What gaskets to get - '78 DT

[DT175 1978]

Hi everybody. I haven't been here in about a year as I haven't made any progress on my project in about a year... until now.

To review - becuase people probably won't remember me, I am not very experienced in working on engines, so I'm trying to learn. I am dealing with a generally poor running '78 DT175, and I FINALLY found a problem that could explain why I can't set the idle and the poor running I experience.

Head Gasket. I'm pretty sure it's leaking... I spotted a clean spot along the edge of the head gasket that just looked "different", and with the bike running, I shot some WD40 at it. The engine running made the oil bubble up just like finding a tire leak with soapy water... I shut it off, and the bubbles quit, started it up and the bubbles started up... repeated a few times to be sure. I'm pretty sure I've got a leaking head gasket.

SO... I'm looking at eBay for a head gasket and also an exhaust gasket as the exhasut will have to be removed to remove the head

I see a lot of gasket kits that say they have everything for a "complete engine rebuild" - does that include the exhaust gasket? They don't detail exactly what's in the kit, and I think I see it in the photo, but I'm not sure...

Link to what I'm looking at: http://www.ebay.com/itm/Yamaha-DT175-E-MX-1978-1979-Gasket-set-complete-New/220378204101?rt=nc&_trksid=p2047675.m1851&_trkparms=aid%3D222002%26algo%3DSIC.FIT%26ao%3D1%26asc%3D16802%26meid%3D613700581762132395%26pid%3D100005%26prg%3D7926%26rk%3D1%26rkt%3D5%26sd%3D290595689978%26

1) Does that have the exhaust gasket - is that what I'm seeing?

2) Do these gaskets look okay - I've seen a couple different reproduction styles, but these looked good to me. Anybody use them or have an opinion? Is there a better option I should be looking for?

Thanks for any info or opinions - I have very little experience and just wanted to check.

Also, I do have it right on the head gasket leaking... right?

Thanks to any and all that respond.

-Matt B.

[Airhead]

yeah the exhuast gasket is there it's on the bottom right of the pack. That looks like a poor aftermarket set...I'd bet money the head gasket in there is a steel one!

I always look for old stock 'Noboru' ones myself...top quality with copper head gaskets just like the OEM ones

[DT175 1978]

yeah the exhuast gasket is there it's on the bottom right of the pack. That looks like a poor aftermarket set...I'd bet money the head gasket in there is a steel one!

I always look for old stock 'Noboru' ones myself...top quality with copper head gaskets just like the OEM ones

Well thanks, for that. I don't want to buy poor quality - that's why I needed to ask. So, steel is not good for the head gasket.

Do either of these look better?

http://www.ebay.com/itm/Yamaha-DT175-IT175-MX175-Complete-Gasket-Set-New-294-/141019949983?pt=Motorcycles_Parts_Accessories&fits=Year%3A1978|Model%3ADT175&hash=item20d571ab9f&vxp=mtr

[url="http://www.ebay.com/itm/Vesrah-Complete-Gasket-Kit-Fits-Yamaha-DT175-1978-1981-/330982663044?pt=Motorcycles_Parts_Accessories&fits=Year%3A1978%7CModel%3ADT175&hash=item4d101aa384&vxp=mtr

I haven't spotted any "Noboru" or NOS, but I can keep looking.

[Airhead]

Vesrah is quite a good make I think but I cant guarantee that the head gasket is copper because I only but Noboru ones...by the way NOS isnt a make it stands for New Old Stock.

ask the seller to break out the magnet to test the head gasket...lots are copper plated steel just to con you!

The beauty of real copper ones is they can be re-used...just anneal them

You should try torqueing down your first though because if one of them wont torque up properly it's probably pulling the thread out of the cylinder and would require a helicoil / recoil fitted, that may be why you have a leak . 15 - 18 lb/ft is the setting

[DT175 1978]

Thanks again. I will try torqueing them first and see how that goes.

Now that you mention re-using... how about that? What does "anneal" mean?

I saw ebay sellers selling old used ones. They said heat it up to glowing red hot and it's good to re-use. Is that really a thing that works? Whould I be able to do that with the one I have (assuming I can get the nuts torques to 18 ft/lb)?

[Airhead]

yeah first check that all your head bolts will torque up to speck...that may be enough for now...if they wont you'll need a re-coil fitting like I said. Yes to anneal heat it up untill it's red then drop it into a bucket of water.

It will only work with copper ones so check it isnt magnetic first

In Europe your bike is known as a DT175MX

For reference

This is for an earlier twin shock bike, by the pack design is the same

http://www.ebay.co.uk/itm/NOS-Noboru-Yamaha-DT175-Top-Gasket-Set-G72-/260825346496?pt=UK_Motorcycle_Parts_13&hash=item3cba66f1c0

[DT175 1978]

Thanks again. I should be able to finally get some work done on this tomorrow. Before I jump in, I have one or two more quick questions about this.

A couple of the nuts and washers on the head are pretty rusty / suspect. I’ve been soaking all of them with WD40 and hitting them with a wire brush and a toothbrush and re-soaking with WD40 to get ready for this. The suspect ones are looking better.

When I go to re-torque the head nuts, should I back them off at all first, to see how easily they turn or maybe so as to start all 6 at “finger tight”? Or do I just set the torque wrench for 18 ft/lbs and tighten only?

Can anybody describe the “criss-cross pattern” my manual says to use… is that like a star pattern for lug nuts on a car… I’m only confused because it’s 6 nuts. After the first nut, do I do the one directly across or go for more of a star shaped pattern?

Once I have my exhaust off, if I cannot complete the head job in one day, do I need to block off the exposed exhaust port and what is the best way to do that?

Sorry for all the dumb questions. I really want to get all of my ideas in order so tomorrow I can dive in hopefully makes some progress.

[Airhead]

With the head nuts, personally I torque them all to12lb/ft first, then up the setting to 18lb/ft, yes do opposites rather than a star pattern

"Once I have my exhaust off, if I cannot complete the head job in one day, do I need to block off the exposed exhaust port and what is the best way to do that?"

Not sure what you mean here, you havent said what you are doing, but using the kicker you can park the piston at TDC to keep mice and spiders from seeking a new home in your motor

Thanks again. I should be able to finally get some work done on this tomorrow. Before I jump in, I have one or two more quick questions about this.

A couple of the nuts and washers on the head are pretty rusty / suspect. I’ve been soaking all of them with WD40 and hitting them with a wire brush and a toothbrush and re-soaking with WD40 to get ready for this. The suspect ones are looking better.

When I go to re-torque the head nuts, should I back them off at all first, to see how easily they turn or maybe so as to start all 6 at “finger tight”? Or do I just set the torque wrench for 18 ft/lbs and tighten only?

Can anybody describe the “criss-cross pattern” my manual says to use… is that like a star pattern for lug nuts on a car… I’m only confused because it’s 6 nuts. After the first nut, do I do the one directly across or go for more of a star shaped pattern?

Once I have my exhaust off, if I cannot complete the head job in one day, do I need to block off the exposed exhaust port and what is the best way to do that?

Sorry for all the dumb questions. I really want to get all of my ideas in order so tomorrow I can dive in hopefully makes some progress.

[DT175 1978]

So, I went ahead and took the seat, tank, and exhaust off so that I could get to the head nuts.

The nuts themselves weren't as bad as I'd feared and seemed to to fuction pretty normally. I did notice that the head nuts were 1/2" and I wondered why they weren't metric? I found that the head nuts were already torqued to at least 18 ft/lbs. Just to make sure the nuts were working I backed them off just a bit and they broke free pretty normally, then I re-torqued them to 12 ft/lbs and then 18 ft/lbs in a criss cross pattern. I put everything back together and fired it up. Nothing seemed different.

Should I just try a new head gasket and then see where I'm at?

Maybe I should just plan to pull the head itsself and decorbanize the head and exhaust and clean it all up and put back together with new base gsket, head gasket, and exhaust gasket then see where I'm at. Everything, including the exhaust port did look kind of dirty and bad.

Not sure exactly what to do next.

[DT175 1978]

By the way - I'm sorry if my posts are getting confusing. I'm trying to be clear, but maybe giving too much info?

Let me know if any questions.

I'm not very experienced and trying to determine what I should do next. The goal is for the bike to run well. I appreciate any guidance.

[Airhead]

You havent described the poor running you are experiencing yet so how can we try make judgements on that?

De-carbonise the piston crown, cylinder head and exhaust port by all means, just gently scrape off the carbon.

It's pretty likely the rings will be worn though and jammed in the piston grooves...you've only just started scraping the surface with this project!

[DT175 1978]

You havent described the poor running you are experiencing yet so how can we try make judgements on that?

De-carbonise the piston crown, cylinder head and exhaust port by all means, just gently scrape off the carbon.

It's pretty likely the rings will be worn though and jammed in the piston grooves...you've only just started scraping the surface with this project!

Thanks - I'll try my best to describe what it's doing.

The bike does start, and it does run and ride. I cannot correctly set the idle - the idle can only be set too high, if I try to lower it, it's too low and dies - I can't find the "in between" to get a correct idle speed. I get best results adjusting the pilot air screw pretty much completely closed.

When I first start the bike and it's idling in the driveway, you cannot rev rpms up high - like it's "stuck". It's better after it warms up. Then it reacts to the throttle more normally.

When I attempt to test ride, the bike takes off normally at low RPM but begins to struggle and sound bad about 3000 rpms... like it's "stuck" and won't rev any higher... it slowly 'works through' that 'rough spot' and eventually does rev to higher rpms. It seems to smooth out as it gets past that "rough spot" and approcahes the shift point.

I have: cleaned the petcock and screen, I'm getting good fuel flow. I emptied the fuel and replaced with new fuel - tank is very clean inside. Installed a reproduction carb, instaclled a new (oiled) air filter, and new (properly gapped) spark plug.

Some of the things above seemed to make mild improvements, the old carb spewed fuel out the overflow, and the new one helped a bit but the overall running condition is pretty much the same.

I sprayed WD40 at some areas hoping to identify leak points and believe I identified a leaking head gasket as described in the first post.

re-torqued the head nuts, still no change.

I'm reaching the end of mechanical abilities. I want to improve my mechanical abilities, but I'm hoping to get some info on what to check or do next... I'm happy to provide any info I can and I appreciate you trying to help.