Engine idles high, then sputters when throttle opens

[wing nut]

http://custommotoredbicycles.com/ez...s_with_usa_made_gear_box4_stroke_crank_parts#
i think this may work for you if you need it
scroll all the way down to the bottom , short tapered shaft

 

[Ooontzler]

Worse come to worse, you could get another engine from ebay maybe with the right parts?

That idea has been sitting in the back of my mind... in another thread it was mentioned that bicycle-engines might still have the "old" style of HS 142f's. If I do go that route, then I'll at least have a spare (broken in) engine to scavenge for parts of I ever blow the other one up.

 

[GearNut]

I say try DAX. I bet a flywheel from one of his Super Titans would work. Ask him first to be sure if he knows about the differences with the "new" and "old" engines and if his source of Super Titans has changed anything about their engines recently.

 

[worksuxxx]

If memory serves me corretly, looking at the flywheel (old version) on the shaft you will be able to see the key cutout portion. The newer version is covered.

Also, you mentioned your gearbox was getting noisey. I will be the first to tell you it is most likely your tensioner. The noise will travel up and make it sound like it's coming from your gearbox.

 

[Ooontzler]

Well, shoot - looks like Super Titans are backordered until the end of April and 4G T-belt transmissions are backordered until June (!) according to bicycle-engines. That's a bummer... I remember reading somewhere that B-E is the source of almost all things Grubee, so if they're out it stands to reason everyone else is out .

In the meantime, my bike is running well - managed to get the engine up to 3.5k RPM, seems to take it like a champ. I'm going to attempt to investigate the tensioner in my chainbox, that is if I muster the guts to go at it with a screwdriver and attempt to crack the bugger open haha.

We'll see what happens in the next couple of months - I'll send out some emails and see if anyone knows anything (or has in stock) the "old" style HS-142f.

 

[The_Aleman]

Hi, I'm late arriving to this thread, but I'd like to try to help. I've been running a Huasheng+4G from B-E for over 3 years and have encountered a number of odd throttle problems over the 8K miles my beloved motorized bicycle has accumulated.

The stock carb can be a notorious buzzkill. It gets clogged very easily and can very well have bunk internals. My own Huasheng is on it's 3rd carb, and I've rebuilt all 3 a dozen times total. My first carb worked for ~ 100 miles and then never worked properly again. My second carb worked for another 1K miles, was rebuilt, worked for another 500, and then went to heck. My current carb worked for 2K miles, went to heck, I rebuilt it, it went to heck in a couple days, I rebuilt it and took some advice from an old-school-minded friend of mine: run a little bit of Lucas or Marvel Mystery Oil in the gas. The idea being that California's fuel wreaks havoc on carburetors and an upper cylinder lubricant is a good thing for these lil engines anyway. He also said he thinks a slight bit of oil in the fuel will help prevent the tiny passages in the carb get clogged as well. I think he's onto something. I've not had a problem since.

Aside from all that, have you tried adjusting the valves? These Huashengs are like the old air-cooled VW engines - you really need to keep an eye on the valve settings for optimum performance. They are almost always off from the factory and they _will_ change over time even if you do set them correctly. Valve adjustment plays a huge role in how these little 49cc engines run!

I'm not inclined to believe you need to change flywheel. These engines are really quite simple: as long as the gap on flywheel magnet is set correctly (~0.016") you shouldn't need to remove the dang flywheel. Any performance problem is almost always one of 2 things: the finicky carburetor (including mix setting) or the valve adjustment.

Link to proper valve adjustment procedure is in my sig. It's very easy to do, and IMHO, should be done first if you haven't already.

Please get back to us so we may assist you further in your MaBing endeavor!

 

[Ooontzler]

Hi, I'm late arriving to this thread, but I'd like to try to help. I've been running a Huasheng+4G from B-E for over 3 years and have encountered a number of odd throttle problems over the 8K miles my beloved motorized bicycle has accumulated.

The stock carb can be a notorious buzzkill. It gets clogged very easily and can very well have bunk internals. My own Huasheng is on it's 3rd carb, and I've rebuilt all 3 a dozen times total. My first carb worked for ~ 100 miles and then never worked properly again. My second carb worked for another 1K miles, was rebuilt, worked for another 500, and then went to heck. My current carb worked for 2K miles, went to heck, I rebuilt it, it went to heck in a couple days, I rebuilt it and took some advice from an old-school-minded friend of mine: run a little bit of Lucas or Marvel Mystery Oil in the gas. The idea being that California's fuel wreaks havoc on carburetors and an upper cylinder lubricant is a good thing for these lil engines anyway. He also said he thinks a slight bit of oil in the fuel will help prevent the tiny passages in the carb get clogged as well. I think he's onto something. I've not had a problem since.

Aside from all that, have you tried adjusting the valves? These Huashengs are like the old air-cooled VW engines - you really need to keep an eye on the valve settings for optimum performance. They are almost always off from the factory and they _will_ change over time even if you do set them correctly. Valve adjustment plays a huge role in how these little 49cc engines run!

I'm not inclined to believe you need to change flywheel. These engines are really quite simple: as long as the gap on flywheel magnet is set correctly (~0.016") you shouldn't need to remove the dang flywheel. Any performance problem is almost always one of 2 things: the finicky carburetor (including mix setting) or the valve adjustment.

Link to proper valve adjustment procedure is in my sig. It's very easy to do, and IMHO, should be done first if you haven't already.

Please get back to us so we may assist you further in your MaBing endeavor!

Thanks for the tips! I'm encouraged by your reports of finicky carbs - I cleaned the slow jet on this carb (the one located under the idle screw) when I first fired up my engine, but haven't yet taken the carb apart any further. Is there a good replacement that you know of/would suggest, or is the stock carb about as good as they get? I've seen some other carbs connected to these engines, but haven't really been able to find a lot of info on which are superior (though I might not know what I'm looking for, haha).

I have not yet adjusted my valves, but I actually have your valve adjustment guide printed out and tacked on the wall of my garage/workshop along with a feeler gauge set haha. Work has been a nightmare the past few days but I'll definitely try to adjust the valves tomorrow morning (after engine has cooled completely) and see how it goes.

Also encouraging to hear your take on the flywheel - I was sort of bumming out about seemingly dead-ending at my flywheel being faulty/inadequate, and the idea of hunting down another flywheel that was subtly different was daunting... I'll adjust the valves and let you know what transpires. Cheers!

 

[Ooontzler]

Well, I was taking off from a stop sign a few days ago and the characteristic rattling sound that my bike had always made since first rev was suddenly much louder. Thinking a screw had vibrated loose, I gave it a little bit of gas to see if it got any worse, and suddenly POP! and bzzzzzz!!!. I thought I'd broken a chain somewhere, but closer examination revealed all chains fully intact. Goram chainbox transmission had finally given up the ghost

I had a nice leisurely and gradual pedal back home, and of course the cover that didn't want to budge on the transmission last time pops right off to reveal a stretched and useless chain. The chain is tiny, a #25 as far as I can tell. Bah. That tiny thing was taking the full brunt of the engine torque, I'm surprised it lasted as long as it did. After a bit of digging around I found a Q-matic with an adapter for a tapered shaft, so that'll be here soon. Expensive lil' bugger but with all American-made parts and universal praise on this forum and others, I think it's the way to go.

Made a few tiny adjustments to the valve clearances, but managed to rip the valve cover gasket in the process (%$&#*$#) so it'll be a few days before I can test it out.

In the meantime, the mountain bike is getting some action and I'm getting some exercise