Piston Burn/Wash Pattern -- What does my weird pattern indicate?

TheWizzerd

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Cool airplane talk aside I would hazard a guess that the roof angle on one of the transfers is slightly off, or there is just something goofy about the shape, so the charge is not coming in perpendicular to the bore axis and/or being interfered with via turbulence in the bore. This can definitely cause a mixing of the exhaust and intake charge and force some of it out. Knowing how these iron sleeve cylinder ports tend to be I wouldn't be too surprised.
Yup, it does appear to me that the left side transfer is off just a bit. After todays ride I pulled the head again to check, and it appears similar to the first. Can only see the transfer wash on one side.

I say the left side as that's where we can see the brown wash, where its clean on the right as you would expect. The left wash is toward the intake as it should be, but roof angle is such that its causing it to leave deposits on the piston. Maybe blowing downward and back rather than up and back.

Sound about right?

However...this will have to be fixed with filler as there are overhangs, and that's what is causing it. They are as identical as I can reasonably get them. There may just be a slight burr/edge on the back side of the sleeve on that transfer causing it. Tough to get in there when not trying to change the heights. If I were opening them up to match the casting, it would be easier....but cant do that on this jug. I mean, I could, but that required additional work to make that work out that I don't feel up to.

I mean, its actually running pretty darn decently now, but.... well, you know......why would I leave it as is knowing something isnt quite right? Well, even if it was right I would still have to do SOMETHING to it.
 
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Deleted member 12676

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possibilities: 1) exhaust port is too high, 2) you over-rev too much, 3) you have a standard engine that has an iron sleeve. The original engines a have a wrong angle on the front of the transfers that don't direct the flow rearward. That and other errors may have been intentional to lessen power so the engines will be low power enough to pass all countries regulations https://dragonfly75.com/motorbike/transfers.html
 

TheWizzerd

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possibilities: 1) exhaust port is too high, 2) you over-rev too much, 3) you have a standard engine that has an iron sleeve. The original engines a have a wrong angle on the front of the transfers that don't direct the flow rearward. That and other errors may have been intentional to lessen power so the engines will be low power enough to pass all countries regulations https://dragonfly75.com/motorbike/transfers.html
Thanks for your input.

These are the durations.

Durations:
Exhaust: 159.5 ( we can call it 160 I guess)
Transfer: 128
Blowdown: 15.7

Blowdown is pretty terrible.

It is indeed a steel sleeve. Single base gasket, decked so piston is flush with deck at TDC , squish set at .8mm

It has decent low end, and runs incredibly smooth for a china doll on the low end, but the power tapers off quite dramatically on the top end.

What do you think?
 
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Deleted member 12676

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I like 175 duration for the street
You can correct the transfer flow which wastes less fuel and gives more power
 

TheWizzerd

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I like 175 duration for the street
You can correct the transfer flow which wastes less fuel and gives more power
I have a piston I ramped that will be around 175 exhaust duration. I will give that shot and if it works out I will port the second jug to that and use a non-ramped piston.
 
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