1968 Yamaha YG5T 80cc Trailmaster timing problem

THAT sounds more like it, and 33 degrees is "way hot" for that tiny motor.

If possible, try to block the advance mech fully advanced when you set it; it probably goes to full advance before it even gets to 2K RPM, and the "spec" was with it blocked at full advance, remember.

It sounds like progress to me.

 

First, I should have said "to the LEFT of TDC" on the degree wheel. Now here's my report:

With the governor blocked open, I could only get it down to ~25° BTDC at idle and it still ran above 30° revving. I had about a third of the adjusting plate range to play with and moved it all the way to the end.

With the governor starting in the "at rest" position (no matchstick), I think I was close to 17°. I'm averaging, I guess, because it's bouncing around quite a bit.

So I tuned it again and drove it at that setting. No real difference. It was sluggish to accelerate and died after one trip around the block.

Could too much oil be a factor? I put in a half gallon of gas pre-mixed at 32:1 just to be safe until I knew that the oil pump was working. I haven't added additional gas yet. By the way, I run non-oxygenated 92 octane in my cycles, but I've heard that some smaller bikes shouldn't use that high an octane.

Now what?

 

I made an error in my earlier calculation (I forgot to divide stroke by 2 to get the radius of the crankshaft )

-1.8mm is 23.896 degrees.

 

Well, I'm probably pretty close to that with the governor blocked open which is what the manual specifies for dial gauge timing.

Also, wondering if I'm running too rich. Still using the method we talked about with the air screw and idle speed. I know I'm past the 1.5 turns out default setting, though.

 

So...I tuned it again and left the idle up a little higher - about 1500rpm - and added a gallon of unmixed gas to the tank. It seems a bit happier. In fact I was able to ride it around the neighborhood and run through the first three gears and it showed no sign of wanting to quit.

Still has no power. Might be a good time to mention again that I had the cylinder honed and put in a new piston, rings, wrist pin, and needle bearing. Did not crack the case, however.

On the way home, while shifting from 2nd into 3rd (I think), I pulled in the clutch lever and the rear wheel locked up and the bike quit. Not good. Glad I wasn't going very fast. Forced the bike to the side of the road even though it wouldn't roll. I was able to change gears, but I could not get the motor free even in neutral. The lever was very tight. After kind of muscling the bike back and forth and playing with the clutch lever and shifter, I finally got it to release and headed back down the road. The minute I pulled the clutch lever, though, it happened again. Now it seems "half-stuck." It rolls with the clutch lever pulled in (difficult), but not very freely.

MAN, am I getting sick of pushing this thing home!

I did disassemble the clutch when the motor was out and inspected everything. Thought I got it back together properly. Sure seemed like it was working fine. I had put in a NOS push screw because the nylon worm gear part on mine had a couple of cracks in it. Then I followed the manual for the adjustment procedure. Also, I'm running Castrol 4T 10W-40 in the clutch/transmission.

Really bummed out right now because I don't see any way I can take this bike down to my daughter tomorrow. This clutch thing makes me nervous because the bike won't be safe to ride until/unless I can fix that.

 

Dammit, Jim.

No, you can't hand it off to your daughter just yet. Something is clearly wrong, although it may end up being something stupid-simple or a show-stopper.

This is one of the challenges with 40+ year old Japanese motorcycles, they hadn't been at this nearly as long as the British, Germans, Italians or even US. Of the Japs, only Honda had truly "mature" products by '68, everyone else was still in a learning curve.

I'd start by revisiting the clutch. It doesn't sound like the motor is locking up "the motor" it sounds like something else is locking up and since you could shift gears, it has to be between the crankshaft and the transmission. And what could that be? The clutch. Something may have broken or is coming apart.

Let's have a look!

 

We're losing containment! I've got to have THARTY minutes, captain.

Thanks, Fitz. I'm going to give it a rest until I get back next week. Probably a good idea right now anyway.

In the meantime, I am wondering whether this will turn out to be a reliable enough ride for my daughter, especially with me being 5 hours away. I'm sure I can sell it and at least break even if not maybe make a few bucks. We'll see...

In the meantime, though, I called a guy back about an '80 Honda CM200 that would be a nice bike for her, although bigger. I'm going to look at it over the weekend. If it seems decent and I can buy it right, I probably will.

But what do you make of my lack of power on the Trailmaster, at this point?

 

I ended up buying my daughter a nice 1980 Honda CM200T Twinstar ($600) over the weekend and getting that tuned up and ready. Taught her how to ride on Tuesday. That was fun..and funny. We had a good time. All her friends now think she's the coolest.

So I'm back to this problem with the Trailmaster clutch. The picture below is of the inside of the clutch cover. The push screw has a nylon worm gear which you can see. For the photo I removed the adjusting screw that pushes the ball bearing up against the pin in the middle of the pressure plate.



Next is a video that shows the movement of the clutch. Like I said last week, I really don't have any experience working with clutches so I'm not sure if this looks correct or not.

I tried to find a way to embed this YouTube video but maybe the forum administrator has not yet allowed that???

 

Not sure if anyone is still following this thread, but I posted a picture and video of the clutch over the weekend. I'm definitely going to need some help on this one. Not sure If I should be disassembling the clutch at this point or looking at the transmission or what...

Thanks.

 

OK, maybe I'll start with a couple of specific questions: Are the screws that pass through the springs and hold the upper/outer pressure plate to the lower/inner pressure plate supposed to be tightened all the way down? My manual provides no details about that. I tightened them down. However, it seems to me that this may not be corrected, because it allows for no movement of the springs whatsoever. Why have springs at all, if this were the case.

If I'm correct about this, how do I determine how much to tightened those screws? By the way, the springs are all within the specified length range.

Thanks!

 

In most clutches you have the basket which is driven by the crankshaft. Inside it is the hub which drives the transmission.

The hub has tall bosses (4, 5, or 6 of them) that the clutch spring bolts screw into.

On top of the stack of plates is the pressure plate. The bosses on the clutch hub should pass through it. The spring bolts tension the springs against the pressure plate. In every clutch I have ever seen the bolts bottom on those bosses.

But your problem is not likely to be in the clutch. Your problem was it locked up tight and died? Unless you have the lever pulled (IE, sitting at a light) the clutch is locked up - that's how it transmits torque from the crank to the gearbox.

 

Thanks, MiCarl. There are six bosses/screws/springs on this clutch. So they're bottoming out inside the bosses, not locking down on top of them? I guess that would make sense. Should I be able to compress the springs a little by pressing down on the pressure plate with my hands?

And the rear wheel locked up when I pulled the clutch lever in.

Also, I realize now that I put the clutch back together dry and I think I was supposed to oil the plates/discs when I reassembled. Not sure if it would have oiled itself up enough as it ran or not.

 

They should be tight, not sure from the fiche how they snug up.

I doubt if you're strong enough. That screw mechanism has a lot of leverage to accomplish it.

I pulled the fiche and here is how it appears to work:

Plate 8 essentially bolts to plate 2. The springs under plate 8 pull plate 2 toward the clutch boss (6) compressing the clutch pack. When the push screw (15) presses plate 8 in plate 2 moves with it and away from the clutch boss (6), unloading the clutch pack and letting the clutch slip.

I THINK the 6 bolts go into bosses standing up from plate 2. The drawing of plate 2 isn't clear.

 

Yes, that's correct. The bosses stand up on the side of plate 2 that you can't see in the drawing.

Thanks.

 

So here's the latest...

This certainly wouldn't be news to those who know me or have followed my posts over the years, but I'm an idiot, as it turns out. I did not bend up the tab washer that holds the hub nut (#13 in the diagram) in place. Thankfully it doesn't look like there was any damage. I didn't ride it very far. When I figured out the clutch problem I decided not to open the motor. I soaked the friction plates before putting it back together last night, so everything should be solid with the clutch.

I haven't tried to start it yet because, unfortunately, I can't get it into neutral. Could not having any oil in the motor cause this? Doesn't seem like it should, but... I can't seem to get it past low gear up into neutral. I can shift it from what I think is 1st into second and back again.

For what it's worth, I think this clutch or at least part of it may have come off a different model. I suspect that the earlier YG1s and the later G6s and G7s are all pretty close, but I'm no expert. Under the hub nut is a tab washer and below that is another washer with a locating tab that mates with a hole on the clutch hub.

 

Not really knowing what to do next, I decided to put everything back together, start it up, and see what was happening. Clutch feels like it's working but I think there's something screwy with the shifter or tranny. Neutral light is lit but it's actually in gear. Still can't actually get it into neutral. Really bogs down when I try to run it in the lowest gear I can get it into. This time I stepped on the shifter and the motor locked up. It is the motor, not the rear wheel or clutch.

I'm guessing that I need to either examine the shifter - which I think I can do without pulling the motor - or open the thing up and look at the transmission. Any advice? I'm definitely sailing in uncharted waters here.

 

Start with the shifter.

And keep something in mind going forward that might help with your diagnostic efforts:

Constant mesh, "sequential" gearboxes like motorcycles have cannot be shifted through all of the gears without rotating the transmission. You need to have the bike on the stand and rotate the rear wheel, or rotate the countershaft if the chain is off; but the gearbox has to be "in motion" to shift through all of its gears.

 

Hey, Fitz. Thought of you today while wandering around at the MN chapter of the AMCA's annual show in St. Paul. Quite a few old Nortons, as well as some other stuff I've never even heard of. The local VJMCA chapter also had a show going outside. Lots of cool bikes.

Anyway, thanks for the info about the transmissions. I was moving while trying to get it up into neutral the other day. I'll be sure to keep that in mind though.

By the way, I cannot for the life of me find a center stand for his bike. I've had three versions of an eBay saved search running for weeks. No luck.

 

Hard to believe it's been six weeks since I had to put this project aside, but...

I finally got back to it today. Last entry was Fitz telling me I should take a look at the shifter. Here's a parts diagram link for reference.

I pulled and inspected the shifter shaft, arm, and springs but I can't see any signs of wear or parts being broken or misshapen. Dowel pins on the end of the shifter appear to be intact with 4 of them being long (#8) and 1 short (#9).

Can I pull the shifter itself out at this point? Never done this before. Seems like if I remove snap ring #16, that the whole thing might slide out the right side of the bike. I'm concerned about whether the shift forks (3 & 4) will stay in place inside the motor.

Any other recommendations?

 

I figured out that the shifter unit/drum could not be removed without opening the motor. Seems kind of dumb now. I guess I was just trying to put off the inevitable, but tonight I dropped the motor again and cracked 'er open.

Although I don't know how to evaluate the operation of the transmission while holding it in my hands, I have to say that I don't see anything that is obviously broken or worn, and things feel pretty tight and smooth. There is one spot on the edge of one of the main transmission bearings where you can see that the teeth of the 4th pinion gear have been rubbing slightly. Not sure why. It's not actually as bad as the photo makes it look.







Otherwise I'd sure appreciate some input on how to proceed. Here's some more pics.












Thanks.

 

In the very top picture, there appears to be a semi-circular "piece" sticking out from the edge of the large bearings' flange, like a washer was trapped when the bearing was installed? It's right by where the smaller bearing's "boss" joins the larger one. Is that what it looks like, or??? Or is it a "notch" in the outer race of the larger bearing and the photo has me fooled?

 

Thanks for responding, Fitz. Actually, that's the wear pattern I described above where the 4th pinion gear (2nd photo) has been rubbing. That's exactly what I wanted to show.

I just went back out to the shop to better analyze why that might be making contact. Here's a parts diagram of the transmission. Not sure if maybe either the expansion plug (#29) is missing or out of position causing the main transmission axle to sit or move too deep into the bore in the case, or maybe the needle bearing (#21) was driven too deep into the bore...or both?

Then I flipped the case over and noticed this...



Do you think the case has been repaired or is this sealant (it's rigid) related to the "expansion" of the plug as a failsafe mechanism? Or maybe somebody got a little over-enthusiastic when driving in a new needle bearing and cracked the case there. What do you think?

I see three left side case halves on eBay varying in price from $75 (Thailand) to $165. Wonder if I could shim it or put in a second expansion plug...

 

Hey, I love both challenges and old bikes.

We gotta think about this for a few. PM MiCarl and have him join in, and backstop me. 1968 was a long damn time ago.

First "pretty damn sure:" That sealant/epoxy metal repair isn't "factory." I suspect that somebody did something as a substitute for the "expansion plug." The fact that it's called that seems to indicate that the case is drilled all the way through, and said expansion plug covers the hole behind the bearing.

Second "unless I miss my guess" the gearwheel isn't supposed to be machining a "pocket" in the bearing race. But there are two apparent possible issues there (Carl, this is where I need you)
1: the smaller bearing DOES appear to be seated too far into the pocket. Maybe not; but does it locate the shaft? If so then maybe it is.
2: the larger bearing (with the rounded notch burnt into it) probably shouldn't be sticking out of the case far enough to BE attacked by the gear.

I suspect you're following a rather inventive PO. Might explain some of the "suspect" parts differences in the clutch.

My recommendation (WWFD?) would be:

-source the larger bearing; and see if you can extract the smaller one without hurting it.
-source the smaller bearing if you do. (Hurt it.)
-See if you can even FIND the "expansion plug."

Like I said, I suspect our inventor has JBWelded a junction-box slug or something similar in place of the plug he couldn't find, and then hammered the bearing in too far because the much-thicker plug wasn't there to stop it..

Likewise, I'm suspicious of the big bearing standing proud of the case; but maybe that's OK and the problem is all because of the smaller shaft being out of place laterally. Which (lateral misalignment) might cause all sorts of shifting isssues.

Carl???

 

Just sent an APB to MiCarl. Here's what I know about parts...

Both the big bearing and the needle bearing are available. Plus, some dealer out in WI supposedly has some of those plugs, according to my dealer.

 

The needle bearing won't be locating the shaft, it won't carry any side load to keep it from drifting.

Possible the large bearing isn't pressed in far enough. Would think the case would have broken at assembly...

I think we're talking about part #1 in the fiche. They call it a "main axle", but I think it's the input shaft. What keeps it from drifting around? I'm guessing the clutch assembly pulls it against the other case? Loose nut in the clutch letting the shaft drift? (#13 in the clutch fiche?)

Impressed by the heft of the shift drum and forks. You suppose they sourced some spare tractor parts?

 

Thanks, MiCarl. Not that anyone should remember this from earlier in the thread, but I did reassemble the clutch at one point without tightening that nut. Actually, instead of a lock washer (#12) and thrust plate/washer (#14) shown in this diagram, I have a tab washer that is bent up to hold that nut in place. This washer also has a locating tab that fits into the bottom of the clutch boss. I didn't bend the tab washer up so the nut loosened. Maybe all the damage to that bearing race occurred at then. But I remedied that, put the clutch back on, and it still locked on me.

Under that scenario, (that I already fixed the problem that caused the misalignment and rubbing), where does that leave me? What else could cause the motor to lock up?

 

I think I'll try to press that bearing in a little further, then reassemble the clutch, transmission, and shifter and put the case together on my bench to see if I can feel any rubbing.

If I don't, and if the needle bearing has no role in locating that shaft , do you think there is enough benefit for me to mess with opening up that epoxy repair and replacing the plug and bearings?

 

If the bearing is good and the plug doesn't leak I'd leave well enough alone.

 

I think that is probably the wiser decision, if the bearing isn't doing any "locating" and just supports the shaft.

 

Just did a quick reassembly of case halves, tranny, shifter, and clutch. When that clutch nut is tightened it draws the shaft up and out of the "pocket" so there is absolutely no interference happening on the other end. The big bearing was fully seated, by the way.

Is there a way that I can evaluate shifter and transmission operation with the motor on the bench?

 

You can turn things by hand and work the shifter to see if it goes through the gears ok. On a vertical split case hard to see what it's doing while you're working it.

 

Doesn't matter whether or not the crankshaft is installed?

 

You don't need the crankshaft. Just turn the clutch. With the crankshaft out and the jug off you stand a better chance of seeing what's going on in there.

 

I hope you can be patient with a tranny virgin...(that didn't come out quite right).

FYI - This bike has a "4-down" sifting pattern.

As I turn the clutch and operate the shifter pedal, the drive axle of the transmission turns freely in the top and bottom positions. I would have thought that when I'm all the way at the top (neutral), the axle would not be turning. No so? Or maybe this is standard neutral behavior. As I recall, I actually did have neutral positions at both the top and bottom of the shifter range.

In all other positions, the drive axle doesn't turn. It does have a few millimeters of free play, though.

Additionally, it gets "stuck" between gears sometimes. I have to try and wiggle the axle while operating the shifter to get it free.

I think that the shifter drum pins are as they should be. There are four long pins that can be engaged by the shifter arm and one short pin that leaves a gap.

 

The transmission won't shift when the gear dogs aren't lined up. That's why you're turning the clutch.

There will be some backlash.

The output shaft will probably turn in neutral, unless you hold it. There is some internal drag that will have it chase along when there is no load.

I have never heard of a 2nd neutral above high gear.

 

Thanks for getting into this, Carl.

I remember from the faint depths of my youth bikes that had fully sequential shifters; if you shifted past top gear it would go back to first again. I think it was the early Suzuki X6 Hustler, but that was tooooo long ago for me to be sure. Maybe Yamaha had the same quandry and solved it that way. Or a "stop" is missing somewhere.

In the course of "getting stuck between gears" might it be locking up?

If the motor is completely "disconnected" from everything, and you're turning the clutch/input shaft and running through the gears, the output shaft should be turning, but at a different rate as each gear is selected. If not, something's not right.

 

Just looked at the shifter fiche hoping to discern something.

Interesting thing - both shift forks appear to ride in the same track on the drum. Instead of sliding on a shaft the forks have a collar around the drum. Looks really beefy.

I can see though with that arrangement that if the drum was rotated too far you could end up with a 2nd neutral or even two gears engaged simultaneously (lockup!). 8O

 

Sure glad the list is back up! I was starting to get nervous...

Thanks again for your interest in this. I'm wondering if you have any ideas as to what I should do next. Is there any possibility that there's some positioning issue with the other shaft? Maybe I should disassemble the transmission shafts/gears and inspect more closely.

Thanks.

 

First I'd try and shift it through all the gears trying to see what happens above fourth (It looks like a 4 speed). If you can shift past fourth I'd be tempted to open it up again.

It'll take some real patient sleuthing to figure out if there is supposed to be something stopping it above fourth gear and below first. Be a good intro to trannys and shifters!

 

I too looked in the shifter fiche. I'm wondering if said "something" is dowel pin #2, stopping rotation in both directions by running up against a "nub" inside cap #21. I don't see anything else that would stop it; the "stopper lever" #17 looks more like a detent lever to me.

We can see the pin #2 in the pics. Take a look in the cap #21 where the end of the shift drum shaft goes. Is there something that the pin has been beating the daylights out of? Or should be stopping against that's missing?

 

Try as I might to get this looked at before we leave for a week of vacation, I just couldn't pull it off. I'll get right to it when we return, though. Thanks!

 

Hey man, no sweat. Holler when you get back.

 

Hi there baytonemus.
I have a similar 1968 Yamaha. Mine is a YCS1c -- your YG5's 180cc "big brother." I recently completely restored mine, so am fairly familiar with most of its workings. I know these old 1960's Yamahas can be a bit difficult, but they also are somewhat rare and very cool! I registered here on the forum to offer my assistance with your project.

I noticed at the beginning of this thread that you were having difficulty with the timing. One thing to note is that your bike has a timing RETARD, not a timing advance. That might help sort out why it was a little confusing. I recently made a video of me setting the timing on my bike using a dial gauge, which really is the best way to do it. Here's a link:
http://www.youtube.com/watch?v=yjvc4912 ... BUhC6Z4_3g

Our bikes are very similar, so here is a link to my restoration thread... its possible there's something there that you might find helpful:
http://www.2strokeworld.com/forum/index ... ic=13332.0

I'm going to send you a PM too.

Best wishes,
Steve

 

Hi, Steve! Thanks for your post. I've read part of your restoration thread but haven't gotten all the way through it yet. Looking forward to finishing that.

I also watched your timing tutorial. I started by using a dial gauge. Because I didn't have any documentation for the rather old gauge that I have, I wasn't sure about converting dial degrees to mm, so I just measured the amount of movement of the piston down from TDC.

I do have to ask you about the terminology you're using, though. Advanced timing, according to the way I've always understood it, is referred to as a value BTDC and retarded timing as a value ATDC. If you're correct about my bike requiring a retarded spark (and I assume that you are), then my service manual is also using BTDC in the opposite way from what I'm familiar with.

For now, I've gone from being mired in a month-long work project to painting my house. My motor is still disassembled on the workbench while I try to diagnose a shifting problem. Once I get that figured out and have everything reassembled, I'll be able trying to time the bike again.

Thanks again!

 

Baytonemus,
Good to hear from you. I can see how my terminology would be confusing. I was thinking about that after I made my post.
When I say the governor is a timing retard, instead of a timing advance I am referring to;
1. Almost all Vintage Yamaha 2-strokes have static timing -- there is no advance mechanism/governor.
2. On most bikes with with a centrifugal governor, its operation provides a timing advance curve for high RPM performance -- you set the timing with it in the "at rest" position.
3. On these few 1960's Yamaha 2-strokes with the governor, it operates as a timing retard to help with starting -- it becomes fully advanced at a relatively low RPM, and offers little to no timing advance curve; it is more or less either all the way off or all the way on.
4. And, as you know, the timing is set with the the governor at the maximum advanced position -- which represents the normal operating position.

Because of all that, the governors on these older bikes are often refereed to as a timing retard -- namely because their primary design intent was to retard the timing for easier starts.

But in the end, its more or less exactly like all the others. When the motor spins at a certain RPM, the timing gets advanced. Its really a moot point.


Even though I read your thread last night, I don't remember what kind of manuals and resources you have available for your bike.

I recently found some Yamaha manuals online for the late 1960's twins. Someone took the time to scan them and make them available in downloadable .pdf format. I know you machine is a single 80cc, but you might find some info that crosses over to help you with your machine.
http://www.yamaparts.com/manuals/

I am not vary familiar with the transmissions on your machine. Have you found a good parts diagram to show the order of the cir-clips, washers and gears to verify correct assembly?
I often used these guy's online parts diagrams, but have never purchased from them:

http://www.powerpartsplus.com/pages/Oem ... _-_1968%29

Odds are you already have most of this info, but maybe someone else can benefit from it being posted here.

Best wishes,
-Steve

 

Hi again, Steve. In your original post I don't think you mentioned that you were talking about the advance governor, you just referred to timing. I was talking about how the timing itself is set, in which case one would obviously turn the motor in a different direction while setting a point BTDC as opposed to ATDC.

I actually purchased an original Yamaha service manual for this bike. It is full of inaccuracies, unfortunately. My guess is that it was actually written for the YG1, and then just updated (almost) for the YG5. One of the most glaring mistakes is that the specs. indicate that the bike has a 6V electrical system. It's 12V. Minor details...

I also use the online vendors parts diagrams. I usually go to either yamahasportsplaza.com or powersportsplus.com. Thanks for the posting the diagram, though. Best working theory is that the problem is actually in the shifter. We'll see...

Thanks again.

 

I'm glad to hear you have some good resources... its funny the factory manual has such errors!
Can you please let me know if you ever discover a digital copy of a 1967-1968 Yamaha YCS1/YCS1c manual? I'm still searching... and it would seem a pity to purchase a good paper version, only to cut off the binding and scan it....

-Steve

 

That's exactly what I did with my paper manual, actually. I just cut the tabloid-size pages down to letter-size, then scanned and sorted. (I have a scanner with an document feeder and that makes it a lot less work.) Afterwards I put the original back together as a spiral/coil bound booklet and added clear plastic covers.

I'll keep my eyes peeled for your manual.

 

Finally managed to carve out a little time to take a look at this again. The pin (#2) about which you asked, Fitz, is actually inside the case and stops up against a protrusion in the case on the top of the second photo below.





The little button on the side is what makes contact with the neutral switch.

At first I thought that pin might be scraping the round protrusion in the bottom of that photo. There is a little scoring on the upper edge. However, when I hold the shifter in my hands and operate it, there seems to be some drag in certain range of it's rotation. Maybe the bore on one or both of the forks is corroded or a bit worn. After lunch I guess I'll pull the forks off and see...

 

Right.

Just below the neutral switch "button" in the lower photo is a trapezoidal, raised boss.

I'm thinking that the large pin, apparent in the upper pic, is what should stop against either side of that raised boss and thus prevent the drum from just rotating on around. Which is what I believe you explained, above. That should keep the drum from going "beyond" high or low gear.