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'78 DT 175 Autolube help with potential air leak?


YamahaDT
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Hey!

i recently picked up a '78 dt175. Everything was running fine until one day I noticed the tube coming from the oiler no longer had oil in it.

after getting the bike back (in a truck) I started looking at what the problem could be. I had recently tipped the bike in the woods, so I first tried bleeding the system. (I drained the tank and added 50:1 until I was certain the pump was working again)

no air bubbles appeared while bleeding, but I continued to bleed it for 30/45 seconds or so. Put the bleed screw back on, started the bike and looked to see if the pump was 1. Pumping, and 2. Was the oil moving. Needless to say after 3 times bleeding the system, the oil pump was working (sped up when twisted, and it appeared trying to push oil up the line.) my first thought was an air leak. After pushing on the tube at the nipple that goes to the pump, I bled the system again, and this time it was working!

it was 3/4 the way up the tube when I pushed on the nipple that I was questioning. Right away all the oil left the line - I found what I thought was the source of my air leak problems as with looking closer at the nipple it appeared it had been marred with pliers at one point.

Seeing that this was letting air into the line, I applied some gasket silicone to the nipple and zip tied it down, I let dry and tried a day later.

the pump worked right away and the oil pumped right on up and it seemed as though my problem was fixed!

fast forward a few days later and about 20miles. I went out to run the bike and to my surprise the oil had left the line. I started it up and the oil started going up the line with a small air bubble. After a minute the oil was at the carb, the air bubble looked like it disappeared and I took the bike out.

after 5 miles I looked down and the oil was only about 3/4 the way up the line with a couple air bubbles. I stopped and ran it to see if the oil was moving up the line. This time it was, but very slowly and was almost bubbling like the pump was working but the system could not keep pressure.

now I am stumped. I thought I found the air leak, but it looks like maybe there is another one, or a seperate problem all together.

some people choose to remove this feature, but my plan is to keep it and getting running correctly again.

has anyone run into this problem before or can shed some light and advice on what to trouble shoot next and how to do so??

Could a carb clean fix this as maybe there are some old o-rings or somethkng? I'm not sure what it looks like inside the carb yet and if a problem like this could spur from the carb side. (I've rebuilt My 75 dt125 carb, but this injects into the side of the engine, so I don't know how he carb differs on the inside)

any advice would be greatly appreciated as I'm pretty stumped.

 

Thanks in advance!

jeff 

 

 

 

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To add, I replaced the hose going from the fitting to the carb, and I can easily replace the one going from the oil tank to the pump fitting, but when it comes to getting at them on the inside where attached to the fitting, I'm not quite sure how to get at. One is crimped with a metal band at the pump (this one goes to the fitting for the carb) and the other is easy with the wire stay, however where they attach to the fitting I would be hard pressed to even get needle nose pliers in there just from looking at it.

Any tips on replacing these?

Thanks!

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As he says,  the seal in the pump will be goosed, and its running into the gearbox, ,  long nose pliers should remove the clips, if the hose is brittal [ old hard,]  just carfully slice it with a Stanley blade ,  then pull off,

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Hey Airhead and Blackhat,

I ended up replacing the hose from the tank to the fitting, and while doing so discovered that the cap on the tank was not secured properly (duh!) I'm not sure if this has anything to do with it, but since ensuring the cap was fully pushed on and tight, and the new hose, oil has stayed in the hoses for the time being. 

I haven't had a chance to ride it to much since making these updates, so it will be interesting to see what happens.

Based on what you said above, if it was leaking at the fitting on the inside, the autolube oil would just run right into the crankcase? Or would this be a leak in the seal of the pump itself if the oil in the crankcase is increasing? I will make sure to check tomorrow to see where the crank oil level is at to double check there is no internal leaks.

Im still not sure how I would get long nose pliers up into where the hose attaches to the fitting on the inside of the case, but hopefully I don't end up having to cross that bridge!

 

Really appreciate the advise and insight! It's been a while since I've gotten my hands dirty with a couple bike projects, but it's very satisfying! Looking to never have to bring my bikes to the shop ever again!

 

thanks!

jeff

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14 hours ago, YamahaDT said:

Hey Airhead and Blackhat,

I ended up replacing the hose from the tank to the fitting, and while doing so discovered that the cap on the tank was not secured properly (duh!) I'm not sure if this has anything to do with it, but since ensuring the cap was fully pushed on and tight, and the new hose, oil has stayed in the hoses for the time being. 

I haven't had a chance to ride it to much since making these updates, so it will be interesting to see what happens.

Based on what you said above, if it was leaking at the fitting on the inside, the autolube oil would just run right into the crankcase? Or would this be a leak in the seal of the pump itself if the oil in the crankcase is increasing? I will make sure to check tomorrow to see where the crank oil level is at to double check there is no internal leaks.

Im still not sure how I would get long nose pliers up into where the hose attaches to the fitting on the inside of the case, but hopefully I don't end up having to cross that bridge!

 

Really appreciate the advise and insight! It's been a while since I've gotten my hands dirty with a couple bike projects, but it's very satisfying! Looking to never have to bring my bikes to the shop ever again!

 

thanks!

jeff

not sure what you mean by leaking at the fitting jeff, I was pointing you towards the seal on the pump drive shaft and if that pops out your 2 stroke oil finds its way into the gearbox not the crankcase, come back here if you struggle with the tubes inside of the pump housing.

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1 hour ago, albosh58 said:

Just by pass the pump and use pre mix,better than seizing up the engine ??.

Pah, heresy.

More mess, more hassle, worse running, costing you for oil you wouldn't use with a pump. I have done both (have been pretty skint at times past) and will use the pump as much as possible.

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  • 4 weeks later...

Hey all,

so after replacing the hoses outside the gear box (haven't attempted the ones from the fittings to the pump) adding back the gasket vs. washer at the bleed screw, making sure the cap is on tight and correctly, and everything else looking correct, the pump continues to get air bubbles in the line during use...

The pump is working when I start the bike and when I pull the cable running to the pump to speed up delivery the oil clearly pumps up the hose into the carb, but after riding, small air bubbles are coming out the fitting the goes to the carb, and eventually it seams as it has lost pressure as more air accumulates where the hose meets the carb.

It looks as though some oil was seeping out around the bleed screw, so I put the old gasket back on, back it with a washer and put the new screw back and the problem continued

the only other hose that looks suspect but does not show signs of leaking is the one from the pump to the fitting that goes to the carb as at the base (the copper part on the pump) it looks a little cracked under the metal sleeve, but again is not leaking.

a question I have is what is he little ball valve looking thing under the bleeder screw? 


Im at a lost at this point, any further advise would be great.

thanks!

jeff

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On July 27, 2016 at 3:29 PM, Airhead said:

not sure what you mean by leaking at the fitting jeff, I was pointing you towards the seal on the pump drive shaft and if that pops out your 2 stroke oil finds its way into the gearbox not the crankcase, come back here if you struggle with the tubes inside of the pump housing.

Hey Airhead,

im back! As you can see above I've been tinkering with little luck. I really can't seem to see a way to get the hoses off than back on inside the case because I just can't see inside.

im getting to the point where I feel changing to pre mix might be the way to go, but I've read and heard both sides it seems there is a clear split between fix it and leave it and just take the thing off.

what are your thoughts?

would I need to re-jet?

i was anticipating being able to fix it, but at this point the time spent on this one thing has been far greater than actually on the seat of the bike as every time it appears fixed the same problem happens.

 

if you could lend me some more wisdom I'd be greatful.

thanks!

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you need to find out where the air is coming from

 

is it loose or hardened and damaged pipe connections or is it seals within the oil pump??

 

I agree you cant get to the connection inside the casing unless you remove the spigot from the casing completely, if you want advice on that then ask

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The hose looks a little cracked at the base - I attached a pic for you to see. I wish it were easy to find the air leak, but I guess it's just a matter of trial and error at this point.

I would need some advise on getting the spigot out if this appears to be the issue, as I thought they were press fit and not necessarily something to fuss with.

If the seals were toast in the pump, would there be any other signs?

In addition, what are your personal thoughts on changing over to mix fuel? If I go in this direction I would need some advise on what this entails as again, I've seen a ton of opinions but not really anything concrete.

Thanks!

afba9262a2342a6d220837189dc78434.jpg

Sent from my iPhone using Tapatalk

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