Dyno tune help, rear cylinder randomly going lean, no reason

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07orangeSD
Minimoto racer
 
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Joined: Mon Jul 27, 2015 12:37 am
Location: Ulster County, NY

Dyno tune help, rear cylinder randomly going lean, no reason

Postby 07orangeSD » Thu May 17, 2018 4:31 pm

Bike is at a shop being tuned (they are familiar with v-twins and work on Ducati / euro bikes).

They are tuning each cylinder individually, front went smooth and is spot on.

The rear is giving them problems, they get it damn near spot on and then it just goes lean for no reason.

They are thinking some debris in the fuel rail or injector/bad injector.

Anyone ever run into this or have any ideas?
07' SuperDuke (Orange)
Full Akra exhaust and Akra tune (will be Dyno tuned soon), R&G tidy tail, Skidmarx screen, Dunlop Q3's, Renthal bars, [Motohooligan air box, secondary's, SAS plates, tank brackets, upper and lower sliders]; Lots more to come.

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No. 47
Master of the twisties
 
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Location: London and Kent

Re: Dyno tune help, rear cylinder randomly going lean, no re

Postby No. 47 » Thu May 17, 2018 6:00 pm

Leaky TB rubber?
'08 ex-Battle race KTM Superduke 990 R No.47
'08 OE KTM Superduke 990 R
'01 Ducati 996S

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Motogoon
Two wheeled terror
 
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Re: Dyno tune help, rear cylinder randomly going lean, no re

Postby Motogoon » Thu May 17, 2018 7:06 pm

Sounds similar to the problem the previous owner was having with the blown up 05 model I bought. They tried everything while tuning but one cylinder just kept going lean. After stripping it down the plug for that injector had some water corrosion and that wire also had an exposed part. It's still not known for sure if that caused the leaness and subsequent piston breaking but nothing else out of the ordinary was found so worth a check I guess!

07orangeSD
Minimoto racer
 
Posts: 66
Joined: Mon Jul 27, 2015 12:37 am
Location: Ulster County, NY

Re: Dyno tune help, rear cylinder randomly going lean, no re

Postby 07orangeSD » Wed Jul 25, 2018 4:13 pm

Little update on this.

Shop has been busy and has just recently got back to the bike.

They though it might be an injector so they were going to pull and check them, and possible swap them.

They pulled the injectors and did a fuel sample.

Injectors are fine they say but the gas not so much.
They found crap in the fuel and some water, they think the fuel filter is breaking down so they ordered a new filter kit and are going to install it.

The fuel was from last fall, was 91 non-ethanol with Marine stabil for winter storage, pulled it out of storage in April, topped it off and added some seafoam and took it to the shop.

So I have no idea how water got in the fuel as it is always stored inside and I don't ride in the rain, etc...

I am hoping to get the bike back by then end of the month, running 100%

Will update and I know more.
07' SuperDuke (Orange)
Full Akra exhaust and Akra tune (will be Dyno tuned soon), R&G tidy tail, Skidmarx screen, Dunlop Q3's, Renthal bars, [Motohooligan air box, secondary's, SAS plates, tank brackets, upper and lower sliders]; Lots more to come.

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RichUK
Two wheeled terror
 
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Location: England

Re: Dyno tune help, rear cylinder randomly going lean, no re

Postby RichUK » Wed Jul 25, 2018 4:20 pm

I have read that it's possible for the exhaust seal (the one that joins the header to the front pipe) for the rear cylinder to leak.
When it does it can draw fresh air into the exhaust and thus fools the rear pipe sensor into thinking the mixture is lean..
Just something to check at least.

07orangeSD
Minimoto racer
 
Posts: 66
Joined: Mon Jul 27, 2015 12:37 am
Location: Ulster County, NY

Re: Dyno tune help, rear cylinder randomly going lean, no re

Postby 07orangeSD » Sat Aug 18, 2018 9:07 pm

Got the bike back, running great.

Did 115hp at the rear tyre on a humid nasty day.

Looks like the fuel filters were shot along with some nasty fuel.
07' SuperDuke (Orange)
Full Akra exhaust and Akra tune (will be Dyno tuned soon), R&G tidy tail, Skidmarx screen, Dunlop Q3's, Renthal bars, [Motohooligan air box, secondary's, SAS plates, tank brackets, upper and lower sliders]; Lots more to come.


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