Mk1 Nexus buyers guide?

[michaelphillips]

if you are sure that its done up tight and the intake bolts are tight, you would think there cant be a leak! so you start thinking the Stepper motor for idle jet is not working....you will have to ask ben how he got hold of his? and is it complete with the stepper motor, as this is only the first part and not the injector side of throttle body, i cant see any issues with changing this part over, the manual just states when you change the injector to then do co adjustment, but even then they are going strictly by the rules .... if the nexus starts easy,even when cold and runs well, you would think the scoot was being fed the correct fuel through the injector and you have sorted the air leak and the exhaust is not leaking so as the manual states below:


Combustion and ignition are managed on the basis of the engine speed and the throttle valve opening.
Further corrections are made according to the following parameters:
- Coolant temperature.
- Temperature of the intake air
- Ambient pressure
The system implements an idle feeding correction with cold engine through a stepper motor on a bypass
circuit of the throttle valve. The control unit manages the stepper motor and the injector opening
time, thereby ensuring the idle steadiness and the proper combustion

so at a punt if the stepper is not working correctly then it would make sense to change the throttle body part first

also be careful, you should not need to undue the injector fuel lines, but if you do... NO HOT ENGINE
The fuel supply system is pressurised at 300 kPa (3 BAR). Before disconnecting the quick coupler
of a pipe in the fuel supply system, check that there are no naked flames, and do not smoke. Act with
caution to prevent spraying in the eyes.

[michaelphillips]

THE THROTTLE BODY IS THE SAME UNIT ON ALL THE 400 AND 500CC MASTER ENGINES.
Sutton want just over £200 http://www.gileraspares.co.uk/spares/pa ... B555&uid=0" onclick="window.open(this.href);return false;

new here for a cheeky £100 best offer http://www.ebay.co.uk/itm/GENUINE-PIAGG ... 25799c87c4" onclick="window.open(this.href);return false;

but bens would be best try, as elimination process

[BenR]

and there was a mention of a pipe that leads to the filter box, somewhere by the injector?? good luck

I'm sure that's just a breather I suppose it could be part of an SAS (secondary air system) system but I'm sure it wouldn't have anything to do with your fault. Did you order a new airbox inlet hose? From what I remember there's no gasket from TB to inlet pipe or inlet pipe to the cylinder as the inlet hose is self sealing. The spare TB I have is still attached to the inlet pipe so you're welcome to have that with the TB i.e no need to order another one. It originally came from an X9 500 but they're identical & even share the same the part number.

[Taipan]

I think I'll try the throttle body as the stepper isnt doing the same thing each time i switch the ignition on and off. My BMW was the same with similar consequences. Complete (educated?) guess work but it wont be an expensive mistake. Next step is to stop guessing and get the codes read. DougL told me about Scootech and they have Piaggio master status and should have the tech to tell me what it actually is.

I must get it sorted as I'm really enjoying it, more so than I did with my last one?

[michaelphillips]

Scootech and they have Piaggio master status GOOD CALL would be the best cause of action, as you will be a hell of a lot wiser, no point spending money i not needed to on certain parts
that 16 times thing,
In any case, when the fault is no longer present,
the data storage is automatically cleared after 16
cycles of use (cold start, running at regular engine
temperature, stop).

[Taipan]

and there was a mention of a pipe that leads to the filter box, somewhere by the injector?? good luck

I'm sure that's just a breather I suppose it could be part of an SAS (secondary air system) system but I'm sure it wouldn't have anything to do with your fault. Did you order a new airbox inlet hose? From what I remember there's no gasket from TB to inlet pipe or inlet pipe to the cylinder as the inlet hose is self sealing. The spare TB I have is still attached to the inlet pipe so you're welcome to have that with the TB i.e no need to order another one. It originally came from an X9 500 but they're identical & even share the same the part number.

Yes the new pipe is on order but Suttons said a minimum of 21 days. I pressure checked the one that's on there and the sikaflex is still holding up okay. Be a lot happier when the new pipe is on there though!

I cleaned up all the surfaces and before reassembling it today. I knew on start up nothing had changed though and the ride with the backfiring and stalling confirmed it. There was so much gunk round the stepper I'll be surprised if it was still working but hopefully i'll find out at the weekend when I fit your one. :fingerscrossed:

[Taipan]

Just stripped it down again, really to have a look at how the hell to separate the throttle cable assembly from the throttle body itself? Whilst I was there I tried flicking the ignition on and off whilst listening to the stepper motor. Sometimes it nothing and some times its a good seven or 8 clicks in quick succession and other times its a single click.

Now being a stepper motor I would expect it to click in steps and cycle through its range but then I'm not familiar with these and of course I could easily be wrong. If any of you Nexus or any other 400/500 Master engine owners happen to be going out to your bike can I ask a favour. If you put your ear next by the left hand side of the engine and turn your ignition on so it goes through its pre checks do you hear any clicking (sounds a bit like a relay) from that area?

I should probably stick this up as a question in the garage forum and maybe on the X9 forum too but I'd be grateful for any feedback from anyone following this thread.

[michaelphillips]

never taken the cable off, not sure if its a central screw, then it slides off intact?
on gts owners club cheekythomas was chatting regarding flooding on start up on 2004 nexus 500 and backfiring on overrun as fuel still being injected and mentioned temp sensor as ... next up is the stepper motor as its what controls the cold start and idle circuit, which seems the most likely as it matches the symptoms http://www.gtsownersclub.co.uk/forum/vi ... 19&start=0" onclick="window.open(this.href);return false;
anyway, been out to scoot today to change the HT Lead and suppressor cap as they are 9 years old thought i would change them as parts arrived.. so my cover was off, so below is what happens:

I TURN KEY TO ON: I GET A 5 SECOND WHIRRING NOISE

I TURN KEY TO OFF: I GET TWO SECOND WHIRRING NOISE THEN ABOUT 5 CLICKS AND THEN 2 SECOND WHIRRING NOISE

did this a few times and its the same every time, this is with the scoot cold engine

http://www.2211works.com/?page_id=7" onclick="window.open(this.href);return false; states the air intake to have:
Air intake: Butterfly valve with position sensor, stepper motor and air temperature sensor

[michaelphillips]

this video might help with regards to temp sensor cleaning " onclick="window.open(this.href);return false;

the throttle cables might just come off the central part as this might be permanently attached to the throttle body , think there are two cables

[Taipan]

Yes, an awful lot of things point towards it being the stepper motor/air temp sensor. From the thread you link to cheeky thomas says,

Has it cured the problem then?? As i would be more looking towards stepper motor issues for stalling.

I've been trying to clean out the aperture and stepper motor and the eml light went off briefly but came back on. So another clue that I'm in the right direction. Thanks for having a listen too.

The air sensor temp probably has a limited life and as its under a £10 It'll probably get one of those soon anyway.