DT175 1978

Haven't checked the old one with a magnet yet, but I will. Thanks again for all of your help. (and for your patience with me) I'm getting a pretty good idea of what things I need to do next, and I've got some work to do, so I better get some work done. I'll come back and post up again if I run into any specific questions, or to report back on how things worked out for me. -Thanks

Okay - another question or two. After doing some research online... now I've got even more questions... My manual (from 1983) says to take the new gasket out of the package, put grease on both side of the gasket, and torque to 18 ft/lbs The internet says: take the new gasket out of the package, anneal it, put aluminum paint or copper gasket sealer on it, torque it 18 ft/lbs, 100 miles later re-torque it. SO... do I anneal a brand new gasket? Do I grease it, paint it, what? Is there an FAQ I can refer to for this?

So, I've had trouble finding quality head gaskets on eBay... I finally broke down and called my local Yamaha dealer, who said he can order me one direct from Yamaha. It would be the Yamaha authorized direct replacement... he couldn't tell me much about who actually manufactures it, or exactly what it's made of. He said it should be the same size and materials as the original - basically, best available. I assume it would be the same one available through "yamahapartshouse.com" - that site brings up a part # 1W2-11181-00-00 which is what I think I would recieve.Link: http://www.yamahapartshouse.com/oemparts/a/yam/50041a8af8700209bc7858e1/crankcase-cylinder The only picture I could find of that part number online is on a completed eBay auction - http://www.ebay.com/itm/Genuine-Yamaha-Cylinder-Head-1-Gasket-MX175-DT175-More-1W2-11181-00-00-NEW-NOS-/321130642303?nma=true&si=EXs%2Bh65nTyRX9ZZCSwKj%2BLmVP2g%3D&orig_cvip=true&rt=nc&_trksid=p2047675.l2557 The price my Yamaha dealer quoted me, while not great, is something I could live with. You guys think I'd be alright with whatever it is that my local dealer would source for me (from Yamaha)? With no help, I'd probably just order it up and run with it.... but I just want to check with you more experienced folks. Thanks.

Okay. Now that's what I want to hear! I want to, get it apart, and then take my time getting everything right. I'll follow your advice from the other thread and check out the piston and rings, decarbonize and clean up everything, and check for any other obvious issues before considering reasembling with new gaskets (and I'll look for real copper / NOS / the brand you recomended.) Sound okay? I'll report back if I run into any questions or issues along the way. Thank you for all of your help over the last few days, I really do appriciate it.

I'm very new to working on bikes and have a question on how to store my "work in progress" while I'm working on it. I'm not able to bring the bike in doors / into a shop. I usually park under a "carport". I need to remove my exhaust system, head, and cylinder on my DT175E. I expect to have enough work to do before reasembly that I have these pieces off for some period of time. It is possible that I may get stuck on something small and end up having the head off quite some time. What precautions should I take to aviod things like dust and moisture from entering the engine? In the carport I normally park under, it stays dry from rain but it is a bit of a dusty area as fine dust from the gravel driveway drifts in pretty heavily whenever a car is coming or going. I also worry about moisture from the air as I live in an area that rains often. I thought that I would just try to cover / wrap up the whole bottom end with plastic or something to cover up the piston and opening (piston in proper holding fixture per shop manual) to keep stuff out. Does that sound okay? Is there a better way? Thanks and sorry for such a 'newbie' question.

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.

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.

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.

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.

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)?

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.

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.

Hey thanks again guys. I appologise, I was getting a bit dispondant. Yesterday was 'one of those days' and I was pretty overwhelmed with my project along with other parts of my life. Thanks again for the good advice. I do have plenty of sockets,open end/box wrenches, screw drivers, pliers, cresent wrenches and basic stuff - it's really just an impact driver and torque wrench that I need tro be well equipped with tools. They're probably both good ideas. And you guys are right - gaskets aren't that expensive. I need to remember that I went into this with the idea of learning how to fix things - because I'm not good at it and I want to learn - so its not supposed to be easy and I have a lot to learn. I think I need to just slow myself down and re-group myself a bit, and continue on when 'my heart is into it'. Thanks for the kind encouragement. I do want to make this thing run. I really want to go for a ride! I'll try to come back and post when I have specific questions. For now, I need to gather some more info and maybe some more tools and parts. Thanks, you guys are great.

Thanks again guys. I guess I would need an engine gasket kit before even taking the left side cover off or taking the reed valve out... I think I'd also need some tools that I don't have. I think I'm in over my head. I really screwed up and did cosmetic and street legal stuff first (brand new NOS seat cover, got the plastics looking good, repalced a broken turn signal and front stop switch) and licensed it with perminate collectors plates... I've got a good looking, fully legal bike that runs like crap. Now I'm way over budget and out of skills to get it running right.... I've wasted a bunch of money I'm never getting back and I think I better quit. If I decide to keep working on it, I'll come back and bug you guys with some more questions when I have them, but for right now... I've lost faith and I kind of just want to just push it over a cliff. I keep throwing good money after bad and I just don't believe that after I go buy a gasket kit, an impact driver, a torque wrench, crank seals, reeds... I just don't think I'll get it running. And then there's the clutch and front forks which I know both need attention that I'm not fit to give, I think the financially smart thing for me to do would be to just quit. I've lost faith. This was just a stupid pipe dream anyway, I don't have the skills to fix things and this isn't going to teach me anything... I should have taken up golf. Thanks Airhead for trying to help. You seem to know your stuff.

Where does that leave me? Still checking this mystery carburetor? Should I rebuild the original before I move on? Have a missed anything? What would you check next?

I have read several posts that seem to indicate that failing crank seals is much more likely than failing reed valve, but I’ve been reading up - I googled crank seal symptom, and I also googled reed valve symptoms and I read several of the results. For crank seals I kept reading: Hard starting, hot or cold, bad idle, runs great in the upper rpms… Well, I do not have hard starting when hot, and it does not run better in the upper RPM range. I’m not too sure that’s desribing what I’ve got going on. For reed valves I read: Idle - rough idling engine that sounds like it is on the verge of dying. Hesitation - Engines with reed valves that are failing can present symptoms of hesitation during acceleration. The engine may fail to respond to the increased fuel flow and then jump forward as the gas is finally ignited. The hesitation in the engine due to failing reed valves can be very frustrating as the power is simply not available when needed Reduced Power - However, failing reed valves reduces the fuel and air mixture. This results in fuel being dumped into the carburetor with no flame to ignite it. The result is reduced power. If the engine is brought up to the higher revolution per minute, or RPM, levels the power may return, but will disappear again once the RPMs drop. Read more: Reed Valve Symptoms | eHow.com http://www.ehow.com/list_7528907_reed-valve-symptoms.html#ixzz29lSYdgPv The failing reed valve symptoms sound about exactly like what I have going on…

Hi guys. Me again. I have posted about this bike and these issues, but I’m starting a new thread with my new updates for the sake of clarity. I’ve checked out a few more things, but have yet to find the major issue. I apologize in advance that this post, and most posts I ever have or ever will make, may be a little long. That’s how I am. The bike is a ’78 DT175. It sat for an unknown period of time, probably very long, and I’d I’m trying to restore it to service with the least amount of hassle. I do not know why it was parked. Here’s what I’ve done so far: Drained out the old gas and inspected the tank – it is rust free and clean. Filled tank with quality name brand 89 octane. Removed fuel petcock and cleaned, including screen – it’s good. Installed a new OEM air filter, heavily oiled with PJ1 foam filter spray oil, Cleaned out air box. Installed a new reproduction carburetor – the old one was spewing fuel out the over flow and had no response to adjustments in the pilot air screw, so I bought and installed a new reproduction carb. Attempted to adjust the above mentioned carburetor. Checked spark visually by placing plug against the engine and turning it over – spark is fat and blue, even with a fouled plug. Installed a new spark plug of the proper gap / type. Here’s the problems I’m having: Hard to start cold. When it’s warm, first kick every time, but cold starts are tough. It is difficult to adjust the idle. (This doesn’t seem to change with any adjustment of the pilot air screw.) It wants to idle too high, seems around or above 2000, and if I try to adjust down the idle to where it should be, it falls too low – too low to idle and stay running. There’s no in between. Sometimes the ‘high idle’ will fall to a ‘low idle’, and sometimes that ‘low idle’ will climb back up to the ‘high idle’. (only a couple of hundred RPM fluctuation) When in neutral, and you slowly twist the throttle, it does not seem to reach proper high RPMs. Seems to struggle a bit to raise RPMs. When you try a test ride, it seems pretty normal as you take off (save for the nearly gone clutch) but as you accelerate it quickly begins to struggle just as you get into the power band… it struggles to raise the RPMs and when this happens it sounds less like a motorcycle and more like an ill frog struggling to make a croaking sound… it does struggle and croak and get through it and past that point and back to sounding like a motorcycle, but by then, the RPM’s at are at (or past) the shift point and approaching the red line. Bottom line, it struggles right through the meat of the power band and sound like a dying frog whenever it struggles. Where should I go next? Crank seals like Air Head said 2 minutes after a joined this forum?

Thanks Flyday Thanks Flyday Not yet - I have an new air cleaner element coming in two or three days, my old one is very nasty, and I didn't want to move on until I get a new one installed. (had to wait for a payday to order it, now waiting for delivery) I'm going slow, one thing at a time, because I'm a bit inexperienced but I'm learning every step of the way. Once I have the new air filter on, I plan to play with carb adjustment a little bit more before moving on. I'm also going to take my new reproduction carb apart and look for asembly errors, just to make sure I'm satisfied with it. Then I should be satsified with fuel, tank, petcock, carb, air cleaner, spark plug, and ready to move on. (might get a float bowl gasket and rebuild the original carb too - I have it all apart and it just needs cleaned and put back together) Then I'm going to try that spray check on my left hand crank seal - you recomend carb cleaner or WD40 for that? I think I should also spray check around the intake manifold / boot and really check out it's condition, make sure it's not leaking. My carb comes off easy enough by just backing off the screws on the clamps, then pushing it back toward the air box, turning it a bit to get the front part out of the notch, then I can get the front part out and take it right off. Okay, it's a twisting, tugging, wrestling match. I was figuring I'd check the manifold and reed valve out when I have the carb off for inspection. SO - I think I need a gasket kit. I want to have a new reed valve gasket in hand before yanking it out..... AND - I've never had the engine side covers off. I need gaskets for the side cover too, don't I? Or do I - I can see reusing the old ones if thy're not bad... Might as well get the full kit before ripping into it...just in case... do those engine gasket kits come with a float bowl gasket for the carb? (I don't think they do)... I'll probably have some questions when I get electrical / resistance testing... like what all to check (igniotion coil, and... the coils in the magneto?) ONE MORE question for now - Do I need an impact driver to take the side covers off the engine? My Clymer manual says it is not advisable to do it without an impact driver. I've been waiting for impact driver and new gaskets before I take the side covers off - Am I being silly? My family wanted something to get me for my upcoming birthday, so I am expecting a torque wrench and an impact driver as gifts within the next few weeks! I should be able to do a lot more!

Thank you. I agree - I'm sure I'll physically have no problem removing the reed valve assembly with the cylinder head on the bike. I don't know why the manual says that. The only reason I could think that they might say to do that is if it's just catagorically unsafe to remove / install the reed valve because you might allow dirt and grime inside the cylnder? But, I'm with you - I see no reason and I'd really rather not have to remove the head to do reed valves. (the same manual says under carberator removal that step #1 is to remove seat, tank, and side plastics - none of which are actually necesary for removing the carb, so maybe it's justthat same kind of thing...) AS a side note, I've - I have a poor running bike. I've had a hard time describing exactly what's wrong, but I've been googling crank seal symptoms and reed valve symptoms... The way my bike runs doesn't exactly bad crank seals, but it sounds to me exactly how they describe bad reed valves, so I better get serious about replacing reeds. Thanks.

Do I have to remove the cylinder head and cylinder to check / change the reed valve? My Clymer manual tells that step #1 is to remove the cylinder head and cylinder and I cannot figure out why that would be necessary at all.

Hi all. Me again. I'm working on my old '78 and I'm still really not sure how far I'm going with this whole thing. A part of me hoped to find some easy quick fix to get her back on the road. Now I'm thinking more and more that I might have to go much deeper and do a full restoration or at least much closer to it. The biggest thing that I am intimidated by right now is rusty nuts on the exhaust and cylinder head. I'm afraid I cannot remove them without breaking bolts, and where that would leave me. I am very new to doing all of this type of work - I did have some expience recently with broken bolts when I was working on the seat's mounting brackets. I broke two bolts. I drilled out the centers, and tried to extract them with an "easy out" - I broke that too along with three little itty bitty drill bits. I eventually drilled them out completely and tapped new threads. One came out perfect, without really damaging the original threads and I retapped in the same threads, but the other, the original bolt's threads stayed in there and when I tapped new threads, they're not in the original threads, if that makes sense... there's still metal from the original bolt in the hole. Even though it's tapped to take the same size bolt, and it turns easily by hand in the nice new threads, I worry that it's not right and is likely to fail (maybe I should have gone up one size on the bolt to fix the problem - but it's not a big deal as it's just seat mount bracket and it is solid. I'm worried about having similar problems if / when I attempt to remove the exhaust and cylinder head. If I break those, how screwed am I? ....and even IF I can get the bike running well without removing exhaust or cylinder head, I hate to have them "un-removable" or I'll be in trouble some day when they do need removed for maintenance / repairs. For now I'm thinking I squirt some WD40 at them and scrub at them with a wire brush whenever I'm bored, maybe I'll get some of the rust off and maybe be able to remove them someday? Any advice in this?

Thanks for the input, oldbikerehab. It's taken me longer than I'd hoped to get the correct air cleaner, but I should have that in a few days. Once I have the new air cleaner on, if that doesn't help things out then I'm going to take apart the reproduction carberator and check for assembly problems, if all looks well, I'll try to adjust the carb for better performance. I am a little worried about it being the right carb - eBay listed it as being for a '78 DT175, but when I go to the manufacturer's web site (zoom zoom parts) they don't list a carb for a DT 175 at all, only for DT125's... I called the number on their website, and they answered and talked to me about it - they say that the one I ordered is right and that it's only on eBAy, and just not up on their website yet.. the 125 and 175 carbs on eBAy do have different part numbers, but I don't know - Zoom Zoom told me that if what I recieved looks like what's in the picture, then it's the right carb... but of course the 125 and 175 carbs look the same from the outside (probably just different main jets?) At any rate, I am not confident in this reproduction carb.... I think I want to rebuild the original carb. We'll see how that goes - the floats were pretty messed up inside - one bent all the way up, the other bent all the way down - like it was done on purpose to wedge the float valve needle open or something. I'm hoping that the floats and float bowl gasket out of the reproduction might fit in the original, of so, I'll just use those parts to rebuild the Mikuni. I'm not going to do anything untill I get the new air cleaner on though. Once I get all that done, I'll post up about it - but I'll probably start a new thread to be more specific to exactly what is going on. I'll make sure to involve a cold beer with all adjustments to reduce stress. Thanks.

Did you install the carb, find that something was wrong, and then take it apart to find this? What I'm wodnering is, if you tried it and noticed something was wrong, what condition did this cause? (how did the bike run with this problem?) My carb off of eBay is aftermarket, and is cheap, I wonder if I should take it apart to look for such issues? If I do that, can I re-use the same gaskets as it's still basically new? I don't have to order a rebuild kit to get new gaskets just to take it apart, do I?

So, I did a couple of things to the bike over the last couple of days. I got the petcock done. I drained the fuel from the tank and removed the fuel petcock, got every last drip of fuel out of the tank, wiped out the neck of tha tank and cleaned up the threads a bit, then disasembled the pet cock. The screen was clear, and I'm not surprised as fuel did not seem to be obstructed, but the seal between the tank and petcock was shot. I came up with something that worked to replace the seal, cleaned all parts of the petcock, and reasembled. It looks a lot better, and it doesn't leak at all anymore like it did before, but fuel comes out at the very same rate and this did not improve how the bike runs. (Oh well, it was still not wasted time). I got a brand new spark plug to replace my old ugly one, check the gap - it's cortrect, and installed. Still not "the fix" for the problem I'm having. My very next move is to get a new air cleaner installed. I wasted time looking for one locally and now I just have to order it online and wait for it. After that, I'm running low on ideas... starting to wonder if it's electrical? Maybe I should check the coil? I did actaully think that it may have run a little bit better after the things I did, but then again, maybe not... I want to get the air cleaner on before I really give it a good test. I'm also wondering if I should tear into that repo carb I bought and take a look, as I've seen a couple of posts about improperly installed O rings strait from that factory.

Hi. 1) What fuel should I use in my 1978 DT175? The easy choises would be 87,89, or 91 octane. Which is advised? 2) I need to order an air cleaner element for the same bike. I can find K&N's that'll fit, or a NOS / original. 3) I figure if I go K&N I'll use their filter oil & cleaner products, but if I get an original - do I just oil it with 30w oil and put a little axle grease on the sealing edge, or is there some better way to do it these days? (use K&N cleaner and filter oil on an original type?) I appreciate any and all input. Thansk. Matt