Brand new GXH50, bogging problem...

[Max-M]

I recently installed a brand new Honda GXH50 engine from smallenginewarehouse.com on my bike (to replace its Hua Sheng 142F). I installed a very nice throttle control linkage that I bought from a guy here on the forum.

I now have just over 100 miles on the engine. Up until my last couple of rides, the motor ran great. But now it's acting a bit quirky.

The engine usually starts on one pull; it wants full choke to start, but I can turn off the choke completely immediately after starting the engine. It idles smoothly. But when I give it throttle, the motor seriously bogs down, and doesn't recover. When this bogging first began happening, it was always after I had ridden a few miles. But now it happens right after I've started the engine.

I can get acceptable performance (enough to ride home from wherever I've wandered) by giving the carb about 1/2 choke. I don't get full power under these conditions, but I can do at least 25 MPH. The engine always idles nicely; before and after putting it under load. And the engine hasn't ever stalled under any circumstances.

I'm using a new gas tank, lined with a Caswell novolac epoxy kit. I've got new fuel lines with a new sintered bronze inline filter. My 87 octane gas is fresh, and treated with Sta-Bil. I've checked the tank's gas cap for proper venting.

Right now, I'm suspecting that my problem may be related to the Honda carb's air/fuel mixture screw. The design of the mixture screw doesn't allow much adjustment at all (as seen in the photo below). Turning the screw within its limited range of motion doesn't seem to make much difference in how the engine runs. I'm guessing that the funky screw head must pop off to reveal a normal head beneath it, but I'm hesitant about getting too agressive with this adjustment screw before I hear from somebody with experience! I'm also guessing that limiting the mixture screw's range of motion has something to do with Honda controlling the engine's emissions...for the U.S. E.P.A.

Any ideas?

..................................

UPDATE:

This morning, after writing the query above, I took out the bike, started it up, and rode 12 miles. She ran superbly the whole time; from startup to kill switch. I got up to 34 MPH a couple of times. I figured I'd ride until the bogging started, but she wouldn't.

I did nothing differently from yesterday: no changes to anything on the bike, same roads, same gas, etc. The only thing that I can think of that's different: this morning, it was about 64F with VERY low humidity of 37% (southeastern Connecticut shoreline). In recent days, we had a serious humid streak around here.

So, I'm cautiously optimistic...

 

[MotorBicycleRacing]

Take the carb off your huasheng and put it on the Honda.

 

[zippinaround]

are these good engines for mb's? i just found a used one on ebay for £20stg says its running?

 

[zippinaround]

87 octane? didn't know there was such thing! the petrol here is 95 octane.

 

[Max-M]

Hi Zippin,

The octane measurement that we use here in the States is different from over there in your country. Your 95 octane is the equivalent of our 87. It's just kind of a Fahrenheit/Celsius kind of thing.

The Honda GXH50 is pretty much considered the 49cc four-stroke engine for motorized bicycles. So that eBay unit is probably worth looking into.

 

[zippinaround]

never knew that! what i do know is that petrol over there is a lot cheaper than here i got 5.5ltrs for €9 thats nearly $12! is there much modding to do to fit that engine to a bike? a bigger pic of your bike would be good!

 

[Max-M]

Hey, my Irish friend:

Yes, I've heard how expensive petrol is over in Europe. Whenever our prices get up around US$4.00/gallon, people over here always say something like, "Yeah, they're high, but it's a lot better than in some countries."

I did basically no modding to my bike to fit the engine. This link will show you some good pics of it. The photos were taken before I switched from the Chinese engine to the Honda, but there's basically no difference in appearance. This is a Hong Kong-based web site run by a British automotive writer...

http://silodrome.com/motorised-bicycle/

-Max

 

[zippinaround]

holy crap! $4 a gallon is super cheap! must try to verify my paypal tomo so i can put money on it! 20 pounds delivered is a nice price for it and i'm sure it was fitted to a cement mixer so was never revved too much! are parts expensive for them?

 

[Max-M]

Parts prices don't seem too bad. Here's a source in the UK: http://tinyurl.com/GXH50parts

When people ask me what the engine on my bike is from, I like telling them how the GXH50 is used on irrigation pumps, powerwashers, generators, etc. I'll have to add "cement mixers" to my list. Come to think of it, Cement Mixer would be a cool name to put on a bike's gas tank! You'd sure get a lot of puzzled looks and questions. So, if you're into puzzled looks and questions, feel free to take my brilliant idea as your own...

 

[Max-M]

Update: The bogging problem with my Honda GXH50 engine has resurfaced. I took the long way home from work yesterday (lots of hills, and riding a little faster than usual on the flats). About four miles from home, after the bogging started, I gave the carb nearly full choke, and I was able to ride fairly normally to get home, although with reduced power. It was a rather cool day, with very low humidity. My gas was new.

Since this bogging problem seems to start only after I've been riding for quite a few miles, I can only guess that it's related to overheating. But I've got a fresh crankcase of 10-30 Castrol GTX. The engine doesn't yet have 300 miles on it.

I'm puzzled. Any ideas?