Honda gx390 engine ticks, burns oil, 72psi compression.

#40Fan

Active member
Jul 21, 2022
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USA
It'll be interesting to see what the starting gap is, at the top of the bore, with the .010" over rings.
 

Oil pan 4

Active member

Equipment
L185 turbo
Sep 21, 2017
412
107
43
NM
It'll be interesting to see what the starting gap is, at the top of the bore, with the .010" over rings.

The rings are overlapping a bit.
Normally when I use +0.01'' rings over the size of the actual bore as file fits they usually have very little to no gap.
Made sure to get actual Honda rings.
 

mikester

Well-known member

Equipment
M59 TLB
Oct 21, 2017
3,125
1,609
113
Canada
www.divergentstuff.ca
Already did the value lash. Ain't the valves. The engine is old, like 20 years old, has the old style cyclone air cleaner. Air filter was improperly installed and was sucking in some dirt when I bought it for $50.
It was an air compressor most of that time. Then I got a hold of it gave it a good tune up, set valve lash, found a seal missing in the carb, put in a smaller air bleed plug and main jet, took the main jet from a 104, to a 100 and then to 95.
I put it on a stump grinder and it was a stump grinder for a few years, now it's a wood chipper. It will probably end up as a pressure washer eventually.

What do you think.
Is the piston rattling around in the bore?
Excessive rod bearing clearance?
Edit: there is no rod bearing, just aluminum.
A new one like this is about $800.
A predator 459cc was about $500 two years ago, after tax with a 20% coupon.
1686570802277.jpeg

I see 90W gear oil and a craigslist ad...
 

Oil pan 4

Active member

Equipment
L185 turbo
Sep 21, 2017
412
107
43
NM
Getting 120psi of cold, never fired compression at 4,000ft pulling on the string.
It will be higher after the rings seat and hot, ect.
I'm thinking this Honda knockoff "f188" piston gives a little bump in compression.
Perfect stock compression 8.2:1 at 4,000ft elevation compression would be expected to be around 102psi, with a thin head gasket 8.7:1 maybe 106psi, barely a different on a gauge. But 120psi would mean at least a car like 9.6:1 compression ratio.
Engine is very much de-CARB'ed.
 
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