I don't quite understand how any carb, once cleaned, would immediately clog and intermittently kick in with all other things in proper working order. Sounds like some bullhockey to me. I would think there is a greater problem in the fuel system itself (debris or otherwise). That, or the carbs are not getting cleaned in such a manor that the clog is actually being removed all the way. So replacing your carbs is probably not going to solve the greater problem. Dump your tank, pull all fuel lines, and flush that badboy out.

 

Thanks for the reply. What's at the bottom of the inlet tube for the jug? I had the carb off several times. I guess I'll check it tomorrow. If I replaced the carb with a clean one there must not be debri in the carb . I'll try your suggestion and look deeper into the lines I guess. There really isn't much to the lines though. It's like a 6" hose and one 4" gas rail. I blew air through the line with the rear carb float bowl removed and gas blew out thru the little screen filter.

 

Thanks for the reply. What's at the bottom of the inlet tube for the jug?

You mean the intake manifold? Not quite sure what you mean here.

There really isn't much to the lines though. It's like a 6" hose and one 4" gas rail. I blew air through the line with the rear carb float bowl removed and gas blew out thru the little screen filter.

Well think of it more in terms of what is happening, assuming it IS a plugged carb. If they are getting plugged up then you may have a contaminated fuel system. Usually, silt or other sludge can accumulate inside the fuel tank. This comes from bad gas, the environment you're in (sandy/dusty), or if the bike has been sitting for a prolonged period. I would immediately flush out all of the gas from the tank, take a flashlight and check out what's in there. Cleaning that tank is going to be a little bit of a project but not too bad. You can always use alcohol to flush it. Don't use water if possible, but if you do need to flush it with water, use alcohol afterwards to absorb and evaporate it out. Then run a little bit of fresh new fuel in it and rinse it out. There may be better ways, but this always worked for me on vehicles.

As far as the carb being plugged up, if that's really the case it should be very possible to clean it in such a manner than it doesn't continue to plug. These carbs might be prone to clogging, but many people are running them without this problem or Yammy would have recalled them. With that in mind, you should be able to rebuild them in such a manner that they are like new--no clogs. If the dealer told you needed new carbs because they were worn out or broke, that's one thing. I have never heard of anyone replacing a carb because they are plugged up. Maybe something is wedged inside them that cannot be extracted. I'm not sure. However, if you take your time and investigate them, I'm sure you'll figure out a method to get them cleaned up properly. Start with some thin pipe cleaners or some other soft metal or plastic wire to insert into the holes gently and see if you feel any obstructions anywhere.

Take some pics as you go along if you find anything in particular that seems doesn't look or feel right.

 

By changing the carbs and the clog still be present I agree that you should check out the tank. Maybe even check out that liquid liner for it

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If there are any doubts about the fuel line or tank, why not just hook up a temp fuel bag and line and test it out?

Are you using the same jets all along? Those dame jets are hard to clean once clogged. And at $5-8 each I've opted to just replace them rather than spend the time and headache trying to clean them.

Just a thought.


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I will try the temp bag and bypass the filter.
If the tank petcock or any tank issue had a clog wouldn't both cylinders not work right? The front cylinder is working perfectly. Compression, Spark and Fuel.

I have used my old jets and the newer ones too.
From the very beginning I never found one piece of crud in my carbs anywhere. The jets were clean and clear, all passages were blown with carb cleaner. I was certain my carb was clean that is why I took it to Yamaha. I thought there must be another issue.

Now with my newer carb installed, and the rear cylinder doing the same thing, I know I was correct in thinking that the carb was not the issue. I could not convince Yamaha though.

Let's say that an 1/8" piece of debri fell down into the rear hole of the intake manifold.
If this happened is there a place where the fuel funnels to a single point before entering the piston chamber?
Could that be were the clog is?

Thanks for all the feedback guys. I feel like there is no answer and you guys give me hope.

 

Update

OK guys....tried the temp bag and filter pass....no luck.
I've ruled out the carb issue.

I decided that since this issue was started with an electrical problems..here's my recap.

-Replaced battery $80
-Replaced both spark plugs
-Replaced both coils $160
-Replaced pickup coil (attached to stator) $30

After doing all of that, that's when I noticed the rear cyclinder was not working. I assumed that I clogged the rear carb. That's what the Yamaha mechanic said, too.

-Yamaha carb cleaning with advice to replace the carb $250
-Replaced carb $250

After getting a new used carb with exactly the same issue, I ruled out the carb as the culprit.

Here is what I tried over the weekend.

-Replaced stator with new stator and pickup coil $150

That's all I did...it was staring and running on the front carb before I replaced the stator.....now I've got more problems....

Now when I try to start the bike...the engine will not roll over...it's just the starter sound. I also noticed that when I try to start it the battery goes from 12 volts to 10 volts to 8 volts to 6 volts. It drops down to 6 volts within 3 seconds during the startup.

I plan to test the rectifier next. It will cost $100.

I'd love to see if my rear cylinder works now....but....

Man I'll tell you...when I was waiting on my new stator..I thought it will start right up and I will be riding again. With a new problem added to the issue, my emotions are rundown. I am dumping money into my bike for no reason you know? It sucks. I've heard that if the rectifier goes bad, it can ruin you whole system...but I'm not sure.

Any ideas guys?

 

Now when I try to start the bike...the engine will not roll over...it's just the starter sound. I also noticed that when I try to start it the battery goes from 12 volts to 10 volts to 8 volts to 6 volts. It drops down to 6 volts within 3 seconds during the startup.

BTW, a voltage drop during starting is normal. As with voltage being high using a charger. Test the voltage after you start the bike and you'll see it will return to normal.

If you had no voltage drop then no current would be flowing.

 

Man if you're going to drop money just to try and see if something is broke, take it to a shop. You don't have to buy a new part just to test if that was the problem.

It's probably something so simple that a good mechanic will pick it up have it running in no time.

Please don't throw money at it. You will end up pretty mad when it's fixed and you have hundreds of dollars of new parts that don't do you any good.

 

Yeah I hear you...that's what I thought when I had my first issue with the rear cyclinder. My frst time taking my bike into a shop...

I took it to a Pro Yamaha shop. The mechanic said that the rear cylinder had spark, compression and no gas. He said replace the carb $1300. I bought a used one from a running bike for $250 and it was exactly the same issue. That saved me $1050 but didn't fix the problem.

What would've happened if I agreed to let Yamaha put a new carb on for $1300. Would they have taken it back off and tried something else if the issue was still there? It was a risk I could not afford to take.

So I thought maybe the spark is just weak or "not timed right?". That's why I replaced the stator. Isn't the stator a part that goes out often?

That makes sense about the voltage drop....since the engine is not even trying to turn over, the battery should drop pretty quickly from spinning the starter.

Basically after installing the new stator, now I have no spark at all. Both cylinders are out now.

I think tonight I will replace the plugs again (in case the new stator blew them?...at least they are cheap ) and then I'll try to test the rectifier.

 

Ok I have an even better idea to narrow it down. First, not sure on the reason the starter isn't working anymore. However, swap the plug wires around. I don't mean just at the plug side, but both sides. This might eliminate that the wires are the culprit. If the front cylinder stops working, then you know what the problem is.

You can check if gas is being pumped out of the carb with it off the bike so long as fuel is in there. Make sure the carb has some fuel in the bowls and open/close the throttle/butterfly valve. See if any gas is exerted. This should give you some idea if the carb is an issue.

If the stator you bought is bad and no spark is being seen, swap back to the old one for the time being. Also, after you get it cranking again, check to see if you have fuel on your rear plug after you try running it.

If the plug has fuel on it (it should be wet or at least smell like fuel badly), then you probably have a bad wire (I hope).

EDIT: Also, is the starter turning over but the engine is not? This is generally due to a bad solenoid. It's a little electromagnet that kicks out the gear that contacts the flywheel and engages the engine. If the the solenoid is not working, the starter will spin freely and never actually spin the engine. Now, if the starter is not working but it clicks when you hit the start button, exactly the opposite is happening. The solenoid is working but the starter motor is either fried or has bad brushes. You may take the starter off and put it in a vise or heavy clamp on to a table. Then hook up your battery charger to it for a quick second to pulse the motor (set the charger to 'engine start'). If it works properly, check that your starter relay is not bad or the wires aren't loose. If you don't have a battery charger, you can use the actual battery but be careful. If the starter is not spinning it will draw a ton of current as it is experiencing basically a short circuit. This could fry your battery.

One time I had a starter that would do exactly this. Once I juiced it with a battery charger it broke free and started working again without ever giving me a problem. Sometimes the brushes get corroded and have poor conductivity to the commutator. Juicing it and running it for a brief period might clear it up. Also, a good battery charger has overlimit current protection. If there is a short, the charger should kick off. However, they are typically built to withstand high loads and don't use chemical reactions to form their current. They are better to use for juicing IMHO.

GOOD LUCK BRO!

 

Yeah the starter is definitely spinning , there is no clicking. I'll take off the solenoid and check it with my meter. I checked all of the fuses including the solenoid fuses earlier and they were ok.
Thanks for the advice. Good idea about the mechanic by the way. I will likely just take her in when I can. This time ill be armed with more info.

 

The rear plug never smelled like gas. I know .... carb right? It just doesn't make sense after replacing the carb. How could the new carb not deliver gas to the rear cylinder too?

 

If the plug smells like gas, then it is NOT the carb 9 times out of 10. This means you are getting fuel. I would hunt down the spark issue before going to the dealer. If you can swap around the wires and the rear cylinder starts working and the front doesn't, then you got the problem licked.

EDIT: I just re-read the post. Thought it said "Plug smells like gas". Sorry

 

I NEVER use a mechanic and have definitely been in situations that have cost me well over 10x what I should have spent to fix a problem. Either due to a need for specific tools, or due to misdiagnosis. Either way, I throw money at things until I get 'em working. However, now that you have eliminated 75% of the problems, the mechanic should be worried about screwing you on the price for something and quote you what is will actually cost.

On a side note: If you have the money to keep trucking along, you will only acquire more knowledge and tools by fixing this yourself. Next time, it will only cost you a small fraction and save you from the dealer.

 

However, now that you have eliminated 75% of the problems, the mechanic should be worried about screwing you on the price for something and quote you what is will actually cost.

Unfortunately for the mechanic stuck working on a bike that the owner has "tried" to fix, he's going to have to double check everything that has been done before by the owner....because it's been my experience that the problem normally lies in something the owner messed up when he "tried" to fix it. That may not be true in this case.....but if not, it would be rare.

 

Rear cylinder fail

Did you figure out what was causing the rear cylinder to stop firing? My '02 star 1100 rear cylinder stopped. I have a service manual but I really don't know where to start on this project. Looks like some oil is coming out of the intake manifold, too.