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Plates have kind of bonded themselves to the steels. Just remove them & separate then carefully seeing you're already in there. The pressure plate will lift as your looking at it but as I say the rest are stuck to each other. Perhaps give the steels a light sand if look like the shape of each grippy bit is showing on the steels. Could very very lightly do the same with the fibers then go ride it & enjoy. With DT250A I think that the pressure plate might need fitting in the right way or won't fit on the hub. Might be wrong but if there's 3 arrows there's likely 3 marks on the hub to give you guidance. You'll know straight away as won't go on to compress plates. Cheers from NZ.

Hi there
My bike was out action for 2 years. it all started fine but  when I get it into gear after releasing the clutch it stalls. I have checked the leaver and taken the side cover off there is some  movement on the plates. Not sure what else is wrong, as why the clutch not working and what is stuck !!!!
please help..
 Regards Alex





 

I had a nice 68, 70 and 71 DT1 all at the same time. Now comes along a 69. This bike is close to the 68. Has the 2 bolt ignition cover, long threaded dunlop rim locks, square swingarm, same paper air filter ( still good) and painted engine. ( which i like). 

I guess i will never be able to retire and stop working on these bikes. I have said I'm done 3 times now. Came across this 69 DT1-B 250. Looks good from 10 ft away. Looks to be all there and pretty much original which is what i like. The owner said it hasn't run in about 3 years. Has no spark, No battery but the gas tank and carburetor were drained and pretty much clean. 
I plan on making a nice rider out of it but i know how that will go? Money pit!  Paid to much for it but Oh well. Don't see many 69's around these days. 1st thing i did was pull the flywheel. what a mess on the condenser. Looks like someone tried to replace it. They didn't even bend the tabs over or down to hold the wires then solder it? So it bent the condenser mt and looks to be touching one of the coils or the flywheel hit it. Re-soldered the wires and straighten the condenser in place. cleaned the points and set the gap to 14thou. Nice spark at the sparkplug now. 

Took the Carburetor apart. The things you find with these old bikes! Look at the needle & seat. *(see picture) Never seen anything like it! plus the float arm was upside down. Look like someone modified the needle? I Installed a new set and cleaned the rest of the carburetor. Also was missing the setter jet o-ring and the pilot jet was plugged.  



Then i took the gas tank off and notice this strange looking long coil mounted to the lower frame bar under the gas tank. has 2 yellow wires connected to the 2 blue wires on the bike. Never have i seen something like this? Almost looks stock but i doubt it. Anyone seen one of these or knows what it is or does? see picture below.





Fuel Petcock was leaking all over the place so i have all new seals coming tomorrow so will see if it lights up and runs. Engine cranks over good, crank bearing has no play in it. Engine turns over nice and smooth. Hopefully top end is good. Feels like it has good compression. I do notice the clutch plates are stuck, hopefully they will break loose. Just want to get it running and test drive before taking the engine out and replacing clutch plates, all engine seals and gaskets. Also will vapor blast the cylinder and head. someone painted the cylinder, should be bare metal like the 68. Installed a battery, horn and brake lights work. That's a good thing. Until next time. 

 

1971 AT1 --- I'm well on my way to getting this bike trail-worthy (thanks to your help). BUT, when I filled the transmission case with oil, all of it slowly leaked out through what looks like the chain sproket area. I'll get a pic up here soon, but what advice do you have on what to do?  On the right side, I had taken apart the clutch and reassembled with a new kickstarter seal, and then put a new gasket on the right transmission case with Yamalube's appropriate sealant, but I have not touched anything deeper in the transmission (). 

I'm pretty sure the oil is coming from the sprocket area. How hard is it to change the seal there?
Thanks!

My ongoing to-do list:
--unfreeze clutch plates (Even with clutch pulled in I cannot disengage motor from tranny) DONE
--replace clutch adjustment screw (frozen. Perhaps I'm not getting enough clutch engagement which is causing the above) DONE
--fill gas tank with vinegar and flush out all the surface rust in interior DONE, but rust came back
--fix kick-starter. I think it is missing a shim, but it is getting stuck at the bottom of the stroke. Not a big deal, but annoying DONE
--do something with the front forks cause they are way too spongy.
--replace kick starter gear cause the teeth are somewhat chewed up NOT DONE -- Replacement I got was the wrong size, but the shim fixed it.
--replace/refit original tool kit
--get safety gear for riding
--Title/Register and ride

Whoo hoo! Got her running .I followed ya'll's advice and took the carb all back apart and used a piece of wire brush wire to push and prod as much as I could. The pilot jet is definitely NOT gonna come out though. It was so torn up by previous attempts that all I did was round it off more....but I did get all of the pieces cleaned up / out, and blew out everything with air.

Started right up. I don't have any experience w/ 2-stroke bikes and have only ridden a 4 stroke a handful of times. Anybody notice any weird noises or anything? It is idling ~1700-2000rpm without choke, so seems fine, right?

To do (I'll make separate posts if needed):
--unfreeze clutch plates (Even with clutch pulled in I cannot disengage motor from tranny)
--replace clutch adjustment screw (frozen. Perhaps I'm not getting enough clutch engagement which is causing the above)
--fill gas tank with vinegar and flush out all the surface rust in interior
--fix kick-starter. I think it is missing a shim, but it is getting stuck at the bottom of the stroke. Not a big deal, but annoying
--do something with the front forks cause they are way too spongy.
--replace kick starter gear cause the teeth are somewhat chewed up
--replace/refit original tool kit
--get safety gear for riding
--Title/Register and ride

I'm hoping I found the right page to find help with my issue.  I have rescued a 1976 DT125C from my stepfather's property.  I know that it had been sitting out for a couple of decades but I wanted a puzzle.  I'm trying to figure out if it is salvageable.  It is somehow locked up but I don't know where the issues is.  I got the jug off and the cylinder, piston and rings are in excellent shape.  I took the clutch cover off and the plates are fine.  I see a little rust in some places but nothing that would keep things from turning.  On the other side, I am stuck trying to remover the cover where the clutch cable passes through and that covers the drive sprocket.  I have removed the bolts but the cover is stuck fast! The clutch cable is stuck and won't move.  I'm not sure what position it's in as the chain is so rusted, the rear wheel won't budge.  I'm wondering if the clutch is pulled in, would that keep me from removing that cover?  Is there something else I'm missing?  I can't believe there would be more to disassemble to get to the drive sprocket.    I can't remove the engine to work on it because the rear engine mounting bolt pulls out behind the cover in question.  Let me know if you have any ideas.  I really want to make this scooter run again. 
 

Hello again everyone! You may remember some months ago helping me achieve my dream of fixing my 1973 DT3 when nobody else could and you may also remember that it was stolen from me in September of last year. I made it my sole goal to get a new one before the start of the 2024 semester, initially my goal was to buy a 1978 DT400 that was nine or so hours away. I managed to get very lucky though because it just so happened that my friend's dad was looking to sell his motorcycle and by some incredible odds it happened to be a vintage Yamaha as well! I talked to him and got a great price for it and now it's all mine! I put about 125 miles on it after owning it for a week or two, and the clutch blew. I'd never worked on a clutch but I bought the new parts and learned as I went along. The oil smelled like barbecue ribs and so did the clutch plates, the friction disks were nearly nonexistant. New ones went in and new oil added and everything's back to normal! 

Now comes the current issue. With 175 miles on the bike I rode it two days ago and put it away for the evening and then took it back out the next morning and it wouldn't start. I grounded the plug against the engine and kicked it and sure enough no spark. I took the bus to an autozone and bought two new BP7ES plugs for it (one for later) as the service manual says but I popped it in the boot and still no spark. Both times, though, I took one for the team and stuck my finger in the spark gap to see if it would shock me and sure enough in both cases I DID feel a weak shock, which probably means something.

I'm used to my DT3 with its caveman banging-rocks-together level ignition system and I believe this bike has a CDI which I am entirely unfamiliar with. I was wondering if any of you have any experience with working on this type of bike and how I might be able to troubleshoot this issue. I am looking in the service manual and online but you guys have been so helpful in the past I thought I would ask you as well. I'll keep you posted and look forward to talking to everyone again!

Thanks, 
Daniel

Pictures in case the attachments don't work:
photos.app.goo.gl/hfNzqcf9eL3GF8KF9
photos.app.goo.gl/nCRMJjVGXxkQYNNM9

Well this is gonna sound insane. I took a plug from my 330i bmw, NGK R iridium. I have a 175 head still here, threaded it in the depth looked fine. Went to the plug resting of the head, tested fine, only problem was having to hold it in the boot since it has a push on end no threads and wouldnt hold in the boot.

Figured f it, threaded it in the head and it fired immediately. Test rode it and it ran amazing. The bottom and mid range was better than its ever been. It pulled very good. There was enough tension of the boot that it held just pressed up against the end of the plug. Go figure, if youre ever in a pinch a NGK R 12120037607 will work.

The only issue I noticed is it pulled really hard to the exact redline mark (8k) and theres a little bog/ slight break up. It def feels like it wants to pull hard past it but get stuck right there. If I modulate the throttle it I can feel it wants to go but something is happening. You think it has anything to do with the points or am I running out of fuel? I have a 140 main and the air screw is almost all the way in.

So overall solution, it was the spark plug that was the problem, theres something up with it to where it would work for a little bit then stop, making this all a very confusion puzzle.

PS, clutch is still slipping, prob gonna need to get new friction plates. 

A puzzling one. I never saw the like before. Took the barrel to work and stuck it in the hot wash to degrease it prior to blasting it.

Took it out and gave it a look over to make sure all the oil and grease was gone.

In the upper fins at the rear was what looked like a honeycomb or wasps nest. Only instead of being made of paper, it appeared to have been constructed of a very hard clay like material.

The hot wash made no impression on it. A new one on me. Any ideas, it being a US bike?

Anyway, barrel was checked for taper and oval (fine), blasted and then given a quick hone for new rings. Just needs paint.

Clutch steel driven plates were stuck in the derust bath and then given a quick turn on the linishing belt. They are useable, but not great. Quite a bit of micro pitting on one of them, but still straight. I should replace it but nah, it will work ok. The rest were not as bad as they looked.  Basically after derust, they were just water marked and most of that came off after linishing.  I have had to refit worse in long out of production trannies.

New Vesrah frictions have been ordered.

New Koyo mains have been ordered.

Found a new genuine yamaha piston at a bargain price. Actually it was the only standard one I could find advertised in the country. It cost about the same as a chingaling cheapo piston.
I guess the bike shop thought it being std size, it would not be in demand.

Circlips and small end ordered. Already have genuine rings in stock as well as a full gasket kit.

Head is going into work tomorrow for a dunk in the paint remover bath and the clutch pressure plate is having a turn on my bench grinder wire wheel.

Apart from the oil pump seal kit and the airfilter, I think that is engine complete.

If everything turns up, I will build it and fit it on saturday morning. Might even have it started this weekend..