TMAX Mark 3 - INJECTOR BALANCING

[MariaB]

I haven't been on here for a long time. But we have just been to Spain on two of our Mark 3s. Unfortunately, there orange one fell off its stand (doing a Ducati 10 seconds after i had checked it was okay) so new paint and levers etc required. Both did 1600 miles in eight days and were great to ride. Even old crates like a mark 3. We have also let one of them go to a guy near Preston. So, now down to having three.

The question this time, is there anywhere on the web (or on here) to tell me how to balance the injectors? And what kit I need. Having had four of them I am well qualified to know how they should feel (eg they all have a little bit of a transmission rough patch at 60 mph which would otherwise worry me if I didn't know that all of them did it). And, as a result of this, it would seem that the orange one is slightly less smooth on a tiny throttle opening. I suspect injector imbalance......But do tell me if i am wrong.

Clive and Maria

[Data]

Hi MariaB,

Unless the injectors (or an injector) has been replaced recently, the injectors shouldn't need any sort of intervention. Usually the injectors come calibrated to the required pressure setting. Unlike on many cars where the injectors often need to be set up before fitting. Some few bikes also require calibration of injectors before fitting.

I suspect what might be the case is your injectors are dirty & might benefit from a dose of fuel system & injector cleaner. When dirty this upsets the calibration & this might be the thing you are aware of. If a cleaner does not help then I'd certainly look around the bike for other causation. This can include the spark plugs, valve clearances & air leaks on the induction side of the fuel system.

There are other things too that can cause this vibration at various revs....but start with the above list. The Tmax 3 does suffer from some vibes & poor fuelling at certain revs so owners have told me. If all else fails you can improve fuelling with a different ignition & fuelling map which can dramatically improve vibes & throttle response. Adding two percent fuel here & there in the rev range is often all that's needed. Flashing the ECU can be carried out by anyone with some knowledge & the gear. Or you can fit a PC3 emulator but I'd personally want the bike on the Dyno to get it just right. All this can dramatically change the nature of the bike with big improvements.

PS. Just twigged, you are probably refering to information regarding " how to balance your throttle bodies"! Not your actual injectors. Normally a fairly easy operation. But I've never done this on a Tmax. It should be in the workshop manual.

[roadster]

If it doesn't have throttle cables then all adjustments would have to be through the electronics and you would need the correct diagnostic equipment. On the other hand if it is not "fly by wire" then holding the throttle at a steady fast idle and measuring or listening to the air flow rate at each intake then equalizing by adjusting the cables is about all you can do for any dual intake twin. There are lots of other approaches such as removing a plug lead on each side in turn and achieving the same speed on each cylinder - could be a shocking experience with modern ignition systems! In any case you have to be sure everything else is correct, particularly valve clearances, before turning to this.

[Ralph]

On other Yamaha twins you can adjust the idle balance this is done via a screw
on the injector throttle body and I don't know it this applies to your scooter, but
don't just dive in with a screw driver as you are only supposed to adjust one body
the other being set at a reference point at the factory, so you need to have a look
for the correct instructions.

[Data]

Or he could use a very cheap to buy throttle body vacuum balancing system. Or take it to a dealer who already has the equipment. It doesn't take long. Definitely do not remove a plug lead & run the bike with a dead cylinder like we all did to bikes of old. On modern bikes it's very bad for the coil/CDI as it needs to discharge at around 40,000 volts. You cannot tune modern bikes by listening to the induction either like bikes of old. The difference in balance only needs to be tiny to produce vibes & you simply won't notice it by ear. It has to be a bigg...ish difference to be properly noticeable. And to carryout adjustment to get it spot on needs a proper balance job.

As Ralph says, check out the procedure or go to dealer is best if you don't have equipment.

[MariaB]

okay thank you. I am sorry if the vibes thing misled you. This is not the problem. The problem is a slight hunting on a tiny throttle opening when in heavy traffic. The other TMAX doesn't do it so much. I definitely think it is throttle adjustment - Yes it was balancing of the throttle bodies i was thinking about. The bike has only done 3000 miles so I don't suspect valve clearances. It might just be a characteristic. My other two don't idle perfectly either. Otherwise they all pull perfectly on anything more than a micron of throttle. I was looking to see where the TB adjuster is as I can't see it. It is not FBW and I do have vacuum gauges and an intake trumpet but unfortunately the latter won't fit in the aperture of the airbus (which is within the from apron). It's not bad enough to go to a dealer and i don't trust them anyway. I change my own belts but haven't yet had to do valve clearance.

[Data]

Yes, the slight fluffing at the start of the throttle opening isn't uncommon on many different bikes. Not usually anything to worry about. It is often down to the weak mixtures that modern engines run. Getting a clean throttle from idle isn't always easy. Also momentary lag of the throttle position sensor motor can cause this. The TPS setting can also be bit off on some engines making this fluffing worse or even causing it. This is normally set at the factory but it can be checked and adjusted on SOME bikes, but not all. Whether it's adjustable on your Tmax will be listed in the workshop manual. But do have a good snoop around for air leaks, another well known cause of this fluffing. Good luck!