690 (New model) Wafer check valve, air pump and evap cannister

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GW

Joined
May 18, 2011
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KTM 690 Enduro
Hi. First post ever here. My new model 690 Enduro has a couple of oddities that my previous 690, which was a 2014, did not have. I thought I would share this and as I go along let you guys know how I decided to live with/deal with these add-on gizmos. My previous  had a twin spark cylinder head which, with the inlet temp monitoring, FI, narrow band Lambda and exhaust cat was deemed efficient enough to pass emission standards at that time. All I did on that bike to restore its self pride as a performance bike was to fit an fmf exhaust canister and Twin Air flat foam filter (from Wayne Puzey) on the standard air box with an open type fine mesh cover. Of course it was very powerful.

This all new motor has additional cylinder head mounted balancing shaft and the cam operating directly on the inlet valves, and only one rocker arm extending across to the exhaust valves -so perhaps those issues of failure are sorted who knows? Time will tell.

But the reason for this post is firstly, to reveal my discovery of KTM's (and Husky's) addition of a wafer check valve behind a cover on the cylinder head and secondly, the evap canister/ fuel vapour contol from the fuel tank.I know the 701 has had this motor for a year or two but this is all new for the latest KTM 690.

On the wafer check valve cover is an outside pipe connected to a rubber tube which leads to a little 12v air pump which draws fresh air via another rubber tube from the air box and it (the pump) tries to introduce this air into the exhaust port via a built in channel in the cylinder head towards an inside point just where the exhaust header bolts on. The wafer check valve allows air to be drawn/pumped in to the exhaust during the rarefaction part of the exhaust pulses and especially during vacuum scavenge (I think). This addition of fresh air into the exhaust header helps to oxidise unburnt fuel and make the bike pass emission tests after the exhaust gases pass through the large oem cat exhaust. (Also it makes the top section of exhaust run kind of hot; this is in the section where the lambda monitors for lean/rich).

I took the large stainless steel heavy oem cat- containing exhaust off and fitted my fmf pipe. It wasn't straight forward but nevertheless easy for me as I can do the required fabrication mod which was to make it Momar clamp friendly and adjust the top bracket. And I put my same flat Twin Air filter onto the airbox. I thought all would be fine but no. No.......it wasn't.

The excellent inflow of air and the performance exhaust with the additional air being pumped into the exhaust makes for quite dramatic popping and backfire on beginning to tap off, deceleration. I think this is because there is now dramatic scavenge, and maybe combined with valve overlap there is some inlet cycle mix just managing to hammer into the exhaust header and this, combined with the hot header and extra air pumped/drawn in through the wafer check valve caused a detonation or two or twenty. (Maybe)

So I knelt down and looked at the pipework, there's a lot of it but actually quite simple and neat..... And I left it all in place. (for now). BUT: I made a same shaped 1mm in-between plate to close the check valve whilst still leaving the cover plate in place on top. (I cut up an old junk desktop cd drive enclosure for the thin steel plate) We were in lockdown at this stage so the test ride had to be a shopping trip and I went to an unnecessarily far shop in the Tygerberg hills. The backfire was gone and the light popping that remained was just that happy crackle that a big single has. I did fill up in Durbanville and that caused its own problems.

The second issue ie: the fuel vapour control system reared its head. The bike started fine at the garage and shortly afterwards I made a roadside stop to call home. When I started up to get going again the bike stalled immediately when I cracked the throttle open to let out the clutch. With a Ffffrrrpoptt! decomp valve sound. Twice.

Back home I knelt down (again!) next to the bike and discovered that the overflow from the fuel tank travels downward via a Y connector to a thick closed-at-the-bottom collector pipe (which is joined to the bottom of the Y section) and then up and all the way forward to a charcoal filled canister and then another suction pipe goes from the plastic cylinder out to a 12v solenoid valve, then to the throttle body manifold side. When I removed the stopper at the bottom of the thick pipe below the Y-piece quite a column of fuel ran out onto my hand. Also, I popped the vacuum pipe off at the throttle body/manifold side and even there the inside of the thin pipe was wet with petrol. so the canister was not really able to remove condensed vapour fully and it caused a fuel rich vapour to be sucked in, stalling the motor.(I think) If the fuel tank is not full you may not experience this as much but off-road there is a lot of shaking and fizzing of petrol  which will find its way down that collector pipe.....And I left it all in place (for now) BUT I removed the stopper from the collector pipe under the Y-piece so the overflow is once again an overflow and I put in an internal block within the thin vacuum pipe near the throttle body. So even when the solenoid valve is open there is no suction.

Another important item was needed from the shops, this time Olive oil from a farm shop on Tygerberg hill. WOW. The bike is now absolutely different; smooth idle, ridiculous snap and wicked wicked acceleration.a very different bike. Not sure if this is an interesting read, but at least it demonstrates that the very high performance motor is not at all happy with all the secondary air system paraphernalia and it is there just to pass the EU tests, probably very frustrating for the design engineers at KTM and Husqvarna. At another stage I will do the removal of the pipework, valves etc. but for now it is functioning exactly the same. It is basically a very new bike so for obvious reasons.......

 
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