Valve spring options for Honda GXH50

[speeeed]

Are there valve spring options for the Honda GXH50 other than the stock spring? I am striking out on my Google search.

 

[Gordy]

Afaik you're out of luck. It's the same struggle with the 79cc predator

 

[DieselTech]

Your best option is to shim them. & I mean shim. Then you got to check for coil bind or bad things will happen. I would start with a .020" shim. Then check for coil bind & if no coil bind then go to a thicker shim like .030" & recheck.

 

[michael whiteman]

First let us all welcome you to the site Speeeed. It sounds like you want to hot-rod your Honda a bit. Most of us here can't afford that engine so there hasn't been much discussion on this subject. DieselTech has the best approach to what you're looking for and it applies to any engine. I just went through all the same research on my 79cc Predator. Some people think it might be a clone copy of your engine, who knows? Take the time to read my two posts and you'll have a better understanding what to look for.

DO NOT put 18lb valve springs in your 79cc Predator

I did this thinking the 22lb springs rated to 7000rpm was just a little too much for my need. There are two YouTube videos showing 18lb springs in a 79cc engine so I followed along. I know to check for coil bind but got distracted and forgot before final assembly. Anytime you change the valve...

motoredbikes.com

79cc Predator: The story on valve springs

I have spent three days and five phone calls compiling information regarding valve springs in the 79cc Predator engine. Unfortunately this information is not found in any one place, and sometime it is inaccurate. My measurements were made with a dial micrometer and some pretty accurate spring...

motoredbikes.com

I assume you have looked on YouTube and found nothing useful. I found conflicting data that didn't make sense along with incomplete comparisons so I did my own and you will probably need to also. To really know the characteristics of your stock springs you'll need to remove one. You can do this without removing your cylinder head. But first roll your engine over till the valve is fully open with the spring compressed. Record an accurate measurement of this compressed spring heigth (not including the retainer) using hopefully a dial caliper. If you must include it, we can subtract it's thickness later. Also get a measurement with the valve closed and a gap between it and the rocker arm. This is the installed heigth. These are the two dimensions that you will be working with. Next remove the plug and run the piston down. Take a 1/4" rope and shove it into the cylinder till there's a wad built up. Now bring the piston up and that wad of rope will contact the valves preventing them from falling into the cylinder. Remove one valve spring. This will give you the normal height.

We can now compair springs between our two engines. There's a chance Predator springs might fit. I have three different sets. Let me know what you want to do..................

 

[michael whiteman]

Does your Honda 50 have a govenor? If it does there is no reason to upgrade the valve springs without removing it. Which brings us to the next question. My Predator has a history of throwing the magnet off the flywheel when exceeding 4000rpms. I'm sure your Honda has a superior design but it would be nice to know first that this will not happen to you. I had to buy a Billet flywheel before proceeding with any mods. Very expensive! You might have to check with the go-kart racing community and get that info. The problem is; these racers are not too concerned with small displacement engines, like ours, and focus mostly on the larger sizes.

BTW.............how high were you planning to rev this engine?

 

[Sidewinder Jerry]

The stock Honda GXH50 max hp is at 7000 rpm (2 hp), its max rpm is 7500, its max torque is at 4500 rpm (2 ft/lbs); this is according to the owner's manual.

I always go by what the owner's manual has for stats/specs rather than stats/specs that have been put in an advertisement.

 

[michael whiteman]

Thanks Jerry. If max rpm is 7500 there is absolutely NO NEED to increase the valve spring pressure ! Just leave it alone and move on to your next idea.

 

[speeeed]

The stock Honda GXH50 max hp is at 7000 rpm (2 hp), its max rpm is 7500, its max torque is at 4500 rpm (2 ft/lbs); this is according to the owner's manual.

I always go by what the owner's manual has for stats/specs rather than stats/specs that have been put in an advertisement.

The GXH50 will rev well beyond 7500. I have seen more than 8500 (no load) from my engine despite having a governor. Mine routinely hits 7800+ RPM (with load) for extended periods of time, thus the question about valve springs. As far as I can tell the GXH50 has no true rev limiter. I asked Honda directly if the GXH50 can overrev, and they responded yes especially without a load.

Does removing the spark arrestor on these things do anything for HP or does it just make more noise?

I assume higher octane fuel makes no difference with such low compression.

 

[Wrench]

The spark arrestor could be a little restrictive especially if it's dirty

Take it off and see if your engine performs better

 

[Gordy]

The spark arrestor could be a little restrictive especially if it's dirty

Take it off and see if your engine performs better

Straight pipe it! Unless you like your hearing.