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Discussion Starter · #1 · (Edited)
hi all,

i've got a 2004 tw225e (japan model) which i've just bought recently from Japan.

Done a couple of test rides and looked perfectly fine except for 1 thing, it was working quite lean.
I came to this conclusion mainly cause :
- Spark plug was on the white-ish side (quite a bit)
- idle worked fine, but used to bog (like striving for fuel) upon mid/full throttle. Low speed cruising never had issues.

One thing to point out is that it has an after market exhaust, a super trapp with a fully open end (would consider this as a straight pipe/open exhaust)

So I decided to up a size of the main and pilot jet. more so when I opened the carb and saw that it has stock jetting at 32/132

Got the 35/135 (since 34 doesnt seem to exist according to our yamaha dealer), and after reinstalling the carb, it started, ran idle for half a minute or so, but then as soon as i gave it a hint of throttle it went off, and wont start again. it looks like its flooded with fuel, infact black fumes are coming out of the exhaust.

Upon checking the spark plug now its complete dark....

do you think I should revert the pilot jet to stock since idle/low speed was ok, and just leave the main jet to 135?
air/fuel mixture was not changed (that it set back to where it was, around 2 1/2 turns if i recall correctly?). Do you think it will help if I add more air to the mixture since it wont even start as it is now? (I also tried removing the air filter completely to see if it starts up but still no effect).

I'm not quite digesting the fact that it went from lean to too rich with just a size (might be the float got stuck?)
Any suggestions would be of great help!
thanks in advance
 

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OK - take it easy

The first thing, is that your custom exhaust has a tendency to make it run lean on the original jetting, but not by that much, so look at the idle jet

Unless you run that thing flat out all of the time, most of your run time is likely to involve the idle jet, which will likely have been set on the lean side to reach emission standards - the TW225E is torquey enough to allow for low rev running, and at less than 30% throttle, the idle jet is likely to be the culprit

So - back to the original jet size - and I'll be back in about an hour once we've beat Croatia to take you through the next bits .....

Welcome to the board ..... :)
 

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ive had many of the jap 225's and most have supertrapp exhausts, the carbs are the same as 200cc (disc models) and all have 132 main jets.

i have only changed the main jet once to a 135 and then i had to adjust the mixture screw quite a lot to stop it popping while engine braking..

i have never changed the pilot jet.
 

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And on that note (the cheers from Croatia) – back to business …..

Set the jets back to original – and make sure your pilot jet is set to between 2 and two and a half turns out – this involves turning the carb in its boots to expose the bottom of the carb, and looking for the brass blank concealing the idle adjustment screw (which incidentally, I can’t believe hasn’t been made into a sticky yet) – but if you search for it, it will doubtless become more apparent

With the idle jet now drawing more fuel, you are halfway there – so now all we need to look at, is the custom exhaust

Whist it’s true that custom exhausts can cause a lean condition, the primary problem is that the owner will then go out and get the “Acme Jet” upgrade, which will be about as much help to you as the Acme anything was to Willey Coyote. We have consistently found that the only comparison in jet sizes between the OEM jets and any other jet on the market, is to compare the distance to the moon to the distance to Mars. What one maker calls a 134, is nothing like what another maker calls it – pure fiction

Start from the original OEM jet sizes, and stick to an OEM size increase – anything else will throw you off plot faster than you can fart

If you try the original pilot jet at two and a half turns out first, you will then have a valid starting point to work from (as long as you place the original main jet back in) – it may take a bigger OEM main jet – it may not – but unless you stick with the OEM jet sizes, you’ll never know
 

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Discussion Starter · #5 ·
thank you both for your feedback

I dont usually drive the TW at full throttle, but i do reach the mid-way and a bit more fairly often to keep up with the traffic. I knew the TW's dont go fast, but mine is like a lazy model. it tops at 70kmh (kmh not mph!), and if u keep pushing u can squeeze out a 75+...maybe. On the net the 200s all reach 65-70mph and thats a huge difference. I weigh under 70kilos. Infact I ended up checking the piston's compression but it read over 130s

Back to the idle jet, I presume you're referring to the air/fuel mixture screw correct? I've never touched that apart for rebuilt and set it up as it was (as you said about 2 1/2 turns).
Tomorrow i'll plug in the stock jets again and see how it goes with idle screw. Oh btw, the new +1 size jets I got are official Yamaha OEM so they should follow the numeric scale well.

Back to the idle screw adjuster, any place where I can buy one of those modded screws that will be long enough to stick out of the carb and lets you adjust it easily in place? its such a pain to adjust this one in place (you have to remove the throttle cable inorder to twist the carb in place no?)
 

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In theory, you should be able to rotate the carb in its rubber boots just enough to be able to reach it (comfortably)

As to “top speed” — the TW200 is capable of between 62 and 65 mph (actual) flat out, downhill, with the wind behind it — any more than that and it becomes “unstable” — which means that you “can”, but personally I wouldn’t risk it

Those figures in relation to the 225, assuming that you have the normal sprocket set-up with regards to numbers of teeth, and that you are running the Bridgestone 203/204 set up, which is standard on the TW225. With the TW225 in its standard configuration, and with the street tires (203/204) pumped up to around 25psi, flat out, you can expect 68mph (actual) — the main difference between the 200 and the 225 is the torque factor at lower speeds — it makes for a more “relaxed” ride, and is less dependent on being in the correct gear at any time

On level ground with no wind (or altitude), you should be able to reach between 60 and 65mph with ease

My first thoughts on this would be to check your sprocket ratios

On the matter of jetting, make sure you have the correct spark plug value in there, and don’t change the idle jet as a knee jerk reaction — just very gradually up the main jet until you get the colour you want — it’s likely to be the culprit here ……….
 

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Increasing the number of diffusor discs in the SuperTrap might be a simple way to run the stock 32/132 jets with better results.
 
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Discussion Starter · #8 ·
Increasing the number of diffusor discs in the SuperTrap might be a simple way to run the stock 32/132 jets with better results.
actually before taking off the carb, I tried reducing the discs (not increasing) to reduce air flow /increase back pressure, it did help, tho it didnt solve the issue (I left it with just 2 discs)

On the matter of jetting, make sure you have the correct spark plug value in there, and don’t change the idle jet as a knee jerk reaction — just very gradually up the main jet until you get the colour you want — it’s likely to be the culprit here ……….
Sorry Purple, kind of lost you in this last part.
What do you mean by value? is it the color or the tip? spark plug is brand new, just few kilometers on it (prior to removing carb). At one point it was dark/rich in color, so I brushed it off slightly to remove that excessive carbon.
Also how can I 'gradually' up the main jet? Next step from 132 is 135 with OEM Yamaha jets.

Oh, and I got some further process updates.

I reverted back the pilot jet to stock 32, and remained exactly the same... So I decided to revert completely to the original setup, 32/132 with 2.5 turns on pilot screw. Much to my surprise, when I thought this would bring back the bike as it was, it didn't. It's still cutting off when I rev a bit past 1/3 throttle (on neutral)

So now... I'm kind of lost as to what is wrong.
The only thing left trying, is getting a new spark plug, and check the gapping again to make sure all is fine. Other than that i'm out of ideas

thanks once again for your great help
 

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Spark plugs come in different heat values – it’s the number on the plug that indicates this – higher is hotter – it should have an NGK DR8EA – so an NGK DR7EA would be cooler, and an NGK DR9EA would be hotter – 8 is optimum for these bikes – it’s just something to eliminate and be aware of. (Rather confusingly, the Champion plug is RA6HC but the same thing applies)

The fact that it first stumbles at 30% throttle indicates the problem lies with the main jet – where you located ?
 

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Reducing the number of diffuser discs in a SuperTrap increases, not reduces, air flow potential and reduces , not increases, back pressure making for a resultant richer air/fuel mix. Increasing the number of diffuser discs might be a simple way to run the stock 32/132 jets with a leaner overall air/fuel mix.
All carburetors work on pressure differentials. Exhaust changes that reduce back pressure result in more force to pull more fuel through existing orifices resulting in a often too rich air/fuel mix.
 
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Fred is quite correct of course

The other reason it may suddenly have been running horribly rich from horribly lean, could have been from the introduction of increased sizes in “both” jets at once. Assuming the idle jet is now back to its original size, you can address the problem area, which seems to be the main jet

By changing three things at once (the idle jet size, the main jet size, and the exhaust plates), you make it harder to correctly diagnose what worked, and what went wrong

So – now we have the idle jet and the main jet back to normal, take Fred’s advice, and re-build that exhaust to where it was before – then we can take a look at the stumble at 30%, the running lean part, and what would seem to be worryingly low performance levels

Once you have the exhaust back together, the first thing I’m going to recommend is a good petrol additive to try and clean out the carb – always try the simple low cost things first – that’s why I asked your location

If that doesn’t work, there’s plenty of other things to look at – but take it one stage at a time ……
 

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Discussion Starter · #12 · (Edited)
Reducing the number of diffuser discs in a SuperTrap increases, not reduces, air flow potential and reduces , not increases, back pressure making for a resultant richer air/fuel mix. Increasing the number of diffuser discs might be a simple way to run the stock 32/132 jets with a leaner overall air/fuel mix.
All carburetors work on pressure differentials. Exhaust changes that reduce back pressure result in more force to pull more fuel through existing orifices resulting in a often too rich air/fuel mix.
you're right, I inverted the terms. But what I meant is that it went richer, hence why it helped a bit (originally mine was running lean)


Spark plugs come in different heat values — it’s the number on the plug that indicates this — higher is hotter — it should have an NGK DR8EA — so an NGK DR7EA would be cooler, and an NGK DR9EA would be hotter — 8 is optimum for these bikes — it’s just something to eliminate and be aware of. (Rather confusingly, the Champion plug is RA6HC but the same thing applies)

The fact that it first stumbles at 30% throttle indicates the problem lies with the main jet — where you located ?
Yes plug is DR8EA, and i changed it for a new one, same result

i'm situated in Malta, at sea level.
I went back to stock 132 main jet but it still goes off at 1/3 throttle.

Could it be I have a clogged passage way? The carb wasn't really all that dirty to begin with, and when I sprayed carb cleaner through the passage ways I made sure the spray came out of somewhere else. But it's not like I know about all the passageways.

Could be maybe I missed a passage or some dirt accumulated while I was spraying around?
I really dont know what I could do more!

*edit* sorry didnt see your last post on page 2.

I've reverted everything to as it was few days ago.
Idle screw, pilot jet, main jet, exhaust, and brand new spark plug.

Fuel happens to be the same as it was in the tank. I can add additives no problem, but the carb is clean since I used carb cleaner whilst it was open for the jet change.

So basically, apart from the 'cleaning' thing, everything is back to as it was, but still cuts off at 1/3 throttle
 

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Then you still have a potentially clogged main jet — at 30% throttle the main jet takes over from the idle jet, and if it’s stuttering at that point, the main jet is running lean. This could be excess air at that point, or not enough fuel — but it only happens when you engage the main jet

Malta huh — was there last December — other than the crazy drivers, nice place to be

Right — you need to get hold of a product called “Redex”.

https://www.holtsauto.com/redex/products/petrol-system-cleaner/

If you add one cap full to the gallon, and run it through the bike, it will get rid of the any “glaze” that has accumulated in your carb (and anywhere else for that matter). In a car engine, it will clean the tank and the fuel injectors etc, but in a bike, it’s basically going to work on all surfaces it comes into contact inside your carb. The stuff needs to soak a bit, but you can run the bike quite happily while it’s working. Make sure you only put one capful per gallon

Start out by adding it to the fuel, and then running the bike for ten minutes (even idling will do) to make sure it gets into the float bowl, and then leave it overnight. Then simply ride the bike as normal, and it’ll continue to work. You should start to see an improvement within the first days ride (hey, even if you don’t it’s still good stuff to have around). Worked a treat on my TW225 after winter storage with the throttle response

Try it first — and then we’ll deal with the “lean” part — you need to get it running correctly first - these carbs are almost impossible to get clean by conventional sprays etc ......
 

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Discussion Starter · #14 ·
(for some reason my last reply didnt show up)

in any case I thanked you all for the support and ideas.
I'll try runnning the cleaner on idle since its not quite ridable at the moment and see how it goes

will let you know once i'll have some updates.
 

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The CV carbs (like the one on your TW225) was a design change from the pre 2001 front drum brake TW200, primarily introduced to cut emissions even further. However, they are far more prone to “contamination” than the older “slide” model carbs – and on the TW200 the slide version was bad enough

I have a 1998 (slide carb) TW200 and a 2007 (CV carb) TW225 here in the UK, both with the same fuel, both over wintered in the same garage. Yet when the spring comes, it’s the TW225 that stutters on start-up, due to “petrol deposits” creating a sticky coating in the carb. Redex (or similar) will dissolve those deposits, and throttle action becomes smooth once again. The UK and Malta both have the same fuel, less than 5% ethanol, so it comes as no surprise that your bike is reacting in the same way

Presumably, your bike had been sitting for a while before it came to your ownership, which only allows those deposits to harden the longer you leave it, so the carb may have been in a “bit of a state” before you got it. Your efforts to clean the carb by hand have probably worked on the idle jet, but not so much on the main jet (as evidenced by poor performance at over 30% throttle)

We recently had a carb thread that highlighted the need to “back flush” the carb, rather than “forward flush” it, which would only serve to compact whatever is in there. It also came to light, that simply blowing down one hole and seeing it come out of another is not always the end of the story – some of these holes lead to two exits, and all need to be clear

Hopefully, this is not the case with your bike, and a simple dose of carb cleaner may well cure it completely, time will tell. But it serves to show that “a little knowledge is a dangerous thing”, and that many is the time someone has come to this board, insisted their carb was thoroughly clean, when in fact, that has proved to be far from the case – it’s an easy mistake to make

Stick to running the liquid carb cleaner through for now – we need to eliminate this first – worry about the rest after you’ve tried the cheapest, less intrusive things first


My motive to posting this this information now, is that I’m out of the country for a couple of weeks after this weekend, and may not be able to re-join the conversation until I get back. In the meantime, if your carb or exhaust needs any further work, trust Fred’s advice – he knows his stuff

As supachip1 points out, you have the same CV carb as the TW200, so despite this being primarily an American site, there’s a wealth of advice members can give you on this particular carb

But for now – stick with Redex – it may yet save you a lot of grief ……..
 
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