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Discussion Starter #1
Recently got an XT350 gas tank. The fuel valve works very hard and since it is around 20 years old I thought I would just replace it.



Looking at it on the bottom is a plastic plug with a square top that unscrews from the bottom of the valve opening a port into the gas flow lines.



Any ideas what the purpose of this was?



Maybe just a simple way to drain some fuel?
 

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Nope. It's a built-in fuel filter. Inside the bowl there's supposed to be a removable, cleanable bronze screen. Anything the screen missed settled into the bowl and never made the pilgrimage to your carburetor.



Deleting those from virtually every petcock now made was a visionary and remarkable bit of social engineering foresight, and the first of many such "improvements" which later lead to the prevailance of carb cleaning threads in the computer age. This in turn has brought us all together with a common misery. Ergo, dirty carbs have brought together persons of vastly disparate backgrounds, faiths and nationalities who may not have otherwise met. How cool is that??



Cumbaya.
 

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The good news is that your TW petcock will bolt right up. Kinda leaves you with a pretty short reserve, though.



My 350 tank uses the modern replacement valve for an XT600. Little longer reserve tube, but otherwise identical to the TW replacement item. 15 bucks or so.
 

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Okay Russ, I've heard you say that the xt350 tank (or is it the petcock too) has a very short reserve. Having never run mine far on the reserve, I've no idea how shallow that reserve is. Is it that there is much of a gallon that is not reachable when the xt350 tank is mounted as we have done on the tw200, or is it that there is not much gas left when the main kicks out and you have to switch to reserve. As I remember, the one time I hit reserve at 184 miles (after much full throttle and a head wind so probably getting less than my typical 85 mph), I still estimated my having something like a gallon on board. So was it not available to me, or is my tank geometry slight different and potentially I really don't have the 40-80 miles I would like to think I have beyond the 184 miles I used on the main (180 + 60 or so = 240 miles or more). Inquiring minds want to know and be forewarned, your prognoses will be tested by a herd of xt350 tank users. Thanks and cheers to the very tolerant Mrs. Lizrdbrth. Tom

BTW Its my impression that petcocks that are tight to turn are merely tightened too tightly with the 2 or 3 screws that attach the face. I experienced one that was too tight after I rebuilt it, and found it easy to loosen without causing any problems with leakage. Before the OP replaces the valve, I'd try to adjust it. That said Russ is correct, the entire petcock assembly is cheap and its also true that the xt350 and tw200 have the very same part number for the petcock (when I last checked on Bikebandit). Sometimes the entire part is cheaper than even half of its constituent parts (I paid over $11 for a couple of gaskets and o rings to go in a petcock that was $16 for the entire unit - go figure. Tom
 

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Tom, I think it will vary a bit with our various installations and mpg numbers. The rear of yours sits a bit higher than mine, so theoretically you should have less fuel available at the petcock than I when you hit reserve, but you're getting far better mileage. On level ground it takes very little difference in tank angle to affect how much remains in the tank at reserve. Again, theoretically you would have a bit more unusable fuel hiding in the "ears" of the tank, but you get nearly 15 mpg better than I.



I figgered with a 3.2 gallon tank I could afford the luxury of a 75 mile warning, so I went with the longer petcock tube.



The only time I've ran mine dry was when I made the beginner's error of leaving the petcock on reserve after filling up. I usually hit reserve somewhere between 150-160 but I never push it.



I used a bit of a misnomer when I refered to the reserve tube. It is in fact the main tube which determines the point where you hit reserve. All the reserve pickups are pretty much flush with the bottom of the tank, and the various replacement items are all identical except for the length of the main pickup tube.



Removing the crapcatcher feature was just stoopit, and required new tooling, to boot.



My version of the justification for doing so is more entertaining and optimistic than the actual justification, which reads as follows:



"Damndest thing. We go cheaper incrementally, year-by-year, yet charge more, and they keep buying our stuff anyway. Go figger."



Humor me for mourning the passing of things that actually served a valid purpose
 

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Discussion Starter #7
Yes I know my TW200 valve will fit. And I know a new valve is available for about $14 and the repair parts even less.



I already ordered a new valve.



Just was wondering what the different shape and the drain plug on this one was for.



Unfortunately the brass filter screen was not in place in this one. If I get a chance I'll post a picture.



Looked at various year fuel valves but never saw anything different than what is on a TW.



BTW - Got the used tank for $50 + $15 shipping. It is spotless inside and not to bad on the outside. The seller did a great job shipping and the $15 was a deal.



Looks like he spent more than that on box, wrapping and foam.
 

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Discussion Starter #8
Maybe to many people were breaking the plastic plug so they got rid of it.



To bad. I would like to find the filter for this housing.







 

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One of the first motorbike mechanic mistakes i made was breaking one of those little bowls on the neighbors' bike trying to remove it.


I guess I thought i could fix everything when i was 14...

Come to think of it, a lot of seriously old motors had a settling bowl inline with the fuel line.
 

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Nice score on the tank. Its a real game changer after the 1.8.



Almost all of the smaller Yamahas use the same petcock now. The longer of two tubes that point up into the tank is the main tube. Once the gas gets below that tube it goes dry and then you switch to reserve until the shorter tube can no longer pick up fuel.



The only difference between the various petcocks is the length of the longer of the two tubes. So Ronnydog's TTR petcock, my XT petcock, your TW petcock, a YZ petcock etc. will all fit, and everything else will look identical, but each will give you a different amount of reserve.



This isn't worth fussing over, but if later on you find that you don't like the reserve offered by the TW petcock you can get a longer one from another model. Just go to the dealer, find a real parts guy and tell him to line them all up on the counter, then pick out a longer one that looks right. If he gives you any grief about year, engine size and tank color just tell him that you know they're all alike and if he's a good parts guy he'll understand what you're doing.
 

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One of the first motorbike mechanic mistakes i made was breaking one of those little bowls on the neighbors' bike trying to remove it.


I guess I thought i could fix everything when i was 14...

Come to think of it, a lot of seriously old motors had a settling bowl inline with the fuel line.


The reason you broke the plastic bowl on yours is that it was plastic. That was one of the first bean counter moves. The bowls were all cast aluminum up until probably the '80's. Somewhere in the pre-TW, mid-80's most Japanese manufacturers had eliminated the filters entirely. Near as I can tell Yamaha phased them out in '85-86.



A lot of Chinabikes still have them. I think some Briggs and Stratton and professional small motors have bowls that will fit them as well. The filter is just a bronze disc, similar to the material in our oil filters. It slip fits over that little round tube and the rim of the bowl holds it in place. Unfiltered gas enters through the center into the bowl and gravity does the rest.
 

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LOTS of things that we older guys once considered minimum equipment have been dropped over the years. Those of you who are younger or are relatively new to the game may not be aware of their absence, or perhaps have seen some things on older bikes and wondered what they were. Some, like chain cases and points type ignitions were made obsolete by by more advanced technolgy. Many were just victims of bean counter mentality, never to return because we kept buying the damned bikes, regardless.



Deleting kickstarters, for instance. Not long ago you couldn't give a bike without one away, for damned good reason. They tried it, we sucked it up, accepted it, bought them anyway. They saved $27.33 in production costs, jacked up the price $300 and now you get a bike which should get you almost anywhere, yet that little, sniggling fear of battery failure maybe keeps you closer to home. Lots of that old junk provided peace of mind and almost any reasonably handy, self-sufficient wanderer could find a way to limp it home unless it holed a piston or threw a rod.



This could be the topic of an entire thread at this point in history. I've had enough TW's apart at this point that I'm sure I could identify at least 20 ways you guys with newer TW's have been ripped off vs. a 1987 model, but only two where you have benefitted. Three, if you count the trip meter.



You won't notice most of them until you actually try to drain your fork oil, or SERVICE your headlight switch so it will last another 10 years, rather than having no option other than to REPLACE it.
 

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The rear of yours sits a bit higher than mine, so theoretically you should have less fuel available at the petcock than I when you hit reserve.

On level ground it takes very little difference in tank angle to affect how much remains in the tank at reserve.


How high above the frame does you tank sit? I am interested in the distance between the flange at the rear of the tank, where the bolt that holds it on is, and the frame where the top of the shock absorber is.



I am under the impression it should be about 1" above the frame (the red line is 1"). Much lower than that and the petcock (with the plastic bowl) will touch the head. Maybe I need a new petcock?



 

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Mine is only 1/8" higher than the stock mount, just further back. The petcock has`at least an inch of clearance in all directions.



Petcock location could be one of those minor year-to-year differences Tom and I have gone back and forth on. Been so long I can't even recall what year mine came from, but I have another one from an '85 XT350 and Ronnydog has one on his. Next time we ride together I'll compare the three for minor differences. It also sounds as if yours either sits further forward or your bump stops are different. As I mentioned before, every TW I've messed with had different bumpstops. They may be one of the items done by hand in production.



I dunno. We only recently discovered that Yamaha moved one of the muffler tabs about 1/2" on late model frames and older mufflers won't bolt on anymore. No change to the muffler itself other than the spacing, so why did they bother? They do stuff like that. No clue.
 
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