DT175 1978

Thanks for all of the good ideas. I actually thought of one more basic thing I’ve skipped over, and that I had better get squared away. (you guys might have assumed I already did) I hadn’t even looked at the spark plug yet. I know, I’m sorry for posting online before checking that – I’m such a “n00b” with this stuff. I was thinking fuel because the carb was spewing fuel and I kind of skipped over thinking about spark at all. The spark plug when I pulled it was pretty ugly. I think it may be black enough to be fouled. Also, while the bike does run, but runs poorly – I worry some of my earlier details may be misleading as it really does not run poorly in as much of a predictable manner as I had previously described. It’s kind of unpredictable in exactly how it struggles. I’m thinking more and more it’s fuel starving or not sparking. My plan, as it stands, is to: Get a new, properly gapped spark plug installed Get a new, properly oiled air filter installed Get the fuel petcock and filters cleaned out and reinstalled. Then I’ll see where I’m at after all of that and report back / ask questions. If I’m still having trouble I’ll look into taking a video, but that’s not easy for me to do (I need my kid’s help LOL) Thanks for all of the help so far, you guys seem very helpful. I’ll let you know how I do. -Matt B.

I just went and messed with the bike on a break from work, trying to get my details strait on exactly what it's doing. It does stall at about 3500, and when it does it, it sounds bad. Hard to describe, but doesn't sound right (it strugles and kind of sounds more "farty" sounding than a good running engine, metalic in it's sound) and then all at once it jumps up to high rpms. (like past the shift point, almost to red line) Just sitting in neutral, and slowly turning the throttle, the RPMs don't to go up past maybe 5000 (and it struggles to get there starting at about 3000). If you turn the throttle quick in little short bursts you can rev it up to and easily past the red line. By the way - mine is also being rescued after sitting a long time. I didn't get enough time to check it out just now as I somehow dropped the cable off the throttle valve again - I don't know what's going on there, maybe I dropped it by lossening the throttle cable too much and messing with it as I don't know exactly where that should be set, but, again this time I think I have it right now... but I'm heading soon to check it out some more, try to get clear details on exactly what it's doing.

Thank you once again. I will check the petcock again when I get home and report back - I do believe it has a hexagon shape at the bottom. So, this situation sounds like fuel starvation? regarding the air cleaner - it is bad. It is very bad and I know it, and haven't got a new one yet. I plan to get a new air cleaner very soon and install that, and I will report back as to whether that changes anything or not.

I removed the carb feed pipe at the petcock, so the fuel flowed from the petcock. The stream that came out of the petcock was about the same diameter as the opening it flowed out of... the fuel came out at a slight arch. I recal thinking it may come out at quite an arch and be hard to catch in a jar as the petcock opening points to the side, not strait down, but it came out at a moderate arch and I was able to catch it just below the petcock. Maybe a rate of 3 ounces per minute.... I don't know, that was a wild guess. It slowed as I got near the end. I may have to check again later and give a better explanation, it's hard for me to describe the rate of flow.

I have removed the fuel line and opened the petcock to drain all of the fuel from the tank. Unfortunately, I do not have much frame of reference to know if the rate of flow was strong or not. I recall thinking it could have come out faster. The petcock does leak a little when I turn it from "off" to "on". No I have not. I didn't think it would be necasary as it's brand new. The problem existed when I had the old carb on, and I went to the new one and the problem still persists, so I thought it must be something different. Do I need a rebuild gasket kit to take the carb apart, or can I just reasemble with the same gaskets (it is new)?

I'm sorry, I may not have been clear... I'm not very experienced, and I don't know all the lingo. I'm not sure that we're talking about the same thing... By throttle closed, you mean "not giving it gas - not twisting the grip" If so, then No, with the throttle closed everything is fine. It starts and idles just fine. When I try to go for a test ride, as I twist the throttle slowly and ride away in 1st gear everything is fine and as I slowly increase the throttle, the engine RPMs slowly increase - just like normal... Up untill I hit about 3500 RPM or so, then, it stays at 3500 RPM and does not respond to the throttle for just a few seconds and then surges up to 6500 RPMS (or just below the red line). If that's what you meant, then I applogize for my lack of understanding. Thanks

First of all – thank you ALL. You guys sound like you really know what you’re talking about and you have all made some good points. It sounds like you guys are all in agreement that crank seals would be the next most likely thing to cause the issues I’m having? I was wondering if a problem in the reed valve would cause this, but haven’t heard that mentioned, so probably not I’m guessing? I think DirtyDT made some points that really spoke to my situation. I think I was hoping to be one of those people who got away with just new fuel and a carb clean. This one, I didn’t fully think about until I had the bike home and had started messing around with it. At first, my thought was to keep costs down and if it blew up on me, who cares. Then I started wondering, if I’m flying down the road at 45MPH and the engine blows and hard seizes, will I be able to pull in the clutch and roll, or will the rear wheel be locked up no matter what I do? I really don’t know. How dangerous is it to blow the engine in your bike while you’re riding? I have a lot to learn… My original thought was spend as little cash as possible. Money is tight and I don’t want to overspend. My intent was to use the bike just around town, maybe one or two miles to work, generally light use. With that said, I guess I still need it to run properly. Here’s the deal – I did grow up riding dirt bikes, but I never really learned to work on them or really to work on anything much at all. I’ve always wanted to be more mechanical, the interest and desire have been there, but I haven’t ever learned. At this point in my life I have fixed a few things here and there, just enough to know that I just need to dive in and give it a try if I’m ever going to learn. Nobody is going to come by and teach me, I have to learn it myself. My thought on this bike is that it would be relatively cheap project for me to learn on. I guess my hope was that I could clean it up, and get it running better (had high hopes just carb would get me there) and then go through it bit by bit, picking out the next thing that bothered me the most, research it, fix it, move on to the next thing that bothers me the most and so on. I was definitely going to apply a “if it’s not broke, don’t fix it” approach. The idea was to figure out what’s broke, and fix that. I do know that a complete tear down and rebuild would be best. I’d like to do that someday, but for now was hoping I could get it in good running condition as is. I really don’t know. Maybe I should rethink the entire project and go ahead and do a complete restoration, but I’m afraid that I’d get in trouble due to lack of mechanical skills, lack of tools, lack of funds, and lack of spousal support for the project. Back to the CRANK SEALS: I have questions about this. Crank seals can be done with the engine in the frame, right? I probably have to drain the crankcase oil first? Then just remove the crank case side covers and clutch and I can get at them? There’s at least some chance that the crank case seals may be the issue causing the problems I’m experiencing? I glanced at my Clymer manual regarding this, but it was a little vague (as usual) so I thought I’d ask.

Thanks flyday58. I have checked the serial number on the frame and the engine and they match, and begin 2A7. I believe it was early / mid production run based on the chart I looked at for '78 (not the lowest serial number for '78, but far from the highest). I bought the bike recently from a guy on Craigslist. I'd say it was a "semi-survivor". It was mostly all there and would start and run as described above, but was visually pretty rough. A classic case of a bike that's been "rode hard and put away wet". It's a sunshine red model, all of the plastics were oxidzed / faded to light pink and some places all the way to white. It had what appeared to be the factory original battery in it (completely dry and crusty, off course) at least I assume it was original because it was old and had Japanese writing all over it. There's a few bent parts (the chain protector, foot peg bracket) and I really think the air filter is original from '78 based on how it looks and how it'll kind of turn to liquid if you rub it between your fingers. So I believe it has just over 4,000 original miles and feel it has recieved maintenance / repairs, at least from the second owner, only on an "as needed" basis. The speedometer and tach. work, which makes me think they've worked all along and it shows aprox 4,300 miles. Other than just cleaning it up a bit, I have added a new battery, reproduction left rear blinker and right front stop switch as well as the carberator I mentioned. The carb is a reproduction. I bought it from eBay (zoom zoom parts) because it was the cheapest one I could find.(free shipping) I'm pretty sure I have the throttle valve and clip installed correctly at this point. It starts and runs with the new carb, actually idles nice, dies when put the choke in after it's warmed up (like it should) and the throttle does work now that I've reinstalled the valve. That's about all I can think of to tell you about it, but if anyone has more questions - ask away. Your bike looks great, by the way. Mine looks almost exactly like that of course, but your's is looking good!

Hi. I just registered and wanted to introduce myself. My name is Matt. I'm working on restoring a 1978 DT175E - It's just like the bike I had 20 years ago when I was a teenager. I'm cartainly no mechanic, in fact I often wish I was better, so that is part of my thinking on restoring a 34 year old bike - to develope some more mechanical skills and to live out my memories of the days before my back and knees hurt. Anyway - I jumped right into a techncal (kind of) question in the Yamaha Workshop forum and got a super quick answer from what turned out to be a mod. (I think I'm going to like this place.) and now I thought I better go back and introduce myself properly to the group. This seems to be a great forum and I look forward to participating (I'll warn you now - there's more questions coming about this '78 Enduro of mine...)

Hello again. So, I mentioned in another thread that I'm working on restoring a '78 DT175 that's just like what I had when I was a kid. Here's what it's doing As the title says, it cuts out at around 4000 RPM and just kind of struggles and then just surges up to about 6000 RPM and generally runs rough. It was also spewing gas out of the carberator overflow whenver I reved up the RPMS high, so yesterday I replaced carberator. It doesn't spew gas and runs nicer at an idle, but it still does the thing where it struggles as soon as you get into the power band and then it surges almost to the red line. Basically, it runs almost exactly the same as before and maybe a little worse. I wanted to clean the air filter when I put the new carb on as it was kind of ugly and who knows how old. It ws dripping with oil, I mean dripping and was actually disintigrating when you touched it. I really couldn't have cleaned it without destroying it. So I did use this old, bad, air filter when I tested the new carb. Could that be my whole problem? The very next thing I want to try is replacing the air filter. What are the chances that's the problem? At this point, I'm not holding my breath (I thought the carb was the problem) If that doesn't get it, what is the next logical thing? Reed valve? Anybody have any idea what's going on here? Thanks, Matt

Thanks for the quick reply. Appreciate it. I'll relax now.

Hi. I'm brand new here, I just registered to ask a few questions (and because I'm a proud Yamaha owner) I am working on fixing up a DT175E - just like the one I had 20 years ago. I have a lot to learn about working on bikes. I am worried because yesterday, I was installing a new carberator that I ordered off of ebay - long story short, I had a hard time wrestling the cable onto the throttle valve, and I dropped the throttle valve and needle on the garage floor. Maybe twice. In my inexperience and frustration, feeling a little "over my head", I decided to put it all together and see how it went. I did wipe off the part that was facing down, I didn't see any dirt on what I was assembling, but I also didn't really check carefully for any marks on the throttle valve (the round barrel part) - I decided to just see how it went. So, I guess it went fine. My problem isn't solved (I'll post that in another thread) but the bike runs almost exactly the same, but I'm worried that I screwed up installing the throttle valve kind of willy-nilly. When I dropped it, should I have cleaned it in carberator cleaner? Should I have been wearing rubber gloves and been a lot more "surgical" about the whole procedure? At the time, I was kind of thinking that this wasn't really the important inner workings of the carberator so it didn;t matter that much. What do you think? Am I okay? No harm no foul, or did I do a bad bad thing by dropping the throttle valve and needle and just wiping it off and slapping it back together anyway? Tell me I'm okay so I can sleep tonight... or tell me what I should do to remedy my mistake. Should I just relax? Sorry it's such a long post. Any help is appreciated. -Matt B, (DT175 1978)