2004 XT660X preignition between 10-30% throttle
 

Hi Guys,

I have a problem...

I bought the bike from a dodgy guy and spent a bit of time fixing it up. I topped up the gas with 98, new air filter, cush drive, airtemp mod, co adjust from 10 upwards to 20 then 30. I was having trouble with stalling at low rpm so I cranked the idle speed. I think that's when I started getting trouble. I thought it was a bad battery as went flat trying to get it started. It charges up quickly but drops way down when cranking.

I've done the accelerator mod, adjusted the idle throttle and tps, installed a new tps even but still getting preignition at around 10-30% throttle.

I've also put an iridium plug in but it's one increment colder.

What can I do to troubleshoot?

My thought is that as I've adjusted the idle and then back to the tps several times, the relationship between the two is off and I need to go back to setting up the throttle plate/cable correctly then do the TPS, then do the idle adjust. The idle screw is set to max right now and it's taking a few twists of the throttle to get it started along with a bit of cranking, about 3 sec.

Could someone tell me how to set up the throttle vs the TPS?

Clarification...
 

Just so I'm clear, I call it preignition because it sounds like it's coming back up the intake so I'm assuming the inlet valve is open and preigniting.

After it pops, there is no subsequent firing of that stroke.

Cheers,

Matt

Update...
 

Just loosened the idle right back, adjusted the slack in the throttle cable. Checked the TPS and with the idle backed right off it was at 20. Now set 17 and I'll go grab a new battery

Sorry, but I'm not too clear by your description of preignition? Preignition, you would notice as a pinking, knocking or diesely sort of sound from the top end under load. Are you saying it is backfiring through the intake/air box?

That's right, backfiring through the intake. What do you think could be the reason?

Just a side question: when setting the CO value, it sounds like a solenoid in the air box is energized...what's that about?

Cheers!

Matt

Right, I understand now.

Firstly, there is something quite amiss if your idle adjustment screw is set to its maximum to get the bike to idle and start. I think this is indicating other problems and you’re just trying to compensate for them with the idle speed?

You can set the TPS, but ideally you set it after you have got the engine idling correctly. The procedure is to set the idle first then loosen the screws on the TPS body so as it can be turned in its slots and rotate the TPS until 0.63 – 0.73V is detected yellow and blue/black wires in the back of the connector. Tighten the screws when the voltage is within spec. All this assumes a good TPS is fitted (which you say has been replaced).

However, as I mentioned, you really need to have a stable and correct idle speed first (1400-1500 rpm) – which you haven’t got. This, along with the backfiring through the intake, leads me to think that your valve adjustment is not within specification – probably the intakes valves are set too tight and are not closing fully after the intake stroke has completed? This may cause a small amount of fuel/air mix to be forced the wrong way through the intake and would explain the troublesome idle, hard-starting and backfiring.
You also need to have the CO set to somewhere around 10-15. (It’s not exact, but roughly what it should be for your year of bike). Also check the throttle angle is between 15 and 20 in the diagnostic mode. If that is way out then you’ll have problems.

Before going any further though I would take the tank off and check the cold valve clearances. Then go back to setting the idle, TPS etc. You can also check the valve/cam timing while you’re at it which, if not right, will cause similar symptoms.

It is also worth carefully checking for intake vacuum leaks as well as these can have serious effects on idle and slow running. The rubber intake hose on older bikes is notorious for perishing and leaking vacuum.

Thanks for your help with this.

What I've done today:

Installed a new battery.

Adjust the idle, and set the TPS to 17. I will check this again when hot and cold to see if there is any drift but it is new and replacing it didn't affect the running at all.

The idle is smooth - perfect.

Blocked off the AIS hose and air box port - made no difference.
I connected back up.

I ran the bike in the portion just above idle where I'm guessing it uses the map and it still misfires.

I added some fuel injector cleaner incase it's a dirty injector and ran for 10mins revving etc.

I sprayed contact cleaner around the carb and hoses - no rev change.

I adjusted the CO to 10,15,20,25. It ran much better around 25 but when riding it, there was little power.

I installed the old plug, the new one was slightly grey.

I don't think it's the tappets but I can't hear them so they could be too tight. I will check them tomorrow.

Could it be any of the following?
Coil, fuel filter, pump, injector, poor wiring/connections, ecu dry solder joints.

To recap: it only does it during the lower portion of the rev range and if you pull the throttle in quickly the engine responds well. It just intermittently stumbles when in the normal range of use.


Thanks,

Matt

maybe of no help at all BUT have you checked the air filter?..snorkel still in?..would you believe mine had a tissue paper in the snorkel when i bought it?.

Thanks for the support mate. Yeah, I put a fresh filter in the bike, on top of that, I've removed the snorkel.

I didn't get a chance to do those other checks yet but it will happen!

Thanks guys!

Matt

Update:

I found that with the CO value way down at 2-3, the misfiring is really reduced to almost nonexistent. I haven't taken it for a ride like this but it's interesting I thought. If I turn the fuelling up via kevs air temp mod, the misfire comes back.

Could this be a dirty injector causing the poor running???

It sounds very much to me that it is running rich at the lower end which is why upping the CO was set lower than expected and why turning up the fuel mod makes it worse. It could be the injector. Could you also have a look and see what part number the ECU has printed on the side. These threads will help in identifying your ECU.

http://www.xt660.com/showthread.php?t=8546

http://www.xt660.com/showthread.php?t=519

ECU model
 

The model number is 5VK-8591A-00, 112100-1870, 12V TBDF08, P.

I've contacted Yamaha about the TPS and ECU recall, they said the TPS recall has already been carried out and the ECU is not affected-there was no recall for the ECU.

Thanks for your help mate.

Is there an easy way to clean the injector? Or should it be replaced?

Cheers

Matt

You could run a bottle of fuel injector/cleaner through the system ,leaving it to idle...redex or similar. I would run a whole bottle through the system with a small amount of fresh petrol.

I've run the bike for a while with the cleaner through in high concentration - it was idling fine so after an hour I took it for a ride. The problem spot had shifted to higher RPM, the lower RPM was fine.

I rode about 800m then the bike wouldn't run. I pulled over and gave it time to cool off or something as it wouldn't idle and any gas would cause it to cut out.

I managed to get it idling and just clutched it back home.

I started it up last night - idling is still difficult so will dump the fuel, inspect the filter while I'm at it. Hopefully with fresh gas it'll be good.

Update to come when I get a chance.

have you checked your plug?..what colour is it?..it is the original now your running?..

Update
 

I got to take the tank off today to check out the filter... I'm surprised it was working! The amount of sediment = about 1/3 cup... rust all over the place.

I've order a new pump with new filter from Alibaba - cheap!

I'll try post pics...

I'll check out the plug - it's the original back in there.


What can I do to clean and prevent rust or does it not really matter?

you can get a petrol tank sealent ..ebay should help. Personally id put some ball bearings/marbles inside with some petrol and aggitate the tank till you feel you got the loose stuff out and flush it out maybe use an airgun..carefull with your eyes tho.

AND keep your eye on the filter..not sure if there's a secondary filter on these..you could add an inline one though..belt and braces and all!

Thanks for the advice Nicrok, great ideas!

I was thinking of trying a product called evapo-rust. It's non corrosive so won't affect the paint, worth a shot!?

I'm gonna take a look for an inline filter and tank sealant...

Thanks mate

Do a forum search re in line filters...due to the fuel injection system i think Kev said that in line filters needed to be able to withstand 3 bar..but i cant remember..im just home after nasal surgery and general meds are still working.

Finally...!!!
 

Hey Guys,

Well I replaced the fuel pump and it still didn't work. My guess was it was a high flow fuel pump, I measured 54psi so I moved on from there and fitter the old one. I thoroughly cleaned the tank of rust/scale and cleaned the filter too as the kit I got had a filter too large for the housing. It was full of rust scale.

I ordered a new injector and waited about 2 months for delivery as they were out of stock.

I finally got to put it back together with the new injector, put in fresh fuel, a new denso plug and gave it a few cranks...

Finally! Sat there purring, did my Rev check and went for a ride. Perfect!

Well almost, it's a little snatchy in 1st and 2nd but I'm guessing that's the chain tension.

Mystery solved!

I don't see any real recommendations for installing an inline filter so I'm just going to keep it topped up with gas to keep the rust at bay.

Thanks for your help guys,

Matt

Well you deserve a medal for perseverance.

Glad you eventually sorted it out. Enjoy :coolsmiley:

Thanks
 

Thanks mate!

I'm a bit hesitant to make any changes... but I will😊

I'll install the new TPS and mess about with the CO and temp a bit - should be fun!