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Discussion Starter #1
Hi Everyone,

I am a new owner of a 98 TW200. I live in Anchorage and I was simply looking for a reliable, cheap, and efficient commuter bike in town. The TW200 was pretty far off my radar, but when I saw the bike and the price I realized it was a good fit for me. I got my license 7+ years ago and hadn't ridden since I bought the bike. This bike has been super easy for me to "re-learn" on. I am definitely enjoying it, and although the bike has about 6700 miles, it is running great.

My only disappointment has been that the bike doesn't seem to be getting very good mileage. I have only filled it up a couple of times, but it seems to be getting around 40-45 MPG. I am driving in light city traffic, mostly going 40-50 MPH. It still has the knobby tires on it. Even with the city traffic and knobby tires I expected better MPG.

The previous owner said that he replaced the sprockets in 2012. He also said that that the carb was rejetted, the intake/exhaust was opened up, and he installed a washable air filter. He also said something about "high flow" and that it runs a bit rich causing the carbon build up on the plug at times.

I understand he did some of this work to increase the top speed. I am a pretty tame rider. I don't take the bike on the highway so I would much prefer to have better MPG than a fast bike.

Any recommendations? Would replacing the jet make a significant difference? Or is my poor MPG more due to the knobby tires and city traffic?

Thanks for any help you can offer.

Jim
 

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Discussion Starter #2
By the way, I am 150 lbs and am driving on mostly flat terrain (no significant hills). I have never had the bike much over 50, but it seems to have plenty of power left at that point.
 

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The previous owner said that he replaced the sprockets in 2012. He also said that that the carb was rejetted, the intake/exhaust was opened up, and he installed a washable air filter. He also said something about "high flow" and that it runs a bit rich causing the carbon build up on the plug at times. Quote]
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Count the teeth on the sprocket, stock is 14 front 50 rear. Not sure what he means when he said he opened up the intake and exhaust, you should check to see that the valves are set correctly. He probably does not have the carb jetted correctly, something's too rich. Check to see if the air filter is clean and lightly oiled. Give it a tune up by the book first. Even with modifications, you should probably be getting around 60+ mpg.

Welcome to the forum Jim. We'll do our best to help you.
 

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My bike has a aftermarket exhaust and higher flow air filter and is jetted accordingly. When commuting on the bike it's all city streets under 80kms/hr.

Because I use my bike on trails it will always have knobbie tires. I do tend to be heavy on the throttle as I'm 6' 260ish lbs. And my bike still gets me anywhere from 55+ mpg (my last tank netted best yet at 71mpg)

Being as you state your bike sat for some time and with the crappy fuel today you may want to clean your carb and do a good tune up. Also maybe look into changing the gearing out for stock in the future.
 

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Hello and welcome! The above recommendations are a good place to start. As well, I would add a god dose of Seafoam to the gas and let that work in the carb since it had been sitting for a while.
 

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Jetting the carb back to stock will help no doubt. I jet rich because I live in the crazy hot and rich jetting runs a little cooler. Come winter I may go back down to stock to get better range. I have also noted about 5 MPG difference from just tire pressure. If you are mostly city you can go up to the max 22 front, 25 rear.
 

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TW's come with a washable (oiled) air filter as standard - treat any thing he has said with a pinch of salt

Sounds like he was trying to make the bike do what it's not designed for - go faster

Any changes to the existing standard exhaust will make no difference, you'll need a completely new set-up to do that - so that's another one you can ignore ("if" it still has the standard exhaust)

As said above, simply change the jet back down to what the bike is designed to run on - until then, rich is better than lean

Not sure how much this will improve the mpg - a little perhaps - more to do with the condition of the engine ........

A word of caution - take it one step at a time, and prove that each step works - take notes ......... you need to be able to reverse anything you do that compromises the running of the bike

The previous owner has fiddled about in there and you don't know what he's done - tread gently .......

(And welcome to the board)
 

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Sounds like great advice so far. My '06 motor is completely stock and I get 60-65mpg on my 44 mile commute. My gearing is 15/50 (non stock) as I am running @ 60mph most of the commute. Mine is a California version originally jetted very lean and ran poorly. I went up a size or two on the main jet, raised the needle and adjusted the mixture screw and it now runs way way way better. Tdubs are very sensitive to carburetor tune so keep checking your spark plug until you get a nice light tan color. Sounds like you are running rich and that explains the poor mileage. I think there are some carb tuning threads/stickies here.

best regards, MAC

P.S. also you could check your float level. I need to do this myself!:dread:
 

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Discussion Starter #11
Wow... thanks everyone for your replies! I will start by counting the sprocket teeth, tire pressure, and air filter. I'll also have a look at the spark plug. I will post back with my discoveries. After that I will decide where to go with the carb. glad to hear better MPG should be within my reach.

You guys rock! :)
 

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My bone stock TW with no changes at all I can set the tripometer to zero when I fill the tank and right around 80-90 miles I go on the reserve and can go at least another 20-30 miles. Running rich means you are not completely burning all the gas going through and your spark plug should be black and oily. The pilot screw can be adjusted which is your air to fuel ratio and as long as the previous owner did not Muck things up it should be able to help. All of this jetting crap seems to do nothing but what it is specifically designed to do. Right from the factory the TW carb is pretty well suited for the type of riding you describe and should only need the pilot circuit adjusted off the very lean factory settings. Larger jets and raising the needle equals more fuel for higher revs if that is the style of riding you do. A TW will likely never win the race no matter what you do to the carb but they almost always make it to the finish line.

I would bring your carb and the sprockets right back to the stock TW as it was delivered. If he changed the exhaust pipe or drilled it out I would go back to stock with that too. Check to make sure the mice did not build a nest on the intake side of the air box, that opening is behind the battery and a good place for critters to hole up.

I will always tell anyone buying a used bike to listen to what the seller says but don't believe a word of it. Half of these back yard mechanics have zero clue about the real running principals of such simple machines and usually do more harm than good. I have owned 7 TWs now and the difference between hopping one up with all the carb and exhaust upgrades nets you the difference between a top speed of 65 MPH to maybe 70 and that might be a stretch. Keep it simple stupid and that is the way I flow with these little but very reliable bikes.

GaryL
 

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if you decide to open up the carb and fool with the jets, I don't recommend going back to stock as these bikes run crappy with stock jetting, but I do suggest that you spend hours reading the threads on this forum as there is tons of information available to you. it takes such a small change to made a big difference in performance that is soooooooo........ easy to miss. these guys on this forum know what they are talking about, all you have to do is go slow and read and ask good luck
 

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What is your elevation above sea level?. All the previous post is good info......we WILL assist you. Just be detailed in your discoveries.
 

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Discussion Starter #15
Hi Everyone,

Sorry for the delay in updating. I've been super busy the past week. Here are a few updates and answers to questions:
-I live at sea level
-I increased the air pressure from 16 to 20 psi in the front and 21 to 24 in the rear
-I am including a picture of the plug... which seems to confirm the suspicions that the carb is running very rich. IMG_20150810_171438165.jpg

I still need to check the sprockets and air filter.
 

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The previous owner said that he replaced the sprockets in 2012. He also said that that the carb was rejetted, the intake/exhaust was opened up, and he installed a washable air filter. He also said something about "high flow" and that it runs a bit rich causing the carbon build up on the plug at times.



Thanks for any help you can offer.

Jim


Back in the old forum days many guys cut up their air boxes to get more flow. They cut off the snorkel and cut holes here, there and everywhere. Many also gutted their stock mufflers and used a hole saw on a long extension to open them up on the insides. I was always chomping at the bit to do this but for every claim of increased power 2 or 3 would say it runs worse now and is just louder! The general fix for this was to rich'n it up with bigger jets. Some would say their dub was now faster than a speeding bullet, but most just scrambled to get their bikes back to running as well as stock. I have a feeling some never did. From that point on I decided not to make any engine mods that are not reversible. Other than tuning and jetting the carb my motor is pure stock and runs super.

JIM, it sounds to me like your previous owner hacked the air box and muffler, then over jetted the carb trying to get it to run half way decently.


best regards, MAC
 

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Discussion Starter #17 (Edited)
Mac,

It looks like your guess is correct. I finally had a few moments to look at the bike tonight. Here is what I found when I removed the left side panel:

DSCN0333.jpg


DSCN0334.jpg
Is this screen stock? Or is that an after market change, too?

DSCN0337.jpg
Am I correct that this is a non-stock air filter? Any recommendations for proper cleaning of this bugger?

Also, FWIW, I counted 47 on the rear sprocket.

I am very interested to hear everyone's thoughts at this point.

Thanks!
Jim
 

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Discussion Starter #18
And, after looking at some pictures of stock exhaust, I am assuming the four holes are non-standard?

DSCN0338.jpg

DSCN0339.jpg

This must be what he meant by "opened up the exhaust"?
 

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Some would say their dub was now faster than a speeding bullet...
You gotta ask, is the speeding "bullet" a 500 or just a 350? :D

To the OP, yes the filter box has been modified as has the muffler. And the bike is definitely running rich. It might be a good idea to replace the airbox and muffler. Either way you're gonna have to rejet the carb.
As for the filter element, I would keep it if in good condition. K&N makes good filters. Their website has cleaning instructions: How to Clean a K&N Air Filter - K&N Filters Cleaning Instructions
 

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Back in the old forum days many guys cut up their air boxes to get more flow. They cut off the snorkel and cut holes here, there and everywhere. Many also gutted their stock mufflers and used a hole saw on a long extension to open them up on the insides. I was always chomping at the bit to do this but for every claim of increased power 2 or 3 would say it runs worse now and is just louder! The general fix for this was to rich'n it up with bigger jets. Some would say their dub was now faster than a speeding bullet, but most just scrambled to get their bikes back to running as well as stock. I have a feeling some never did. From that point on I decided not to make any engine mods that are not reversible. Other than tuning and jetting the carb my motor is pure stock and runs super.

JIM, it sounds to me like your previous owner hacked the air box and muffler, then over jetted the carb trying to get it to run half way decently.


best regards, MAC

I just don't get why folks chop up their bikes trying to obtain better performance. All I did was open the air/fuel mixture screw a tiny bit.

 
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