New China girl carb problem..help!

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cryptgrrl

New Member
Apr 17, 2017
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ohio
I have built several of the chinease bike engine kits on different style of frames.i just finished a crusier style for my fiancé,all of the sudden same issue.would not run unless choke 2/3rd s open.tried everything. idle adjust,throttle adjust just as I was ready to douse the bike with gas a lit in on fire I dissembled the carb bowl.the main jet had come lose and was interfering with the float.also the pin holding the thin metal arms ontop of the float was misaligned.
I could not believe this.but lets be honest this is a sweet little engine but I have had some strange little quirks pop up. just something to check.
 
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Dead66

Member
May 11, 2016
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Pawleys Island
Since you al are here, I would like to ask about my speed carb. I was have lots of trouble with what I think is 4 stroking once up to speed. I would have to slightly let off the throttle to get it to run smoother at top speed, and still I was not getting the most out of her.

I had a nice, short , aluminum intake manifold but realized I was using the gasket that came with the stock manifold. The opening on the nice aluminum manifold widens to better match the port. But the gasket was sticking out and blocking flow. I put the original intake on and got much better results. But am still have less than top performance. I also have to keep the sponge filter removed to get enough air.

I have just received a set of drill bits, so I am going to try making the jet smaller and see what jet sizing can do for me. (I already worked with the needle adjustment and now have it set on the second notch from the top which is best at this point.

Should I get a proper gasket for the aluminum intake?

It seems as though it should give me MUCH smoother flow if I were to clean up the gasket issue. Anyone have experience?
 
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Potato_In_Exhaust

Member
Feb 2, 2017
156
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California
Dead66 said:
Since you al are here, I would like to ask about my speed carb. I was have lots of trouble with what I think is 4 stroking once up to speed. I would have to slightly let off the throttle to get it to run smoother at top speed, and still I was not getting the most out of her.

I had a nice, short , aluminum intake manifold but realized I was using the gasket that came with the stock manifold. The opening on the nice aluminum manifold widens to better match the port. But the gasket was sticking out and blocking flow. I put the original intake on and got much better results. But am still have less than top performance. I also have to keep the sponge filter removed to get enough air.

I have just received a set of drill bits, so I am going to try making the jet smaller and see what jet sizing can do for me. (I already worked with the needle adjustment and now have it set on the second notch from the top which is best at this point.

Should I get a proper gasket for the aluminum intake?

It seems as though it should give me MUCH smoother flow if I were to clean up the gasket issue. Anyone have experience?
Click to expand...
Try running the bigger bore intake without a gasket and see if it runs any better before buying the matching gasket. Just make sure to tighten it real well.
 
Tyler6357

Tyler6357

Well-Known Member
Mar 15, 2012
1,293
294
83
Santa Barbara, CA
Dead66 said:
Since you al are here, I would like to ask about my speed carb. I was have lots of trouble with what I think is 4 stroking once up to speed. I would have to slightly let off the throttle to get it to run smoother at top speed, and still I was not getting the most out of her.

I had a nice, short , aluminum intake manifold but realized I was using the gasket that came with the stock manifold. The opening on the nice aluminum manifold widens to better match the port. But the gasket was sticking out and blocking flow. I put the original intake on and got much better results. But am still have less than top performance. I also have to keep the sponge filter removed to get enough air.

I have just received a set of drill bits, so I am going to try making the jet smaller and see what jet sizing can do for me. (I already worked with the needle adjustment and now have it set on the second notch from the top which is best at this point.

Should I get a proper gasket for the aluminum intake?

It seems as though it should give me MUCH smoother flow if I were to clean up the gasket issue. Anyone have experience?
Click to expand...
I agree that you should use the gasket that is fit for the intake otherwise you don't take advantage of the upgraded intake and parts of the gasket could break away and get sucked into the case. You might be able to use a razor blade and cut it to fit but I would recommend just getting a port matched intake gasket. However, having said that, I still think you will need to jet down to stop the high end 4 stroking. If you see a lot of smoke that is a sign it's too rich. Also, just something to keep in mind while testing, in my experiences, I have found that my bike will 4 stroke when I first start it but it will go away when it gets warmed up so I think it tends to run leaner as it gets hot.
 
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Dead66

Member
May 11, 2016
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Pawleys Island
Yes, it does run better as it gets hot.

The weird thing is that there is no smoke, and doing a plug pull test shows the plug to be dry. Not white. But dry. So I am scratching my head as to whether it is indeed a jetting problem.

I fly gas rc engines and they 4 stroke, but rarely on wide open throttle. So I am a little unsure of what I am hearing. But the motor will go from a nice ZING sound to a BLATBLAT BLAT sound. The BLAT BLAT BAT is very fast. So if I am up to speed and I give it full throttle, it will blat blatblat. But if I ease off the throttle just barely, it will run smoother AND faster.

I assume that is 4 stroking?
 
Tyler6357

Tyler6357

Well-Known Member
Mar 15, 2012
1,293
294
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Santa Barbara, CA
Dead66 said:
Yes, it does run better as it gets hot.

The weird thing is that there is no smoke, and doing a plug pull test shows the plug to be dry. Not white. But dry. So I am scratching my head as to whether it is indeed a jetting problem.

I fly gas rc engines and they 4 stroke, but rarely on wide open throttle. So I am a little unsure of what I am hearing. But the motor will go from a nice ZING sound to a BLATBLAT BLAT sound. The BLAT BLAT BAT is very fast. So if I am up to speed and I give it full throttle, it will blat blatblat. But if I ease off the throttle just barely, it will run smoother AND faster.

I assume that is 4 stroking?
Click to expand...
What you describe sounds like 4 stroking. It can certainly 4 stroke at one throttle range and not others (at the top end or at the bottom end) The fact that the plug is dry don't mean much since that is where ignition occurs, the color is a better indicator, a dark black indicates a rich condition and a white indicates a lean condition, light brown is good. Also, you should remember, it can still 4 stroke and not have excessive smoke. If you do have excessive smoke that usually means that you are running very rich and might have to jet way down or that you are running a very oil rich gas mix. But it sounds like you are almost there, just make the jet a little smaller. But before you do that, take care of the gasket, and test it for any change. It's certainly possible that you will see a change with a larger gasket and won't have to change the jet at all. I don't think you should try no gasket and just attempt to make it extra tight, you could strip the threads and it still won't work, at least not for long, you have to have a gasket on there. In the old days guys used to cut them out of cereal boxes, haha, and some guys still cut their own. This guy cuts his own and sells them on ebay--> http://www.ebay.com/itm/Upgrade-Mot...848090?hash=item41c25e831a:g:BsUAAOSwhlZYublL I've gotten some from this guy before and he will combine shipping costs if you buy more than one---> http://www.ebay.com/itm/Motorized-B...850934?hash=item3f50577e76:g:GhYAAOSwA3dYG8g~

It is good to make your own jets. I think it's better that way. Do you have extra jets or just the stock one? I think the stock one is a #70. Here are some slightly smaller ones if you don't want to mess with making your own.---> http://www.ebay.com/itm/281779435448?_trksid=p2055119.m1438.l2649&ssPageName=STRK:MEBIDX:IT
 
Tyler6357

Tyler6357

Well-Known Member
Mar 15, 2012
1,293
294
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Santa Barbara, CA
Oh, one more thing I forgot to say and I can't stress this enough. When you are testing jets, it is always better to be a little on the rich side rather than being on the lean side. Leaning it out can really wake up your engine but if you make it too lean you won't be getting enough oil and you will run it extra hot and excessive heat will cause engine failure. When it's 4 stroking you will lose power but at least the rings won't break or the piston won't seize up or other very bad things from too much heat won't happen. Too much 4 stroking can cause a blown head gasket if it has a load and misses at the wrong time though. It can be tricky to get just the right jet size but caution on the side of rich.
 
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Tyler6357

Tyler6357

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Mar 15, 2012
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Santa Barbara, CA
Something else you might check before you attempt to mess with the jet. First, a clogged air filter can restrict air and cause a rich condition and 4 stroking, you can try taking the air filter off and testing the bike to see if there is any change. Second, if the exhaust pipe is clogged with oil and other gunk the back pressure can restrict the air and cause a rich condition. You should check these things.
 
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Dead66

Member
May 11, 2016
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Pawleys Island
Tyler6357 said:
Something else you might check before you attempt to mess with the jet. First, a clogged air filter can restrict air and cause a rich condition and 4 stroking, you can try taking the air filter off and testing the bike to see if there is any change. Second, if the exhaust pipe is clogged with oil and other gunk the back pressure can restrict the air and cause a rich condition. You should check these things.
Click to expand...
I really appreciate ALL the help I am getting! In response to this particular post:

I cut the silencer pipe out of the stock muffler and drilled a couple extra holes in the cap. I don't think it is clogged.

I DID take the filter off and it runs better. The filter is clean except there is a bit of oil on it (I have forgotten to turn off gas flow in storage at times). Does a little bit of oil on filter do much restricting?
 
D

Dead66

Member
May 11, 2016
81
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Pawleys Island
Tyler6357 said:
What you describe sounds like 4 stroking. It can certainly 4 stroke at one throttle range and not others (at the top end or at the bottom end) The fact that the plug is dry don't mean much since that is where ignition occurs, the color is a better indicator, a dark black indicates a rich condition and a white indicates a lean condition, light brown is good. Also, you should remember, it can still 4 stroke and not have excessive smoke. If you do have excessive smoke that usually means that you are running very rich and might have to jet way down or that you are running a very oil rich gas mix. But it sounds like you are almost there, just make the jet a little smaller. But before you do that, take care of the gasket, and test it for any change. It's certainly possible that you will see a change with a larger gasket and won't have to change the jet at all. I don't think you should try no gasket and just attempt to make it extra tight, you could strip the threads and it still won't work, at least not for long, you have to have a gasket on there. In the old days guys used to cut them out of cereal boxes, haha, and some guys still cut their own. This guy cuts his own and sells them on ebay--> http://www.ebay.com/itm/Upgrade-Mot...848090?hash=item41c25e831a:g:BsUAAOSwhlZYublL I've gotten some from this guy before and he will combine shipping costs if you buy more than one---> http://www.ebay.com/itm/Motorized-B...850934?hash=item3f50577e76:g:GhYAAOSwA3dYG8g~

It is good to make your own jets. I think it's better that way. Do you have extra jets or just the stock one? I think the stock one is a #70. Here are some slightly smaller ones if you don't want to mess with making your own.---> http://www.ebay.com/itm/281779435448?_trksid=p2055119.m1438.l2649&ssPageName=STRK:MEBIDX:IT
Click to expand...
I only have one jet but I do have a nice set of drill bits to make it smaller.

Should I make it like 4 or 5 sizes smaller and work back up? Or should I make it one size smaller, check it, then fill hole and drill smaller....

Seems like I could make it 5 sizes smaller, test it, then continue to drill it out all the way back up. Decide which was best. Fill hole one more time and then drill to correct size?


On the air filter, should I use silicon to seal the connection between the carb and intake?
 
Tyler6357

Tyler6357

Well-Known Member
Mar 15, 2012
1,293
294
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Santa Barbara, CA
Dead66 said:
Should I make it like 4 or 5 sizes smaller and work back up? Or should I make it one size smaller, check it, then fill hole and drill smaller....

Seems like I could make it 5 sizes smaller, test it, then continue to drill it out all the way back up. Decide which was best. Fill hole one more time and then drill to correct size?
Click to expand...
It's usually best to work down. Like I said, you don't want to go too lean. You want the biggest jet you can have without 4 stroking. Since the stock is 70, you could drill a 68 and test for 4 stroking, if it's still happening, drill a 66 and try again. Don't forget to get it hot to get an accurate test.

On the air filter, should I use silicon to seal the connection between the carb and intake?
Click to expand...
No, I wouldn't use silicon. Also, if it runs better without the air filter I would just buy another one. They get clogged and dirty and need to be replaced every once in a while and they are cheap---> http://www.ebay.com/itm/1pc-Air-fil...ash=item4ae02c73ba:g:ZsIAAOSw7NNUGpNC&vxp=mtr This is true for the fuel filter also.
 
D

Dead66

Member
May 11, 2016
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Pawleys Island
I have no issue buying another filter. I am just confused because this is one of those plastic mesh filters with LOTS of open space. I actually wonder how it could possibly filter anything smaller than beach sand. When I say it is oily, I mean the bottom have is wet. It is not wet AND dirty. It seems to me that I would need a filter that actually filters small particles, no? For example, this filter is not filtering the small dust coming off the rear tire. It simply passes through....

But if I got a filter that actually filtered better, I don't think it would run well at all???
 
Tyler6357

Tyler6357

Well-Known Member
Mar 15, 2012
1,293
294
83
Santa Barbara, CA
Dead66 said:
I have no issue buying another filter. I am just confused because this is one of those plastic mesh filters with LOTS of open space. I actually wonder how it could possibly filter anything smaller than beach sand. When I say it is oily, I mean the bottom have is wet. It is not wet AND dirty. It seems to me that I would need a filter that actually filters small particles, no? For example, this filter is not filtering the small dust coming off the rear tire. It simply passes through....

But if I got a filter that actually filtered better, I don't think it would run well at all???
Click to expand...
I really don't know. I really don't have that much experience with the NT Carb. I upgraded to a RT type carb for my bike, it was one of the first upgrades I did and the RT carb has a completely different air filter, so I really can't answer your question.
 
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Dead66

Member
May 11, 2016
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Pawleys Island
Whoopsie I was wrong. I used a #72, sorry. It was dark and I could not see the markings so I just counted the spaces, but I counted in the wrong direction. I went smaller than the #70 and used a #72.

I only drove for 10 minutes. Once she warmed up there was no 4 cycling at top end. But it took 5 minutes for that to happen. At the end of ride I cut motor off at full throttle and pulled the plug. It was brown. Not wet. Not white. Really looked no different than before. I am now wondering if I should give it another try with a # 74?

Once she warmed up she was zinging pretty good. I don't want to run her too hot. But I do wonder if she should not have been running better before 5 minutes of warm up riding to get rid of four stroking?
 
crassius

crassius

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Sep 30, 2012
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diameter matters, but also how long the passage is thru the solder and brass - both effect flow rate
 
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