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Discussion Starter #1
Hi folks,
The bike has been sitting for three months in garage with battery being properly taken care of. I took it out for a 150 miles drive on sunday. Except for the hiccups around 3200-4000 (which I am planning to get rid off with a PCV) everything went well. The last 10 miles driving in town the engine would make kind of a fart (sorry for that) or suffocated bangs from under the tank. This morning same behavior at any temperature range (one to three bars). Valves clearance was taken care of about 10000 miles ago. Since the symptom made its appearance all of a sudden I suspect maybe loose gasket, air intake boots or something arround air leak.
I haven not checked the spark plugs but I think they are past due.
Except a loose clamp, what would be the correct order to proceed in a proper diagnose and fix?
1) Loose boot / lost tbs end caps
2) Loose air filter gasket
3)New Iridium NGK CR8EIX
4)TPS
5)TBS
Thanks for the great support!
Cheers to all

Mandrake
 

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Classic symptoms of the throttle body being blown off the intake boots. Fix time is about 15 minutes.

- Loosen or remove fairing parts so you can tip up the rear of the tank. You don't have to remove the tank or disconnect fuel lines.
- Look to the intake of the rear cylinder and follow up to the throttle body. You should see that the intake boot is off or partially off.
- Wipe dry the flange on the throttle body.
- Loosen the hose clamp on the intake boot. The first time I did this, it popped back in place. The second time required a mild shove on the throttle body to seat properly.
- Tighten the hose clamp tightly.
- Replace tank and fairing parts
 

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Discussion Starter #3
Now backfires and on-off behaviour even at high rpm

The front cylinder boot was not well in place. Now that I have fixed this issue (which I think was the consequence of something else) I get lots of backfires (especially if I run at a steady 3500-4000 rpm). If I rev up the engine it runs in a on off way, undrivable. Do you guys think that I just might be some crap clogging the injectors and ore the mesh filter in the gas tank ? It happenend about 20000 miles ago but the dealer took care of it.
I measured the fuel delivered after three key turns: 4.2 us fl oz. I remember reading in some post that it should be 10 or more onces every three turns.
What would be the correct procedure in order to inspect the injectors to make sure I am not overlooking anything on the fuel line department?
Thak you all for the help.
A very sad italian vstrom rider...:bom_sad3::bom_sad3:
 

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Cowboys aint easy to love
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Sounds like what happened, just once, to my Vee about an eon ago. I "fixed" it (the first time) by re-inserting the rear TB into its boot. NOT! The second fix I had to use a crowbar to torque the TB over into its boot while tightening down the clamp with gorilla-strength. I fully expected to break something before it was all back together. What looks like a solid connection may not be -- and it will cause the symptoms you're experiencing.
 

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Discussion Starter #5
Ok but what about the fuel flow?

What you say does make sense but I double checked for proper fitting and absence of cracks (I experienced a crack in the intake of my honda xl 25 years ago which took lots of attention to be spotted).
I still think that rut in the engine is a good candidate as the bike ran well till I hit the low level in the tank las sunday when I guess all the debris made it to the mesh filter. The bike ran ok when starter on a fuel tank. It should't take to long to take the fuel pump out.
Any advice for the fuel injectors?
 

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Discussion Starter #6 (Edited)
Fuel pump bypass done, now running on one cylinder

The pump base and mesh filter were full of rust. The tank is now clean but a treatment is to be scheduled.
The amount of fuel being delivered is now almost three times what it was before which means 4.2 us oz per single key turn.
Now that the bikes runs better the real problem is far more clear: one of the cylinder does not run until 4500-5000 rpm! The next area of investigation will be spark plugs, coils, injector (electrical connections and dirt).
I am still looking for a documented procedure to check the injectors.
Even if I am satisfied with the fuel filter bypass, I wonder if a water manometer be used to measure what the effective pressure is in the circuit...
 
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