much at low rpm/throttle openings as pre-mix does. The pumps are very good, just keep the air out of them and check the adjustments.
post #5 of (permalink) Old 07-22-2005, 05:12 PM
Evmo
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Re: 1979 DT175 smoking

Thanks for the info.
I know that it should be smoking a little bit but it seems to be on the exessive side. Although I can't know for sure since i have nothing to really compare it to. Are there any pics i could see anywhere?
post #6 of (permalink) Old 07-24-2005, 05:33 AM
Yamaguy
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Re: 1979 DT175 smoking

I don't have any handy, if I think of it, the next time I fire up my Ct3, i'll take a few. The only other place that excessive oil consumption can come from is the engine sucking the oil from the transmission/primary drive and burning it as well. the best way to check that without a lot of trouble is to change the tans oil, put the exact amount in to come to the upper mark on thre stick or whatever level it uses, and then ride it around a while. It wouldn't use much, as it would have to be a bad oil seal on the crankshaft or a very slight leak in the seal between the where the two sides of the crankcase meet, but if you need to keep topping off the oil, then that's where it's coming from. Then you pull the engine, dissassemble and refresh the seals/etc. Not hard, but time consuming. Face it, it is far from new. All of my old two strokes are disassembled and redone so I don't need to go looking for what went wrong....I already have a clear idea as to what condition they are in. probably nothing you wanted to hear...but. As for photos: look at an off-road motorcycle race in a magazine for a starting line photo...lots of blue smoke there. But as I said earlier...until you really hold on full throttle for a bit, usually a higher gear, the oil that is under the piston won't be blown out and it will smoke quite a bit until cleared out. Full throttle in 4th ot 5th for a good 30 seconds or more after the engine is warmed up should blow the cobwebs out of it and maybe it will improve. Pullt the removeable portion of the silencer/spark arrestor and clean it out really well after you run the engine hard. I put mine in the BBQ grill and cook it until all the carbon is burned off and it is a light grey in color. All the combustion stuff ends up back there and can actually clog it. that's why I switched to synthetic oil injector lube..I ran synth pre-mix years ago in my YZ and found that I had no carbon build up at all, just a slimy coating all over everything...good enough, petroleum based oils left a slimy coating and carbon.

Hope this helps.
post #7 of (permalink) Old 07-25-2005, 10:40 PM
Evmo
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Re: 1979 DT175 smoking

Thanks For the info!
I'm going to take it out and give it a good run this weekend. Hopefully your right and things clear up a bit. I'll also give that synthetic oil a try.
post #8 of (permalink) Old 07-29-2005, 06:09 PM
Yamaguy
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Re: 1979 DT175 smoking

Sorry, I've been out of town on business...how did it go? Those things can last quite a while, I had a CT1B that I put over 45000 miles on, wore out a cylinder and a crank running it constantly. (ran out of rebores, needed another cylinder and started over.) Anyway, if the ring grooves aren't stuck full of carbon and there isn't much ring ridge on the top of the cylinder, you should be able to get about 8-10K out of a bore before needing to rebore it. They make pistons in .25mm increments, and Wiesco makes them past where Yamaha stops in sizes. Sometimes new rings halfway through the piston life will help out, but modern rings are so good that they usually last the life of the piston. keep it carbon free and properly lubed and you'll have a nice bike that is a lot of fun.

The two yamaha shops I worked at many years ago, both owners would take new 175s out of stock for their own personal use, when they could have had any bike in the shop; that says most of what could be said right there.
post #9 of (permalink) Old 07-30-2005, 01:19 PM
Evmo
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Re: 1979 DT175 smoking

Well thats good to know. The odometer seems to be working fine and it only reads 4400 miles, so i think i can get a lot of use out of it. I havn't been able to really take it out yet as i still need to get tags for it. I have a friend with about 20 acres that i can use on Sundays but last Sunday i was down in L.A. and this sunday i forgot is the San Jose Grand Prix and there no way i'm missing that, so i have to put it off till next weekend. I'm really itching to take it out though. Riding around the block is getting pretty old and i think my neighbors are starting to hate me.
post #10 of (permalink) Old 07-30-2005, 07:44 PM
Yamaguy
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Re: 1979 DT175 smoking

Well, let me know how it works out. I'll try and keep up with this , but I may on the road this week.
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