Freestyle I'm scratching my head at this one...........

[CARBONX2]

Check the squish, I found on my DASA 1200 that the clearanace was too small, msv was 40+.

 

[JonasOlson]

Thanks @Jyzmbe @Blue @sneds @tntsuperjet @CARBONX2
I really appreciate all the feedback I can get.

Thanks for the info @tntsuperjet
But still.. I cant see any detonation on my "good" piston though.. Do you?

It´s black and might be lean, but I dont see any signs of deto..

 

[tntsuperjet]

And you almost never will on the rear Cyl.
It will 99% of time only kill front Cyl.
The rear Cyl will only die after the front or if the rear is much leaner.
Why??
Crank flex, rear Cyl runs about 4deg retarded in timing from front due to crank twisting under a load.
None of the common ignitions on the market have Cyl trim ability so you will kill the front Cyl every time.
I have a pile of these Pistons from customers in there Dasa motors on pump gas.
Both stock ign and MSd Total loss.
Welcome to pump gas and 8 series plugs in a high performance motor.
It will eventually bite everyone

 

[tntsuperjet]

Look familiar.
I had already pitched the other two dead Pistons.
But the domes should tell you what the piston looked like.
All three only front Cyl

 

[tntsuperjet]

The Cyl in the pic are new, not part of dead Pistons

 

[tntsuperjet]

Can you elaborate more on when we should be changing to a 9 series plug?

Simple, anything with 185 deg ex port with over 165psi.
Or 11to1 comp ratio up to 16to1 valves closed.
After 16to1 you should be in 10 heat range.
If you have fouling problems with 9heat range that tells you your setup needs tuning.
You should be able to run a 9 heat range plug most the summer.
Or 40 plus gallons min before plug starts to show wear or fouling

 

[CARBONX2]

On Msd Tl on a DASA 1200, slot the hole on the pickup for rear cylinder to advance it 4deg to correct for crank twist?

 

[Kawastyler]

Is Cranktwist a problem of strokerrank?? Means more stroke gives more cranktrist???

Thanks, Andy

 

[stefan]

Sub

 

[JonasOlson]

Thanks @tntsuperjet

So.. What do you suggest to these customers thats ride pumpgas on these high performance skis..? Like myelf..

 

[Jyzmbe]

I've been following this from the beginning. I'm a concerned owner of a new pump gas dasa 1000. Only suggestion would be to run the 9 heat range plug and inspect front cylinder for deto and correct piston wash?


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[cookn]

I thought I knew stuff until I read this. Really cool info here

 

[Waldbjoern]

Good luck checking signs of deto. This was 6 hours into my new engine - my front cylinder




Same cylinder, same settings, two hours of ride time later




Look at my prior post for further info.

DASA 1100, 8h of use from new.

And for record, parts were warrantied by DASA, so they didn't share same thought about deto..



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[tntsuperjet]

Good luck checking signs of deto. This was 6 hours into my new engine - my front cylinder

View attachment 318840
View attachment 318841

Same cylinder, same settings, two hours of ride time later

View attachment 318842
View attachment 318843

Look at my prior post for further info.

DASA 1100, 8h of use from new.

And for record, parts were warrantied by DASA, so they didn't share same thought about deto..



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This motor didn't die of detonation, look at picture, all edges are sharp, color cold grey and chunks have no signs of heat .
This motor snagged a ring on power valve. Can see it didn't have enough power valve to piston clearance in the pic where engine was stil healthy.
Soon as u felt it was broke in and started running it harder for more consecutive tricks she said good night
That also doesn't appear to be stock Dasa 1k bore. Can't read Pistons. Power valve is much closer then the standard Dasa

 

[Waldbjoern]

That also doesn't appear to be stock Dasa 1k bore. Can't read Pistons. Power valve is much closer then the standard Dasa

It's stock 94mm bore - and the pw clearance were way too big, so DASA has delivered two new power valves so they can be matched to the new sleeves/bore/cylinder.

I've bin told that the exhaust ports were unfinished, and the edges were too sharp. With a 94mm piston, the cylinder to piston clearance, when cold, is huge, so you need rounded edges to help push inn the piston rings, so they don't catch the exhaust port during warm up.



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[tntsuperjet]

All Dasa motors need heavy chamfer on exhaust ports. They run a very large exh port.
but no diff if it snagged the valve or the port. Same result. You will still have the cold grey looking piston with similar damage to deep piston without the visual signs oh heat.
The only difference is one snags the ring on port then rips out of piston.
The demo will break the ring land on piston then snag the port.
Two very similar looking failures, but port snag will be missing all the signs of heat and or pitting

 

[JonasOlson]

So now when I have to bore mine up to 95mm, do I have to like shims the powervalves ? :S
I mean.. The piston gets 0.5mm closer..

 

[tntsuperjet]

Is Cranktwist a problem of strokerrank?? Means more stroke gives more cranktrist???

Thanks, Andy

Crank flex is a problem with all engines.
Basic theory, more power more flex or twist.
Some of the aftermarket cranks have less twist then others.
So far the cranks I have tested the PHP with 4340 center section has least twist of all the cranks I have tested.
Those be, DASA, ADR, crank works, WSM, OEM.
The signs are rear Cyl has different wash pattern then front.
If you know how many LB FT of torque your engine produces you can tq load the crank in a jig and measure the crank twist by putting same LB FT of torque on crank and see the amount of deflection or twist.
Then if you have a real ignition you can trim the Cyl timing curve in a stepped power setting to keep both Cyl in correct timing.
Keep in mind you can't do a mechanical offset as this will lead to rear Cyl running more advanced under light and moderate loads and will only be correct timing at full power.
So it's a compromise with most current ignitions.

 

[NewName]

Is it really that much, like 4 degrees?
It must be around 0,92-1,0mm deflection at 82,5 hub then. Sound like a lot to me out of mechanical point...


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[tntsuperjet]

ADR 10m crank at 120 LB Ft is 3.8 deg deflection