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[Lance0964]

Hi everyone,

First post here.
I got a 17 Slim S with around 5000 km(3000miles) on it. I bolted SE585 cam in and 2-1 exhaust around 4000km. But didn’t like the loss of low end power. So, I pulled the head off and sent out for head work. Meanwhile, I took the cylinder off and putting SE 10.5:1 pistons in.

However, I found out  the cylinder wall have some light scoring. Then I took off the pistons. The skirt of pistons are worn. Pistons are covered by the carbon build up on the top. The most unbelievable thing is the piston rings are out of orientation. The gap of the top and second ring are close to each other (please see attached pic).

I’m planing to bore and hone the cylinder, then put a set of +.010 pistons in.

Question that I can’t figure out. What caused the damage on cylinder wall and piston skirt? How can I avoid it happens again after rebuild?

Thanks

[Lance0964]

Pic

[Lance0964]

Pic1

[Lance0964]

Pic2

[Lance0964]

Pic3

[HD Street Performance]

I can't see how the head work is going to help low end. The tune is likely off and scoring from excessive heat. The tune helps the loss of low end and also the heat.

[MCE]

Head work (with a bump in compression) will help build more TQ all over the curve.
A better valve job (than stock) will improve cylinder fill, which will pick up some TQ
all over too. JMO

But yeah, heat did this one in.

[johnsachs]

Hi everyone,

First post here.
I got a 17 Slim S with around 5000 km(3000miles) on it. I bolted SE585 cam in and 2-1 exhaust around 4000km. But didn’t like the loss of low end power. So, I pulled the head off and sent out for head work. Meanwhile, I took the cylinder off and putting SE 10.5:1 pistons in.

However, I found out  the cylinder wall have some light scoring. Then I took off the pistons. The skirt of pistons are worn. Pistons are covered by the carbon build up on the top. The most unbelievable thing is the piston rings are out of orientation. The gap of the top and second ring are close to each other (please see attached pic).

I’m planing to bore and hone the cylinder, then put a set of +.010 pistons in.

Question that I can’t figure out. What caused the damage on cylinder wall and piston skirt? How can I avoid it happens again after rebuild?

Thanks

Why is it unbelievable that the piston rings are out of orientation ? Rings will rotate due to the crosshatch.
John

[Lance0964]

Why is it unbelievable that the piston rings are out of orientation ? Rings will rotate due to the crosshatch.
John

Thank you for pointing that out. I thought they are out of orientation from the factory.

[Lance0964]

I can't see how the head work is going to help low end. The tune is likely off and scoring from excessive heat. The tune helps the loss of low end and also the heat.

Thank you for the comment. I will check with local shop to get my bike dyno tuned.

[Lance0964]

Head work (with a bump in compression) will help build more TQ all over the curve.
A better valve job (than stock) will improve cylinder fill, which will pick up some TQ
all over too. JMO

But yeah, heat did this one in.

I will look into it. Thank you.

[JKM]

Looks like you're from Ontario somewhere.  There is a real lack of quality dyno-tuners here.  Most shops simply use a downloaded map, which can lead to this.

What fuel tuner (SE, PC, Thundermax, TTS) do you have on the bike?

[Lance0964]

Looks like you're from Ontario somewhere.  There is a real lack of quality dyno-tuners here.  Most shops simply use a downloaded map, which can lead to this.

What fuel tuner (SE, PC, Thundermax, TTS) do you have on the bike?

I'm from Rocky mountain of Alberta side. To be honest, I haven't tried any dyno shop yet and the closet Harley dealer is doing dyno run with TMax. I bought a Power Vision from Fuelmoto last year and did a few auto tunes(basic) with pre-load map since I just did cams and exhaust. But I can feel that dyno tune is really needed. And I'm definitely gonna bring my bike to the dyno after changing the pistons.

[HD Street Performance]

The compression addition is the torque plus. The pipe is far more influence on the shape and torque production throughout the curve.

[trippy]

In regard to the Carbon build up on the piston crowns, thats due to the breather system in operation from the factory, fit an external breather/catch can and that will reduce it.