OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Engines Questions On Victa Two Stroke Engines Decomp valve

I build my carbys in front of the telly at night and I haven't come across a non working decomp valve in ages the ones I seem to end up with are trashed beyond repair. The reason I started looking for these valves was because yesterday a mate brought his Victa 24 over because it had a spark plug in the decomp and he hurt his shoulder trying to start it. It had had the spark plug in there since he bought it but it had begun to aggravate his shoulder recently

And then you come across these Powertorques that have not been fitted with a decomp valve, not sure just what Victa was thinking when they came up with this cheap idea. I wonder just how much cheaper they were to buy new, probably not much cheaper I guess

Yes NornK,
I had a chinese PT a while back without a decomp valve..... maybe the compression was lower.....But as for a spark plug in the hole. I'd put another one in......
Older engines with lower compression might not miss a decompres valve...
cheers
speedy

I just put another head on and drill out the decomp hose port non the carby and it is then as it should be. Just some beancounter at Victa thought they would be smart is the only reason for it.

The head with the port blanked off is actually different to the standard head. It is a low comp head with more material removed from the inside of the dome.

Hey Bigted, do you know if the dv affects compression in a small way, once it's running, due to an imperfect seal, or to put it another way, is an engine with the lower compression head with no dv end up more powerful because of this blanked off port?

I don't believe the dv affects compression unless it is worn or basically stuffed. They do seal up pretty good, like any valve should. When the motor is running the valve does not pulse but rather stays closed all the time. The High comp head will deliver more torque. If you want maximum grunt with no possibility of compression being affected in any way use a high comp head with an old spark plug blocking the hole but be prepared to dislocate your shoulder once in a while and replace the starter rope a lot more frequently.

Good answer bigted, I am pretty confident the decompression valve does what it's meant to. I never pondered whether it pulses out just stays shut but it makes sense since the piston is moving very rapidly even at idle and every up stroke is a compression stroke. The PT certainly lives up to it's name. It rolls it's eyes and tells you "is that the best you can do" when it tackles 2 foot grass.

And those low comp heads go straight in my scrap bin. Yes MF they do tackle tall grass well, up on the back wheels and just push it in

Lol NormK, I just push it in level, steady as she goes and take in the sounds of it eating away under load. Reminds me of a V8 actually.