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73 MX250 fixer upper- part 2

  • hackman101
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73 MX250 fixer upper- part 2 was created by hackman101

This is kind of an add-on to my introductory post. It was what I wanted to post, at least a variation of the one that disappeared on me.I finally got to disassembling the bike. Removed the front wheel since it was in the way for the removal of the expansion chamber and the tire needed to be replaced anyways since it was dry rotted so bad. Huge cracks/splits made it appear like the tire was in pieces. Successfully got a new tire and tube installed without pinching holes in the tube. The rim locks did make it a bit more difficult to get it back on. The brake was a bit stiff too, so took that apart and got the pivot cleaned up and lubed. Works real easy now. Still need to lube the cables. I would like to get one of those clamp looking things to do it with, looks like it makes a slow job easier and much quicker.

 

I seen in some post(s) that the liners fail on old brake shoes???? So, this is a thing???? I had no idea I would be dropping this much cash on fixing this bike up as it is, but things keep adding up if this is yet one more thing.

I am jumping the gun a bit; I haven’t even written all the other stuff I have found out yet. I am trying to keep everything in chronological order as I give the blow-by-blow account. Just a reminder too… this bike was running the last time I recall albeit over 35 years ago, perhaps even 40 years. I stop riding it when I found a mouse nest in the air filter, and I figured it may only need a cleaning out at best when I did get back to working on it. Back on track. I got my feet wet on doing the few things mentioned, so now its time to get the cylinder off and see what the extent of the damage the mouse nest caused. Got the head off. The piston was down a bit so I could see the cylinder walls, looked great no scoring that I could see. I dared not move the piston even at this time since the mouse nest could still fall into the bottom end. This is why I have not kicked it over in all these years, just in case the piston was in the proper spot to block the mouse trash from going any farther. Next was the reed block. I really hoped it was going to be good news but the piston was in the located such that the piston ports were perfectly lined up with the reed assembly. Bummer. Popped the jug and crap was all inside the lower end.  I paused for the longest time trying to sort out how to clean this mess up in the simplest way I could. The only conclusion was to split the cases. I started to remove the other items around the motor to pull it. WD-40’d everything and gear shift, footrests all came off easily. The brake pedal on the other hand, did not. It was the only thing I missed with the WD-40. I thought everything else came off with no issue, this won’t need any. I did not want to wait for the WD to “work” so I went for it and sheared the bolt right off.  Oh well, live and learn. I drilled out the bolt out far enough to remove it, but not so deep to drill out the threads so I can recover them. I have most, but not all of the engine mounting bolts out, this is how far I have gotten to date. The weekend coming, I will progress a little more with you guys’ help if possible.

 

Along with the question asked about the brake shoes and other suggestions that would help with what has been done to date, I have a few questions.Since I am splitting the cases to clean out all the debris from the mouse nest. Is there any way to clean it up without removing the transmission gears? As in sealing off with tape and plastic or anything like that? This is just a shot in the dark, I think I will need to buckle down and just remove everything and clean it all out, since my power washing to the outside did not clean everything off as good as it needed to be.Still not done yet! I forgot a few more things.When I power washed the engine, I was concerned about the breather for the CDI compartment since it didn’t have a tube, has taken on water since the bag I put over it held on with a rubber band immediately blew off. I got the cover off after some tribulation since I overlooked one screw still holding it on and I could not figure out why this thing was stuck on so bad. Then I found the screw, it came right off. Then I noticed the nut for the rotor was all the way out to the end of the crank. No marks inside the cover, but the rotor appeared to be tight. Not that I knew what to expect. When the jug was off and I could now turn the crank to lower the piston skirt into the case, I noticed the rotor (thanks RT375 for the proper terminology) was loose after all. The time when I checked it before the magnet on it kept it steady. This is something I already posted about. The keyway is mangled along with the woodruff key which is a sorrowful looking thing.

  

Oh, I did manage to pull one of my rusty shaft shocks off too, so it could be measured for some cheap new ones. I plan to only clunk around. I definitely do not need any high end shocks for that. Just something to keep the rear wheel from bottoming out. Are there any recommendations out there?Now that is everything. Sorry about the long read. I felt I needed to get all the details out.
1964 Honda 50cc C110
1960s Yamaha 65cc scooter
1960s Honda 65cc w/ 90cc engine mashup
1971 DT1-E modified to MX kinda...
1973 MX250
Last edit: 25 Sep 2021 08:44 by hackman101. Reason: Some words were not in the right spot
25 Sep 2021 08:40 #1

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Replied by msavitt on topic 73 MX250 fixer upper- part 2

caveat - don't take advice from someone less knowledgeable than yourself!

The crank area is separate and sealed up from trans.  So since you got the jug off you could invert the motor and flush it out with BBQ fluid, which I love!  Since bike is really old then perhaps after this you take off side covers, mag, pop old crank seals and flush out bearings.  A bit crude, but if you do this well you can save a ton of time if the trans operates good...and you need to replace seals anyways.

Re brake shoes, I wish I had taken a pic...when I took my '71 DT1E apart the front linings were thick but the glue had failed...had I ridden this bike I could have cut my aspiring hobby short!  So I think new shoes are a must.

Bike looks really nice, good luck with it!
25 Sep 2021 10:13 #2

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Replied by hackman101 on topic 73 MX250 fixer upper- part 2

I am still gonna split the cases. Looking inside the lower end everything is so tight in there I can depend on just a flushing to get everything out. I MUST see if it is clean, not just hope it is. I got the engine out and the piston off which needed to be driven out. I supported the piston with a wood block cut to size to fit under the piston with the engine on its side. It came out pretty easy, but it was really snug. 



Cleaned up the piston top, I will need to look up what the numbers mean, unless somebody wants to chime in what they mean.

 

The cylinder walls looked pretty good too. There is cross hatching still present over much of the cylinder walls. They are visible in a close up of the picture. I removed the ring and set it in the bore, the gap looked pretty big but I have to invest in a set of feeler gauges to check the gap to be certain. An observation, back when I had my first bike. a DT1E, When I was researching putting an MX jug on it, or maybe it for something else since it was bored many times, that the ports were to be or should be beveled to the cylinder, so there are no edges for the ring to hang on. The reason I bring it up is when I was thinking about this when I ran my finger down the bore to check the bevel at the ports, the top and bottom edges where the ports meet the cylinder seem almost sharp. It probably would cut if I ran my finger along it with a little pressure, but I'm not gonna try it. It might hurt....

 

When I removed the engine, I seen how bad of a job I did with the power washer. So I put the jug and head back on along with the reed assembly and covered the openings with heavy plastic, set it on a piece of plywood and fired my power washer back up. This time I got it real good. Some places still took a wire wheel on my drill to clean, but it can now be split.

  


With everything snug on the bolts some water still got by but I took it all back apart and dried up anything that was wet. I sprayed WD-40 over the important places. 

 

Before I go any farther, what do I need to check before I split the cases? Any side play tolerances?? FWIW, I grabbed the crank and tried to shift it left and right, there was no side play there to be noticed.
1964 Honda 50cc C110
1960s Yamaha 65cc scooter
1960s Honda 65cc w/ 90cc engine mashup
1971 DT1-E modified to MX kinda...
1973 MX250
Last edit: 25 Sep 2021 20:23 by hackman101. Reason: Some words were not in the right spot
25 Sep 2021 20:21 #3

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Replied by RT325 on topic 73 MX250 fixer upper- part 2

Its on 3rd oversize now 0.75. You get one more go from yamaha genuine piston kits then have to find an aftermarket kit to get past 70mm bore size.
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26 Sep 2021 03:47 #4

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Replied by hackman101 on topic 73 MX250 fixer upper- part 2

Thanks, I thought that was what the 75 may have been referring to. Since the cylinder still has visible cross hatch, I would like to presume this was a recent rebuild, speaking of hours on the motor. I will check the tolerances to se sure, since I have it in this state of disassembly
1964 Honda 50cc C110
1960s Yamaha 65cc scooter
1960s Honda 65cc w/ 90cc engine mashup
1971 DT1-E modified to MX kinda...
1973 MX250
26 Sep 2021 08:56 #5

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Replied by hackman101 on topic 73 MX250 fixer upper- part 2

Today I managed to get the right side cover off and the forks from the triple trees removed. The fork seal replacement almost looks like a no-brainer, once I figure how to get the seals out. The Clymer book I have covers 2 different kinds of forks, and I think these seals are retained by a circlip. I cleaned one tube up a little where the seal is but it wasn't obvious, since there was crud and corrosion, besides getting late.

Earlier after I had the side cover off, which by the way, very glad I am going this route.... so far.... is that the clutch compartment had some unsavory white stuff in the bottom. I don't know what it could be, but it needs to go.

  

Wanting to proceed farther since the clutch was the next thing to remove, I did contrive a way to keep the whole thing from turning while removing the nut. Or at least attempt to remove the nut.

  

I imagine it may be barbaric to some of you, and I only tried for a short while, seeing how tough the nut is going to be to remove, I held off going any farther until I got some feedback from you guys. I did tap the ratchet with a hammer a few times. Nothing is broke.

I know there are tools out there that will do what I need, and I could rent one if the local auto store (O'Reillys). What to call it, I would not know.
1964 Honda 50cc C110
1960s Yamaha 65cc scooter
1960s Honda 65cc w/ 90cc engine mashup
1971 DT1-E modified to MX kinda...
1973 MX250
The following user(s) Liked this Post: Sneezles61
26 Sep 2021 18:42 #6

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Replied by Hammer on topic 73 MX250 fixer upper- part 2

Hackman101,

Try using a clean rag between the clutch gear and the gear on the crank, it'll do the job without breaking anything.  Also, when you are done with the restoration, think about adding an 8 oz. brass weight to the rotor shaft; it will make the bike MUCH more tractable and less prone to stalling. They have so little flywheel weight, it was easy to unintentionally stall the bike under hard breaking, etc.   A picture of mine is below.

Hammer 
Who, More than Self, His Country Loved.
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26 Sep 2021 19:35 #7

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Replied by hackman101 on topic 73 MX250 fixer upper- part 2

The rag is a great idea. I have a wood shim in there now. My biggest concern was keeping the inner and outer part of the drum steady while trying to break the nut free. I think I will need to adjust my approach on that. Lower it more so I can get more leverage on the ratchet with a pipe extension, instead of using a hammer and the shock it generates through the drive train.

By the way, how would the brass weight be added to the rotor. Balance would be a issue for sure if not done properly.
1964 Honda 50cc C110
1960s Yamaha 65cc scooter
1960s Honda 65cc w/ 90cc engine mashup
1971 DT1-E modified to MX kinda...
1973 MX250
Last edit: 26 Sep 2021 20:48 by hackman101. Reason: Added more info
26 Sep 2021 20:43 #8

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Replied by RT325 on topic 73 MX250 fixer upper- part 2

Rag won't stop the center with nut turning once the plates are out but ok to undo the crank nut except i use a reasonably thin piece of alloy in between the gears to bite on. There's a special holding tool for the clutch center. But here's a thought i've never tried but if you stacked some of the plates back in going normal steel fiber steel etc & stack in as many as your vice grips will spread to & starting & ending with a steel. Then two sets of grips squeezing them together in between opposing drum fingers. Then your alloy in the crank gear & should hold. Alloy underneath crank gear not on top to undo clutch nut as the clutch turns backwards. Stack the plates as far towards the back that your clamping tools will allow as finger will be stronger. I had one steel & one fiber screwed together for one of my smaller motors & worked a treat every time so might only need a minimal number of plated to squeeze. Seen fingers broken using the tire lever idea but i know you're being careful showing us. If you had an air impact rattle gun or an electric one it'd come off holding the center by hand with a rag or a good glove.
Last edit: 26 Sep 2021 21:35 by RT325.
26 Sep 2021 21:31 #9

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Replied by RT325 on topic 73 MX250 fixer upper- part 2

Here's a trick. Bit hard on the spring posts but at least you have 6.
26 Sep 2021 21:40 #10

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