1985 125m

[Bernard3rd]

Hi Everyone,

I added a new wheeler to my co(o)llection. Along with my 85 250R, and 83 185s, I now have added an 85 125M. Is the engine stout and reliable? Are there any areas prone to failure? it needs a little elbow grease and the wheels need a good bead blast and repaint, and the seat needs a new cover. But overall, it is in pretty good shape. Does anyone know what aftermarket pipes are available for this trike?

[ps2fixer]

I suspect the ATC110 pipes would be similar, never researched aftermarket exhausts for them though.

As far as common problems, the ratchet shifter system can be a problem. The bolt used was too short from the factory, and the boss breaks off. Seems the "fix" is to use a longer bolt, and if you know a good welder, add gussets to it. Another issue I see less of is the shifter ratchet tooth breaks off sometimes, I think it's from more shifting abuse than a design flaw. Same basic design was used for the ATC90 and ATC110. Swapping that part out is really easy compared to fixing the broken boss, or replacing the right crank half.

I bought two ATC125M's (84 and 85) and both had this issue.

Related thread with photos of the broken boss: http://www.3wheelerworld.com/showthr...ission-Problem

If it shifts funny at all, pop the side cover off and check it out. If not, then probably not a huge deal (longer bolt wouldn't be a bad idea), just don't force it though the gears or run into stuff with the shifter and you should be golden.

[hippyplz]

I have had a problem with the ratchet shifter system also, dratv use to carry the replacement parts. 90/110 exhaust wont work for the 125m, they mount differently at the head.

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[Bernard3rd]

Thanks for the info hippyplz & ps2fixer.

ps2fixer, can you tell me the part # of the bolt to which you refer?

https://www.babbittsonline.com/oempa...580/shift-drum

I suspect that it is part #16: BOLT, GEARSHIFT DRUM STOPPER ARM PIV 90023-041-000 90023-041-010

If correct, into what specifically does it thread, and if I were to find someone to weld some gussets, to what specifically should the gussets be added.

Thanks so much for the info. I do plan to use this trike to get a fair way off of the beaten path and I'd assume that this sort of failure would leave a fella stranded.

Regards Gents

[ps2fixer]

If the boss breaks, the shifter doesn't return to it's spot, there's a spring wrapped around the boss and presses on the spring loaded arm. Also yea it's #16 in the diagram. It bolts to the right center crank case housing in a boss (raised up section of metal which is drilled and tapped all the way though). The bolt is really short, like 12mm, but the boss + thickness of the metal is like 16mm and it always breaks right where the bolt tip stops. The gusseting is just to add webbing to the boss, so basically the case is flat, with a raised up cylinder, you'd add some wings to it, kind of like the base of a home made rocket if the rocket body is the boss, and the platform is the main crankcase housing.

Funny, 2 of 2 I could find on ebay were broken, one was repaired.

This one was repaired, you can see the welds and such and the fact it doesn't look factory at all lol. Bolt boss is top left corner of the pic.




This one is broken off like all of the ones I've seen broken. They even have a fancy arrow pointing to it. Ironically both are about the same price lol.

[Bernard3rd]

Thanks for the post ps2fixer - this helps. Is this part fairly easily accessible by removing the black outer case on the left side of the 3 wheeler, or is there more to it? Will any other parts come off if the case is removed?

Thanks!

[ps2fixer]

If I recall correctly, it's pretty easy to get at. I think you have to take a couple extra things off related to the shifting, but nothing super deep like you don't have the split the center cases.

[Big G]

Nice find - still has original tires. Must be nice to live in Arizona...from the picture it looks like it's warm and sunny there - even in December! Here in B.C. it's been a month of windy rain storms

[ps2fixer]

Nice find - still has original tires. Must be nice to live in Arizona...from the picture it looks like it's warm and sunny there - even in December! Here in B.C. it's been a month of windy rain storms

RAIN!?! Down here in Michigan we have had a couple inches of snow, it's melting today though lol.

It seems every location has pros and cons, AZ is a great place to buy metal things with little to no rust, horrible place to buy plastic, rubber, or electrical things because of the sun rot. Michigan is a great place for interior parts, but metal rusts like crazy here from the excessive salt on the roads (doesn't apply to ATV's so much). Wiring is hit or miss depending on what it's from and how it was treated. It seems engine wise, down south and in the warmer areas the engines get used till they die. Up here it seems they hold up a bit better, lower temp, better maintenance or something. Of course nothing is idiot proof.

[Bernard3rd]

Yes, the weather here in AZ is very nice from late Oct through mid to late April, but in the Summertime, forget about wanting to be outdoors or working on anything in the Garage. Some people have AC for the Garage in the Summer, but I haven't wanted to have that expense yet...

The 125M is overall nice shape, and that these are almost certainly the original tires speaks to overall low use/miles of the machine. The wheels are fairly rusty but I think that it is more surface rust, and I intend to have them blasted and repainted. My first 3 wheeler was a 1972 ATC 90, and this seems like the most evolved version of that basic platform, so I kind of wanted one. For the price that I got it, I really couldn't resist.

[HondaPilot]

If the boss breaks, the shifter doesn't return to it's spot, there's a spring wrapped around the boss and presses on the spring loaded arm. Also yea it's #16 in the diagram. It bolts to the right center crank case housing in a boss (raised up section of metal which is drilled and tapped all the way though). The bolt is really short, like 12mm, but the boss + thickness of the metal is like 16mm and it always breaks right where the bolt tip stops. The gusseting is just to add webbing to the boss, so basically the case is flat, with a raised up cylinder, you'd add some wings to it, kind of like the base of a home made rocket if the rocket body is the boss, and the platform is the main crankcase housing.

Funny, 2 of 2 I could find on ebay were broken, one was repaired.

This one was repaired, you can see the welds and such and the fact it doesn't look factory at all lol. Bolt boss is top left corner of the pic.




This one is broken off like all of the ones I've seen broken. They even have a fancy arrow pointing to it. Ironically both are about the same price lol.

Greetings from an AZ Newbie,
New to all of this, ATCs, the forum, and having similar issues with my recently purchased 84’ 125M. I have studied every associated post on this site and beyond that the CT bikes that have the same issues. I have learned so much on this site. I appreciate this thread as I too am in AZ and just getting into this to teach my son how to work on machines.

So I started by rebuilding the carb and changing the oil as prescribed, Dialed it in, and got the engine idling well. I was able to get it to shift into first but it would slip out of gear and I could not shift it beyond 1st. When I would try to get it to shift into neutral or 1st the idle would raise and well, not shift. So, like you pulled the right side of the case off only to not only find the boss snapped off but somebody must have removed it and the stopper arm from the case because it’s not possible for it to pass to the other side of the case (unless disintegrated) and there is virtually no damage in side the case.

So with that said it’s at the fabricator waiting for instruction. I have a super tall order, especially for a newbie.

If any of you guys have your case open can you tell me what the length of the boss is and the diameter? The Length I am looking for is measured from the face of the case (where the boss meets the case) to the end of the boss.

I have a spring and bolt on order so that the fabricator can use it as a reference for gussets etc. I was considering using a longer screw with a bushing or bearing in lieu of the short shoulder bolt but with the new fitment i just care about making it last.

At this moment the fabricator and I discussed cutting a piece of aluminum stock to match the diameter of the boss. Grind both the case and stock to receive the weld. Bore it, thread it, and get a long screw to screw the new boss to the remaining threads in the case to hold it in place while welding. TIG weld in shorter runs to control heat.

First I need the length of the boss. But they also know how it’s supposed to work. So we may be able to back calculate if from measurement? I could stack a washer to shim it if I am slightly short? Let me know your thoughts?

I appreciate your input!
Hope this is considered relevant and not a hijack!
A.

[ps2fixer]

The bolt shouldn't need a bushing, it's not much wear for the amount of spring pressure and it's only used while shifting. The boss is the problem. For the height measurement, once you get the arm and spring in, that should be a good reference point on the height. It has a spot on the shift drum it rides so should be pretty easy to identify where it should be at. 100% get a longer bolt, it will tie into the meat of the case and of what I've read, that alone keeps them from breaking, so that + gussets should be a solid fix.

One thing to remember, the crank case is cast aluminum, I'm no expert on welding AL, but make sure whatever route you go, the metals can fuse together well.

It's been a while since I messed with mine, but I think the arm had a bit of slop on the bolt, so even if it was off like 1/8th in it would probably be close enough to work. Maybe make it slightly too tall, then mill it down until everything lines up right, easier to take away material than to add it.

Good luck with the project, might be a solid option to keep an eye on ebay for the right center crank case that isn't broken.

Ironically, the atc90 and the atc110 had a very similar shift system design, however it seems they didn't have the same problem. I didn't check over the 110 engine I have opened too much, but I don't recall any design differences that were clearly the fix/cause of the problem. Maybe the 90/110 had a longer bolt.... nope just checked the part numbers, they used the same bolt, also used in a ton of other machines including bigger atc's.

https://www.partzilla.com/product/ho...bb3aa705756bc0

Here's a diagram of the 125m setup, might be a handy reference point to look at. The spring hooks on the arm, and the other side goes against the crank case if I recall correctly, the center of the spring loosely wraps around the boss but it's also pretty skinny spring, the base could be made a fair bit larger I'd think. The whole design is to make the shift drum move into the correct angle to be in a given gear and to keep it from popping out of gear. If I remember right, the shift linkage system pulls the drum roughly half way into gear, and the spring pushes it the rest of the way which is why it doesn't want to stay in gear with that part messed up.

https://www.partzilla.com/catalog/ho...m-a/shift-drum

Anyway, good luck with the project.

[keister]

it needs a little elbow grease and the wheels need a good bead blast and repaint, and the seat needs a new cover. But overall, it is in pretty good shape.

That is a very nice example of a survivor. Great condition! Those are original tires on original wheels. I wouldn't be breaking those down if they hold air. People pay good money for those. Congrats on this nice score.

[Jim mac]

whats a sign if the boss is broke on a motor sitting on a shelf? I've got a extra 125m motor, id like to see if its broken or not. can you feel it by moving the shifter? jim

[ps2fixer]

About the only thing I can think of is to shift it into gear while turning the output shaft (the sprocket). It should positively shift into gear and shift into higher gears. If it gives a fit, pull the engine over a few times or if it's in neutral, spin the shaft some to help coat things in oil to make it easier since the trans was designed to shift while running. If it won't shift into higher gears, then there's a chance the boss is broken, but also the ratchet system from the shift lever can have one of the teeth broken off too or similar issues with the linkage system. A bent shift fork could cause shift problems too, but I suspect the weak link would be in the linkage system.

If you drain the oil, the cover pulls off easily, you'd just need the gasket to put it back together correctly, so I'd say the best way to check is to physically look at it. While it's apart, a longer bolt would be ideal, but I don't know of a bolt that can be used directly. Maybe a standard bolt and a washer the correct size, or made to be the correct size would work.

It's also worth a mention, this flaw is only in the 84-85 atc125m engine, not the 86 and later models.