TW200 Forum banner

1 - 20 of 34 Posts

·
Registered
Joined
·
158 Posts
Discussion Starter #1
I received so much information from the forum about jetting and performance that I wanted to report back my experience so far and keep a log of the progress for others to get a starting point.



A little background:



I have a 2008 that I purchased new from the dealer in 08. It now has 2100 miles on it. The base gasket leak is just starting to appear and it has generally been problem free for the past 3 years.



I built a motorized bicycle about 4 years ago and after I learned that I had to have a license and insurance just like a car I went and took the safety class for my license. After 2 days on a motorcycle there was no looking back. My motorized bike could do 30+ mph and after a front blowout I realized a mountain bike wasnt made to go that fast. So I purchased a TW200 new at the dealer to get a few years experience wanting a KLR or something someday. Now 3 years later I will probably never get rid of my TW200 because it is so much fun. But I wanted a little more power.



I had always noticed that at about 50 mph on an incline here in the central valley of California the bike would ping a little under a load. And on the flats it would surge at about 45 mph on hot days like someone was rolling the throttle back and forth ever so slightly. I never thought twice about it until I started reading some posts on the forum about jetting. Starting the bike on cold (40f) days was a chore. And after winter (Dec - Feb) storage I would have to use a squirt of fuel in the air box to get it started.



So I started with a teardown and noted that my main jet was a 126 not the 128 that a California model is claimed to have. hmmmmm



I went to the local dealers and none of them had any help with jets. All the 120 and 130 series jets were gone. Cycle gear had a 127.5 Large Round Mukini and 130 Large Round Mukini. I knew that the small rounds were the ones to get but took a chance because I had noticed pgilles had used large rounds. I also grabbed a 130 Keihin Jet because it looked so similar to a small Mikuni.



I received some spacers for the needle from a forum member. (Thanks MaineTW)



So with all that I started changing things.



I started with just 2 washers on the needle (.01 shims) .02 total. What a boost of speed and power. I rode it for about 3 miles and loved it.



So I went for more. 1 more washer added (.03) total. This time it was even stronger and pulled hard through the gears. Its like a brand new bike.



I decided to start jetting. I pulled the float bowl and put in the 127.5 Mikuni large jet and it wouldnt seat more than 2 turns. 1/8 inch from seating correctly. I wasnt going to push it. Same for the 130 Mikuni. So I installed the 130 Keihin small jet 130 and it went in perfectly. If I had to compare then I would say the 3 jets I have would be compared to Yamaha jets like this.



127.5 Mikuni = ~129.5 Yamaha Jet

130.0 Mikuni = ~132 Yamaha Jet

130 Keihin = ~131 Yamaha Jet



This is just my best guess based on my reading and the comparison I made with a loupe in my garage. They were all so close in size. The only one that was easy to compare was the 126 that I pulled from the carb. It looked smaller.



I dropped another washer in (.04) total and the Keihin Jet and my bike hauls a$$ now. I love it. I must warn that if you jet your bike take a day or so to get used to the new power. I pulled out of a corner today and the front end slipped a little when I punched it. The front likes to pull up with all the power. I cant wait to go to work tomorrow its that much more fun.



I ordered a Yamaha 125, 128, 130, 132 (They call it a 132.5 now) from the dealer to fine tune it in the next few weeks and try and narrow down just where the keihin jet falls in the order.



I also ordered a #34 pilot jet just to have it for future play use. And a South African or whatever they call the model needle jet with the five slots to adjust. Some forum members had speculated that you cannot get the needle with the slots and clip but my dealer ordered it and said they had 1 in the US and 5 in Japan so it was coming. I'm hopeful. The pilot jet that I ordered is from another model but from what I can tell it fits the TK carb. I'll let everyone know. Here are the part numbers.



Jet: Pilot #34 - 5LB-14342-17-00

Needle: South African model slotted needle - 5LB-14336-00-00



A few other notes. My screws didn't strip at all in the 3 times or so I had it apart because of the proper Japan screwdriver. I plan to switch them anyway but just wanted to mention it. Also, at first I removed the carb and getting it back in is a pain in the a$$. So I rotated it like some members suggested and that worked great. Just pull the tank, loosen the screws, and remove the throttle cable and rotate the carb.



Right now I have the Keihin 130 installed and the 4 shims and its running top shelf. More to come.
 

·
Registered
Joined
·
614 Posts
Nice write up Larry, I can add some information here. #34 pilot jet is a TW125 part as is the adjustable needle and clip on European bikes. If anyone needs to go richer on the main a TW125 has a #134 main jet, but I don't recommend that rich on a standard 200 or even 225.
 

·
Registered
Joined
·
158 Posts
Discussion Starter #5
Great write up, about to do some jetting my self. BTW whats your altitude?


I'm at 300 feet elevation. Central Valley of California. Its been very mild the past month in the 80's somedays but mostly 70's. It usually 100 here by now. I'll be seeing everything from 80's to 110's this summer so it should be interesting to see what some different combinations do.



I've noticed in the morning 40 to 50 degree weather it runs a little stronger. I believe the colder it is the richer it gets. So I think I may need to adjust a little richer come summer to get my morning performance. Someone correct me if I have this backwards. I'm still very happy.



Its been about 25 degrees cooler on the engine temps. 300 average at the head before with a 10 mile communte. Now 275 - 280 on average with the same ride. A slow commute, I stay mainly on the off roads.



I forgot to mention that you can hear the proper jetting in the sound of the bike. I has a very steady running sound with a different pitch when its tuned right.
 

·
Registered
Joined
·
614 Posts
Cold air is denser than warm air, there fore has more oxygen and needs more fuel. (cold=bigger jet, warm=smaller jet))



Although on a TW this is pushing it to the extreme, if you could notice any real difference in day to day riding you must have a very sensitive butt dyno.
 

·
Banned
Joined
·
10,664 Posts
Cold air is denser than warm air, there fore has more oxygen and needs more fuel. (cold=bigger jet, warm=smaller jet))



Although on a TW this is pushing it to the extreme, if you could notice any real difference in day to day riding you must have a very sensitive butt dyno.


Actually, North American TW200s are jetted very lean when new and proper jetting makes more difference than just about any other mod done alone. Most North American TW200s are 1 3/4-2 full turns closed on the pilot screw, needle .5mm lower, and main jet 2 sizes smaller than that which is the norm for the rest of the world. Compound the problem of overly lean jetting with E10, which requires 4% more fuel flow than E0, and proper jetting makes an easily noticeable difference. The symptoms described in the original post are typical of engines running too lean.





I have replaced 2 TW200 slides for people and done likewise on many other bikes to restore proper functioning of their carbs after they were drilled out. Drill at your own risk.
 

·
Registered
Joined
·
158 Posts
Discussion Starter #10
I wanted to post a little update.



Like I originally posted I ordered the part 5LB-14336-00-00 (Carb Needle) for South American or whatever country TW200's. It arrived yesterday and I am happy to report that it is slotted with a c-clip. No shims needed for this needle. I had to order it from Ron Ayers because the were one of the only ones that showed it on the search. I ended up finding it at Stadium Yamaha also.



Secondly 288-14343-65 is the part number for the #130 jet like querty suggested in his carb tuning post. I now have a 125, 126, 128, 130, and 132 and plan on doing some testing when time permits. But I am pretty sure the 130 is in between the 128 and 132 just by looking at it. Not positive but it looks that way.



If anyone is interested I can measure the different clip positions on this needle before I install it. It may help with shimming questions.
 

·
Registered
Joined
·
181 Posts
I wanted to post a little update.



Like I originally posted I ordered the part 5LB-14336-00-00 (Carb Needle) for South American or whatever country TW200's. It arrived yesterday and I am happy to report that it is slotted with a c-clip. No shims needed for this needle. I had to order it from Ron Ayers because the were one of the only ones that showed it on the search. I ended up finding it at Stadium Yamaha also.



Secondly 288-14343-65 is the part number for the #130 jet like querty suggested in his carb tuning post. I now have a 125, 126, 128, 130, and 132 and plan on doing some testing when time permits. But I am pretty sure the 130 is in between the 128 and 132 just by looking at it. Not positive but it looks that way.



If anyone is interested I can measure the different clip positions on this needle before I install it. It may help with shimming questions.




If its no trouble that would be great. Thanks for the write up, i've been looking for more info on doing the needle shim, made a decent difference on my old bike. Im not sure about tinkering with the jetting though, previous bad experience.. and really I could live with it the way it is, but I like the "runs cooler" part and if a little performance improvement is a side effect, I can live with that!



I guess a "this needle works great" would be good, i suppose laying them side by side would give good indication of which clip to use.
 

·
Registered
Joined
·
181 Posts
If its no trouble that would be great. Thanks for the write up, i've been looking for more info on doing the needle shim, made a decent difference on my old bike. Im not sure about tinkering with the jetting though, previous bad experience.. and really I could live with it the way it is, but I like the "runs cooler" part and if a little performance improvement is a side effect, I can live with that!



I guess a "this needle works great" would be good, i suppose laying them side by side would give good indication of which clip to use.




Gathered a needle , 130 jet (im 2500-3000 elevation and ride higher), and a bowl gasket, just need a little time now.

Any tips on removing the carb?

Prev bike i was able to twist it enough to access the needle without completely pulling it.

Doubt that will be the case here, especially with the jet.
 

·
Registered
Joined
·
663 Posts
GFL, you didn't mention what year your TW is, as that typically determines whether you have an early or late carb.



The jet sizes make a big difference between the two carbs. I just wanted to bring this point up because I am rejetting my early carb as well.



Information I have gathered indicates that on the early carbs like I have a 130 would be way too rich, with optimal at seal level probably being a 118 or 120. Late model carbs can run larger jets.



I hope I have this information right and await correction by the more learned members who have replied above.
 

·
Banned
Joined
·
10,664 Posts
GFL, you didn't mention what year your TW is, as that typically determines whether you have an early or late carb.



The jet sizes make a big difference between the two carbs. I just wanted to bring this point up because I am rejetting my early carb as well.



Information I have gathered indicates that on the early carbs like I have a 130 would be way too rich, with optimal at seal level probably being a 118 or 120. Late model carbs can run larger jets.



I hope I have this information right and await correction by the more learned members who have replied above.


Folks with early carbs report joy with 116 main, 118 if heavily modified.



Remember, best to start with the main, then needle, then pilot. Reason is the main is more likely to affect midrange needle is to affect wide open. If the order is reversed, usually raisning the needle will richen the pilot, requiring readjustment. Then, increasing the main will richen the needle, requiring readjustment, which will then lean the pilot, requiring readjustment. If you do the main first, it is almost never necessary to retuin the main after settting the needle, and if you do the pilot last, it is almost never necessary to retune the needle after doing so. Once can certainly tune in any order desired, but main-needle-pilot significantly reduces the chances of having to do steps over.
 

·
Banned
Joined
·
10,664 Posts
Thanks Qwerty! Your guides on this subject are very helpful.
de nada



I'd hate to see anyone go through the trial-and-error process I went through learning to tune carbs. I wasted a ton of time and money developing my butt-dyno method. I don't do plug chops and rarely look at a plug--all carb tuning I do is just paying attention to how the bike is running. The bike will always tell you what it needs. It is up to the rider to listen and make the adjustments.
 

·
Registered
Joined
·
181 Posts
de nada



I'd hate to see anyone go through the trial-and-error process I went through learning to tune carbs. I wasted a ton of time and money developing my butt-dyno method. I don't do plug chops and rarely look at a plug--all carb tuning I do is just paying attention to how the bike is running. The bike will always tell you what it needs. It is up to the rider to listen and make the adjustments.




mines an '09. I'll follow the steps as listed. I figured to start, I'd swap the main, then, I'd try to find the clip position that raises the needle least but yet a little over stock.

Hope for the best, I'm not doing it for the love of doing it, more for the love of seeing it run the way its supposed to.
 

·
Banned
Joined
·
10,664 Posts
A clean rejet will definately improve a North American TW. Funny thing is, everyone complains about how bad one particular modle or another is, but virtually every carbed bike sold in North America has room for improvement. Most EFI bikes also. They use Power Commanders to do the same thing. Your governments at work.
 

·
Registered
Joined
·
181 Posts
OK so i couldn't wait until next week, had a day off so i tore into it.



I broke the rules on the order of which to start with.. I had fear of float bowl screw strippage so i opted to just change the needle and adjust the pilot screw until my new JIS screwdrivers arrive (good excuse for more tools!)



This does seem to have improved low to mid throttle acceleration, Im not really sure i need to do the larger main but I might just to see what gains can be had. I get a very slight lean feel at full throttle, not bad at all but there.



If anyone is wondering, the multi-position needle has 5 slots for the clip, out of the package its in the 3rd (middle) clip position which seemed to match the stock single postion version, i went down one to raise it slightly.

I'm sure i could have found some stainless washers that would have accomplished the same thing, but already had the needle.



Small hands would have been nice, couple small burns from adjusting the pilot screw, other than that, a good experience overall.
 

·
Registered
Joined
·
918 Posts
OK so i couldn't wait until next week, had a day off so i tore into it.



I broke the rules on the order of which to start with.. I had fear of float bowl screw strippage so i opted to just change the needle and adjust the pilot screw until my new JIS screwdrivers arrive (good excuse for more tools!)



This does seem to have improved low to mid throttle acceleration, Im not really sure i need to do the larger main but I might just to see what gains can be had. I get a very slight lean feel at full throttle, not bad at all but there.



If anyone is wondering, the multi-position needle has 5 slots for the clip, out of the package its in the 3rd (middle) clip position which seemed to match the stock single postion version, i went down one to raise it slightly.

I'm sure i could have found some stainless washers that would have accomplished the same thing, but already had the needle.



Small hands would have been nice, couple small burns from adjusting the pilot screw, other than that, a good experience overall.


I usually use a vice grip or pliers of some sort to loosen the float bowl screws. Then a standard phillips can remove them. You can re-install and tighten them in the same fashion, although you can usually get them tight enough with a standard phillips...it's just breaking them loose that the pliers come in handy. Then when you're near a hardware store you can pick up some M4x10mm socket heads to replace them with.
 
1 - 20 of 34 Posts
Top