I'm perplexed...

Discussion in '4-Stroke Engines' started by Max-M, Jun 27, 2013.

  1. Max-M

    Max-M Member

    My bike is a cruiser with a Huasheng 142F 4-stroke, and a Q-Matic drive. Since getting the bike ready for the summer after its New England winter nap, it's been running great -- really feeling "dialed in." The engine is quite new. I'm only starting the second season of some rather light, short riding. I'm using a new, clean, sintered bronze in-line fuel filter, and my gas tank is brand new, thoroughly cleaned and lined with a state-of-the-art novolac epoxy tank liner from Caswell.

    But on one of my rides to work recently, the engine suddenly started to bog, and wouldn't go much more than 10-12 MPH. I was able to get it to run well enough to get home by choking it about halfway.

    Then upon further examination, I found that the idle was fairly "stumbly," not the nice smooth idle I had before. I eliminated the possibility of air leaks between the carb, the intake manifold and the engine block by spraying these areas with WD-40 and looking for bubbling. Then I removed and disassembled the carb completely. I made sure that the float bowl was moving freely, and that it was actually capable of floating, and I thoroughly cleaned all orifices with Gumout carb cleaner and canned compressed air. I cleaned and reinstalled the pilot jet, and then reinstalled the brass slow jet screw by turning it out my usual 1.75 turns.

    Next I took my valve cover off, and found that both the intake and exhaust valves were too tight. I reset the lash (COLD) to .004" intake and .006" exhaust. The plug (previously pulled to get the piston to TDC) was completely black.

    I replaced the plug with the same one I had before: an NGK CR7HSA. Through trial and error, over a few months, I determined that this plug is the right one for my motor. I set the gap on the new plug to .026" and screwed it into the Huasheng's little Chinese head.

    My crankcase ventilation tube is securely attached to my engine block and to the carburator's airbox. The air filter is clean and lightly oile per specs.

    I also checked the connections on my kill switch wiring because I heard that that could cause idle and bogging problems.

    I emptied all of the 87-octane fuel out of my bike, and I bought a few gallons of 89-octane for the bike's plastic 5-gallon storage can. I thought I'd try a slightly different octane -- and a different gas station for scientific purposes! I added the appropriate amount of Sta-Bil to the gasoline as I usually do

    I gassed up the bike, and finally, I refilled the crankcase with Mobil 1 10-30 synthetic (I had previously drained the old oil from the engine when it was hot).

    But my problem persists: The idle is stumbly (but not really all that bad) and I can accelerate for an 1/8 mile or so (with a bit of hesitation/bog at times). Then when I brake the bike to a stop, it ALWAYS stalls. I can restart it by simultaneously twisting the throttle, pulling the starter cord. It will easily start, and it will easily idle. And with the rear tire lifted (I have a center stand) I can rev the engine pretty high and let up on the throttle, and the bike will idle instead of stalling out as it does when it's under load and rolling to a stop.

    I'm baffled! I feel like I've covered all possibilities of air flow, fuel flow, valve and plug settings -- even the addition of neew gas from a high turnover gas station.

    Any help will be greatly appreciated! Thanks.


  2. Old Bob

    Old Bob Member

    While it may not be causing the problem you have that tank liner from Caswell is garbage. We did 2 dirtbike tanks and it lasted less than 6 months,do a google search and you probably will see a trend that supports this.

    Get some fresh gas ditch, the Stabil. The condition you describe sounds like its lean.

    "my usual 1.75 turns."

    try adjusting it
  3. Max-M

    Max-M Member

    I'm guessing that in using the Caswell phenolic novolac epoxy, that you've either applied it improperly (poorly-prepared inner tank surface), or that the dirtbikes' plastic tanks are getting "bopped" or badly vibrating and cracking the inner sealant. I've heard that it's not such a good product for light plastic tanks. Also, why would you apply any kind of liner to a plastic tank anyway?!

    Many people screw up their installation of the phenolic novolac epoxy liners. All recommended steps must be followed to a T. I was actually able to let mine cure for almost two months before putting gas in the tank, and the tank has worked superbly. Friends of mine who have used the Caswell product have had years of good service from it (mostly after using Kreem-brand on other tanks, and watching their ethanol-laced gas dissolving their expensive Kreem liner.)

    As far as those "usual 1.75" turns, I tried a MUCH broader range while trying to diagnose my engine: 1.75 - 2.25 turns (and more).

    And if you read my post again, you'll see that (as you suggested) I did drain the tank and refill it with fresh gas. Also, I've been using Stabil in a lot of different engines for years, and have no intention of stopping
    Last edited: Jun 28, 2013
  4. Old Bob

    Old Bob Member

    Dirt bikes have had steel, aluminum,fiberglass and plastic tanks. caswell has a problem.When you figure out what you did to fubar your bike let us know.
  5. jaguar

    jaguar Well-Known Member

    When you spray the intake, dont look for bubbles. the inside of the tract has a vacuum, not a pressure.
    Check for a change in ignition timing or a loss of cylinder compression (valve blowby or bad rings).
  6. IbedaYank

    IbedaYank Member

    mind posting links to back up this claim.
    As Caswell was never intended to be used on any tank NOT made from metal
  7. Old Bob

    Old Bob Member

    As far as know, and don't quote me because I've only been in manufacturing for over 30 years but steel and aluminum are metals...
  8. BigBlue

    BigBlue Active Member

  9. Old Bob

    Old Bob Member

  10. Big Red

    Big Red Active Member

    I've also had problems with this carb doing exactly the same thing. I cleaned it TWICE and nothing. Then I had a friend clean it, (Ocho Ninja,) and it ran great. Now, I'm not TOTALLY stupid, I know how to clean a carb, BUT I obviously missed something. Or Ocho just has a magic touch with these things, I don't know. Take EVERYTHING apart one more time. Run a thin wire through the low speed jet. Same with the main jet along with carb cleaner and comperssed air. It really does sound like it's the carb.
    Big Red.
  11. jaguar

    jaguar Well-Known Member

    I had a cheapie fuel filter on my gas line and the slow jet was getting clogged every other ride till I turned the filter around. Seems like some of the paper from the filter was coming off and clogging up the jet.
    Don't rely on the cheap metal filter inside the gas tank.
  12. professor

    professor Active Member

    Rig up a different gas supply with a new filter. You are running out of gas -even if your current tank if full.
  13. Big Red

    Big Red Active Member

    Jaguar and professor both have good ideas. By using a different fuel supply with a GOOD fuel filter you eliminate the possibility of anything else being clogged. (tank, filter, lines, ect.) If it wont run then, take a closer look at the carb.
  14. Max-M

    Max-M Member

    Thank you all for your responses so far.

    I've got a sintered bronze in-line fuel filter (and no filtering inside the gas tank). I've shut off the fuelcock with the engine running, and have let the engine run until it was out of gas. At that point, through the clear housing of the fuel filter, I can see that the filter has no gas in it.

    When I turn the fuelcock valve to OPEN, gasoline quickly fills the filter. So I know that there's no blockage up to the filter.

    The sintered bronze filter element looks very clean, but my next diagnostic step will be to bypass the filter by temporarily running a fuel line directly from the fuelcock to the carb. If my problems persist, I'll at least know that I'm good from the tank to the carb.

    Also, I've cleaned the slow jet as part of my total carb ******, and I've run the engine with the gas cap off of the tank to make sure that the cap is venting.

    I'll keep you guys posted!
  15. Big Red

    Big Red Active Member

    Not a good idea to run without a filter, even for just a minute. Any crap in the tank will go directly into the carb.
    Big Red.
  16. Max-M

    Max-M Member

    Thanks for the advice, Red. Yeah, I guess it wouldn't make any sense to risk clogging the carb by running unfiltered. My scientific diagnosis method would be out the window!

    I'm going to find another sintered bronze, clear filter somewhere locally tomorrow if I can.
  17. Big Red

    Big Red Active Member

    Kragen's/O'rielly's sells a pretty good little filter in the SMALL ENGINE DEPT. for about $3. Don't go to the auto section,those are way too big. Ask where the small engine stuff is. Get the clear one, the little red one they sell is crap.
  18. Max-M

    Max-M Member

    Well, gents, I believe I figured out my problem: I happened to notice some very fine droplets of motor oil on the headfins on the shaft side of my engine, and on top of the stainless-steel gearbox cover that's adjacent to those fins. Apparently, the Chinese use cylinder head casting techniques that result in thin spots and other problems.

    My wife has high-powered dental loupes with a very bright LED light array mounted between the lenses so that she can clearly see inside her patients' mouths. I borrowed the loupes and took a look at my Huasheng, and I clearly saw very fine pinholes in the metal between the headfins.

    These pinholes would explain why my engine would run somewhat OK until it was hot: the hot metal would expand, making the holes larger, sucking in air (and spattering out a bit of Mobil 1) and causing the engine to bog.

    So instead of risking an unsightly and messy repair with JB Weld, or something along those lines, I ordered a brand new Honda GXH50.

    My wife was surprised to see the engine on display in our kitchen this morning! I think it's a beautiful little piece of technology. Now, I'm hoping for raging reliability, and many miles of fun this summer and fall. I'll be bolting it into my bike frame some time in the coming week...

  19. MotorBicycleRacing

    MotorBicycleRacing Well-Known Member

    The cylinder on your huasheng has a iron liner inside the aluminum casting.
    Where between the fins are you saying it was coming from?

    Your new Honda has the same iron liner.
  20. Max-M

    Max-M Member

    MBR: I saw pinholes between the fins, on the rounded external cylinder area. So, the Huasheng has an iron liner?! Now, this has really gotten baffling! I first saw the spattered oil on top of my gearbox cover, and I assumed it was coming from between the valve cover and the head.

    At any rate, once I have the Honda engine mounted, I'm going to do a postmortem on the Huasheng to see what I can find.