Typical gen 2 injector self destruction.





Boosted Cycle Perf

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There’s been a few recent discussions recently about gen 2s having idling issues, or down on power. In those threads I talked about the usual problems I see when I flow test and ultrasonic clean gen 2 injectors.

Take this bike for example. It’s a nearly showroom condition 09. It rolled 2501 miles on my test ride. The new owner of this bike picked it up from the dealership, and rode it 200 miles right to my shop to drop it off for a turbo kit. When he got there he made mention that it seemed a little jerky at highway speeds. But at wide open throttle around 6-7k rpm the bike feels like it hit a wall from HP falling off. I was almost certain I knew what I would find when I pulled the throttle bodies off once I saw how low the mileage was. I took it for a quick ride and sure enough it did exactly as he said.

On tear down for the turbo prep, this is what I find.
1601285

1601286


1601287


1601288


There’s a few things going on here, but they all stem from dirty injectors.

The black goop on the back of the intake valves is from fuel puddling on the back of the valve. When these injectors get dirty, you don’t get a fine precise mist out of the tip, but more like a mist with drips. But those drips sit on the backs of the valves and boil off leaving carbon buildup.

On the underside of the throttle bodies there’s that same carbon goop. The injectors are pointed coward and away from the throttle bodies, how did it get up there?

Good question. Either the spray pattern is so messed up that it’s spraying upwards. OR- the more likely candidate is all that gunk on the back of the intake valves also gets on to the valve seats and causes the valves not to seal. So on the combustion stroke, exhaust gases are forced back up in to the intake runners, blowing the carbon back upwards.

I did a super low mileage stage 1 08 Busa last year. Had the same symptoms in stock form, only the owner rode it almost 1k miles before dropping it off. (Just bought it to go turbo) The runners were completely black, and the injector tips were clogged up good too. First time on the dyno with 4 psi the bike only made 180hp on 4psi. Did a hot compression test and found it to have 135psi across the board. But I did notice the intake runners were lookin a little cleaner from the fuel. I could see lots of crap built up on the valve seats and figured the loss of compression had to be due to that. Turns out that’s exactly what it was. 200 miles later on e85 cleaned up the runners/valves, and compression jumped to 225 in all 4.

The root cause of this havoc is how the tips of the injectors are designed. There’s a metal screen if you will with 8 TINY holes. They are not made from stainless steel, so the tips rust and start partially blocking these holes causing irregular spray patterns. Usually with a few weeks of the bike sitting the detergents in the fuel clean them out. But after several months or years of sitting they always take a turn for the worst and you could potentially end up like what I’ve shown here.

What’s the fix? The best way to avoid this is to get out and ride! But if you ride irregularly, or know the bike is going to sit up for months at a time, put some fuel stabilizer in it and ride the bike for a few miles before you store it.

I’m going to take pics or vids of these injectors in the flow bench. I’m suspecting they may leak a little when closed, and the spray patterns will be all messed up. I’m also going to do a compression test on the bike as well.

More to come!
 

Kiwi Rider

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Thanks so much for taking the time to write this up and share your work with us.
I for one get a lot from this, the backs of my Gen 1 intake valves were wet black crusty baked carbon, a lot like the pics you put up.
Your explanation really made me think, re the injector spray pattern, and the probable cause of this build up... but my throttle bodies were not speckled like these in the pics.
I had assumed it was caused by heavy breathing of the crankcase ventilation of oil mist in to the intake and the high mileage of my engine being a contributing factor.
I’m keen to see the pics of the injector spray patterns!
 

Boosted Cycle Perf

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Thanks so much for taking the time to write this up and share your work with us.
I for one get a lot from this, the backs of my Gen 1 intake valves were wet black crusty baked carbon, a lot like the pics you put up.
Your explanation really made me think, re the injector spray pattern, and the probable cause of this build up... but my throttle bodies were not speckled like these in the pics.
I had assumed it was caused by heavy breathing of the crankcase ventilation of oil mist in to the intake and the high mileage of my engine being a contributing factor.
I’m keen to see the pics of the injector spray patterns!
I appreciate that. It’s nice to hear that. Usually it’s something along the lines of “you clearly don’t know what you’re talking about...”
 

Kiwi Rider

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Boosted Cycle Perf

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So are you going to do a leak down test to be certain the leakage is through those crusty ex valves?
And providing it is the ex valves leaking, what’s your approach on cleaning the seats?
Upper engine cleaner soaking ?
I’ve seen this several times here recently, I know for a fact it’s through the valves. The pictures are of the intake valves.

On the other bike that I mentioned and posted pics of I was looking for solutions and found an expanding foam for cleaning carbon buildup out of the intake ports of direct injection engines. Those engines are prone to excessive carbon build up because there’s no fuel running though the intake runners to keep them clean.

Sounded like a great idea until I read several forum posts about the cleaner washing down the cylinder walls. So no go on that.

On that first bike I ended up running the bike with the air box off and shooting carb cleaner down to start things off. Then ran a tank of e85 through it and checked the runners. They looked brand new. E85 is EXCELLENT at cleaning out engines. Then did a compression test. All the numbers jumped from 130s back up to 220-230s. Changed the plugs because they looked like crap after burning all that junk off, and slapped it on the dyno and made 280hp.

This is the bike.
 




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