Losing power at full trottle

GoldenMotor.com

Greg58

Well-Known Member
May 1, 2011
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Newnan,Georgia
If you don't have a chain breaker you can use a grinder, I had to use mine when I changed to the #41. Just grind the riveted end flush with the side plate and tap the chain apart, I do this on chain up to #80 double roller at work regularly. If you have a tractor supply or ace hardware locally thay should have the 1/2 links in stock, they do at the stores here.
 

Groove

New Member
Nov 2, 2012
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Lexington, KY
Thanks AGAIN for the tips. I'm going to be tinkering in the garage this weekend. I think my chain breaker will work for the 41 chain. I've got the Harbor Freight breaker.

How much tension should I try to get? Pretty darn tight but not like a piano? Or do I want to leave some slack at first?

Lastly, do you guys use the master link, or simply join the chain manually?
 

nightcruiser

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Mar 25, 2011
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Thanks AGAIN for the tips. I'm going to be tinkering in the garage this weekend. I think my chain breaker will work for the 41 chain. I've got the Harbor Freight breaker.

How much tension should I try to get? Pretty darn tight but not like a piano? Or do I want to leave some slack at first?

Lastly, do you guys use the master link, or simply join the chain manually?
After having the master link break on the kit chain (both of them they provided with the kit broke in quick order) I decided not to use master links any more. The kit chain was slightly more reliable without a master link. Even though I'm guessing a #41 master link should be plenty strong I decided to go without it and just mend the links with the original pin I tapped out. (If you want to do this you can't grind down the pin as suggested in the above post).
As for the tension, you don't want piano wire tight, you don't want loose. You should be able to move the chain up and down about 1/2 inch when the tension is about right. Mine is a little looser than that, I had initially worried that I might need to tighten it up a bit, but after many miles of riding with no problems I forgot all about it.
 

kkalan

New Member
Jan 4, 2013
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VA
thanks for the advice, what I did was put a few spacer plates behind the rear mount to take up chain slack and add 2 tensioners on the rear wheel axle. I am running a 415h chain if I find that it starts slacking I will upgrade to the 41.
 

Russ McClay

Member
Jan 21, 2013
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Taipei
I'm a newbie here, but my engine was bogging down while I was breaking it in at 16:1 gas/oil ratio. Once I increased that to 24 and higher, the problem went away. Also...I put about 100 miles on it before it started running really nice.

-r
 

nightcruiser

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Mar 25, 2011
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After break in with a bit more oil, a 32:1 mix is what I run, I think it's the right mix. Others run with less oil, I prefer to keep my engine lubed up well...
 

kkalan

New Member
Jan 4, 2013
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VA
Ok I still have problems! I changed the gas to 32:1 ratio, new plug gapped to .024 and I still bogging at full trottle. I noticed if I back off the throttle a little on flat ground the rpms will increase slightly. I also noticed that if I hit a small downhill the bike will open up and I can maintain the higher rpm for a long time on flat gorund. It is like a hump I have to get over then she will open up. Any thoughts?
 

nightcruiser

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Mar 25, 2011
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Ok I still have problems! I changed the gas to 32:1 ratio, new plug gapped to .024 and I still bogging at full trottle. I noticed if I back off the throttle a little on flat ground the rpms will increase slightly. I also noticed that if I hit a small downhill the bike will open up and I can maintain the higher rpm for a long time on flat gorund. It is like a hump I have to get over then she will open up. Any thoughts?
Sounds like your carb is not tuned up just right yet. At WOT the dampering from the air filter and muffler along with the size of your jet and float setting is what is mainly effecting the mix. So you need to do some analysis of what condition your motor is in when it is bogging at WOT. Is it lean? Is it rich? Then take some measures to correct that condition.

When you tune a carb you should tune it to run well at WOT, then adjust the e-clip on the needle to run well in mid throttle range, then use the idle and air/mix screws to adjust the low end. There are lots of ways to figure out what condition your motor is running in, some can use their ears, eyes and nose, but doing a plug chop and then reading the plug is the best way to go. (FYI, a plug chop is done by riding the bike into the range you are trying to analyze, then all at once hit the kill switch, drop the throttle and pull in the clutch. This leaves your spark plug to reflect what was going on in your motor at the very moment you did the plug chop) After you let the motor cool, pull the spark plug and look at it to see what it looks like. Here is a link to an awesome web page that shows pictures of plugs and tells you what condition they were running under, http://www.dansmc.com/spark_plugs/spark_plugs_catalog.html , compare your plug to the chart to determine what condition you are dealing with...

That said, there are a couple of tests you can do while riding to help figure out what is going on. After reading about your experience on hills I get the feeling you may be needing a little float adjustment, here's a simple test you can do to see if your float may be filling the bowl a bit too high. Warm up your motor and then turn off the valve on your fuel tank while riding. If your bog goes away after a short while riding (before you eventually run out of fuel) then you are probably running rich at WOT, and adjusting the float to close the needle valve when the fuel level is lower in the bowl would probably fix you up. I don't recall you mentioning exactly which carb you are running, which is very important when you are talking about tuning your carb! :) If you have the CNS carb then you have an extra enrichment jet (referred to as the choke). With this carb you can simply run into the throttle range you are concerned with and open up the enrichment jet for a bit. If the condition worsens you are probably already running too rich, if the condition improves then you are probably too lean since the extra fuel from the enrichment jet improved the situation. Ultimately it's always a good idea to keep an eye on your plug to make sure your not running too lean and hot, 'cause that can cause you to burn up your motor prematurely.

Bottom line, you probably need to tune your carb a bit, so let us know what carb your running and someone will help you....

PS you should wait until you are done burning through a couple gallons of break in fuel and are running a standard fuel mix before you do too much tuning on the carb, as the fuel mix will also effect how your motor runs. Also, you want to make sure you have no air leaks anywhere before you tune your carb because air leaks have a huge effect on tuning. And your air filter as well, you need to keep it clean, and if you change to a different style air filter (or exhaust) you may have to tune your carb again.
 

kkalan

New Member
Jan 4, 2013
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VA
I am kinda new at this and this may seem like a stupid question, but the screw on the side of the card is that for the setting the idle? Looking at the pictures my plug looks good?? I will try to float trick with killing the gas. I am wondering while it will rev with help and then stay there after the hill?
 

nightcruiser

New Member
Mar 25, 2011
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I have a standard stock carb.
There is really no standard stock carb, different kits come with different carbs. There's the NT, RT, Speed and CNS carb, these are the 4 most common carbs for motorized bicycles. The first three are pretty similar, having one jet and one cable. The CNS is a little different in that it has three jets and two cables, one for throttle and the other for "choke" (which is actually an enrichment jet instead of an air choke.) The first three carbs all have regular air chokes on the air filter and should tune up pretty much the same, the CNS is slightly more complicated because it has so many jets.

So, either look on the carb for some markings (NT, RT, SPEED or CNS) or at least let us know if you have one cable going into the carb or two, or post a picture if your stumped....
 

crassius

Well-Known Member
Sep 30, 2012
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It would be good if you could listen and determine if it is 2-stroking or 4-stroking when it bogs down. If 2-stroking, you might guess that it is too lean, while 4-stroking might be too rich. You could then try changing the float level a bit before trying a diff jet size.

OTOH, I'm a firm believer in only running these engines at the 'sweet spot' for cruising, and almost never hit WOT when I ride.
 

nightcruiser

New Member
Mar 25, 2011
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I am kinda new at this and this may seem like a stupid question, but the screw on the side of the card is that for the setting the idle? Looking at the pictures my plug looks good?? I will try to float trick with killing the gas. I am wondering while it will rev with help and then stay there after the hill?
You're doing fine, we all have to start somewhere....

Before I go deeper into how the carb operates I should mention that it is possible your problem with bog at WOT may be caused by slow flow of fuel from your tank. Sometimes the gas cap doesn't vent properly and restricts flow, so loosen your gas cap a bit and ride WOT and see of the bog goes away. (thats the easiest possible situation) Also, the fuel tanks usually have lots of crap in them that can clog the fuel filters (I always clean mine out before I use them). So make sure the fuel filter in the end of the fuel valve (that goes into the tank) isn't clogged. I didn't like that fuel valve and filter setup so I bought a better fuel valve (from SickBikeParts.com) and use an inline fuel filter instead. This gives me great fuel flow and I can see it in the filter so I don't have to guess...

The carbs generally have two screws, one for setting the idle and the other for setting the air mix. The idle screw simply holds the slide in the carb open a bit to rev the motor and set the idle, the further you screw in the idle screw the more the slide is opened the faster the motor idles (its just like twisting the throttle a tiny bit). Once the idle is set the air mix screw should be adjusted to where the motor idles the fastest. The idle and mix screws only really effect the way the motor runs at idle and at very low RPM, once you are at mid throttle or higher these adjustments have no effect on how the motor runs.

If you're new to carbs it takes a bit to wrap your head around what is going on, at least these carbs are about as simple as they get. Basically, when the piston goes down it causes a suction that draws air through the carb and fuel up through the jet to mix with the air. There are a multitude of factors that determine how much air and fuel get drawn into the motor, which makes up your "mix". The main factors being the jet size, the float setting (how high the fuel level is in the carb bowl) and how much resistance the air filter and exhaust are posing to the flow of air through the motor.

Tuning a carb is not done in one step, the carb has essentially three ranges of operation and there are ways to tune each range for optimal performance. The three ranges and parts that tune them are:

WOT: At WOT the main jet size and float setting have the most effect on the mix, as well as how air is flowing through the motor due to the air filter and exhaust. To tune at WOT you adjust the float setting, adjust the size of the main jet, and/or adjust the amount of resistance the air filter or exhaust is posing to air flow. It's a balance of these factors that set your mix at WOT. WOT tuning should always be done first since any changes to this balance will effect how the motor runs in all throttle ranges.

Mid throttle: Once the WOT tuning is set you set the mid throttle mix by adjusting the e-clip setting on the needle. If you move the clip up (away from the pointed end that goes in the jet) the needle sits further in the jet and restricts the amount of fuel drawn from the jet more, thus leaning out the mix. If you move the clip down the needle comes further out of the jet allowing more fuel to flow making the mid throttle range more rich.

Idle/Low RPM range: At idle the slide is nearly closed, the needle is deep in the jet and so air and fuel flow are greatly restricted. The idle screw props open the slide a little allowing a bit of air and fuel to flow. The air/mix screw allows air to flow through a separate passage to let your motor breath a little. The idle and air mix screws only effect the tuning at idle and in the very lowest throttle range.

Understanding this it is easy to see that your motor may be running in a couple different conditions depending on the throttle range. For instance, if you're lean at WOT you could set the e-clip low to richen the mid throttle mix, your motor might be running fine mid throttle but running lean and hot at WOT. This is the reason you do a "plug chop", it's like getting a snap shot of whats going on in the motor at the very moment, 'cause if you ride home at mid throttle and kill the motor then inspect the plug it might look fine (in the above example), but if you do a plug chop after running WOT it might look hot and lean.

Hope I didn't confuse you, just trying to get you caught up with the basics so you can understand this better...
 
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nightcruiser

New Member
Mar 25, 2011
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I will try to float trick with killing the gas. I am wondering while it will rev with help and then stay there after the hill?
My previous post contained all the general information about how a carb is tuned so you have all the basic knowledge, your above comment about performance on a hill makes me think a small float adjustment might be what you are needing in your situation. The reason being, when you are going up or down hill your carb is tilted, the fuel is slanted in the carb bowl and that will effect how the float operates, it may open up and flood the bowl a bit or it may close off and make you burn down the fuel level in the bowl a bit. At the bottom or top of the hill the fuel levels off in the bowl but the amount of fuel in the bowl is abnormal for a sec. This could explain what is going on when you're going up hills, if I understand you correctly.

Turning off the fuel valve will make the fuel level start to drop in the carb, thus imitating a lower float setting briefly so you can try and determine if your float needs adjustment. Usually if you are rich at WOT lowering the fuel level in the bowl (via float adjustment) is in order, if you are lean at WOT your fuel level in the bowl may be too low and you may be drawing the fuel from the bowl faster than the needle valve can replace it. In my experience the float adjustment can have a big effect on the overall mix with these carbs, and is a good place to start when trying to tune them....