I'm perplexed...

Max-M

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Sep 22, 2011
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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.


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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
 
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
 
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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.
 
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).
 
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.

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

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...
 
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.
 
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