New Carb, no power

[remichi]

I broke my old NT carb while screwing on the air filter. (The aluminum snapped) I was lucky to be able to get a new carb in Kenya but somehow it is not giving the same results as the old carb.

It is exactly the same type carb, the NT type. The engine runs but not great as said before. When starting I always need choke on, then turn off, turn on again, and keep repeating untill engine will run with just the choke off.

Besides this the engine sometimes backfires.

The worst problem is that the engine seems to have very little power suddenly. The slightest hill and I have to help the engine get up the hill. Also when opening the accelerator after I went over a speedbump it just does not want to go.

I'm attaching some pictures of my new homemade air filter. Made from a candy tin. Do you think I should also put holes on the side of the tin facing the engine? Or will it get too windy in the carb/air filter?

http://www.flickr.com/photos/michisunited/8580066426/in/photostream

http://www.flickr.com/photos/michisunited/8578960595/in/photostream/

http://www.flickr.com/photos/michisunited/8578955241/in/photostream/

The c clip on the needle was in the middle, I put it to the absolute top because the spark plug was black. During a ride today this new setting did not have any difference on performance though.

Thanks and hope you can help me get power back to my engine.

 

[supercub]

If your plug was black, that would mean a oversize jet or the float is getting stuck. A long wam up time would mean that your main jet is clogged. From the factory the carbs will most probably have dirt and metal shavings inside. Take the carb apart and clean it with carb cleaner spray. Stick a strand of speaker or lamp cord wire through the jet. Put the needle in the slot next up from the middle. Start with the stock air filter.

 

[Toadmund]

When starting I always need choke on, then turn off, turn on again, and keep repeating untill engine will run with just the choke off.

Too lean, not enough fuel, choke on enriches fuel. Bowl filling up too slow, float needle clogged.

Besides this the engine sometimes backfires.

not sure

The worst problem is that the engine seems to have very little power suddenly. The slightest hill and I have to help the engine get up the hill. Also when opening the accelerator after I went over a speedbump it just does not want to go.

Dirt in your jet hole got sucked up from bowl?

I'm attaching some pictures of my new homemade air filter. Made from a candy tin.

Are you using 3M pot scrubbers as filter element? I was thinking of using the non-abrasive blue ones if I made a filter.

The c clip on the needle was in the middle, I put it to the absolute top because the spark plug was black. During a ride today this new setting did not have any difference on performance though.

Now I'm confused, did you leave the choke on at the time when you pulled the plug?


Take off your carburetor, check it out, my intuition tells me that a piece of your filter element is clogging your float needle or your jet or somewhere.

I also think there is very little info to go on.

 

[crassius]

I'd check float level, then put needle & jet from old carb into new carb.

I'd also try it once without that filter.

 

[remichi]

That's a good idea Crassius, I think I'll try exchanging the needle and jet from the old carb, and maybe even the metal part moved by the float.

Toadmund, the filter I use is green abrasive sheets used for doing the dishes about 1 cm thick that they sell here in Kenya. The sheets are about 20 x 20 cm so I can cut it to the size I want. What do you think, shall I put holes on the other side of the tin as well?

I noticed that when I ride the bicycle by myself it has a lot more power than when my wife rides on the back with me. This makes sense of course, but even with her on the back it used to have much more power than it does now.

 

[2door]

Have you tried running it without the air filter?

Needing a lot of choke is usually a sign of an air (vacuum) leak. The NT is a great little carburetor and is forgiving. But it needs to be sealed to the intake manifold as does any carb. Any gasoline compatible sealer will work.
Keep in mind that the needle clip position is only a consideration up to about 3/4 throttle position. After that the main jet orifice size only determines fuel flow

On a non related subject, you might want to consider removing the small spring on your clutch cable. It really doesn't do anything except increase the pressure required to disengage the clutch. Most of us throw that spring in the spare parts box. The larger one is a heat/abrasion shield that keeps the cable away from the cylinder fins. Keep it.

Tom

 

[Toadmund]

Toadmund, the filter I use is green abrasive sheets used for doing the dishes about 1 cm thick that they sell here in Kenya. The sheets are about 20 x 20 cm so I can cut it to the size I want. What do you think, shall I put holes on the other side of the tin as well?

Yeah, I noticed that and knew right away, because I was looking at them in a store, I figured the blue ones would be best if I made a filter with those because they are non abrasive, in the case a bit a abrasive material came off, although unlikely.

If the airflow is good you don't need more holes.

 

[maniac57]

Sounds to me like a float problem. Does fuel dribble out of the back of the carb when it's running poorly? Give it a good cleaning and swap jets from the original carb. Just because the new carb is "new" does not mean it has the right jet for the engine...Strip the old carb and put the parts on the new carb body. Good luck and keep us informed!
Also, I always use a in-line fuel filter between the tank and carb to prevent dirt getting to the float needle and seat.

 

[remichi]

I went to Nairobi City centre today and got a smaller fuel filter than I had, hopefully it will fit just above the carb without me having to cut too much of my copper fuel pipe off.

I asked around for NGK spark plugs (B6HS and B5HS) which they didn't have. They only had B7HS, and now in one of the posts here on the forum I read that one also will fit. So I should've gotten that one. Shops are closed tomorrow (Sunday), so will have to get it next week.

What is the difference between NGK spark plugs B5HS, B6HS and B7HS? Some shops also had BP7HS and BP6ES. Nairobi is about 15 degrees celsius in the morning and in the afternoon up to 30 degrees celsius, at an altitude of 1700 meters.

Will take the carb apart tomorrow, change the jet and put in the fuel filter. Was hoping to replace the spark plug but that'll have to wait.

 

[crassius]

B5HS is the hottest, while B8HS is the coldest that can be used in these - the same numbers with the "P" in them are extended tip plugs which work in some engines, but get hit by the piston in others

hopefully, getting the carb right will solve all problems and you'll only need the new plug as a spare

 

[nightcruiser]

If your new carb is the exact same as the one that broke, you could move the float and jet over from the old carb into the new carb, and use the SAME AIR FILTER that you had when it ran well and it should run pretty much the same. (make sure you don't have any air leaks at the carb or intake) Even though the carbs are the same model, that is no guarantee that the jet is the exact same size, or the float has the same setting, and a different air filter will provide different resistance to air flow and that will always effect your mix.

 

[remichi]

So in a hot location the B7HS plug will do fine I'm guessing.

Forgot to mention that at some car parts shops I also found sealant. It's Magpow RTV Silicone Gasket Maker in a tube. Colors available are clear, grey and black. Would this work to seal the carb to the intake or is this not the right kind?

 

[Toadmund]

Some here say silicone sealant is not gasoline resistant, the package instructions also say that. Ha Ha! (even the gasket sealant)

Look for something called Permatex, I think the stuff in the grey tube is what you want, if you can't find it and in doubt about what to get you can talk to a mechanic.

 

[remichi]

Put the jet and needle of the first carb in the carb I bought last week. Then put a piece metal from a coke can between the carb and manifold to keep away air leaks.

So far it seems to have helped. Bike has a lot more power again.

Next week I'll go to the city and get a new spark plug and maybe some sealant.

When I read about soldering the jet, what do people mean exactly? Do they solder the side where the float is or the side where the accelerator cable is?

The back wheel has 4 broken spokes again so that'll be the next thing to fix. These roads in Kenya are terrible!

 

[Toadmund]

I just soldered mine. (1st one ever)
I took a thumb tack, placed the side where the screw slot is on the thumb tack.

I did this for two reasons, to stop the solder from going in to the screw driver slot, the hole for the micro drill bit is already started.

So I heated up the jet with some flux paste (optional?) and melted in some lead based electronics solder (easier to melt and drill than silver based) into the big hole side of the jet.

Then I sort of made a less than perfect fill so I cleaned it up with a regular sized drill bit and I drilled out the jet to a .65mm size with a .65mm micro drill bit at the screw driver slot side. (would have went between .70mm and .65mm, but I only had .65mm, will widen it somehow if I have to)

Note, keep solder off the threads, otherwise you will be trying to scrape it off your tiny jet with a sharp knife. (Don't ask me why I know this )

 

[remichi]

I measured that when the piston is all the way up, the distance from the piston to the top of the spark plug thread is 2.4 cm, while the spark plug that is in there now is 1.3 cm from top of thread to bottom of the spark. This would mean I can get a spark plug that is a bit longer. Are there any real advantages to these longer spark plugs? Or will the NGK B7HS do just fine?

 

[crassius]

some folks feel that it runs a bit cleaner & the extra length adds a bit more compression - I don't know for sure

 

[remichi]

On the way to work today the c clamp was all the way down and the spark plug turned out to be all black. Moved the clamp up a notch and spark plug is still totally black. Moved it up a notch to the middle position and will see tomorrow what color the spark plug is.

Will try to get the NGK B7HS spark plug some time next week.

 

[nightcruiser]

On the way to work today the c clamp was all the way down and the spark plug turned out to be all black. Moved the clamp up a notch and spark plug is still totally black. Moved it up a notch to the middle position and will see tomorrow what color the spark plug is.

Will try to get the NGK B7HS spark plug some time next week.

I haven't reviewed this entire thread, so I have made some assumptions...
First of all, I assume you mean "e-clip" instead of "C-clamp"??? The "e-clip" controls how deep in the main jet the needle sits, and it controls the mix at MID throttle. When you get up above mid throttle the effect of the e-clip position is minimal, at that point the size of the main jet, and the overall flow of air through the motor is what is effecting your mix. So, if you're too rich at WOT then adjusting the e-clip on the needle isn't going to do it for you, you would need to adjust the size of the main jet, or allow some more air to flow by either reducing the resistance to air flow in the air filter or muffler...
Also, are you still running break in mix with lots of oil? That could explain the black plug, you might want to run through all the break in fuel and move on to at least a 32:1 mix before you worry about it too much... Although not the best situation, an oily black plug is safer for your motor than having it burned clean and white, at least your motor is getting lubed and not burning too hot....
When tuning one of these carbs you need to tune for WOT first, adjusting jet size and air flow so the mix is proper at WOT, THEN adjust the e-clip position on the needle to set the proper mix for the mid throttle range, and the air/mix screw and idle screw adjust the mix at idle...

 

[remichi]

Yes I meant e-clip and not c-clamp.

Did some reading and similar to your advice decided that I might need to change the jet. I am at 1700 meters altitude here in Nairobi with average temperatures between 15 and 30 degrees Celsius at the moment. Towards which jet size should I be looking?

In another post I read that 2door is at 6000 feet and uses a jet at 0.024. Problem is that I cannot find those super small drill bits here in Kenya I'm sure. I'm thinking how I can get a new jet to Kenya, the postal system here is not too great.

Maybe I'll have to tinker with the exhaust and air filter setup. The exhaust is a 3 piece exhaust which is kept together by a bolt. I welded 2 pieces together with some spot welds so that it would not come loose every time. The 3rd piece is still attached with the bolt as before. The exhaust also has an inner baffle with some holes in it.

For those who have not seen my bike:
http://www.flickr.com/photos/michisunited/8167235124/in/set-72157629595539665/