One other thing. The bike is stock, apart from a D&D pipe. At least, as far as I know.

 

are you running on one cylinder?

 

The first time the problem started, after the oil change, it jumped between two cylinders and one. This time it ran on both cylinders, just very rough, until it died for good.

 

Sounds like a fuel related issue to me as well.

You could pull the plugs and see what they look like. You could be starving for fuel (light color) or dumping in too much (dark/wet).

Definitely check the tank and filters/screens, but I'm thinking the carbs need to come off and be gone through.

If you want them gone through, cleaned, rebuilt, adjusted and looking/working like-new, talk to Gordon at www.customcarbservices.com.

He will make sure they are right, so you can cross that off the list.

 

Sounds like a fuel related issue to me as well.

You could pull the plugs and see what they look like. You could be starving for fuel (light color) or dumping in too much (dark/wet).

Definitely check the tank and filters/screens, but I'm thinking the carbs need to come off and be gone through.

If you want them gone through, cleaned, rebuilt, adjusted and looking/working like-new, talk to Gordon at www.customcarbservices.com.

He will make sure they are right, so you can cross that off the list.

Thank you. Yes, I think it is burning quite rich. Whenever I rode it (when it was running), my clothes would end up smelling like exhaust/unburned fuel. Thanks for the customcarbs intro. When I bought the bike, the PO also gave me an extra set of carbs. I can send those to Gordon immediately, and remove and inspect the existing carbs myself.

 

Pull the floats and make sure the need and seat aren’t stuck or sticking


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Good point. I hope you're right. That would be an easy fix.

 

every time my gen one acts up, it gets carbs cleaned. I always find the idle jets plugged or nearly plugged. I also just replaced the choke cable, that was broken at the y section, as well as the little fitting that the choke cable end goes into on the front carburetor. I believe they were allowing air to leak past due to the nature of the breaks. The choke has never worked right, but does now!. Bike runs like a top again. Just went through this same problem for the third time in about five years with my 2001. We don’t have a good source for ethanol free gasoline here, and I have many bikes. The fix is to ride the bike, and not let gas sit in it. Anyway, I know this now, and will just do annual carb cleans from now on. I’m betting your idle jets are dirty

 

I'll check that and get back. Thanks.

 

It sounds like a fuel issue but given the problem is intermittent, it might also be carbon-fouled spark plugs due to burnt oil (a common problem on old two-strokes) from the oil overfill. Was there lot of oil in the airbox?

If the plugs are fouled, do not clean, replace them.

 

Not much oil in the air box, just heavy residue. I bought some new plugs, which I will install this weekend. Thanks for the advice. And yes, I am old enough to remember the two strokes, having raced them for years.

 

I'm breaking it down this morning to replace the plugs and clean and rebuild the carbs. Here's a few interesting tidbits I found thus far. I'm using ziptech800's guide titled "Dangers of a Lo-Carb Diet" (which is fantastic) to remove and clean the carbs. It would be nice if the pics and links worked, but I can't complain. One of the things he stressed when removing the airbox was to remove the hoses from the "PVC" oil condenser to the base of each cylinder is a certain way. Specifically, he said remove the rear hose at the condenser (at the top), and remove the front hose at the cylinder base.

I was surprised when I found my front hose was completely removed from the base of the condenser, just hanging there. The coil area was also oily, I guess from oil coming from the unhooked hose. I don't know if this would cause the bike to run erratically, but maybe so.

 

Next I unbolted the radiator to give me room to remove the front spark plug. When I pulled off the plug cap I found that the rubber boot between the wire and the cap was cracked. And I had a hard time unscrewing the cap from the wire. When I finally pulled the wire out of the cap I found a strange white substance at the top of the cap. It looked like someone tried gluing the cap to the wire. And at the end of the wire I could see no copper. Maybe this was arcing. Don't know.

 

Plugs look black and sooty. The rear one especially. It also has oil on it. As I mentioned earlier, I thought the bike was running rich because I smelled like unburned gasoline after I rode it. For anyone who's turned a wrench or two, you know the smell of an engine running rich. Maybe this was an issue, fouling plugs (or a symptom of carb problems). Now I am preparing to pull the carbs.

Also, I removed the gas tank to check the petcock filter and inspect for rust. The petcock filter was perfectly clean, and no signs of rust in the tank. Oddly, I hear something rattling around in the tank. Will check that later to see what it is. Right now I want to tear into the carbs.

 

Looks like you are hot on the trail, Geo. Those plugs are BLACK.

 

My thoughts exactly. I found some other weird stuff too (cracked fuel line, buggered TES diaphragm, etc.), but I'll get to those in the morning. No much gunk in the carbs, surprisingly.

I'm still trying to find the front plug drain hole. Don't know where to look.

 

Yup. Fouled plugs at least.

Look on...I think the left side of the cylinder head. It's about a 3mm hole.

 

Oh crap, I was looking down the plug hole. Thank you.

 

 

Your OTHER left, GC! 🤣

 

No, but I am going to Home Depot this morning. I can pick one up. Why?

A test light that is.

 

A test light that is.

Shit! Nevermind, I was reading the quote in your signature. Too much wine last night.

 

TES diaphragm pinched, and fuel line cracked.

 

When I was removing the carbs last night, I marked a hose "front carb vacuum hose". Now I cannot figure out where it goes. I know it does not go to the sync port at the base of the front carb, because it has the rubber cap on it. Any ideas?

 

When I was removing the carbs last night, I marked a hose "front carb vacuum hose". Now I cannot figure out where it goes. I know it does not go to the sync port at the base of the front carb, because it has the rubber cap on it. Any ideas?

 

Haha, if you don't have one, it is a great, inexpensive tool to have, but yes, that is my signature. I'm often trying to help people diagnose their bikes here but a lot of the time people don't have a test light or multimeter or they have a multimeter but are not confident using it.

A test light is 100x easier to use than a multimeter, and cheaper, so to try to save myself from explaining how to use a multimeter along with how to use it to test, I recommend the test light.

 

i've never used it to sink, so i removed it and put the cap on the sink port

 

The vacuum hose on the Rear carb pulls the Petcock valve open to allow fuel through and can be pulled off when required for Carb-Balancing. The front Vacuum spigot just has a cap on it that is removed to allow a tube from a Carb-Balancer when required and then put back on.

If you don't have a cap you can make one out of a bit of fuel pipe and block one end with some RTV or even a bit of twin-pack epoxy or similar

The short vacuum hose on the fuel pump side operates the Fuel pump and assists fuel flow.

 

The vacuum hose on the Rear carb pulls the Petcock valve open to allow fuel through and can be pulled off when required for Carb-Balancing. The front Vacuum spigot just has a cap on it that is removed to allow a tube from a Carb-Balancer when required and then put back on.

If you don't have a cap you can make one out of a bit of fuel pipe and block one end with some RTV or even a bit of twin-pack epoxy or similar

The short vacuum hose on the fuel pump side operates the Fuel pump and assists fuel flow.

Yes, the vacuum hoses at the base of the carbs I am familiar with. When I put the carbs back on I have a capped hose on the front carb and I installed a T in the vacuum hose between the base of the rear carb and the petcock, for ease of syncing. The two vacuum hoses I'm referring to are the ones you identified in the picture you attached. They are near the top of each carb, on the righthand side of the rear carb and the lefthand side of the front carb. They look like they port to the TES.

In the above diagram I outlined the two lines in red. Mine are simply open.

 

This has been quite the trilogy. I zipped everything back together yesterday, and the bike fired up after finally getting fuel. The idle was around 1,300 and all seemed well. I went for a test ride and the bike ran flawlessly. In fact, I noticed it was no longer jerking at low RMP. Previously, when I ran through my neighborhood at 25MPH in second or third gear the bike would pulse, like a built V-8 loping. I thought this was normal, and it sounded pretty cool. On this test ride, the loping was gone, and the engine purred like an inline four.

I rode for about 10 minutes, low RPM, high RPM, various speeds, and the bike ran wonderfully. Then it didn't.

Shortly thereafter, at a stop sign I noticed the idle had risen to around 2,500 RPMs. Then the loping returned. Then the throttle began to bog. Then I lost one cylinder (don't know which, I was trying to get home). Finally, the engine died about a block from my house. All of this occurred gradually, from the initial high idle to the stall. In all, it took about 2 miles at around 25 MPH to die. Fuck.

It was doing the exact thing it had before I cleaned/rebuilt the carbs. I tried firing it up after it died and it would try to start (choke on or off), but would not make the final jump to running. All of this crappy running until dying began last week after I changed the oil (which is odd in itself). But after I cleaned the carbs, it ran better than it ever had (until it died).

I also found a bunch of other things wrong when I had it apart for the carbs. I realized fixing them all would've not allowed me to identify the source of the problem, once I've fixed it, but I did not care. I simply wanted the bike to run.

Here is everything I did/found when I had it apart:

• Pulled off the petckock to inspect the filter. It was perfectly clean.
• Replaced the spark plugs. They looked black, oily and fouled, especially the back one.
• When I removed the front spark plug cap, the wire to the coil fell loosely out of the coil. It was not securely screwed in. The cap was also cracked. I had an extra new front coil, so I installed that, along with the cap and wire.
• Cleaned the carbs and used K&L rebuild kits. Both carburetors were almost spotless. I could not find any gunk in any of the ports. This surprised me.
• Both carbs had obviously been worked on because the pilot screw plugs had been removed. Each was set at 2.5 turns out. Also, the jets were stock, 137.5 and 15. And, the jet needles were in stock order (washer, e-clip, donut), and the diaphragms were good. When I put them back together and lifted the pistons, they took a half-second to settle back in so the diaphragms were working.
• I did notice the TES diaphragm on the front carb had been pinched when it was rebuilt the last time. So I replaced that.
• Also, the short fuel hose between the carbs was cracked, so I replaced it.

All in all, I found a few things wrong, so I expected (barring my doing something wrong) the engine to run better when I buttoned it up. Like I said, it did, and then it went to crap. I will try firing it up this morning, but I don't expect it to start. It is doing the same thing it did when I took it apart, so I don't think it is a heat issue. The first time it did this it was still cold; this time it was 10-minutes hot. Same thing.

When I first started it yesterday, I did notice it still smelled like it was running rich. I pointed this out in another post that it smelled rich (pre-carb rebuild). But, everything I found was stock, so I don't know why it's running rich. I will pull the rear plug this morning to see if it looks fouled. I don't have time to pull the front this morning. I will also pull the air filter and spray starting fluid into the carbs to see if it will fire.

Still I'm puzzled. The motor is getting all the things it needs to run, but no run. Crap.

 

check the plugs. they might point you in a direction as to which cylinder

 

Yep. I expect black.

 

Rising speeds from idle can be an Air-leak into the carbs. Spray some Carb cleaner/WD40 around the carbs @ idle. If it rises there's a leak. Make sure the rubber carb seals from inside the air box have not got malformed on refit.

 

Thanks. I can't spray the carbs because it won't run. I checked the airbox seals, and they are properly seated. The problem is intermittent, so I don't think it is a fuel issue directly. Indirectly the rich fuel may be fouling the plugs. Otherwise, sounds like ignition issue.

 

This morning I pulled the rear plug, and it actually looks good. I expected heavy fouling.

Recall, I replaced the plugs yesterday, so this plug only has 10 minutes run time. But I expected more oil and soot. Back to the drawing board. I will try to fire it up later this morning, possible with some starting fluid.

Because the problem is intermittent, it is sounding more (to me at least) like an ignition problem. Weird stuff going on.

 

Just to put a thought in your mind, if the bike is misfiring that means the fuel is not being ignited, so that air/fuel charge will be expelled on the next exhaust stroke. It will smell like fuel. That doesn't necessarily mean it has a AFR issue (like rich or lean) just that there is fuel not being burned.

 

That's a good point GC. Meaning it's not necessarily ignition. But the smell of unburnt fuel is all the time, not just when it misfires. Once it starts misfiring, it's cooked. It's going to die soon, and it is not going to fire up again unless I change the oil, or clean the carbs, or change the plugs, or some other shit. Maybe it will restart if I add air to the tires. Who knows.

 

Okay, I just tried starting it. It would not start. Simply spinning the engine with a few fires here and there. For grins I shot some starting fluid in the airbox (filter removed), and the bike started. It ran very roughly, SV325ish, but it started. Scared the crap out of me because it's loud as hell without the filter in. Nevertheless, this is the first time I was able to start it in all three times it crapped out, without changing something (oil, plugs, carb, etc.).

If anything, it is progress. This seems to narrow it down to a fuel, rather than ignition issue. Thanks golden chicken, straticus, TeeRiver, Mad8V, JayV, and all others for your advice.

Oh shit! I just realized the rear plug is still out. I took it out this morning to look at it, and did not put it back in. I just started my f--king bike without the rear plug in. No wonder it was so f--king loud. No wonder it sounded like it was missing a cylinder. This is hilarious, but sad. Something tells me I should leave mechanic-ing to the professionals.

Anyway, I think it is progress. I've got to get back to work. But, this evening after my wife and I walk the dogs, and open a bottle of wine, I'm going to see if it will start again with the starting fluid (and with the rear spark plug installed). I'll call it drunk wrenching.

 

Something tells me I should leave mechanic-ing to the professionals.

As a professional, let me be the first to admit stuff like that happens all the time. We just fix it and move on after we realize we screwed up.

 

We have a saying in the Aircraft Painting game.

" It's not how you F**K up, it's how good you are at Un-F**king up ;-)

 

I started it last night, with the help of some starting fluid squirted into the carbs. It popped and sputtered, and while it was warming up on choke the front carb would pop, releasing a puff of vapor. It did these single, distinctive pops about every five seconds. And it was only the front carb. After it had warmed I released the choke and the popping pattern stopped. But the motor still ran very rough. Here's what it sounded like.

The pattern that it has followed is it will run like this for a minute or two, then it will start loosing a cylinder, then it dies. Then it will not start, except for this time where I was able to get it started with starting fluid.