jbhome Posted July 1, 2012 Posted July 1, 2012 Hello all, Well after too many years, (had a CT1 that was almost new) I just bought a 79 Dt175. Started first kick at sellers house, then died like out of gas, but it had gas ( very old). cleaned carb, replaced gas but no vroom. Tank off checked all connections, battery 6.0V but little or no spark at plug. Metered trigger line to coil and see a pulse when I kick it. On/off switch working. I think the ignition switch kill circuit is in parallel with the on/off switch so I'm assuming him switch works. metered the coil from the common wire to trigger wire, and plug lead and seem ok though I don't know what value range is good. Does anyone have more detail on the did system wiring. What wires do what. Does the does the did system require the battery. Any hints on testing the did unit? Sorry for all the A's but the days are getting shorter and I've yet to turn a wheel. Thanks in advance for any and all help and suggestions. Have a great summer, Jim Brooks
Moderator Airhead Posted July 1, 2012 Moderator Posted July 1, 2012 Hi Jim this is what you need DT175MX Ignition checks There were two versions of ignition systems on DT175MX bikes. The mk1 version from the earlier bike had a 7 wire CDI the early bikes had a round section swing arm. The mk2 version had a 6 wire CDI, the red wire is absent on these. These bikes have a square section swing arm. The HT cap (AKA spark plug cap) unscrew it off the HT lead, it is supposed to be a resistor cap so should be around 5K Ohms The ignition coil primary...Orange wire to battery neg should be 1 Ohm +- 10% The ignition coil secondary...HT lead to battery neg should be 5900 Ohms +- 20% If the readings are much higher, check the ignition coil has a clean ground connection. Yes and the ignition coil mounting is a wiring harness ground point too, so check its clean and bright there. Disconnect all the wires from the CDI. Then using your multimeter on the loom side of the connectors. Black probe on a clean part of HT coil ground point Red probe on...... Orange, Meter to 200 Ohms, expect 1 Ohm (HT coil primary) Brown, Meter to 2k Ohms, expect 420 Ohms for mk1 and 300 Ohms for mk2 (Magneto charge coil) White/Red, Meter to 200 Ohms, expect 12.4 Ohms for mk1 and 10 Ohms for mk2 (Magneto pulser coil) Red, Meter to 200 Ohms, expect 13.6 Ohms for mk1 only. (Source coil 2 or high speed coil) Black female connector, Meter to 200 Ohms, expect dead short repeat for black male connector Any difference in the results for the two black wires may possibly be rectified by cleaning the front engine mounting bolt and a little of the frame behind the bolt head, then tighten to torque spec. Black/White, Meter to 20K Ohms, with ignition off expect dead short, with key on expect open circuit, with kill operated expect dead short (Engine kill operation) If all these tests are good you would be well advised to try another CDI. If they are not good...reading higher...disconnect and clean any plugs/sockets you find along the way, if the magneto coils are reading lower, new ones needed if more than 10%...or so the book says Finally, if you are working with a box full of mixed parts! Mk1 1 flywheel is Mitsubishi F3T250, it has two slots in the face of the flywheel Mk2 flywheel is Mitsubishi F3T251, it has four slots in the face of the flywheel
jbhome Posted July 1, 2012 Author Posted July 1, 2012 Thanks Airhead. I'll check that out today. Some further details. When I first tried the bike it started and reved probable to redline sticky throttle. Checked slide/cable ok so tried again. Started, idled so off I went. Pulled strong in 1, 2, 3 then started to bog like fouled plug or out of gas. after that, no even a pop when I kick. On a side note found this link www.transmic.net/en/analog.htm. Looks like a good alternative to the used CDI'S on ebay. This so reminds me of my ct175. Intermittent dead. Turned out the points wire coming out of coil passed through coil frame. Vibration wore insulation away and shorted out wire. That took a while to find. Thanks again for your help and your patience. on another note. At 33 years, are the copyrights for the Yamaha manuals not expired? Seems like they should be in the public domain by now. Just my thought and you know what that is worth. Jim BTW did I tell you how much I hate auto correction?
NE0 Posted July 1, 2012 Posted July 1, 2012 on another note. At 33 years, are the copyrights for the Yamaha manuals not expired? Seems like they should be in the public domain by now What makes you think that? Before using original material, you needed to obtain permission...............Having been the editor of a car club magazine for 7 years, there was a bit about copyright which one had to be aware before using it or making it public! Literary, Dramatic or Artistic Works Copyright lasts for 70 years after the year of a known author's death. For unknown authors it expires 70 years from the end of the calendar year in which the work was first made available to the public. If a work is produced by two or more authors then the copyright lasts for 70 years after the death of the last of the authors to die. Which manuals are you referring to? The Haynes type manual? then Haynes being the publisher and author will not be giving it up as they still publish the books. If you mean the Yamaha manuals by Yamaha for use by Motorcycle dealers/repairs, even though its no longer published, then the above will still apply from the date it was copyrighted/first published on the inside cover. You'd have to ask Yamaha to make it public, but its highly unlikely to make it to any meeting as an agenda item, it will not be a priority at all......making money will be on the agenda along with performance and the like! Regretfully Copyright is not open to public debate or your own interpretation of it, or your own understanding of it, or how you can justify using it. It's a law, of which if you break it, and a client wants to take it further, you will lose. Lawyers making a living out of this sort of thing!!!..........on behalf of the client who is agrieved of course!!
jbhome Posted July 2, 2012 Author Posted July 2, 2012 wishfull thinking? Paid $120 for an official Yamaha manual for my th only to receive a photocopy of a photocopy. Barely legible. I get the point though. My local Yamaha dealer fax the schematic and with your help and some research I've figured out the wiring. Kicking the engine over, I get about 4V P-P one red and white red. Ohms from the coils at the first connectors are correct for magneto power but not the pulse lines, however the voltage from them seems to be reasonable. I'm rechecking at the CDI connector now. Again things look normal. Given I see 10's of volts from magnetron power but volts at the orange coil line seems like the cdi is bad Jim BTW I give up with the spelling. My #$% tablet keeps changing so please bare me. Again, thanks loads for the help, Jim
jbhome Posted July 2, 2012 Author Posted July 2, 2012 Ok some progress. I have a blue spark. Took carb off and re-cleaned, removed emulsion tube and cleaned squirted carb cleaner everywhere, Blew the heck out of everywhere and put it back together. Started then stopped again. Kicked for a while. Plug is dry... The inside of the carb has a white residue on everything. not thick. What can I use to get rid of this. Even with the carb clearner once it evaporates, the white deposits show up. BTW what is the best way to remove/install the carb? I've been loosening the cylinder head clamp and the air box clamp and leaving the rear boot on the carb but I'm concerned about the stress when I put the carb in. Would a blown crank seal do any of this? It seemed like it was going to run ok cept the rubber plug on the side of the carb had fallen off and I stopped it to put the cap back on. Argggh! Thanks, Jim
Moderator Airhead Posted July 2, 2012 Moderator Posted July 2, 2012 Ok some progress. I have a blue spark. Took carb off and re-cleaned, removed emulsion tube and cleaned squirted carb cleaner everywhere, Blew the heck out of everywhere and put it back together. Started then stopped again. Kicked for a while. Plug is dry... The inside of the carb has a white residue on everything. not thick. What can I use to get rid of this. Even with the carb clearner once it evaporates, the white deposits show up. BTW what is the best way to remove/install the carb? I've been loosening the cylinder head clamp and the air box clamp and leaving the rear boot on the carb but I'm concerned about the stress when I put the carb in. Would a blown crank seal do any of this? It seemed like it was going to run ok cept the rubber plug on the side of the carb had fallen off and I stopped it to put the cap back on. Argggh! Thanks, Jim so you have a spark...what was it then c'mon? Plug is dry...then it is very likely the crank seals are gone, you may get a temporary seal by squirting some engine oil at the left hand seal through the slots in the flywheel...perhaps you may draw enough vacuum to get a re-start but may be short lived...a good way to prove though if it works white stuff in carb...if it bothers you buy a set of those little scratch brushes...just the job
jbhome Posted July 2, 2012 Author Posted July 2, 2012 Welll...... The seals have it. Sprayed wd40 around crank and it started and ran for a couple of seconds then died. Thanks for the hints. Are seals hard to find? What is the best/safest way short of case splitting to remove the seals.? Watched a guy on youtube punch/crease in the metal edge of the seal(releave pressure then worked on a screwdriver to lever it out? Old plug looks pretty black so I guess both seals would be appropriate. Again everyone, thanks for your help and your patience. Have a great ride Jim
Moderator Airhead Posted July 2, 2012 Moderator Posted July 2, 2012 seals will be still available from yamaha i think although i have never done it this way, you drill two very small holes into the front face of the seals 180 degrees apart, then screw in some appropriately sized self tapping screws and pull on the screws to remove the seals, A few other things to consider... You will need a flywheel puller, dont be trying with a 'legged' type, and smething to hold the engine solid while you both undo and torque up the flywheel nut, I use a chain type filter wrench and some rubber strips For the right seal you will need to lock the engine from turning so you can undo and re-torque the pinion nut, on this side I use a clutch tool but in the past i have removed the cylinder and passed a bar (socket extension) through the small end onto wooden blocks either side of the con-rod. Also for the RH seal you will find a spacer collar behind the pinion, it slides on the cranshaft and enters the seal, this collar is sealed to the crank by an O ring so buy one of those too I wouldnt advise holding the opposite side of the crank to the nut/bolt you are working on of course doing it the lazy way (and who could blame you) assumes your crank bearings are in great shape Have you a parts list Jim? Again...what of the spark issue!
jbhome Posted July 2, 2012 Author Posted July 2, 2012 Re the spark issue. It had little/no spark so I started there. Pulled/reseated all connectors, went through the ohms test above. Net result I get a nice blue spark. Re the flywheel puller, I lucked out and bought one for a Suzuki and it fit perfectly. I Just happen to have an electric impact driver and taking the flywheel off was a breeze. Torqueing is a little more difficult as I don't have the flywheel holder but fifth gear a friend and lots brake seems to work. Re the clutch side I've used a rag between the crank/clutch gear. Seems to work well enough. Re crank bearings, the engine sound good when it's running. No rattles or vibes so for now it's just seals, assuming the flywheel side is not corroded too much. I'd still like a way to remove the white deposits(aluminium oxide?) from the carb. Any suggestions. Re parts list, I've been using the Yamaha OEM websites with exploded views. Do you have something you could share? So we're OK with the spark issue? Seems my lot in life to piss people off without even realizing it. Remember. The shiny side goes up! Jim
Moderator Airhead Posted July 2, 2012 Moderator Posted July 2, 2012 so you have a spark...what was it then c'mon? Plug is dry...then it is very likely the crank seals are gone, you may get a temporary seal by squirting some engine oil at the left hand seal through the slots in the flywheel...perhaps you may draw enough vacuum to get a re-start but may be short lived...a good way to prove though if it works white stuff in carb...if it bothers you buy a set of those little scratch brushes...just the job
jbhome Posted July 2, 2012 Author Posted July 2, 2012 Maybe the spark was a finger problem or maybe my old eyes couldn't see it in the bright lights. All of the connections looked fine and the signals from the trigger coils seem to be reasonable. It started with the old black plug originally then stopped don't know. It's working. When I sprayed wd40 into the area behind the flywheel, it started immediately, ran for a few seconds and died so I'll order seals tomorrow. The white stuff is not in chunks like some of the pictures I've seen it's just a powdery deposit in the bowl and lower carb body. It's probably OK.
flyday58 Posted July 6, 2012 Posted July 6, 2012 White stuff is just surface (aluminum?) corrosion. I cleaned mine as per Airhead's advice, no probs. I pulled the left crank seal by drilling a small hole, screwing in the app sized screw and pulling, popped right out. Two notes: A) Make sure your drill bit stays away from the edge of the seal, or you may snag the case, like I did. AA)When you install the new one, don't over-drive it - it can go too far. Note the depth of the old one before you remove it, then try to match the depth on the install.
jbhome Posted July 11, 2012 Author Posted July 11, 2012 Well.... I'm back again. Got a flywheel side crank seal and replaced it. I pushed the seal in a bit far, expecting a sholder so it's about 70 mm below the case shoulder. Should have read the post above but that's how it goes. I smeared some grease on the both inner and outer seal faces as well as the OD of the seal. The bike started almost immediately. Idle was a bit unsteady. Tried to ride it and as soon as I let the clutch out/load the engine,it started to baff and wanted to stall. I have not done the clutch side seal yet. If I let it sit for a minute or two, it starts first/second kick, idles for a couple of seconds, then dies. Reving it seems to keep it running. Pulled the plug the first time and it was wet. Second time not. The oil light is on but it's smoking a reasonable amount so not going there just yet. Any sage advise greatfully accepted. Jim
NE0 Posted July 11, 2012 Posted July 11, 2012 My advice would be to stop trying to fix it piece meal and simply take the whole engine out, strip and restore it, that way you can renew all the bearings, seals, gaskets etc. its a simple motor, will take you less than 2 hours to strip it down completly (taking digital photos as you go). Its not expensive to do and that way you'll know everything is done and will last for a few more years, i did mine last year and its been perfect since. in the time you've been trying to sort it , you could have put it back together and it's not as if you've been relying on it to go to and fro from work as it doesn't go now!......go on, bite the bullet and take it out!
jbhome Posted July 12, 2012 Author Posted July 12, 2012 I would if the fund said yes. Right now it is saying no no no. I had noticed a small red puddle developing under the bike so I decided to have a look at the oil pump. It looks good, all nice and shiny. The gush of oil and ??? something that didn't mix with the oil.. water??? was impressive. When I took the pump off, I found the seal most of the way out of the pump. Guess that would explain the drip and full cavity. I'm wondering if having the pump open like that might have contributed to the weird operation of the engine, drawing air through the pump, into the oil feed channel into the carb??? BTW how does one take the hoses off? The one with the spring clamp was easy. The other seems to have a tubular clamp and didn't seem real interested in coming off. Jim Doing a teardown at a more modest pace.
Recommended Posts