savage octane compression test

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S

smoose

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what should the compression be of my savage octane v1? I performed the compression test cold and achieved 75 psi dry and with a few drops of oil it achieved 85 psi, should it not be at least 110 psi to 150 psi?
 
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ok, that sounds normal to me, would sure like another owner, of the same model truck that performs well, to post their compression test results so I had another vehicle to verify against. thanx for the reply.
 
the piston and sleeve look just fine, so I ordered a new ring for the piston, I will post my results once back together and have re tested the compression.
 
What's the gap on your piston ring, when it sits in the sleeve?

I measured mine to somewhere in between 0,3 and 0,35mm (0,012 - 0,014" )

Recommendation for a cylinder this size is min 0,1 - max 0,15mm (0,004-0,006")
 
I measured the sleeve diameter to be pretty close to spec 27,7mm and the piston to about 27,6mm. So the piston to cylnder clearance is about 0,1mm. From what I can find on the internet, a good clearance would be about 0,05mm but 0,1mm seems to be ok.
 
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Okay, cool I'll measure mine tomorrow evening and post the specs of the piston sleeve and ring gap near the top of the sleeve, I'm still waiting on the new ring i ordered.
 
my piston and sleeve and ring end gap inside the sleeve measurements: piston 27.58mm and the sleeve 27.71mm and the ring end gap .032" which is too much according to those specs, will compare once I have the new ring.
 
What? Ring gap = 0,032" = 0,8mm? That's a HUGE gap, I thought mine was big at 0,3mm (0,012")
Will be interesting to hear what the new ring will be.

Piston and sleeve we have more or less exactly the same measurements.

I think the piston ring gap on mine could not really be the reason the engine isn't running at all, at least not by itself.
 
No that definitely is not the reason. Mine still ran and idled fine just lacking power, which makes it difficult to hit the shift points. I bought this truck used and I think it wasn't broken in properly. Is your truck still not running?
 
I think I still have quite a low compression. I'll do some measurements when I am back again. Going away for a week, so won't have any results in a week and a half or so.

I think it was about 70 psi when I did the compression test last time.
 
I installed the new o.s ring into the sleeve and now the end gap is .005" which is right in spec, re tested the compression and now I have 90 psi... with a drop of oil its over 100 psi before broken in
 
Great! That's really good to hear. It does show the importance of correctly made piston rings, in terms of gap. Means I should replace mine too.

I think it is becoming more and more clear that HPI didn't have any control over manufacturing quality on these engines. They seem to be all over the place. I bet it's the same reason for my blow back issues.

But then, with the reed valve and a new ring, my octane should start pulling wheelies soon too ☺
 
right on! on my truck the plastic reed valve was missing lol, no big deal, will have to put a new one in. should help with the low end performance.
 
I have also spent some time considering the purpouse of the "air restrictor". The thing is, that restricting the air prior to the carb, will act like a choke. That is exactly what the choke does, it restricts the air entering the carb. What then happens is that the negative pressure in the carb will be greater (more negative pressure), this results in the engine drawing more fuel, while getting less air, resulting in a very rich fuel air mix, which help starting a cold engine.
The only explanation of the "air restrictor" I've heard so far that seems reasonable to me, is that it is preventing the air filter from catching fire, but I am not convinced about that either.
 
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