[Oldad]

This seems to be a familiar problem on the forum, but after searching numerous posting here, I have yet to find one that offered a solution that solved my problem. My appologies if I missed one.



Here's the deal. Bought an 05 dub about two weeks ago. It had sat through at least part of last winter. Barely got it started at the seller's place but bought it anyway. (Not the best decision.)



Anyway, once home, got it to run but mostly with the choke on, and still had trouble keeping it running. Assumed carb dirty, so jerked it off, dismantled, cleaned with carb cleaner and compressed air, reassembled with original parts, installed, ran better, but still had trouble keeping it running. Actually drove it about four miles here around the farm. I also drained all the old fuel and replaced with fresh and installed a new spark plug.



Okay, today I pull the carb off again and rebuilt with an aftermarket carb kit purchased from the local Yamaha dealer. Result: engine starts and idles fine, but when the throttle is opened, it dies as if it is running out of fuel. This is pretty much the way it has always been dying.



At times you can start, open the throttle and it rev's up, but after less than a minute, sometimes seconds, it sputters and dies, as if running out of fuel. Yes, I've check the fuel flow from the tank.



I'm beginning to wonder if my problems isn't fuel.



Could it be that the ignition system is capable of maintaining a spark at low rpm's but breaks down as soon as engine speed increases? Of course, I've run across references here on the forum to problems with older CDI units, but none seems to match my problem exactly.



I did take a look at the coil, testing it in accordance with repair manual. Its resistance on primary and secondary coil did not match exactly the manual's specs, but how far off spec do you have to be to be a bad coil? Primary coil resistance measured 0.5 ohms vs. 0.18-0.28 spec, and secondary coil measured 17.3 ohms vs. 6.32-9.48 spec.



Since it's not exactly in spec, I plan to replace the coil, but may try testing with another multi tester first.



If that doesn't work, I guess I'll look at the CDI unit. How to do that, though, I'm not really sure.



Does any of this make sense? Am I going down the right path? All suggestions would be greatly appreciated.



I hate the thought of taking the dub to the dealer for service, with all of the vast knowledge here on this site.



I got the TW to ride here in the Shawnee National Forest, but so far, all I've done is work on the darn thing. Help! Please!

 

[FortPayne]

It could be the cdi but pretty unlikely. Bike's just not that old.



It screams carb problem doesn't it? So...



Float getting stuck or adjusted wrong? Lets in plenty of fuel for idle but when it needs more there just isn't any there.

Check the carb boots for air leaks. Lean condition would require choke yada yada.

Next, verify the carb rebuild kit was correct. Many times on here rebuild kits cause problems, wrong year or jet size.

The vent tubes aren't clogged are they? Heck new ones might not have them for all I know.

Crank it up, let it warm up 3 or 4 minutes. Can you rev it? How about if you baby it and increase idle slowly? Back off before it dies and try again.



Your coil sounds fine to me. Mine was also out of spec but fully functional.

Before I would buy a new cdi I would swap one out if I had access to see if that clears it up. They're expensive and ya can't really test them to see if they're bad due to the nature of their malfunction.

 

[assquatch20]

I'll second float adjustment, improper jets from the dealer, and clogged venting. Try it with the gas cap off as well, as that's a vent that can get clogged. If it's a Cali model the tank vents differently, but the procedure to check is the same.

 

[rbm]

Did you remove or replace the pilot jet? Mine acted the same way you're describing, the pilot jet was partially blocked.

 

[Oldad]

Did you remove or replace the pilot jet? Mine acted the same way you're describing, the pilot jet was partially blocked.

Yes, the kit did include a new pilot jet. And it had a new air idle adjuster which I changed out too, after pulling the aluminum cap off the old one. I noted that the original adjuster screw was only backed out 1 1/4 turns, but I set the new one at 2 1/2 turns per recommendations on this forum.



If anything the float was set slightly low. But since the carb is inverted when this measurement is taken, would that not result in a slightly fuller bowl?



I'll check for venting as well, but it seems like it would take quite a while to create a vacuum in the fuel tank, for no more fuel is being drawn.



It's raining all day here so I might as well go back into the carb again today. I'll try to check out all your suggestions.



Thanks so far.

 

[Leisure Time Larry]

Did you change out the gas? If it's over a month old, change it out and use some fresh stuff. Also, make sure you installed all of the carb parts properly. I lost the silvery nozzle that goes under the main jet holder once. Ran fine at idle using the pilot jet, but once I gave it throttle, it ran like crap and died.

 

[Oldad]

lrppcer,



You nailed it. I didn't leave the silvery main jet nozzle out. I just put it in the wrong place.



Went ahead and adjusted the float and put the nozzle in right. Fired right up. Runs like a champ.



Thanks to everyone that steered me back on course. You guys are great!



Jeff Jones

Shawnee National Forest, IL

 

[Oldad]

Actually, I was a bit premature on that celebration. Idle problems persisted, but finally resolved yesterday.



FINALLY. It's fixed. Hallelujah! After removing, dismantling, reassembling, installing the carb four more time last evening, I think I figured it out.



Assuming I still had a passage still blocked on the carb somewhere, I was going to tear it down again for another cleaning and inspection, but at the last minute I thought I ought to recheck the float level. I'd checked it before with the clear plastic tube connected to the float drain, but had considered that my symptoms might be caused by low fuel level in the bowl. Hooked up the tube again. Opened the drain screw and low and behold the fuel level came up about 8mm lower than spec.



It took four tries but finally got the float set right, or at least right enough. Each time I'd try to set the float height with a caliper, then install and check again with the clear tube method. It's not as easy as it seems it should be. I'm still a bit confused by the instructions regarding when the "float needle contacts the seat but does not compress the needle spring". You definitely cannot just turn the carb upside down and measure. The needle spring will compress for sure. I had to tilt the carb more than 45 degrees for the needle to contact the seat and still not compress the needle spring.



Anyway, since then, she fires up, idles smooth and seems to have more power at all speeds.



I know this account does not lend great insight into carb adjustment, thought I'd pass it on anyway, considering the number of carb tuning inquiries posted here.



I guess my advice is: Be thorough. Check everything.



Oh, and one more revelation. If you put in a new idle air adjuster, be sure to use the right size o-ring ahead of the steel washer in front of the spring.

 

[TomGleinser]

I had the same problems exactly after a few months of light use. I thought the carb might be gummed up with Ethanol so bought a new carb since the bowl is not removable. It is riveted together. I'll have to drill out rivets, I guess. The new carb ran fine for about 20 minutes and then went back to idle only with choked fully. Push in the choke it dies, give it any gas, it dies.

Thanks for any help.
Tom

 

[Tweaker]

Tom your problem sounds like dirt or junk getting into the carb. Did you drain and flush your tank? Do you have a fuel filter between your tank and carb? I ordered some 90 degree filters to put on my bikes because I found a small particle in my pilot jet along with bad running from old gas.

I had the same problems exactly after a few months of light use. I thought the carb might be gummed up with Ethanol so bought a new carb since the bowl is not removable. It is riveted together. I'll have to drill out rivets, I guess. The new carb ran fine for about 20 minutes and then went back to idle only with choked fully. Push in the choke it dies, give it any gas, it dies.

Thanks for any help.
Tom

 

[Tweaker]

Oldad congrats on hanging in there and solving your problem and to the forem for all their assitance.

 

[littletommy]

Welcome to the forum!!

Riveted carb bowl? Tell us more please. What year bike do you have etc?

I had the same problems exactly after a few months of light use. I thought the carb might be gummed up with Ethanol so bought a new carb since the bowl is not removable. It is riveted together. I'll have to drill out rivets, I guess. The new carb ran fine for about 20 minutes and then went back to idle only with choked fully. Push in the choke it dies, give it any gas, it dies.

Thanks for any help.
Tom

 

[TomGleinser]

Yep. it has a fuel filter between the tank and carb. I changed it although the old one looked clean and gas freely flowed through it. Thanks.

 

[jbfla]

I had the same problems exactly after a few months of light use. I thought the carb might be gummed up with Ethanol so bought a new carb since the bowl is not removable. It is riveted together. I'll have to drill out rivets, I guess. The new carb ran fine for about 20 minutes and then went back to idle only with choked fully. Push in the choke it dies, give it any gas, it dies.....
Tom

What carb do you have?

Stock TW (Teikei) carb bowls are not riveted on.

jb

 

[jtomelliott49]

Congrats Olddad. You are to be commended for your persistence. I am super stoked that you have cured your problem. And Tom, you will solve your problem as well. This group of gearheads will steer you through this.

 

[DanBarwick]

Ok, I'm next in line for a miracle cure.

History: I have a 2006 that was hard to start, but then ran fine. Folks on here suggested a clogged pilot jet. I ordered the carb kit from pro cycle and installed the new pilot jet. Now it will only start if I give it gas while starting. Won't idle at all - dies as soon as throttle is released.

I've gone from bad to worse. Ideas??

 

[DanBarwick]

Follow-up: I decided to take the carb apart and have a look.

One thing I found was that the pilot screw appears to have no washer or O ring. Is it possible those things are stuck in the recesses of the hole? I didn't want to go digging around in there if they just typically fall out.

 

[littletommy]

That's probably what's causing your latest problem on the bike. O rings can do that, usually no, but sometimes, yes. You better find it. Put on a new one and re install.

 

[DanBarwick]

Thanks - how the heck can I find out the size of the washer and O ring if they weren't there?

 

[DanBarwick]

Follow up question: is it possible that my O ring is simply at the bottom of the idle screw channel? I can't even see in there very well with a flashlight, but it looks like there may be a dark ring down there. Does friction hold it firmly in place, by any chance?