[CT3 175 Runs Runs but then Doesn't]

Hi all.

When I first said hello in the bar a few weeks ago, I didn't think I'd be posting so soon, and I'll apologize in advance for rambling on.

I have a CT3 that I've shaken awake from about a 30 year nap in my garage, but it's doing something that is really frustrating and I'm hoping someone can help look into the future and tell me what I'll find.

I'll start by saying that I've chemically cleaned all rust from the tank (I believe) rebuilt the carb, replaced the air cleaner, new plug, changed all fluids.

It now starts easily, seems to run smoothly at low to medium RPM (5-6k) or so. The real high end isn't as good I remember when it was new, but I chalked that up to a need for minor tweaks and minor wear and tear (but now I'm starting to think that's a hint of what's really going on here).

I have the shop manual and am just scratching my head at this one so far. About the only think I haven't done yet is stop to replace the crank seals that I already bought because it seems to work OK to start.

Anyway, the story is this:

As I said, it starts and runs OK at first.

Once in a while it stumbles slightly at sustained acceleration after a few minutes. Maybe some scum found its way to the carb? It's only a slight stumble.

It will run fine for about 20 minutes at medium speeds.

Next, after running around the neighborhood for a while, I decided to go on a longer ride.

This requires speeding up quickly from 0-45 to get on a main road at one point because of where I live.

The first time I did this, I felt it miss/lug a bit, bit it straightened itself out and ran better.

However, at 3.5 miles from home, you'd have thought it ran out of gas or someone shut off the ignition, because the engine totally died.

I could then start it easily again and it would idle OK, but would not go above 3k without stalling. After trying multiple kicks with the throttle open a bit, it would sputter once through the exhaust once in a while (lean?) but wouldn't stay running at anything but idle.

I tried to pull the plug, but, idiot that I was, had forgotten to put the plug wrench back into the tool kit.

Now I had the enviable task of pushing 200 pounds of bike back home (mostly up small hills) in 90 deg heat - we're talking fun.

I got the bike home, took a cold shower, and went back outside pulled the plug and it was fouled with a mixture of gas and oil. I cleaned it and it ran fine again. OK, I'm thinking - if I just had a wrench, I wouldn't have had to tempt cardiac arrest that morning.

Next, after making sure I had tools, I went for another ride.

I drive around for a while, it seems OK, so I try yet another longer ride in widening circles around the neighborhood.

After a while I get brave and try the long ride I had tried earlier.

I get the same stumble after max acceleration onto the main road, but this time it dies completely 20 seconds after that.

Stupidly confident, I stop (like I have a choice) and pull the plug expecting to see it fouled.

It looks like it came out of a manual for descriptions of perfect heat range operation - tan color, no soot, no nothing wrong.

I see I have gas getting to carb (changed to clear fuel hose which helps).

I have spark just fine.

Pulling the started plunger makes it not run at all.

I can still run it at idle, but no high RPMs.

I call my daughter (the one I'm planning to ride this with) and she drives over a gallon of water to cool off the engine thinking I have some sort of heat related issue and I splash the engine are so that it's cool to the touch and try again.

No change.

Outside air temp still 90 degrees (ideal for exercise), so I push the bike 2.5 miles home and decide not to go to the gym that day.

Today I am convinced that when I go outside it will start fine, but I'll probably tear the carb apart looking for a clogged main jet maybe.

I could swear that I read about this happening to someone else in this or another forum, but I'll be darned if I can find it anywhere.

Any suggestions?

Addendum:

Of course when I tried to start it today it was as expected. I hadn't touched it since yesterday, it started fine and ran OK. Between 3-5k RPM it often isn't exactly right, but it's not bad either. (It sometimes seems to hesitate and then surges running extremely well.) I drove it around the neighborhood for about 20 minutes and opened it up almost all the way a few times where it ran fairly well. However, this time I wasn't foolish enough to go too far and sure enough, all at once it quit the same way as before, but less than 1/4 mile from home. It will idle OK, but other than a quick burst in neutral on starting if you crank the throttle it would never stay above 3K RPM for more than a second or two. I let it cool down to touch and it's still misbehaving. Spark seems to be OK still. I thought I had found something when the battery voltage was very low (<1V) and I found out that even though I had replaced the battery, the ground connection from the battery to the frame had enough rust on it to prevent charging. I charged the battery for 10 minutes while I cleaned the connection, sprayed the area with WD40 and used a star washer under the terminal, but no change to the situation - it still starts and stops.

I just pulled the carb and there was a small bit of dark brown granular residue in the bowl but no clogs in the main or pilot jet to be seen. I'll have to put an in line fuel filter in there, but finding one that fits comfortably has been a real issue because there's not much room. When I rebuilt the carb, I couldn't find a kit, so bought the main jet O ring and the gaskets individually but didn't replace the float valve and seat because they looked OK (as without a kit were pricey to buy). I was sure to check the float height, which was fine. Oh well. Off to buy some carb cleaner spray (and probably get an adult beverage) before reassembly and think some more...

Any ideas would still be most welcome.

Hi, Have you checked your float height? Many times I get bikes that the float height is set way too low. A lot of times people will go for the floats if the bike starts to spew gas from the carb when it's just time to clean it up. The bike will run ok untill there is a high demand for fuel, the bowl gets dry before anymore fuel can flow into the carb and it can show up as simply as a lean condition at hard accel or wide open throttle position to complete motor stall depending on how far out of whack they are? Just a thought, stu

[CT3 175 Runs Runs but then Doesn't]

Hi All.

First, thanks again for the suggestions and info.

I had most of the day off today, so was able to get some dip and completely disassembled the carb, let it soak, and once it was as clean I put it back on with a new fuel filter (which looks as ugly as sin itself)and fired it up. Seemed to run OK and drove around for about a half hour. The problem was that by the time I got on the road the sun was setting and the temp had dropped to about 80 or below, so I think it's still inconclusive as a fix. (Fact is, I was a bit of a coward and didn't want to to risk pushing it home several miles in the dark, so didn't stress it as much as I might have.)

I did however, find a few things in the total teardown that I missed before - while the main jet nozzle was always clear, I didn't take it out before and when I did this time I noted that there was some dirt in the space between the tube and the wall. The tiny pinholes that were spread up the length of the tube might have been partially blocked by that dirt.

Also, although the float needle and seat were clear, there was a little bit of dirt in there after I removed the seat.

Current situation: it didn't fail, but by next weekend I'll have had time to go on a long enough trip to give me more confidence.

Remaining issues:

The throttle slide isn't really smooth. I neither see nor feel any burrs on it and the carb throat feels clear in the space where it moves, but once in a blue moon it sticks (usually at wide open) which I must deal with somehow. It just doesn't move as freely as I think it should. Any suggestions appreciated.

I want to keep the inline fuel filter, but the one that I have is really too large. Problem is that I did a lot of searching just to find this ugly but serviceable one. All the small ones I saw were in on one end and out of the other, which would bring things too close to the exhaust pipe (plus curving the fuel line without kinking it is not especially easy). Any ideas for a source for one that others have used with a CT3 would be really helpful. The problem is that there isn't much space there and the inlet and outlet have to face almost the same way to get to the carb without issues.

The idle is beautiful, but certain throttle settings are uneven. With a gradual throttle increase it will go through periods of stumbling a little and then marvelous surges where everything works perfectly. It's got about 4.4k miles and the only obvious thing I can think of past the carb is points or timing. I haven't replaced the points because I don't have a dial gauge handy to set timing, but I may break down and buy one unless there's a good way to cheat that. My inability to accurately set the timing (at least with what I already know) also keeps me from removing the points to look them over closely. I did drag a business card through them and pulled out a little dirt the first time, but they show no evidence of arcing because I haven't seen anything there since (which should at least tell me the condenser is good). It's shocking what people want for a set of points these days, but it goes with the territory of restoring old toys, I guess. Any better ideas as to what might be causing the rough spots?

[Lt2 stator compatability]

Hello everybody! I have a question about magneto compatibility. I have a 72 LT2 with a fried mag. it's a 6v system with three coils and 4 wires + neutral sw. wire. Does anybody know if there is another yamaha model that uses this same mag? yamaha parts shows nothing on the LT2 except crankcase a fish. looking at other models iv'e found varying part no's some with two coils some with three. I assume the three coil models are 6v and the two coil are 12v. anyone have a wiring diagram or manual for an LT2 or 3? I think maybe the gt80 would work but would nessesitate swapping bulbs to 12v? Ive had no luck locating a replacement and would rather not spend the $200 on a rewind if there's a compatable part available for a more attracive price. thanks stu

[Yamaha YG-1]

Hello

I picked up what i believe to be a 1964 Yamaha YG-1 on the weekend. I called Yamaha with the serial numbers (Y20864465) and they agreed on the date/model but with some uncertainty.

I would like to make a restoration project out of it, but im not sure where to find information.

Ive searched around and have not seen anything that looks like an official service manual, and to my surprise have not found any dedicated forums or websites for the bike.

Has anyone been through this? owned or restored one?

Any help is much appreciated.

Thanks, Jake