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Discussion Starter #1
The other day I broke the TW(87) out. Did the annual carb cleansing( done this one twice before w/no probs )Fired her up 3rd kick. Let her warm up 10min or so, and went on a great 15min ride. I parked it waited 30 min went on another ride and about 2min into the ride she starts sputtering?/cutting out. This seems wierd to me cause if it was the carb it wouldnt have let me ride for 15min no probs. Any help or experience would be greatly appreciated.
 

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Bad gas, some junk coming from your tank and clogging the carb, or you're running out of gas.
 

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Bad gas, some junk coming from your tank and clogging the carb, or you're running out of gas.






yea because if you look closley imto your tank,when your on reserve, you can see gunk in the bottom. my tw did that before i cleaned the tank out.
 

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If you let it sit all winter with E10 in the tank you are getting what you deserve. Over time the ethanol forms a layer in the bottom of the tank with the gasoline floating on top. Fuel preservatives slow the separation, but do not stop it. When you pulled the tank to access the carb, you temporarily mixed the ethanol and gasoline. Allowed to sit for a few minutes, the ethanol will settle out rather quickly the second time around. Result is straight ethanol in the float bowl, which will not run well, if at all, in an engine tuned for gasoline.



Solution is to dump the contents of the tank into a car or truck with nearly a full tank of fresh fuel for dilution purposes--best way to rid yourself of aged fuel in an environmentally responsible manner. Refill with fresh fuel and ride happily.



Best permanent solution is pre-emptive action. When you park the bike, turn the petcock off, hold the bike upright, and run the engine until it quits. Pull the enrichment knob, then restart to drain the dregs. Alternatively, you can mess with the drain screw, but that's usually asking for trouble from a stripped screw head. Fill the tank full to the brim with fresh fuel and stabilizer to minimize condensation. When returning the bike to service, drain the tank into a cage, refill with fresh fuel, turn the petcock on, and go. Much easier to do than messing with a carb cleaning every spring.
 

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... Fill the tank full to the brim with fresh fuel and stabilizer to minimize condensation. ...
You had previously recommended emptying the tank and using a fogging oil spray. Have you changed your mind?



jb
 

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Discussion Starter #7
Ive never used ethanol. This is the same gas that goes in my XT and my boys 50. When I stored it for the winter I drained the carb and filled the tank with non-ethanol gas. I drained the old and put in fresh 91(no ethanol). When I first started her up she ran great. Wouldnt bad gas have been an issue from the start. I rode it 6-7 miles before it started the weird stuff. Ive ran out of gas before, this feels a little different.
 

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... This seems wierd to me cause if it was the carb it wouldnt have let me ride for 15min no probs.
If you don't think it's a fuel/air/carb related problem, what's left? ... ignition and/or spark problem. And if it's intermittent, or only when the bike warms up, it may be hard to find.



You can begin by removing the spark plug and checking for spark (when the motor is acting up).



jb
 

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You had previously recommended emptying the tank and using a fogging oil spray. Have you changed your mind?



jb


I left out the "E0" part. Glad you caught that omission.



Just because a gasoline is sold as 91 octane doesn't mean it isn't contaminated with 10% ethanol. That is a very common misconception. E10 can be any octane. Are you sure you had E0? Did you test for ethanol content?



Tdub acts weird with 91 (R+M)/2 octane gasoline or gasohol. She just doesn't like high octane.
 

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Discussion Starter #10
So last night tinkering I noticed that the sparkplug wire was a tad melted to the head bolt, I taped and ziptied it. Then went on a 10 mile ride no probs. Think this could have been my culprit. Oh yea giant red banner out front of the gas station says no ethanol. Never tried lower octane before, might have to steal some from the tractor.
 

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The higher the octane of gasoline, the slower it burns. Most engines work best with a certain octane fuel, with the octane needed dependent on dynamic compression ratio and thermodynamic characteristics of engine parts. More octane than is necessary can actually reduce engine performance.
 

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Discussion Starter #12
So I tried some of the tractors gas today before we went to the local ride area. TW ran great for the first hour, then back to the same post 1/4 throttle bogging with a lean pop. Let her sit for an hour or so then did 10 laps perfect, sat for 10min fired it up and same problem as before. Seems like an intermittent vacuum leak. I sense a new carb in the near future.
 

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Yikes! A new carb is lots of money. Are you sure the boots are still sealing?
 

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Discussion Starter #14
I did the ol starter fluid around the boot trick. No rev. Other than the cdi, carb replacement would be my next step correct?
 

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Unless the carb body is cracked or broken, it should be able to be repaired for less money than a new carb ($275-300).



And what happens if you buy a new carb, and the problem turns out to be in the ignition system?



I would fully check out the ignition before thinking about a new carb. This may be a time when it is advisable to get professional help rather than randomly replacing parts.



jb
 

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Unless the carb body is cracked or broken, it should be able to be repaired for less money than a new carb ($275-300).



And what happens if you buy a new carb, and the problem turns out to be in the ignition system?



I would fully check out the ignition before thinking about a new carb. This may be a time when it is advisable to get professional help rather than randomly replacing parts.



jb


I agree, jb. Throwing expensive parts at a problem isn't diagnosing. Find the problem, then fix it. Not always easy to do with an intermittant problem. Could be a coil, CDI, spark plug, contaminated gas, plug wire, dirty/broken wiring connctions, rubbed insulation, bad safety or kill switch, etc. I'd do the free stuff first, like clean the filter in the petcock and check the bottom of the tank for water or crud, clean and tighten all wiring connectors, check switches, etc. costs nothing, and you might get lucky.
 

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My shortcut to determining whether you have a spark problem vs. a fuel problem:



I've cut the alligator clips from the end of an inductive timing light and replaced them

with a battery tender plug (You could also hardwire the power leads to the battery) which allows me to operate the light while riding. I put a piece of inner tube around the trigger, then go for a ride. Watch the light when the bike craps out, but leave it in gear with the throttle open as it slows even if it "bucks".



Light flashing steadily along with rpm when bike takes a crap: Fuel problem



Light out or random and/or intermittent: Spark problem.



Everything mentioned in the other posts are potential sources of your problem, and you'll still need to put in the work to isolate your exact problem.



If you don't already know it, '87's are "1 year only" bikes, now approaching 25 years old and use a CDI and charging system which to my knowlege are no longer available from any source. So you'll want to be extra diligent in checking virtually EVERY other component which could be responsible for the problem.
 

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Discussion Starter #18
Thanks Lizrd. Thats a cool technique. So if I find out it is the CDI, am I totally screwed? Or could there be other culprits causing a spark problem?
 

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Thanks Lizrd. Thats a cool technique. So if I find out it is the CDI, am I totally screwed? Or could there be other culprits causing a spark problem?


I developed that method in self-defense after two consecutive '87's gave me fits, CDI's in both cases. That by no means guarantees the CDI is your problem, but at least you won't be chasing a non-existent fuel problem and it will give you a place to start. If it turns out to be the CDI unit yer not totally screwed, but fixing it won't be cheap.



I've converted a few '87's to the later model charging, ignition system and wiring harness which is actually far easier than it sounds, but requires a later model parts bike to be cost-effective. Wrecked or abused complete bikes can sometimes be found for less than the cost of the CDI units alone.



Awhile back someone reported that they had some success using the later ('88-00) CDI in an '87 by dropping or combining one of the wires. I've never done it, but maybe they'll come forward.
 
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