Compression rate

Begonnen von Pederkr, 27 April 2019, 17:32:07

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Pederkr

New Piston
New Bore
New rings
New Valve
New Valve springs


Is this normal or to high
Manual sayes 7,5 - 1


Pederkr


rolf

It is ok....may the piston is a little bit higher....ot the head shorter....nothing to worry

Kurt in S.A.

As a rule of thumb, I take the 7.5, add 1.0 for the atmosphere and then multiply by 14.7.  Should be around 125 psi.  I also think you're good.

Kurt
Kurt in S.A.

strichzwojan

What bike do you have?
R 26?
1:7,5 is the rate of compression.
We are talking about compression measured in bar.
My R25/2 reaches 8,5 bar when kicking the starter (warm engine)  10 times.

9 bar is fine!

Jan

Pederkr

Zitat von: strichzwojan am 28 April 2019, 20:12:02
What bike do you have?
R 26?
1:7,5 is the rate of compression.
We are talking about compression measured in bar.
My R25/2 reaches 8,5 bar when kicking the starter (warm engine)  10 times.

9 bar is fine!

Jan


Yes it's a R 26, and this is cold engine
I'm confident that its OK, but i think the engine works a little harder than before the rebuild.

Peder

Borgward

Zitat von: Pederkr am 30 April 2019, 18:49:44
I'm confident that its OK, but i think the engine works a little harder than before the rebuild.
Peder, this is normal after your rebuild with new piston and rings - just run it for 1000 - 2000 km  :bike:

Hubi

Pederkr

Zitat von: Borgward am 30 April 2019, 19:10:07
Peder, this is normal after your rebuild with new piston and rings - just run it for 1000 - 2000 km  :bike:

Hubi

Thanks, i'm working on it. But these dayes it's only 9 degree and a chance for rain & snow.
I will attent the Nordland treff in 2 weeks time in Upplegen, so i think i will put some km on the engine.

Grüss

Peder

Pederkr

#7
Here is the reason for the bad preformance. The new piston that I got inserted my engine is too low. Possibly for a stationary engine, even though the seller said it was for Izetta and should fit.

Normal Hight 74 m/m
This one 71 m/m
3 m/m higher compresion champer is to much


Woops  ::)

strichzwojan

Standard pistons are quite flat. Have a look at the tuning pistons at Ulis.motorradladen.de
Your Piston does not look that bad. It has a "dome" on top, and the compression of 9 bar you measured, is fine.

Jan

Pederkr

Zitat von: strichzwojan am 19 Mai 2019, 15:25:40
Standard pistons are quite flat. Have a look at the tuning pistons at Ulis.motorradladen.de
Your Piston does not look that bad. It has a "dome" on top, and the compression of 9 bar you measured, is fine.

Jan

Yes but if you look at picture 1. the piston is at O.T. but is missing 3 m/m to get to the top of the fire ring in the cylinder. I think that the piston sit's to low in the chamber.
The space for the valve is smaller than the original, tha make me belive that the dome is also to low.

Stationary engins like generator, or pumps do not need a lot of Rev and to reduce wear, it has a low compression.

strichzwojan

You are talking about bad performance. Is your R 26 on the road again now? What is the topspeed? Acceleration from 0 - 80? My R 25/2 does this in 17 seconds. 98 kg driver...  :(

Jan

Pederkr

Zitat von: strichzwojan am 19 Mai 2019, 18:40:27
You are talking about bad performance. Is your R 26 on the road again now? What is the topspeed? Acceleration from 0 - 80? My R 25/2 does this in 17 seconds. 98 kg driver...  :(

Jan

Im not on the road again, have to find a new piston. Normaly i do not go past 80 km/t have no power in 4 gear
I will keep you posted when i get on the road again probobly in a day or 2.

Pederkr

If i compare the old piston (left) whit new piston (right) i can see a different in hight of the piston body, and the piston dome.
Also the center of the guideon pin is not offset.
Maybee i have solved the klang klang klang sound when the piston is turning in TDC

New Piston is on it's way  :juhuu:


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