Alright so let me start off by saying its a 66cc FM80 on arm have a stock nt crab jet pin is set in the middle. Having a problem. It idles fine when sitting. It accelerates and slows down fine but keeping at a speed above 20 its sounds like its 4 stroking and feels like its going in and out of power. No idea what is going on. I am running 74:1 using 1 packet of Opti-2. New sparkplug set at .022. Any suggestion(s) would be super helpful
keeping speed problem
- Thread starter proneto911
- Start date
Sounds like you have the typical rich running condition most all these engines have until the main jet in the carb is sized down.
Several of us use wire gauge drill bits, a small propane torch and a small piece of solder to solder and then redrill the jet to a smaller size.
If this isn't something you want to attempt sickbikeparts.com sells the differrent size 5mm jets that you can buy.
Several of us use wire gauge drill bits, a small propane torch and a small piece of solder to solder and then redrill the jet to a smaller size.
If this isn't something you want to attempt sickbikeparts.com sells the differrent size 5mm jets that you can buy.
Yes like MBR suggested move the clip up to lean it out.
Many of us have found that the second from the top notch seems to work good and that may help some at low to mid rpms, I still would bet you'll need to reduce main jet size but getting the clip where it works best is also important.
Many of us have found that the second from the top notch seems to work good and that may help some at low to mid rpms, I still would bet you'll need to reduce main jet size but getting the clip where it works best is also important.
I tried the plug turns a light color not the tan/chocolate color way lighter
That's what I had it at 2nd from the top but running 74:1 some reason turns the plug almost white its not that chocolate/ tan color. Unless I'm looking for the wrong color. But at the 2nd notch it was doing this.
Alright so I'm going off this guide to figure out what is going on an plug color please let me know if any of it is wrong. http://www.motoredbikes.com/showthread.php?24867-NT-Carb-Tuning-Basics
if the plug color gets white or even close to white then you're to lean.
Have you made any changes to the jet size or is it stock size?
Ive never seen one of these engines run lean on a stock size jet unless there is an air leak somewhere and then usually the idle is purdy jacked up.
do a good check of the carb and make sure the float level is set right, I cant honestly tell a measurement for setting the float height since I just eyeball mine since I know by how it sits when carb is held upside down when its where it needs to be.
If float is set right, there are no air leaks and the main jet is the right size, your engine should run fine with the needle clip set on second notch from top of needle, this setting has always worked for me on all my NT and NT Speed carbs.
I you're running stock size main jet and getting an almost white plug color running Opti2 @ 74:1 which is what the small packets mix is because I have also used those packets over the years, Im prone to think you may have an air leak because the stocm just size should be huge for the mix ratio, Of course Im not saying 100% you have an air leak, but something doesn't add up when you say you're getting an almost white plug color.
check float level and maybe set it to allow a bit more fuel in, make sure the fuel is actually flowing good from tank to carb, the kit gas tanks can have junk in them that can plug up th3 tiny screen thats one the shutoff valve which will starve the carb at higher rpms and can also cause the lean run condition.
Im thinking that you have a restricted flow to the carb or float is set wrong possibly if you know for sure there isnt an air leak and it idles real good.
The needle has NO effect on it after 1/4 throttle or so. In fact, if ya never brought it down to idle you could take the pin out. He can try moving the clip, But it'll have no effect on top end running. The smaller jet is a good idea though. sounds like it's running rich. Moving the clip up a notch may improve idle richness, but He's not having a problem with that.
fatdaddy.
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How many miles on this engine?
You won't get good performance from a new one or one with less that a couple hundred miles. It will run but will continue to run better as you accrure milage.
Plug color running Opti-2 oil is not an exact or accurate way to judge. From what I've been able to determine, local fuel additives will react with Opti and can produce some misleading colors. All of mine are shades of grey. None of them have ever been anywhere near the brown range you hear is best. And my engines run good and have many miles on them. One member here was getting shades of red with Opti.
Just a thought but you're not running without a muffler, are you? An open exhaust will cause a lean run and that can give you the plug color you're seeing. It will also not do your engine any favors.
Tom
You won't get good performance from a new one or one with less that a couple hundred miles. It will run but will continue to run better as you accrure milage.
Plug color running Opti-2 oil is not an exact or accurate way to judge. From what I've been able to determine, local fuel additives will react with Opti and can produce some misleading colors. All of mine are shades of grey. None of them have ever been anywhere near the brown range you hear is best. And my engines run good and have many miles on them. One member here was getting shades of red with Opti.
Just a thought but you're not running without a muffler, are you? An open exhaust will cause a lean run and that can give you the plug color you're seeing. It will also not do your engine any favors.
Tom
Very true, needle is only for idle and very low rpm mixture balance.The needle has NO effect on it after 1/4 throttle or so. In fact, if ya never brought it down to idle you could take the pin out. He can try moving the clip, But it'll have no effect on top end running. The smaller jet is a good idea though. sounds like it's running rich. Moving the clip up a notch may improve idle richness, but He's not having a problem with that.
fatdaddy.
He says his plug color has been almost white, that isnt a rich condition sign but rather a lean condition sign, since I think he still has the stock main jet in carb, it seems as though he might have a fuel supply restriction issue like float setting or shut off valve filter screen being partially stopped up causing engine to starve for fuel at higher rpms.
Of course I may be missing something else in the mix here but, I have never seen a stock jet in an NT carb cause a white plug color since they're always to big to begin with and with him running a 74:1 mix that should make the rich condition even worse but instead he says his plug is almost white, something else besides jetting going on here it seems.
The claim of the almost white plug color is what has thrown me off of the rich run condition being the problem, it may well be a combination of things rather than just one issue.
Im curious to know what he says finally fixes the issue.
Excellent point fatdaddy on how the needle works.
Sorry about the delay in mileage guys the engine has around 500 by now since Aug last year. I finally attached a old Garmin GPS to the bars and get a good 4-5 hours on battery life drive it no ware near that long normally.
Ok so was tinkering with the carb there isn't any fuel restrictions looked for that and emptied the tank as well, nothing. The float according to that link I posted earlier was low so 19mm I raised it up to 21mm like in the pictures. Went around the block a few times got around halfway the second time and got a dramatic change in speed I can get up to about 30mph normally top is 31.4 on the GPS but couldn't get over 10-15 I'm like **** what happen bet it was something with the float. Got home 5 min later took the plug out, thought it melted somehow and OMG the oil almost pure black. So took the carb off and put it lower to just in-between 19-20mm its working for now. I haven't gone around the block a few times yet going now to see if everything is good. Will post when I get back.
And on a side note going through wheels like hot cakes need that hub sprocket adapter lol going to undo the chain after I fix this till I get that adapter. Just got my refund in so going to get a few things.
Ok so was tinkering with the carb there isn't any fuel restrictions looked for that and emptied the tank as well, nothing. The float according to that link I posted earlier was low so 19mm I raised it up to 21mm like in the pictures. Went around the block a few times got around halfway the second time and got a dramatic change in speed I can get up to about 30mph normally top is 31.4 on the GPS but couldn't get over 10-15 I'm like **** what happen bet it was something with the float. Got home 5 min later took the plug out, thought it melted somehow and OMG the oil almost pure black. So took the carb off and put it lower to just in-between 19-20mm its working for now. I haven't gone around the block a few times yet going now to see if everything is good. Will post when I get back.
And on a side note going through wheels like hot cakes need that hub sprocket adapter lol going to undo the chain after I fix this till I get that adapter. Just got my refund in so going to get a few things.
Ok so it does seem you're not to lean, hope the changes help get it where you want it.
Yes the hub adapter makes a nice improvement, on 12ga spokes I dont worry much about the rag joint set up, but Ive had spok3 broke on tow different wheels with 14ga spokes in the last year, Im gonna switch over to using the hub adapter on all my bikes that I can and Im only gonna use the stock coupler on 12ga spoked wheels from now on if at all possible.
Yes the hub adapter makes a nice improvement, on 12ga spokes I dont worry much about the rag joint set up, but Ive had spok3 broke on tow different wheels with 14ga spokes in the last year, Im gonna switch over to using the hub adapter on all my bikes that I can and Im only gonna use the stock coupler on 12ga spoked wheels from now on if at all possible.
Sadly still getting the same result with sound and feeling. Going to get the jet kit and if I have enough for the hub kit ill get that as well in the mean time bike is out of commission till that hub is done don't want to pay for anymore wheels. Only one spoke is broke right now so it seems ok but its the wheel is definitely slowly wobbly.
Dang-it, hope you have it fixed and running the way you need it to soon, keep us posted on how its going.
Map
Map
The needle on an NT and Speed carb has effect by changing the size
of the opening because the needle is tapered.
The needle is still in the emulsion tube reducing the flow of gas at full throttle.
The needle does not come completely out of the opening at full throttle so
why would you claim it has no effect?
Pin? Take the needle out and see how your theory works.
That said if you still have 4 stroking try a smaller jet but put the clip
back in the middle position.
Once the needle is up, it's a very small thing in a very big jet tube. it has very little lf any effect on top end speed or fuel intake. the rest is done through the intake of air depending on how far you open the slide sucking fuel into the intake. once its up 1/4 or so, that little needle don't do jack. Maybe map can explain it better than I did.
fatdaddy.
fatdaddy.
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Nope, well said, you did a good job brother.Once the needle is up, it's a very small thing in a very big jet tube. it has very little lf any effect on top end speed or fuel intake. the rest is done through the intake of air depending on how far you open the slide sucking fuel into the intake. once its up 1/4 or so, that little needle don't do jack. Maybe map can explain it better than I did.
fatdaddy.
I call it a low speed mixture needle, that is precisely why it has notches and a clip to raise it just slightly while at part throttle so the amount of fuel the engine gets is limited until the engine revs and is able to get more air flowing in, to me its similar to a regular flow control needle on an old briggs or tecumseh carb but the difference is that on the slide carb its variable.
Im not saying that my opinion on this is 100% correct but this is how I understand it and 8 know that needle does very little of anything once it moves a particular distance from the main jet because more fuel cqn flow around the needle in the emulsion tube that can actually even be pulled through the main jet, this is what makes it a non factor once it moves so far up away from the main jet, it no longer restricts the fuel flow since it will allow more fuel to pass then can be pull3d through the jet.
Dang here I went and gave more $ .02 than I had intended.....lol!!!