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XJ6 Upgrade Help


XJ6-boy
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So after upgrading the throttle bodies on my XJ6 to ones from a FZ6 Fazer I'm now wondering if the air box needs to be modified to allow more air to pass thought. On my original investigation it looked like their was very little difference between the air boxes and being not sure if the Fazer one would fit under my tank kept the original xj6 one. can any one help in letting me know if the Fazer one will fit under the tank of an xj6 or some other mod to increase the air flow (please remember that the air temp sensor is mounted inside the air box.

Thanks XJ6Boy

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So after upgrading the throttle bodies on my XJ6 to ones from a FZ6 Fazer I'm now wondering if the air box needs to be modified to allow more air to pass thought. On my original investigation it looked like their was very little difference between the air boxes and being not sure if the Fazer one would fit under my tank kept the original xj6 one. can any one help in letting me know if the Fazer one will fit under the tank of an xj6 or some other mod to increase the air flow (please remember that the air temp sensor is mounted inside the air box.

Thanks XJ6Boy

Great that you have fitted fz6 throttle bodies, i would think that the airbox is not going to be that restrictive. Maybe you need to turn your attention to fueling.

if (am i am trying to remember) you have gone from 32mm (standard xj6 body dia?) to 36mm (fz6 body dia?) that equates to an increased cross-sectional area of about 25% - you then need to add more fuel to compensate. The XJ6s ecu may be able to enrich the mix to some amount when cruising (due to closed loop / oxygen sensor effects), but other than that the injectors will never be supplying enough fuel to match the increase in air. Not sure if the fz6 injectors are the same parts as xj6, if yes maybe a power commander and a run on a dyno/autotune would do the trick.

How does the bike feel when ridden? a guy on the american forum, was toying with fz6 or r6 cams, and i guess ultimately you might need to do that as well (maybe transplant in an fz6 head?) and even look to raise the rev ceiling (though bigger bodies and a power commander might suffice).

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Thanks for that, I can confirm that the injectors are identical for the fazer and the xj6, as are many engine bits, the cam idea I’m not sure on as you only gain 0.6mm additional opening on one exhaust valve and the same on one inlet valve the other valves open the same and with the ignition timing on the xj6 being earlier it kinda compensates. Sounds and runs great and you can feel a little extra power when cruising although waiting for better weather for a proper test as these engines seam to need to be warmed though properly before they perform. not sure about a power commander though as I know very little about them other than they don't do one for the xj6 (as yet) please enlighten me on this subject.

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Thanks for that, I can confirm that the injectors are identical for the fazer and the xj6, as are many engine bits, the cam idea I’m not sure on as you only gain 0.6mm additional opening on one exhaust valve and the same on one inlet valve the other valves open the same and with the ignition timing on the xj6 being earlier it kinda compensates. Sounds and runs great and you can feel a little extra power when cruising although waiting for better weather for a proper test as these engines seam to need to be warmed though properly before they perform. not sure about a power commander though as I know very little about them other than they don't do one for the xj6 (as yet) please enlighten me on this subject.

http://www.ebay.co.uk/itm/DYNOJET-POWER-COMMANDER-PC-5-YAMAHA-XJ6-N-D-E22-008-/140584818707?pt=Ricambi_e_Accessori_Moto&hash=item20bb821813

http://www.ebay.co.uk/itm/Dynojet-Power-Commander-PC-V-Yamaha-FZ6R-2009-/380137202786?pt=Motorcycles_Parts_Accessories&hash=item5881f16462

also

http://www.ebay.co.uk/itm/CENTRALINA-COMMANDER-YAMAHA-FZ-6-R-09-11-TECNOPOWER-005-/250800028087?pt=Ricambi_e_Accessori_Moto&hash=item3a64d8b9b7

btw the airbox of the xj6 is bigger than the fz6 - i did see it written somewhere.

i would definitely get it on a dyno - you don't want to wreck the engine for the sake of £40 and a bit of advice from a tuner.

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  • 10 years later...

I am surprised to know that there is any gain from 32 to 36mm TBS, it doesn't make any sense that Yamaha of all people, makes almost same bike, goes all the way up to reduce the TBS diameter, just to have lower performance. It's beyond me, i dont understand why they would do that.

Now... the XJ6 is definitely a bike that shouldn't exist anyway, its clearly a downgrade in everyway to the FZ6, the only superior thing on the XJ6 is the cam chain tensioner that is hydraulic... and i personally like the power more on the XJ6, i know the FZ6 is more powerful, but is a useless power, is way up on the revs, the XJ6 power is more useable more realistic to the engine size.

That being said i always thought that it was weird changing the diameter of the tbs and i had curiosity knowing the performance difference. Becauise i dont think it's costs... i think they would cost the same to produce.

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  • Moderator
On 12/23/2022 at 11:15 PM, leorojasma said:

I am surprised to know that there is any gain from 32 to 36mm TBS, it doesn't make any sense that Yamaha of all people, makes almost same bike, goes all the way up to reduce the TBS diameter, just to have lower performance. It's beyond me, i dont understand why they would do that.

Now... the XJ6 is definitely a bike that shouldn't exist anyway, its clearly a downgrade in everyway to the FZ6, the only superior thing on the XJ6 is the cam chain tensioner that is hydraulic... and i personally like the power more on the XJ6, i know the FZ6 is more powerful, but is a useless power, is way up on the revs, the XJ6 power is more useable more realistic to the engine size.

That being said i always thought that it was weird changing the diameter of the tbs and i had curiosity knowing the performance difference. Becauise i dont think it's costs... i think they would cost the same to produce.

smaller TBS would make for more torque lower down at the expense of HP

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Smaller valves and softer cam timing will also work with smaller tbs for better torque. s the FZ is the sports variant and likely to race, a manual cam chain adjustment weighs less and is more reliable, if more labour intensive. 

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