What are the valve gaps for the Huangsheng?

[Irish John]

Anybody know the correct valve gaps for the Huangsheng motor? I was told they'd probably be same as for Honda GXH which I was told were .07 both valves which is not what I've heard here. Any help would be appreciated. Also I don't find I need sealant to put the rocker cover back on. The original gasket works fine cos there's no pressure there.
Whatever the valve gaps are I fdound that adjusting them many ways I got to eliminate any valve noise but that wasn't what the engine wanted so I set them at the gaps they seemed most responsive at and that was 0.09 - 0.10 exhaust valve and 0.08 inlet valve. They rattle a bit at low revs but this is what makes my Huangsheng sing.

MBC EDIT: THIS THREAD HAS BEEN MOVED

 

[Irish John]

I've fixed the valves by adjusting them while running - bit messy but it works. When I adjusted them to stop the rattle completely it ran quiet as a mouse but the motor didn't like it. The best setting rattles a bit at low revs under load but that's how the motor seems to like it. Afterwards I measured the gaps and it was0.09 - 0.10 for the exhaust and 0.08 for the inlet valve.
This definitely seems the best setting performance wise for what it's worth.

 

[HoughMade]

Can you quantify the performance difference at all?

 

[Irish John]

Can you quantify the performance difference at all?

Yes HoughMade, when I tightened the valves they ran quiet but the compression was too low - noticeable when pulling the starter rope - too tight and there was nil compression - the difference between no compression and good compression is very minimal on the screw adjustment - and it responded badly when opening the throttle. I could tell it wasn't liking it. This is with the bike up on a stand. By loosening the valves minimally I got it to respond well to throttling up and down then I closed gaps a bit until I reached a point where the rattle was at a minimum and the response to sudden throttle open and closed was best. There was a bit of forwards and backwards doing this to get it right. Not very professional I'll admit, but it feels good on the road now. Wish I could find a way to give the motor more pulling power on hills and quicker accelleration. The manual hasn't got the gaps stated in it but says to do them every 200 hrs or 2000 kms.

 

[HoughMade]

Thanks!

 

[cruiser66]

Hua Sheng valve settings

Hi Irish John,

The settings for the Honda are .08 +/- .02mm for the intake and .11 +/- .02mm for the exhaust. When I got my Hua Sheng I measured the valve clearances before running the motor to see what the factory settings were.
My measurements were .003" (.0762mm) on the intake and .005" (.127mm) on the exhaust. These are of course cold measurements and are essentially the same as the Honda specs.... Honda specs taken from Honda GXH50 owner's manual page 15.

http://www.honda-engines.com/Engines_owners_manuals/ownersmanuals/37Z4C603.pdf

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[Irish John]

The local Honda dealer, a reputable family owned farm supplier, told me that the Honda was 0.07 for both valves. What I want to know is if the rattling under load at low revs bad cos when I shut it up by tightening the gaps the motor didn't like it and had very little compression. I think the rattle is necessary and I'm putting up with it so the motor runs responsively. That said I wonder how much wear is being inflicted on the centrifugal clutch when the spped drop below 25 km and the engine struggles. It doesn't like low speeds and this bike wouldn't be great in a funeral procession or even stop start traffic. Maybe I should go back to the 56T and ditch the 48T but I had trouble with the 56T on hills as well as the fact that it's just a bit too large and the chain hit the chainstays enough to wear a mark on them. Lack of grunt is the only real problem I have with this motor. Pity the 120cc or 160cc Honda shaft won't fit the Grubee gearbox cos with a GXH50 label the police would never know. The engines all seem about the same size dimension wise. I suppose it might pull the spokes to bits if it was 4 horse power.

 

[cruiser66]

Hua Sheng low speed performance

Hi again Irish John,

I edited my reply on the valve settings to show the source. My Hua Sheng setup does not run like yours at slower speeds. There is no clatter or roughness from a dead stop and I can go as slow as I like by just tweaking the throttle to maintain speed. However, I have the JL Hoot gearbox which I run with 5 to 6 ounces of 75W90 gear oil. I have no trouble maintaining 20+ mph on the steepest hills in my area and I weigh over 215 pounds. I think part of the slow speed noise or roughness might be coming from the clutch. Are you running oil or grease? I have not adjusted my valves, they are still the same as from the factory. A slight ticking from the valves at idle is normal and desirable for good compression and to prevent the exhaust valve from burning. I am using a 36T sprocket which is pulled very easily with this setup.

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[Irish John]

Hi again Irish John,

I edited my reply on the valve settings to show the source. My Hua Sheng setup does not run like yours at slower speeds. There is no clatter or roughness from a dead stop and I can go as slow as I like by just tweaking the throttle to maintain speed. However, I have the JL Hoot gearbox which I run with 5 to 6 ounces of 75W90 gear oil. I have no trouble maintaining 20+ mph on the steepest hills in my area and I weigh over 215 pounds. I think part of the slow speed noise or roughness might be coming from the clutch. Are you running oil or grease? I have not adjusted my valves, they are still the same as from the factory. A slight ticking from the valves at idle is normal and desirable for good compression and to prevent the exhaust valve from burning. I am using a 36T sprocket which is pulled very easily with this setup.

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Cruiser, I wonder how many sprockets on your front chain drive sprocket? What sort of gearing ratio is this JL Hoot gearbox because it sure sounds as if it is a totally different rig - the grubee kit would struggle on the flat with a 36T but if it went down a slight slope it would probably do 50 mph. These rigs are totally different and whatever the gears are bathed in would make almost no difference to it's speed. Where did you buy your kit? I think it's the kit I'll soon be trying out and I want to make sure it's the same. Does it pull away as well as a 70 HT? Mine sure doesn't but on a 20 km trip it is much faster than the HT and takes 60% of the time to complete the trip. What is the max speed of your rig? I don't mean flat out but comfortably cruising on the flat at nearly full throttle with no headwind. Mine cruises at 45 km\hr comfortably on a 48T. On a 44T it hit 60 km\hr on the flat into a headwind and not quite at full revs.

 

[cruiser66]

Irish John,

I mentioned the gearbox lube in reference to your wondering how much punishment your centrifugal clutch was taking with your low speed problems. I initially ran my gearbox with just grease, but I did not like how rough the clutch engagement was. Slow speed operation certainly was not smooth. Gear oil makes it feel like a torque converter. I have a single chainring up front with seven gears on the rear derailer. The JL Hoot, I believe, has about a 5:1 reduction while the Grubee is more like a 3:1. With the original 48T sprocket, I was barely able to do 40 kmh tops. I now am able to cruise at 45 kmh comfortably. I have reached 55 kmh without overreving the engine. Since I am the only motorized bike in my area, I have no idea how my acceleration would compare to a 70cc HT. The 4 stroke can certainly accelerate much faster than just using pedal power. The hills in my area are not too steep but I would have to stand on the pedals to climb without the engine. The engine easily climbs these hills at 40 kmh. The "upgraded" variant of the JL Hoot is what I am seeing on eBay right now. The angle cut gears are supposed to run more quietly and I believe the overall ratios are the same. My older style has the vented filler plug on top with a drain plug on the bottom. This has been eliminated on the newer model.

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