Huasheng 49cc Jetting Sugestions:

GoldenMotor.com

Boardie

New Member
Mar 22, 2011
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Under the Redwoods, Ca.
Hi All,

Fist off, let me state what a great forum this is.

I'm in the planning stage of my 1st motorized bike build. I have a 1950 Schwinn Panther frame & locking (with key) springer fork I picked up on Craigslist.

I have the EZ Motorbike kit with the HS 49cc engine, I also have the stainless steel flex exhaust pipe and I am planning to use the Sick Bike Parts 4 stroke air cleaner.

My Questions are: Any jetting suggestions using this exhaust & air cleaner? Has anyone found a source for jets or are they just drilling out the stock jet?

Ride safe,
Boardie
 

ocscully

New Member
Jan 6, 2008
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Orange County, CA
Performance parts and tuning is something pretty new for these engines. The flex exhaust kits from EZ and the Air Filter from SBP have been pretty much it. Just this past week AGK has entered the fray. affordablegokarts: 49cc Parts As for jets you can use the ones from the Honda Carb and they are available in several sizes but most of them are actually smaller in size than the stock Jet that came with your HS motor.

ocscully
 

flex man

New Member
Feb 24, 2011
253
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Woodland Hills Ca.
Hi
I am running the SBP air cleaner and Quentons flex pipe and my plug is a nice light choclate color so I think the jetting is right on you will feel a slight increase in power very slight But enough to make it worth your wild It looks better sounds better breaths better...............If you re jet get some hard data first to make sure your not going in the wrong way......Flex..
 

freewheeling frank

New Member
Mar 10, 2009
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ridgway colorado
i just solder the jet closed then drill it out. i am at 7000ft so i have to lean em up alot from stock, i run to 10,000 ft often. hobby lobby has a set of micro bits real cheap i use the second to smallest bit and its slightly larger than a dog hair, juust dont go too lean, or you can overheat, have fun frank
 

Boardie

New Member
Mar 22, 2011
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Under the Redwoods, Ca.
Thanks All,

I think I'll just start out with the stock jetting, reading the plug and take it from there.
If I need to change the jetting, I'll try and obtain several Honda GX50 main jets, drill them, starting with one drill size larger than the HS main jet and drill the other Honda jets 2 & 3 drill sizes larger and see how that goes.

Thanks again,
Boardie
 
Hi Guys,

Been running the flex exhaust & stock jetting on the HS motor for at least 2 years. Plug reads a little on the heavy side, however if the intake breather is removed [for DYNO testing] the plug turns a nice chocolate color.

Have fun,
 
Hi Guys,

Been running the flex exhaust & stock jetting on the HS motor for at least 2 years. Plug reads a little on the heavy side, however if the intake breather is removed [for DYNO testing] the plug turns a nice chocolate color.

Have fun,
 

agk

New Member
Oct 2, 2010
151
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Santa Barbara CA
Thanks All,

I think I'll just start out with the stock jetting, reading the plug and take it from there.
If I need to change the jetting, I'll try and obtain several Honda GX50 main jets, drill them, starting with one drill size larger than the HS main jet and drill the other Honda jets 2 & 3 drill sizes larger and see how that goes.

Thanks again,
Boardie
Boardie, starting with the stock jet and taking it from there is your best bet. Some are stating they changed the air filter and are getting a good plug reading with the stock main jet. This would imply no real performance gain, but maybe just a cosmetic change.

The reason we change an air filter is for an increase in air flow. If airflow has been increased the plug reading will show a lean condition. To correct the lean condition a larger main jet should be installed. With the increase in fuel from the larger main jet and the increase in air from the high flow air filter an increase in horsepower will result.

As a reference we installed a high flow air filter in the stock air filter box of our 49cc HS engine. Our engine would not climb over 6000 rpm. Checking the spark plug confirmed a lean condition. We were happy as this demonstrated our high flow air filter was flowing better than the stock filter. The stock main jet measured .021" which is equal to a #75 drill bit. We drilled the main jet with the next larger drill bit. After a ride at normal engine speed we took a plug reading. We continued drilling the main jet in increments until we had a good plug reading. We ended up drilling our main jet to .025" which is equal to a #72 drill bit.

We don't recommend drilling your main jet to the same size as ours without trying the stock main jet first and then drilling in increments from there. Different air filters will have a different rate of flow. Our elevation and climate may be different than yours which could result in a different different size main jet as well.
 

thatsdax

Member
Feb 22, 2008
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www.thatsdax.com
I agree.. A different main jet could be the cure. The slow jet is just to tiny to work with. Any change to the slow jet is well.. Too hard to do.. Work with the fast jet. I will see what jets I have that will fit that motor and see if I have something that will work. Enjoy the ride
 

silverbear

The Boy Who Never Grew Up
Jul 9, 2009
8,325
670
113
northeastern Minnesota
Welcome to the forum. You have a great bike to work with and are going to love the combination. I have the same engine, Q matic in a 50 Panther and it is a fine riding and good looking bike.
A couple questions to clarify for myself this drilling out of the jet. If I understand correctly the stock jet is not being replaced, but drilled out to a larger size in increments, testing along the way by reading the spark plug. Soldering the jet closed first would be if you were going to a smaller jet size. Is this correct?
SB
 
Just a few comments.........

I am at sea level and live a few thousand feet from the Alantic Ocean. The HS motor in stock condition produced a very rich condition [plug was black], after installing the Flex exhaust kit the plug was a dark brown. After removing the air breather [for DYNO testing] the plug was a perfect chocolate color.

My next test was to check the Honda GXH50 motor on the DYNO. In stock condition [exhaust & air breather] the jetting was very close. After changing the exhaust and removing the air filter, the motor went very LEAN [plug was white]. I then checked the main jet in both carburetors and found the Honda to usa a smaller jet. The HS jet was .021" and the Honda was .019". After installing an HS main jet in the Honda carburetor it was very close to correct with the flex exhaust and the open air breather.

The most important information I can pass along is "not all climates are the same" and jetting can vary widely. As an example, I raced Yamaha 250 twins [DS6 & DS7] and the jetting in Mendon, OH was 2 sizes smaller than in Decatur, IN. I often raced in Ohio, and then drove to IN. [less than 50 miles away] meaning the same bike, same day, just different jets. While it is true, 4-strokes aren't as sensitive to main jet size as a 2 stroke, it still can have a major effect in both performance and motor life.

Easiest way to test main jet size is to "kill" the motor at wide open throttle, and check plug color. If you simply ride normally, seldom at WOT, the plug reading will not indicate the main jet correctness. I normally run at WOT for approx. 1/2 mile before checking the plug.

Silverbear........
You are correct! You only solder if the jet needs to be smaller, and you will soon find out as many continue to increase the jet size until too large [went too far], and will need to reduce to a smaller size to start over again.[called trial & error]

Have fun,
 
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agk

New Member
Oct 2, 2010
151
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Santa Barbara CA
Easiest way to test main jet size is to "kill" the motor at wide open throttle, and check plug color. If you simply ride normally, seldom at WOT, the plug reading will not indicate the main jet correctness. I normally run at WOT for approx. 1/2 mile before checking the plug.

Have fun,
This is a really good point Quenton is making on the proper way to take a plug reading. Checking the spark plug in an engine that has been sitting at an idle will not produce an accurate reading nor will running the engine at a cruising speed. I stated running the engine at normal engine speeds before checking the plug, but I should have expanded on that. WOT (which is pretty normal for us haha) is definitely where you want to run the engine before checking the plug and changing a main jet. Thanks Quenton
 

agk

New Member
Oct 2, 2010
151
4
0
Santa Barbara CA
Easiest way to test main jet size is to "kill" the motor at wide open throttle, and check plug color. If you simply ride normally, seldom at WOT, the plug reading will not indicate the main jet correctness. I normally run at WOT for approx. 1/2 mile before checking the plug.

Have fun,
This is a really good point Quenton is making on the proper way to take a plug reading. Checking the spark plug in an engine that has been sitting at an idle will not produce an accurate reading nor will running the engine at a cruising speed. I stated running the engine at normal engine speeds before checking the plug, but I should have expanded on that. WOT (which is pretty normal for us haha) is definitely where you want to run the engine before checking the plug and changing a main jet. Thanks Quenton
 

trialnerror

New Member
Oct 21, 2014
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wisconsin
trial & error only works if you take note ,or (keep track), of the last attempts you made, and calculate for the next.
Otherwise, Yes, you will have to start all over again.
 
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