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Discussion Starter #1
Hello all, im 17 and i just purchased my first TW200. After much research i still have some questions. I rebuilt my carb, trying to get it back in was a two hour, two man job... The carb simply would not fit, if it was snug up against the air box rubber it simply would not reach all the way to the engine seal vice versa. I know it has all the parts and they are original. Now it is sitting snug to the engine but the carb intake side is about a 1/4"+ not on. Me and my very experienced father could not clamp and stretch it over the remaining length no matter what, we even used a heat gun. My other problem is when i get up to about 60 km the bike starts to miss, (as if i were letting off and on the gas) stopping me from getting up to 4th gear. Plug is new, Im thinking the coil is starting to go? History of the bike is its has 11000k and the dealership did all the old guys maintenance plus been sitting for 5 years. Ive done all the regular maintenance to the bike. If you want me to better describe or video what happens at higher speeds, i can. Any suggestions would be appreciated,,, Thanks.
 

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Hi Will,

Congratulations on your new TW and welcome to the forum!

On older bikes like yours, shrinkage of the rubber boot between the carb and the airbox is a pretty common problem. I am not sure if anyone has come up with a solution for this besides just buying a new replacement boot.

Brian
 

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Discussion Starter #3
Thanks,

Does anyone know where i can find one? I cant see any on ebay. Will my local Yamaha dealer carry one for my 1990? I live in Canada.
 

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My local Yamaha dealer would not have that in stock, but would get it for me in a week, at a stealership price. I usually order from Rockymountain Atv or bike bandit. Welcome!
 

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My TW was also standing for a couple of years and it took me some time to get it going

It looks to me like you have a problem with getting enough fuel flow at high revs. I suggest that you take your fuel tank off and rinse it properly.

If it is rusted on the inside take it to a bike shop so that they can remove the rust with acid and then coat the inside of the tank.

Then also the petcock has filter screens on it inside the tank and they clog up and get brittle and prevent the fuel from flowing properly when they get old so I recommend that you remove the filter screens as well and then put an in-line fuel filter between the carb and the fuel tank.

That's what I did with my TW and now it is running smoothly!
 

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Discussion Starter #7 (Edited)
I think you are right. There is minor rust, enough if i stick my finger in there and rub it around my finger will be slightly brown. But the rust spots are only small and spotty. I could see evidence of this in the carb. I've seen videos on youtube of guys cleaning the fuel tanks with vinegar. As for the petcock, setting it to the off position still leaks fuel. It hasn't been touched in 25 years so this is all expected. I kind of wanted to keep the original petcock and i heard they make rebuild kits so i might do that. I don't think my problem its electrical or spark related because the fuel only cuts off at higher speeds. But then again its choppy not smooth when its struggling for gas. The bike also takes about 5x longer to fully warm up as my 09 honda crf100 did. I think i saw somewhere that this is normal for these bikes so maybe that's not a big deal. -Thanks-
 

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As mentioned by Brian, your air to carb boot is shrunk and needs replacing. My 1987 is in the same shape and if air is getting in around that seal then you can expect to have performance issues up in the higher RPM range. Any dealer or after market supplier will have the new boot or get it. I have never found a way to stretch them back out or get them to seal so just bite the bullet and get a new one.

Read my tutorial about bringing back a sitting bike and do the tank, petcock and carb cleaning before you even start looking for deeper issues. Take the petcock apart and you will likely find gunk in behind the turn lever and one or both of the screens on it all gunked up. No free fuel flow and you can be sure of running issues.

GaryL
 

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The petcock and carb boot are not expensive and should just be replaced.I used the POR kit to clean my tank and line it and mine was so bad inside I thought I would have to replace it.
Where in Canada are you? We don't see too many TW's up here.
 

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My 89 has the carb boot issue, and for the short term you can tighten it in up on the motor side and put self sticking foil tape on the air box side side, such as high temperature duct tape. Make sure it is air and dust tight. Its pretty easy to blame your mechanical skills until until you figure this one out, isn't it?
 

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Discussion Starter #12
I'm in Canada which makes getting parts a lot harder. The Canadian dollar is so far down right now everything from the USA is costing extra. I heated the crap out of the boot, stretched it and bought some tighter clamps to get it to stay on the carb. Working for now. I will do the petcock tonight and update you guys.
 

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Discussion Starter #13
I miss read what you said. Im in northern bc. Cornelis- do they ship to Canada?
 

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Petcock assemblies are so cheap that its the same whether you rebuild yours or buy a new one. Tanks can be rinsed with diesel fuel and BBs , but by all means install an inline filter, and carry a spare until you know how much gunk you are sucking out of the tank. New screens on the petcock will be better than not having them. Your reserve will be useless if you don't leave the original fuel outflow system intact. Enjoy the ride. Tom
 

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The above post are about dead on on your choices. Sometimes you can make it easier to put the carb in by rotating the rubber boot on the air box side
it's offset a little and will "twist" in the airbox giving you clearance to get onto carb. You can also experiment with removing the rubber intake manifold, put it
onto the carb and rebolt. The thing is though, the rubber has gotten harder than Chinese arithmetic and may not seal proper. If your cheap or impatient though this might get you back on the road. Cleaning the petcock filter works too but, install an inline filter if you don't coat the inside. Coating works way better than just removing the rust. Dang rust is hard to filter out. I wouldn't fret much on high speed misses until you fix air leaks. Shop around some on the internet for parts, it's amazing the variance. I've seen dealer (Stadium Yamaha) parts cheaper than Rocky Mountain for the same thing.
 

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Discussion Starter #17
I cleaned the petcock and fuel tank with vinegar. Lots of crap in there. Petcock will be fine for now, rubber gaskets inside are good. I made my own gaskets from fuel line for the petcock screws as they were rotted. I will do a proper fuel tank clean/flush in the next week and re-coat the inside at the same time. Next is thing to do is the valves.. I should check the oil filter too.. There is fresh oil right now.
 

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Discussion Starter #19
I think im keeping it 100% original for now because its so dam cool. I don't want a cheap chinese petcock on there either.
 

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You can get all the parts you need for about $37 US at rockymountainatv.com. They ship to Canada.

Look for the OEM parts icon. It took me a while to find it.

 
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