oldbikerehab

Congrats! Glad to see you got it sorted out after all the headaches. And you've set the quality DT bike pron bar quite high in the process! Have fun breaking it in.

I'll second the trail wing. I have a set on my DT and when I've been caught in some heavy downpours I've been able to fully lean the bike with no trouble on wet city streets in a rush to get home. I've tried them in sand, mud, gravel, and grass - all good. As far as a 50/50 trail/street, I've no complaints. As for putting the bike up for the winter, nope. I won't use it to commute but I can't wait for the first snow so I can fire it up in the alleys around the neighborhood and do doughnuts in the empty lot near my house.

I thought the same thing a few days ago when I parked in a bike lot and noticed that almost every other bike that wasn't a Harley had at least one Monster sticker. I even saw a guy riding locally with Monster stickers all over his bike and a "Monster green" mohawk glued to his helmet. I can't stand the stuff but apparently they put some kind of crack in it that bikers can't get enough of. Chippy, be careful with that stuff before you start sprouting a mohawk from your helmet! Kidding aside, nice job on the bike! I bet it's a fun one!

Where are you in the US? I'll come catch that thing if you're pushing it off a cliff near me. I was in the same boat as you about this time last year and spent at least a month of gorgeous riding weekends kicking my leg off on my beat up DT175E craigslist find with the same plan as you- to rebuild an old bike without previous experience but a decent knowledge of design and things mechanical. Now, I have a DT that runs like a mf and is a blast to ride, on an off road. Yeah, it's got a nasty oil leak but that's because I made the mistake of ordering some generic oil seals off the bay. Now I know. You should check out my intro, it's got a few of the many lessons I learned in the 7 or so months that it took me to rebuild mine. Such as- Don't waste money on tools like torque wrenches etc. If there is some type of large chain auto parts store near you, they usually have free tool rental with a refundable deposit. Though I bought all that stuff and I'm glad I did. Also, keep it smokin'. I didn't understand and blew a hole in my piston. You can do it. Your gray hairs will increase and you will likely curse that bike and wonder WTF you got yourself into. But seriously msg me if you do decide to get rid of it. I'm pretty broke right now (mostly because of all the money I wasted on first timer f-ups on my bike, new tools, parts, paint, chemicals- it adds up) but I'd be interested if it doesn't turn out to be too far gone and you aren't too far away.

That was it! So nice to see both gauges working again!

A few things I've found with my 30 something dollar Chinese carb: Besides the o-rings being shot and requiring me to get new ones, the throttle adjust screw and pilot air screw don't tune the carb properly when set according to the DT 175E specs for Mikuni, as listed in my Clymer manual. I had to back the pilot air screw almost all the way out and tighten the throttle adjust screw in almost all the way to get my bike to idle at 1300 revs. Also, mine was sold on ebay as being for the dt175, the manufacturer's website lists it as being for a 125cc. Add in some unmarked mystery jets and needle and you've got a cheap carb that can be made to work. I have my needle raised to the max so it's kind of a fire hose setup. I get a pretty boggy throttle response from idle to 1/4 throttle, but 1/4 to WOT is a MF to hold on to. Not that I necessarily think your carb is solely to blame for your problems, but you'll want to get it set right. If you've got a bit of patience and some hair to pull out along with some basic mech skills, you'll get that old mare kickin' ass again. Oh, and you need beer to make this whole thing work.

Thanks, Airhead! I'll tear into it later this week and hopefully be back with a working speedo.

After removing the functioning speedometer and cable from my DT175E for painting, I reinstalled it with a new cable and it worked for a few short miles around town before going dead. It seemed to skip, dropping to 0mph, then popping back up to speed, and did this for another mile or so. I pulled the whole front wheel, cable, and speedometer and cleaned all thoroughly with solvent, re-greased, and reinstalled. Everything seemed to spin fine in the wheel assembly. I took a drive with the cable disconnected from the speedo but connected to the wheel and could see that the inner cable wasn't spinning. Next, I connected the cable to the speedo unit and connected the wheel end to my drill. Spinning in either direction wouldn't make the needle jump. I tried driving around with the old cable as well and still didn't get any response. Any ideas on how I can figure out just where the system is failing? Are there particular alignments I need to be aware of? The only area I haven't checked is the actual odometer, speedometer mechanism inside the housing because I can't figure out how to get at it without breaking the housing.

Link to 1978 DT175E piston parts I mentioned. http://www.powersportsplus.com/parts/search/Yamaha/Motorcycle/1978/DT175E/CRANK+-+PISTON/parts.html#uloc8

fwiw, I put together all the parts in the piston kit you linked, but OEM and including a new bearing for $108 delivered. Looks like it would be about $112 for you so something went up a bit, but fair enough if you don't mind throwing in an extra 20 bucks for OEM. Shipped from U.S. (Georgia, I think) in a week + a few days.

Nice ride, zibzer. These are fun bikes and I only wish I could find a second one. An inline fuel filter isn't a bad investment as part of your tune up, especially if your tank is nasty. I use straight gas in the tank with the oil pump on my DT so I'm assuming filters work ok with premix. Don't forget to check the air filter and clean and oil it well.

Gordon Jennings article on mix ratios in relation to horsepower and varnishing for anyone interested. http://www.bridgestonemotorcycle.com/documents/oilpremix6.pdf

The main changes I've made since I burned a hole just like this are to run the whole mix rich, for starters. After this last rebuild, I asked my local bike mechanic to give the bike a look. Timing (which was most people's guess as the culprit initially) checked out fine, compression was tight, no leaks, etc. Their end suggestion was to run my mix rich by raising the needle and shimming the oil pump stroke because a lean mix of junk gas was what probably did me in. Their argument stemmed from the Gordon Jennings article I think I linked in one of my threads about how 2strokes get more horsepower and and varnish less with more oil. I also went back to a 16 tooth sprocket on the front instead of the 18 I was running. So far, I've not repeated the trip I blew a hole on but I've run the bike for maybe 2 miles at a time around 5000revs. Mostly tearing it up around town lately. I've been using the same NGK B8ES plug since my rebuild 500+ miles ago btw and I switched to Yamalube 2 stroke oil. I wasn't really even smoking with the mix I was running when I blew a hole but now I will fog the block when I leave in the morning but after that, just a puff when I take off from the light for the rest of my ride. So far, so good. I'm also running the same cheap imitation carb as you flyday58, and realized all the o rings were torn and bad like yours so I replaced them. I haven't tried messing with the jets since nothing is stamped on the generic thing so I wouldn't know where to begin. Question for those who've been riding DTs and working on them for years and years: What is the safe redline for revs over a long distance on an old DT? (Assuming that timing, etc. is set correctly, mix has bike smoking a bit, idles good, and all seems well with the way it runs.)

It seems like it should work to me too. I just can't figure out why Yamaha would go to the trouble of incorporating an adjustment screw with a locknut and a lock washer when all you have to do is adjust the cam. I can only guess that it's intended for when someone seals the transmission in the case and needs to fine tune. Maybe if the neutral ball is close enough, things fall into place. I guess I'll soon find out if I need to split the case again . . .

After splitting the cases on my 1978 DT175E, I got the transmission in place and aligned the shift drum neutral ball indicator just off the neutral indicator on the case, the gears spun freely, and I followed the clymer manual through sealing the cases back together. I installed the cam pin, cam, shift arm, springs etc. until the manual says to push the shift arm down into 1st gear to check the alignment of the index marks on the cam and upper part of the shift arm. My marks were not originally in line, so the manual says to adjust using this eccentric screw and locknut. I dont have a deep socket to loosen it so I just lifted the upper shift arm and turned the cam until the outer marks lined up as seen in the photo above. Now, with the shift lever pressed down and index marks lined up and everything spinning freely. . . Will aligning like this work? I don't want to get the rest of the bike together and find out that I the transmission is jacked and I have to take it apart again. Any tests I can do to make sure everything is aligned?

I just posted this comment in another thread about gearing mods. "If you know how to really tune the bike and make adjustments to fuel, timing, air flow, exhaust, jets, etc. to compensate for the possible strain your initial change may make on the bike - go wild. Otherwise, go standard. " Inspired by the wisdom of DirtyDT.

I have two extra teeth (18) on my front sprocket and stock (49) on the rear and get about the same top speed/rpm specs gains as flyday58 on the same bike. Dirty's comments on a bike's original design and standard being good are spot on though. I'm about to switch back to the 16t/49t original spec. Mostly because I want to see what the bike is supposed to be able to do and tune from there. If you know how to really tune the bike and make adjustments to fuel, timing, air flow, exhaust, jets, etc. to compensate for the possible strain your initial change may make on the bike - go wild. Otherwise, go standard.

Ah yes, and then there's the timing. I didn't realize that octane and timing were so closely related. I am glad that you brought it up because one thing the owner said at the shop was that while my old gas may have played a factor, he thought that my timing was the ultimate problem and that we'll put a timing light on it later. If anything, it will be nice to know exactly what my bike is tuned for when all is said and done. Lessons learned.

Thanks Cynic! Good call on the shim, that's the type of feedback I was hoping for and I'm going to add one to my order. I'd really like to be able to have the bike run the way Yamaha designed it and not mess with adding stuff to the gas tank. I don't think the Suzuki 250 mentioned in the Jennings article has an autolube, thus the premix. What's the consensus on octane in a 2 stroke? I was filling up with 87, but I'm wondering if I should be using 93 when I get it running again.

Thanks for all the feedback! I finally took my top end off to check things out and bring it by the shop for an autopsy. Here's a look at why splitting the cases is in order. The pin looks spent with some bluing on the ends. The good news is it looks like I can get away with a honing and stick with the 3rd over piston, if they are actually in stock as the parts website says. I put together an order for ring set, piston, piston pin, circlips, needle bearing, all OEM for $99 + shipping. Then I cleaned the piston rod. Are the brown rings where the needle bearings end anything I need to address or just standard wear? The needle bearing came out easy, I don't see any bluing from heat and don't feel any scoring with my fingernail. Is a new piston rod in order or can I use my old one? One of the mechanics at the shop said I need to run a light premix (Maybe an oz of castor or 2stroke per tank) in my tank on top of the autolube pump when I get things back together. He also recommended I read this article by Gordon Jennings. http://www.bridgestonemotorcycle.com/documents/oilpremix6.pdf Jennings makes a pretty solid case for more oil in the mix = more horsepower and less varnish buildup after some pretty conclusive testing. Anybody here run light premix on top of the autolube? Flyday- I am/was still running the junk carb and will be trying to source out what I need to rebuild my Mikuni. Also, aside from lacking the intake ports, I've been told that there is also enough of a weight difference (Wiseco=heavier, if I remember correctly) to create a noticeable difference in performance. Main question now is, should I go for a new piston rod, or stick with my old one and save $45? Are the pretty much good as long as they aren't broken?

Yo thinks the feed tube tucked in above the pump came off. That was actually my biggest fear on my bike because they were nearly impossible to get on and Yo didn't have wire to put on them, so Yo thought that was what happened on my flapping noise adventure yesterday. Next time Yo have it apart, Yo'll twist some light wire around it for peace of mind. Yo don't know if you caught my post yesterday, but "when Yo started to hear a flapping sound from the cylinder" is my new my new cue to clutch in and kill it. Three cheers for clear tubing though.

I think you're right about the lean mix, 2wheels. This bike's never really smoked a lot except if I wind it out when warming it up cold. My needle's in the middle position, but a cheap carb + junk fuel, and then climbing a steep hill was the final nail in the coffin. The plug is actually cooler than the one recommended in the original manual and my elevation varied around 400-800 ft. You can bet when I get this thing back together I'll be on it with the WD40 looking for leaks though. That reminds me, I'd better order new gaskets. Hopefully I can just have the cylinder honed at its 3rd over and I won't have to have it bored to the 4th over. Thanks for the advice!

That's insane! You'd think the U.S. would cut you guys in on our global oil thievery, err I mean oil surplus derived through nation building.

No doubt about your prices, Cynic. When I was working in Scotland back in 2001 I thought you guys were getting boned at 78p/Litre but you're probably double that by now with no real rise in wages either. People will start freaking the !@#$ out a $4/gal here. You were at about $10/gal last time I heard.

I'm now wondering if I might have also had an air leak at the carb. I'd noticed that it had a slow leak thing going on and planned to tighten it next week when I put my new cable on. Does this make sense, that a leak at the float bowl would have been leaning the mix?