OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Engines Questions On Victa Two Stroke Engines Compression Testing of 2 Strokes how?

Hi All

I finally found the compression gauge

So would like to see how bad my Victa is (clubman)
https://www.outdoorking-forum.com.au/forum/ubbthreads.php?ubb=showflat&Number=33263#Post33263

just if someone can point me to a "how to do this"
as a step by step (if one exists)

Just that I read in this thread
https://www.outdoorking-forum.com.au/forum/ubbthreads.php?ubb=showflat&Number=31138&page=1
"remove the decompresser and plug it with a spark plug? "
so now I am wondering on that?

I did try it with the gauge with and without a T-spoon oil
(from other threads I'd read)

there was a little change, say 5~7 PSI
but yes a bit it seems
but this threw a spanner in the works for me ..on the Decompressor

oh & does the throttle have to be an any particular position?..just checking

I know that they are different motors but I think they basically function the same..so humm

Just trying to get this right

Also what is a normal range for the victa compression psi/kpa ?
(that would be viable for operation)

I got 600 kpa near 90 psi
with decompresser in place
so that maybe totally meaningless numbers..
I wont post the picture just in case it is

again Thank you for your Help

Cheers

90psi with the decomp in place sounds high.

There is no compression test result for Victa engines.
There is no compression test result for Briggs and Stratton engines.


Do you know how i test a victa for good compression???

With the muffler and inlet off, when you spin it if it makes squeltching sounds shes a good'un.



To actually run, they dont need stuff all compression. But the motor will smoke and be low on power.
To run well they do need good compression.





What are you wondering on the decompressor???
Get a 3/4 spanner, unscrew it and put another CJ8 plug in the hole it came out of.

Again thank you Bob

Rolf well just call me a Dill
no wonder I couldn't find any info on that Bob and actually later I found a post by Grumpy I think who mention that on B&S..(someone did anyway) ..humm maybe it was in the manual or their site..anyway somewhere

Actually the manual Gergory's 55/87 (early Engine types page 9)says stick a bit of fuel line on decompresser gently suck to close valve and and then test by disconnecting spark plug, opening throttle put mower on side rotate engine shaft by rotating blade holder, in each revolution you should have two points where resistance or compression is felt..(one higher, one lower) Summarizing it

They give no values thought..just say more or less
you'll figure it out by empirical methods.... trial and error
meaning you'll get use to knowing good from bad..:)
Experience being the best teacher I suppose..which is true enough

Thank you for your method too, I'll add it to the book

it was Just in regard to the other post linked in the above

yeah the CJ8 I guess is just to make sure you got a
"closed valve" scenario as in air tight seal


I'll reply as to why on the other post as this was just more a separate question as in "how to do it"..

Cheers, much appreciated

If you had a good known engine, you could do a compression test and use that to establish a 'base line' as far as condition goes.



With a briggs, anything over 60psi and it will run. 80psi is better. But valve clearances can affect these outcomes.
Its not much harder to just pull the head off and look.
Sure you cant see worn rings, but for the 1 in 20 or so that smoke bad from worn rings you dont loose much on time.

Ive never tried on a Victa. But there are more variables than a 4 stroke.
With a Victa, its just easier to pull the muffler off and look at the piston/bore. If its not too good, check the inlet side (new o-rings here are a good idea anyway), if thats ok it will be fair, if its not its stuffed. Lift the starter off and check the bottom of the bore too, if it turns out ok, chances are it might have needed a starter o-ring anyway. Pull the head off if its not looking too good. Best idea is to remove or at least loosen the decomp and plug before you take the head off.

Thanks again Bob

Yeah sadly dont have new or redone one to compare to..

Yeah I was thinking that replacing both O rings wouldn't go astray at all
Especially the starter one, as it seems this one can be a problem..it has seen 11 years plus action
at the lest a few hundred hours of rattling its wheels off
(which are stuffed really)

Thanks for the tips with the head removal..will bare that in mind

I think your Idea of a full "Visual" is a better gauge then psi
really

its not so hard to do & look for damage, as you said
in that regard a more accurate assessment of the situation

cheers... I'll read the others mate