Sparkplug, whaddya reckon caused this?

[Gregor]

Took the whole exhaust system off to get to the engine breather pipe, needs a damn good clean before I can see what’s what.Now the exhaust is off I can look in the exhaust ports to see if the valves stems are actually moving when I turn it over by hand.Save that little treat for my next day off.

At this rate I’ll be able to justify a proper bike lift

[Gregor]

Well latest exciting news.....

Engine breather okay, exhaust valves can be seen moving when looking into the ports.

Wrangled the throttle body out for a good clean and inspection, rubber joining boot between throttle and cylinder head has a split on the inside, can’t see if it goes all the way through to the outside so new boot ordered anyway along with injector seals.Need to give the throttle body a good clean on the outside before I pull the injector and check that’s not partially blocked also turn the engine by a hand and see the inlet valves moving.

When I last ran the engine it seemed to get awful hot very quickly, I think I’m probably delaying the enevitable top end strip for either excessive carbon build up or damaged exhaust valve from running with the holed header pipe.

It’s been good to strip the bike down anyway and have a good look at things that have been unseen for 13 years.

[Taipan]

Well latest exciting news.....

Engine breather okay, exhaust valves can be seen moving when looking into the ports.

Wrangled the throttle body out for a good clean and inspection, rubber joining boot between throttle and cylinder head has a split on the inside, can’t see if it goes all the way through to the outside so new boot ordered anyway along with injector seals.Need to give the throttle body a good clean on the outside before I pull the injector and check that’s not partially blocked also turn the engine by a hand and see the inlet valves moving.

When I last ran the engine it seemed to get awful hot very quickly, I think I’m probably delaying the enevitable top end strip for either excessive carbon build up or damaged exhaust valve from running with the holed header pipe.

It’s been good to strip the bike down anyway and have a good look at things that have been unseen for 13 years.

As I'm sure you know, if it does, that would certainly cause the problem you were having, slow return to idle etc. I suspect its more likely to be soemthing like that, as burning valves out due to weak mixture used to happen at sustained open throttle runs more than normal town riding with a near constantly varying throttle.

[Gregor]

Just had an email back from Fowler’s Yamaha saying the rubber boot connecting throttle to head is out if stock, discontinued and no longer in production which seemed bloody strange considering the tenere was in production from 2008 to 2016 and shares this part with the old MT03 and is marketed as a proper Adv bike.

Found an alternative on ebay for £6 as opposed to Fowlers £28 hoping its of comparable quality.

[Gregor]

I’ve never worked on a FI bike before, bar all the various sensors needed to manage the engine the simplicity of the throttle body surpised me.




Not cleaned anything yet, still waiting for the connecting boot to arrive.



Looking pretty grimey in there.
Not sure if its normal because the oil breather vents to the airbox and quite a but of oil mist gets forced out with sustained high speed running.I always see a cm or 2 of oil in the drain tube from the airbox after long rides.Need to look at the sealing around where the snorkel and filter meet judging by the grime stuck to the oily residue.

[Gregor]

I’ve had the Injector out and connected to a 12v supply and gives a good healthy spray with a can of aerosol carb cleaner piped into the inlet.









The manual barely covers the throttle body in detail just a method for testing injectors and TPS etc but I’m wondering if the cold start circuit where coolant is piped into the base of the body and out a again may be faulty, there’s little info available on this but presumably there is a plunger in there that is pushed open by coolant pressure this restricts air that enters via the pilot inlet until the thermostat opens cutting the coolant flow off shutting the plunger.The plunger might be seized, when I block the outlet and syringe water in I see no movement on the shaft visible through the pilot air inlet.

That might be complete bollox from me anyone know for sure how it operates?

Can’t post a pic at the moment hosting site playing up, will do later.

[Gregor]

Coolant inlet/outlet on the bottom right, shaft visible through the large air inlet on the bottom left.

It looks like the plastic cap on the lower left side is there to accommodate lateral movement of the end of the shaft leftwards.

I’m not keen on removing that part of the throttle until I understand what’s going on in there.

[Horse]

carbon build up

Ah, higher compression head, performance mod!

[Gregor]

Well the fast idle plunger is operated by coolant temperature change not pressure as I’d wrongly assumed.

Resting or cold state



After injecting near boiling water through the coolant inlet the shaft moves to the left. Apparently operated by wax melting inside the plunger......... how quaint.

[Lutin]

Excuse my ignorance, but what difference are we supposed to be seeing in the photos?

[cheb]

Just underneath the nut and stud there's a bit of the plunger visible in the second photo. next to the cast boss.