Who are you using for jetting parts?
Honda gx200 mods for power and efficiency
- Thread starter oil pan 4
- Start date
If i need one or 2 jets ebay sellers can get them to me in about 3 days.
If I need other parts especially timing advance keys NR racing. NR racing might take 3 days before they even send it but they're cheaper.
I do believe most if not all GX200's come with a dished piston. You can swap in a flat-top pretty easy which should increase power a tad.
I have an older GX160 (old enough it came with a dished piston) That I would use as a snowblower engine in the winter and both a water pump and pressure washer engine in the summer. It always did whatever job I asked of it, however it had very little power in reserve.
I swapped out the dished piston with a flat-top, installed a CL-1 cam, valve springs to keep things in control, and left the timing alone. The difference in power was night and day, plenty of power in reserve, runs perfectly fine. This cam works just fine in the rpm range I use it 3400-4000 rpm.
This GX160 came with a #70 main jet and needed an 85 to be happy afterwords. Lots more power, a GX200 should respond very similar.
Since this engine is used on an air compressor you will be concerned with off-idle response when more air pressure is commanded. I can assure you even with the cam no low rpm response has been sacrificed.
I have an older GX160 (old enough it came with a dished piston) That I would use as a snowblower engine in the winter and both a water pump and pressure washer engine in the summer. It always did whatever job I asked of it, however it had very little power in reserve.
I swapped out the dished piston with a flat-top, installed a CL-1 cam, valve springs to keep things in control, and left the timing alone. The difference in power was night and day, plenty of power in reserve, runs perfectly fine. This cam works just fine in the rpm range I use it 3400-4000 rpm.
This GX160 came with a #70 main jet and needed an 85 to be happy afterwords. Lots more power, a GX200 should respond very similar.
Since this engine is used on an air compressor you will be concerned with off-idle response when more air pressure is commanded. I can assure you even with the cam no low rpm response has been sacrificed.
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Yeah have an old gx390 that had a dished piston. It needed to be rebuilt and when I rebuilt it I used a cheap Chinese flat top piston. It makes 125psi of cold compression at 4,400ft above sea level. That's supposed to be the top end of compression on a new engine at sea level.
Ran the gx200 air compressor hard and dipped in the probe thermometer.
It was 80F today and the oil hit 200F.
So a 30wt oil seems like it would be great.
It was 80F today and the oil hit 200F.
So a 30wt oil seems like it would be great.
How are you getting 125psi? Is your compression release non existent or disabled?
After seeing this thread, I think we know why Oil pan's mower has a glowing exhaust. Leaned out carb and advanced timing.
I backed off the exhaust valve valve rocker nut 2 full turns.
Timing advance should put less heat into the exhaust.
3000 years ago when carburetors ruled the earth the ignition system and carburetor were linked in a manor as to disable the vacuum advance at idle, to put more heat into the exhaust to make the catalytic converter work better at idle and reduce idling NOx.
If you're vacuum advance line broke or fell off you could get a glowing exhaust when driving on the highway or the very least a glowing catalytic converter and about -5mpg off your normal highway fuel economy, cause all that heat was going out your exhaust instead of doing work.
Of course you are correct that retarded timing increases exhaust temps, but excessively advanced timing also increases engine temps.
More like .080''. That was only to get a compression reading without the compression release activating. When I was finished with the compression check 8 set the valve lash for whatever it's supposed to be, several thousands of an inch, I think it was 7 or 8 thousands.
Gotcha. What was the difference between the dishes and flat top pistons?
Factory ignition timing on an air cooled engine is around 20 to 22 degrees, which is close to 1980s epa approved smog motor timing where you set the base timing for like 4 degrees and get up to another 20 degrees or so of mechanical advance. In epa approved mode your probably running around 24 degrees of base and mechanic advance at 3600rpm at sea level.
Depending on altitude you want more like 10 to 20 degrees of base timing to get the most power and even more vacuum advance, another 12 to 16 degrees to get the best fuel economy. That's assuming NOx be darned. Bump the base timing to closer to 10 degrees and a more aggressive mechanic advance now you're running more like 30 to 36 degrees of base plus mechanic advance at 3,600rpm, at sea level. Above 4,000ft you could easily be running 42 to 48 degrees all in with base timing, mechanical and vacuum advance without EGR.
I'm at 4,400ft above sea level so my 9:1 compression ratio Honda air cooled motor is running more like a 7:1 compression ratio, lower compression ratio needs more timing.
If I remember correctly you want around 3 degrees timing advance going from sea level to 4,000ft, I looked it up a long time agowhen I moved here I think it's 3 to 4 degrees. So when I put a 6 or 8 degree ignition advance key in it's like someone at sea level going 3 or 4 degrees which is fairly conservative. Factory timing is 20 to 22 degrees on these little engines. Now pretend I'm at sea level, so I'm running more like a 4 degree advance timing key. Not so scary is it now?
The stage one tune up kits sold by the go-karting websites usually including a 4 or 6 degree advance key because they're assuming you live near sea level as something like 80% of the population lives between 1,000ft and sea level.
In this case the normal compression test for a new gx390 at sea level with a dished piston should be 125psi max. I'm at 4,400ft above sea level and I'm getting 125psi with the flat top piston and thin gasket. At 4400ft I should be seeing more like 100 to 105psi on a new bone stock gx390 with a dished piston and thick head gasket. So the flat top Piston and thin head gasket has bumped compression at least a full number.
I had a #69 used Honda carb jet in there running for a while, swapped it out for a new #68, still runs great. When I pull it it hits on the first compression stroke. If it doesn't start on the first pull it's either out of gas, the gas is turned off or the run/stop switch is in the stop position.
The plug is nice and clean even after running up to 40:1 two stroke gas for several tanks.
The plug is nice and clean even after running up to 40:1 two stroke gas for several tanks.
It has the correct jet for 4,400ft above sea level and factory ignition timing, which for 4,400ft would make it slightly retarded.
