Brand new GXH50, bogging problem...

Discussion in '4-Stroke Engines' started by Max-M, Sep 6, 2013.

  1. Max-M

    Max-M Member

    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...

    adj-screw-carb.jpg
     
    Last edited: Sep 6, 2013

  2. MotorBicycleRacing

    MotorBicycleRacing Well-Known Member

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

    zippinaround Active Member

    are these good engines for mb's? i just found a used one on ebay for £20stg says its running?
     
    Last edited by a moderator: Dec 18, 2015
  4. zippinaround

    zippinaround Active Member

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

    Max-M Member

    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.
     
  6. zippinaround

    zippinaround Active Member

    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!
     
  7. Max-M

    Max-M Member

    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
     
  8. zippinaround

    zippinaround Active Member

    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?
     
  9. Max-M

    Max-M Member

    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...
     
  10. Max-M

    Max-M Member

    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?
     
  11. Max-M

    Max-M Member

    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?
     
  12. Max-M

    Max-M Member

    After further research about the possibility of overheating:

    I read this in a June 2011 thread on this forum:

    Too much oil will cause the oil to foam up because it is being hit by other parts of the rotating assembly. Once it foams up it loses some of its ability to draw heat out of the engine. This is very bad especially on an air cooled engine. You are better off just disconnecting the low oil sensor and just keep a close eye on the oil level. I had this explained to me by a small engine expert. I never would have believed that more oil could be bad but it is very bad for these engines. Go figure...

    If having an oil level that's a bit too high is causing my engine's oil to foam, and therefore causing the oil to be less effective, and causing the engine to overheat: could this overheating effect the carburetor's functioning? (As I mentioned before, my engine runs great for many miles on each ride before the bogging problem starts. And since I can limp home if I turn on the choke, I'm assuming that this situation is related to the carb.)

    Anyway, I'm going to lower my oil level a bit, and see what happens. Then I'll eventually disconnect my Honda GXH50's low-oil cutoff feature, with Irish John's great instruction sheet as my guide (PDF attached). I don't know if the low-oil cutoff sensor could be related to my bogging situation, but it's really unnecessary for me as I really keep my eye on my oil, and I'd like to eliminate that gadget as a future source of engine trouble.

    Again, any thoughts will be greatly appreciated.
     

    Attached Files:

    Last edited: Sep 18, 2013
  13. darwin

    darwin Well-Known Member

    OP I would clean your idle jet out, if the oil is overfilled best symptom would be your air breather being soaked with oil. Check the oil with the motor level and standing straight up. Thatsdax has a good video on you tube for cleaning the idle jet out.......also next time it bugs out on you try running it with the cap half way on and see if that fixes it, if so cap isn't venting properly.
     
  14. Max-M

    Max-M Member

    Thanks, Darwin. I've ruled out the overfilled, foaming oil idea. Loosening the gas cap is also something that I've tried. But cleaning the idle jet on the Honda, I haven't. I've cleaned the idle jet plenty of times on Huashengs, though...nice easy procedure.

    Last night, I drained the not-so-new gas out of the bike's tank into my 5-gallon can, and then dumped my bike gas into my car. I then bought a few gallons of fresh gas...at a busy, high-volume gas station on the other side of my town. I'm going to see how the Honda runs with the fresh gas, and then clean the idle jet if the bogging persists.
     
  15. Max-M

    Max-M Member

    Well, the fresh 89 octane gas made no difference. And even though the idle is fine, I pulled out the idle jet/slow jet and cleaned it. But I've still got serious bogging, unless I run at nearly full choke. So obviously the engine's not getting enough gas flow, right?

    To recap my situation:

    - factory-new Honda GXH50 with only 150+/- miles on it
    - fresh 89 octane gas
    - gas flows freely from tank, through filter, to carb
    - new sintered bronze inline fuel filter
    - clean idle jet
    - engine starts on one pull and idles nicely

    But, after letting the engine warm up a bit, twisting the throttle results in complete bogging of the engine. I can ride with decreased power if I give the engine full choke. And sometimes, I can start up the bike and ride for 10 miles before the bogging starts. That's confusing to me; I think the problem has gone away, and then eight miles from home, the bike starts bucking and bogging!

    As you can see in the closeup photo of the Honda carb at the beginning of this thread, the adjustment range of the air/fuel screw is only about a quarter of a turn.

    When I first installed the engine, it ran just fine. But after putting about 120 miles or so on it, this bogging started.

    I'd hate to think that the factory-set valves would be causing this already.

    This is really getting annoying!
     
    Last edited: Sep 22, 2013
  16. Quenton Guenther

    Quenton Guenther Motored Bikes Sponsor

    Be sure to check the pilot jet as it is the biggest issue with fuel flow. If partially plugged it can respond to heat and cause your problem. The jet is located below the mechanical idle setting screw. Remove idle adjustment screw and lift [gently pry] the jet from the carburetor. It is very difficult to clean and most often cleaner and air don't get the job done. Use a strand from a "frayed" cable to force the obstruction from the jet. Never use a drill bit as it can easily open the jet size too large.

    Are you using the Honda or HS carburetor?

    Have fun,
     
  17. Max-M

    Max-M Member

    Quenton: I'm using the stock Honda carb. I pulled out its pilot jet and cleaned it yesterday.

    I noticed that it doesn't look the same as the Huasheng's pilot jet, once you pull it out. On the Honda jet, there's no visible brass at the end of it. On the Huasheng carb's pilot jet, the brass, with the tiny jet-hole, is right at the end of the black plastic part that gets pushed into the opening on the carb. The jet-hole is apparently recessed on the Honda's pilot jet assembly, so I decided to just blow it out with my mouth. It was obvious that I had air flowing through the tiny hole. I'm going to try again with a pair of dental loupes with an LED light attached (a tool of my wife's trade). Hopefully I can see the hole, and get a strand of wire through it.

    But the bike ran well today. No bogging on a long ride. But it's been unpredictable when the bogging has come back in the recent past, so I'm just cautiously optimistic.

    Until I read your reply to my post, I didn't realize that the pilot/idle/slow jet is the biggest issue with fuel flow. I thought it was just of concern for the carb's idle.

    Thanks Quenton, and I'll keep you posted on my progress.
     
  18. Quenton Guenther

    Quenton Guenther Motored Bikes Sponsor

    After reading some of your earlier post on this issue, I noticed you might still be using the oil sensor. If so, I would unplug it, as most of our customers reported intermittent ignition problems with it connected. We were also informed it often triggered when leaning into a corner. As far as I know, neither the Honda or HS motors have any problems with oil usage, therefore the sensor can be safely disconnected. Just check the oil often.

    If you don't solve the problem, we will gladly loan you a Honda carburetor to try if needed. Of course you will have to pay all shipping costs concerned.

    keep us posted.


    Have fun,
     
  19. Max-M

    Max-M Member

    Thanks for that Honda carb offer, Quenton. I'll keep that in mind.

    I did disconnect the oil sensor a couple of days ago.

    This morning, I had a nice, fairly trouble-free ride to work. At one point, after a long nearly full-throttle stretch, I started to slightly feel the bucking/bogging coming on. So I backed off the throttle a bit for 20 seconds or so, and then resumed the WOT activity without trouble. It seemed as if the float bowl was emptying before it could replenish the fuel. My fuel flow from the tank, through the inline filter up to the carb inlet is a good strong gush; no fuel restriction up to the carb. Could it be that I'm emptying out the bowl faster than it can replenish?!
     
  20. Big Red

    Big Red Active Member

    I HATE the carbs on those things. they clog every time ya sneeze, Are ya using an inline filter. ya GOTTA use a fuel filter with those touchy carbs. Give it a real good cleaning Just dont sneeze on it or it'll clog up again. yer high speed jet is clogged.
     
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