Hi Folks, Hope somebody can help with this one. I have a 2009 Neos 50 4T, which refuses to idle. It's the fuel injected version. It starts fine, and seems to rev OK, and will in fact run fine at normal road speeds. I can hear the idle control valve operating, and the motor revs up and down when returning to idle, as is normal on cold start. It just wont idle. I was wondering if anybody else with a 4T neos or similar engined Yamaha ped had suffered from the same issues, and how did you resolve them? I'm a bit concerned that the throttle body is dead, which is big bucks for what is a slightly untidy commuter bike. Thanks, Mark.
OK, Did some more investigating on this one. Got the manual from the local Yamaha dealer. Checked everything, valve clearances, plug gap, compression (195psi before it blew the gauge off)etc, all were OK. This bike has a fuel injection system. It has a unified throttle body, with the idle control valve, air pressure (MAP) sensor, air temp sensor and the throttle position switch all in one. Everything but the air temp sensor is in range. The air temp sensor should be 5.7k ohms to 6.3k ohms. It's reading 2.1k ohms, which is clearly out of range, and may well be affecting the tickover. So I'm off down to Maplins to get some dummy load resistors, and I'm gonna see if a mid range value lets it tick over. Incidentally, the reset procedure for the throttle body on this one is, Ignition on for three seconds, then off, repeat twice more then allow the bike to idle for ten minutes. Looks like I'm gonna learn lots about the ECU on this one! The throttle body is £370, so be warned! If you go to look at a Yamaha 50cc 4T scoot, and it won't tick over, be negotiating big bucks off the price! Cheers, Mark.
I am currently looking at this problem on one of these at the moment I have the Yamaha diagnostic tool and it does not ptoduce a fault code so it is now down to measuring and testing, luckily I have access to another Neso 4t so I can substitute parts and chaeck it out will post results as I find them.......anyone got access to a workshop manual on the net ?
Ok where do we go I have today purchased the Yamaha diagnostic reader ....no fualt codes recorded but bike will not idle at all , I have another Neos 4t that has done 276 miles available and have swapped out the throttle body ...no change.....swapped out injector.....no change....fitted my parts from the faulty Neos onto the good Neos and it runs "A" ok ....so it is not the fuel injection system ????? Next I removed the exhaust and started the scooter it idled no problem ...... so swapped out the good exhaust from the 276 mile Neos and fitted that ......would not idle at all ....so is it back pressure.......not sure I will check the valve clearances as I am thinking it may be exhaust gases cannot escape cylinder quickly enough at tickover .............any ideas out there ?
Further on and no results .....valve clearances checked and ok......so now time to check the ignition pickup and generator to see if the signal is beling lost a tickover............watch this space it won't beat me Grrrhhhh!!!
Got the answer to this thread at last the bike is now fixed had to take it to local mechanic who assisted with the diagnosis and repair......................it turned out to be valve clearances ! On the exhaust valve even though it checked out fine when measured with guages (it was on it's tightest setting) .....so move rocker arm to the side remove shim and fit smaller size reposition valve onto shim pad and start up..........hey we have idle. The exhaust valve was open all the time and introducing hot exhaust gases into the cylinder and creating a weak mixture and no amount of adjusting using the Yamaha tool would alter it . The valves are very small and must suffer from excessive valve on the bike this one had 9000 miles on the clock..... it will require a re-shim soon but I will put some miles on it and then have it re-done after a few miles many thanks to Rod @ Streetrod Motorcycles Fleetwood UK. Hope this helps out other folk out there.
The valve clearances to clarify was checked twice before and was within spec but albeit on the tightest limit.....it seemed that it had to have a little extra clearance possibly due to expansion and gap closing up so don't always accept the first measurement as being ok ....if it is very tight put some slack in and test again...
Hi. I know this is an old thread but has anyone found what make/model universal diagnostic scanner that can adjust the Rev limiter on a 4T Neos’ ECU?
