49cc 4 stroke HuaSheng dying after warm-up

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foxy_zoom

foxy_zoom

New Member
Jun 5, 2011
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Flagstaff, AZ
I've been dabbling in the moto-bikes for a couple of years and decided to upgrade to a 4 stroke for better reliability. I live at 7,000 ft above sea level. Recently my bike has been dying on me after it warms up. It almost seems flooded? I do plan on a tear-down-clean-up-re-build in a couple of days when I have a day off. Anyone have any advice for carb and air settings for the greater altitude? And any other sugguestions would be welcome as well :)
 
Dan

Dan

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May 25, 2008
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*bump*

Not owning one, I am of no help but am sure some one can help out.

Would try the regular and easy stuff. Check plug, fuel/filter/venting and air/filter. If it had been running OK, not sure it would be an altitude problem but am no expert.
 
A

agk

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Oct 2, 2010
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Santa Barbara CA
At 7000 feet you will definitely need a smaller than stock main jet. We are sea level and when we raced at Willow Springs which is only 2500 feet, we had to use a smaller than usual main jet. Maybe you can leave the stock main jet alone and just add a high flow air filter.

I recently added a high flow air filter to a customers 49cc 4-stroke. I drilled the main jet to .025" as I've done before. I couldn't figure out why the engine was running rich with this combination as I've done it before with no issues. Instead of going to a smaller main jet I just drilled some breather holes in the air box cover. This allowed more air to flow and I ended up with a good plug reading.

I guess my point is, at your elevation the factory jetting will be too rich. You can either go to a smaller main jet to reduce the amount of fuel or you can use a high flow air filter and/or drilled out filter box to increase air flow.
 
scotto-

scotto-

Custom 4-Stroke Bike Builder
Jun 3, 2010
6,505
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Ridin' inSane Diego, CA.
What AGK said and or check your fuel filters, especially the one on the petcock that's inside the fuel tank. When they clog, it will kill your engine. Also if a tiny tiny piece of sediment gets into and internal jet or orifice, it can clog and shut down your motor by fuel starvation. In that case, take off the float bowl and check for sediment and blow out with compressed air gently.

How many miles or hours on the engine at that altitude? Was it running fine before and for how long till this problem surfaced? More info will help with a diagnosis.

dnut
 
foxy_zoom

foxy_zoom

New Member
Jun 5, 2011
7
2
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Flagstaff, AZ
Thanks for all the responses!
The bike was running great for several months, and I think it might be a combination of the altitude, needing a cleaning, and the change in the weather. Monsoons are starting, and it's of course getting a lot warmer.
My wireless speedo has a serviced reminder setting (it's set for every 200 mi) and I have changed the oil three times. So, I really don't know how many hours, but I would say that if my speedo is running correctly, it's got around 600 miles on it. That sounds like a lot, hmm....
Anyways, I put a new rear drive sprocket on, I got the manic mechanic hub adaptor with a 22t sprocket, I can't wait to see what my new top speed is! Total P.I.T.A. to install, had to fiddle with the chain and tension pulleys for a while to get the chain in a good position.
I'm cleaning the carb today, looking at videos and stuff to learn how to take it apart and all that. Any good links out there for the huasheng carb?
Where would I get a smaller jet, and what would you sugguest I look for? I think I will try drilling some holes in the air box while I have it off the bike as well.
Ok, back to work, and I'll post again once I get it all back together!
 
MotorBicycleRacing

MotorBicycleRacing

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Jul 28, 2010
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foxy_zoom said:
Anyways, I put a new rear drive sprocket on, I got the manic mechanic hub adaptor with a 22t sprocket, I can't wait to see what my new top speed is! Total P.I.T.A. to install, had to fiddle with the chain and tension pulleys for a while to get the chain in a good position.
Click to expand...
22 tooth sprocket????? That is too small to bolt to a MM adapter.
What size were you using before getting what kind of top speed?

I see from your album that you are running the Hoot geared box.
You have my condolences, 600 miles is a lot for that box....
 
Last edited:
foxy_zoom

foxy_zoom

New Member
Jun 5, 2011
7
2
0
Flagstaff, AZ
You assume that I know any of this ;-) I'm mechanically inclined, but not trained, and no mentors either. That's why I'm on here, to learn how to do stuff. The clutch does feel a little boggy now with the new sprocket, so I see what you mean. It's starting in on the rainy season, so I won't be riding much right now. What's the smallest you think I could go with that gear box? I want to keep the MM kit for better rear torque.
 
MotorBicycleRacing

MotorBicycleRacing

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Jul 28, 2010
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foxy_zoom said:
You assume that I know any of this ;-) I'm mechanically inclined, but not trained, and no mentors either. That's why I'm on here, to learn how to do stuff. The clutch does feel a little boggy now with the new sprocket, so I see what you mean. It's starting in on the rainy season, so I won't be riding much right now. What's the smallest you think I could go with that gear box? I want to keep the MM kit for better rear torque.
Click to expand...
No problem, bro. just trying to help you out.
I have a Hoot box in pieces so can count the teeth to figure
the ratio reduction unless someone reading happens to remember.

Sometimes making the sprocket larger will make your 4 stroke bike
faster but you have to run the numbers. You don't want to over rev
those motors too much. Redline is about 8000 rpm

How fast did it go with the 32 tooth?

I really wouldn't count on that Hoot box lasting for too long though.
 
foxy_zoom

foxy_zoom

New Member
Jun 5, 2011
7
2
0
Flagstaff, AZ
I have only done a quick around-the-block to test it after the rebuild, theres not enough room in the neighborhood to get top speed :) I was reaching almost 30mph though. Where would I find info on the gearing ratio? The sprockets are only $20-30, so I wouldn't mind getting another one. And if the clutch dies, I'll get another one of those, too ;)
And call me Sis, not Bro :p
 
Otero

Otero

Member
Feb 1, 2010
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Foxy,
Not that it will help at this late date, but thatsdax.com has a video that explains
how to clean your main jet using a single strand of wire from a brake cable. That's
just FYI for anyone coming to this thread with a problem such as yours. It's
a fairly common cause of trouble with an HS 49 x 4stroke, but a simple fix.
 
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