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TOPIC: New project! '77 DT250

New project! '77 DT250 09 Jan 2018 11:17 #1

  • clausenfoto
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Hello! First post here and I would like to thank everyone on this site, your knowledge has already helped a bunch!



I picked up this '77 DT250 a week ago for $200 off the local Facebook for sale group. Bike had good compression and was just missing lighting, shift lever, front brake cable, and seat foam and cover. (Speedo/tach and some other stuff came in a crate)

I plan to get this bike fixed up and on the street. Usage will be about 80/20 road/dirt since I have a '93 RMX250 for my dirt duties. First up was to get the bike running! I downloaded and printed out the manual, and got to testing the electronics. Looking at the wiring diagram, I knew i had all the pieces to run, but was not getting spark once I plugged in the condenser. After confirming the values on the condenser were in range, I dug into the stater. OHM values seemed to be close enough to in range here too, so I was a bit stumped.



I ended up pulling the stater to clean it up (was already pretty clean) and inspect the wires. Everything looked good here, so i figured it had to be the points. I had never messed with a points system before. With everything back together, I could tell something was off because the points were opening about 1/4 inch at max. The points adjustment screw was pretty chewed up as well so I could tell that someone had been really messing with it before. I found a thread on here that said to set the gap to .014" which I was able to do with some trial and error. I could not easily adjust with the flywheel on, so i would make a small adjustment, throw the flywheel back on and measure. Got the gap perfect with a feeler gauge after about 4-5 tries.



I threw a spark plug on and bam! I had a nice blue spark! I knew the bike would run at this point! I threw my RMX tank with premix on and kicked her over. Second kick she sprang to life! It was kicking back a bit, so i think timing might be a bit off, I will need to get a dial gauge and set it correctly. Have not dug into the carb (previous owner had cleaned it) so I am sure I will need to adjust the jetting (I live at 8000ft). I just have a cheap pod filter on there now while I am working on it, and its surprising how much noise is covered by the stock airbox/filter, you can really hear it sucking with the pod.



My issue now is that the clutch does not work. There is no resistance with the clutch actuator arm. I started to removed the clutch cover last night, but it was stuck on pretty good after removing all the bolts. Tapped around with a rubber mallet which did not help. Looking at the parts schematic, It looks like there is a screw (90149-08105-00) that might adjust the push rod travel, but not sure. Hopefully it is something easy like that, because that is all that is stopping me from getting a first ride on this thing! I got a shift lever off eBay and confirmed that it shifts through all the gears.

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Last Edit: by clausenfoto.

New project! '77 DT250 09 Jan 2018 15:35 #2

  • FrankC
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That screw no 12 in the diagram is for adjusting the clutch. It should not interfere with clutch cover removal. Did you pop the oil pump cover off. There should be screws in there as well. Sometimes they can be easy to miss if there is caked on oil or dirt. Wish you the best. That is one beautiful bike.
www.boats.net/parts/search/Yamaha/Motorc...0D/CLUTCH/parts.html

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New project! '77 DT250 09 Jan 2018 15:53 #3

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I know that the screw would not interfere with the cover. I was just guessing that it might have something to do with the reason the clutch actuation lever has no resistance.

I did remove the oil pump cover and removed the screws under there. There was also one or two screws covered in grime on the bottom, but I made sure they were all out before attempting to remove the cover. Oil pump had been removed previously, but i do have it in the box of junk that came with it.

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Last Edit: by clausenfoto.

New project! '77 DT250 09 Jan 2018 16:33 #4

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Hi, you can see on the base plate where the screws have been so that's a good place to leave it unless worried about it being played with. tighten the flywheel TIGHT or the buggers love shearing key off. points max of 15 & shouldn't kick back unless you kick it 'lightly'. Love these old girls & had one for years mostly as a ride to work bike but also forest trail rides. If there's timing marks visible & reliable [like a timing tab on end of coil screw hasn't been bent] you could just loosen the points screw & bring them up to touching the cam at that point & tighten the screw so should open 'then' but a bit of a fiddle as things move or twist when tightening. Should be able to do 'that' with flywheel on although can appreciate how you've been doing it albeit slowly. Check the key again!!. With the clutch i wonder if the adjuster has come undone in which case it'll be rubbing on the case possibly but most likely last person in there has lost the ball bearing 18 at a guess. All the screws to remove clutch cover would be shown in a 'partzilla' pic if ya dial it up but will be one under the oil pump cover but they stick on pretty good over the years. sometimes i'll use a block of wood & a hammer. Get stuck on the dowels two which you'll find on the partzilla pic--ok i'll find one lol www.partzilla.com/catalog/yamaha/motorcy...250d/crankcase-cover & in saying that, i can't see a hidden screw in the oil pump cover area. Talking RMX, i got given a burnt out one which i got up & running for no cost & goes like a rocket, no power valves & all just made up blank offs at full open. Bit pipey [cammy] min us the valves but enduro flywheel makes it ok & still pulls well off idle just rolls on hard about 1/4-1/3 throttle. Have a good [well better than this one] RMX & the powervalve benefits are pretty obvious. Anyway--good luck from NZ.

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New project! '77 DT250 09 Jan 2018 16:48 #5

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I did scratch some marks into the stater plate before removing it so that i could get it back in the same spot. I am hoping the clutch is something simple like a missing ball bearing.

The RMX rips! You can really feel it when the power valve kicks in!

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New project! '77 DT250 09 Jan 2018 17:03 #6

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the mouse family was on first start up & it all went constipated as wife came out to see what the smoke was from & cries out MOUSE!!, Lots of them.

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New project! '77 DT250 10 Jan 2018 09:07 #7

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I came across a thread with those pictures when i was browsing earlier. Gnarly!

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New project! '77 DT250 10 Jan 2018 12:49 #8

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You will know if the clutch is adjusted right when the pointer on the end of the actuator lever lines up with the nub cast into the crankcase. You have to push the actuator lever forward (toward engine) to check this. If it doesn't line up adjust screw in center of pressure plate. Again, the clutch actuator lever has to be manually pushed forward to make the proper alinement. Also,the clutch cable itself should have plenty of slack or slop so as to not effect the clutch adjustment.

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New project! '77 DT250 11 Jan 2018 09:49 #9

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More progress! I was able to pop the clutch cover off by using the claw on a hammer to lightly pry between the tach cable housing and the frame. It popped right off. Everything looked fine inside, but clutch was not working. I took off the plates and center carrier and removed and cleaned the arm/rod/ball/screw. Lubed it all up and put it back together. Had to put the plates back in a few times, but after lining up everything like the manual says, and adjusting the screw, the clutch works! Everything looks good inside the motor. No notching at all on the clutch. Those plastic gears in there do scare me though, although condition looks perfect.



This thing is ready to take a test ride now after I get another gasket. I am also going to remove the oil pump gear and install a block off plate while I am in there since the oil pump had been removed. I would like the get the injection system working again at some point.

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New project! '77 DT250 11 Jan 2018 10:22 #10

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It is weird like you said about having those plastic gears- they last pretty much the lifetime of the bike. The engines and transmissions in the enduros are quite bullet proof. Many have set for 20 years and with a carb cleaning and oil change just start back up with a few kicks.:Buds
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