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High Performance Bicycle Engine Tips and Motorized Race Bicycles We all want our bicycle engines to push our bikes faster. Get exclusive engine modification tips and suggestions from us. Also check out some of our racing members builds

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  #1  
Old 01-22-2016, 03:19 PM
brywink04 brywink04 is offline
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Join Date: Jan 2016
Location: new york
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Default building my motor up-need help

Hello, i just finally have been able to do a few long rides with out having any chain problems.. but anyways, i had my choke get stuck on the carb that i bought so i pulled the air filter off the carb and noticed a lot of oil and sitting in the carb and in the filter. i dont have reed valves on it and i took th boost bottle off because of it making it run poor. also i noticed that when your riding the longer you ride the less power the motor seems to have. but if you stop shut the motor off and restart the motor all the power is back till you ride for a little while. i know its not a heat problem. im thinking its because of not having reed valves and then having an expansion chamber and the bigger carb. the longer it runs the richer its getting? so where a good place to get a reed valve it? and are there offset intakes for the reed valves? because right now i have about 2mm between the air filter and the frame.

my pipe; http://www.ebay.com/itm/80cc-motoriz...IAAOSwrmdTpZzG


carb; http://www.ebay.com/itm/181759241885...885%26_rdc%3D1
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  #2  
Old 01-23-2016, 09:18 AM
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sbest sbest is offline
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Join Date: Nov 2015
Location: Nova Scotia
Posts: 339
Default Re: building my motor up-need help

Reed valves and boost bottles are not needed to make these engines run well.
The chain, the choke, and poor running are small details that need careful attention.

Look at the chain as an example. Why repeated problems?
Was it lined up when you put it on? Was the tensioner on the bottom chain?
Where the bolts tight, but not crushing the tube? These are all details that cannot be missed.

So, when it goes wrong, do you just return it to the way you had it and hope for a better result?
Or do you stop and try to analyze why it failed?
Do you try to put it to the way the manufacturer intended, or modify for improvement?
Modify for improvement is not the first thing you should jump to.
You just bring in new problems without solving the root cause.

So, your running problem.
Understand 100,000s of these engines run well without reeds. You don't need them.
So what then? Let's note your symptoms:
1) oil sitting in carb and filter (this is normal, no worries. I can explain if you want)
2) the longer you ride the less power the motor seems to have
3) if you shut the motor off then later restart, the power is back for a while
4) does not seem to be a heat problem (no reason given)

The history:
1) chain problems (solved)
2) Choke sticking on new carb (solved)
3) boost bottle installed with carb, rough running (solved, removed)
4) Tuned pipe/muffler combo (and modified carb) put on with new installation.

This is a case where modifications might be bringing their own problems.
You proved it with the boost bottle and just don't know about the pipe and carb.
Do you think more mods would help? NO WAY. Get back to basics.
As much as possible, return it to the way it was designed and known to run.
Put the stock carb and pipe on it for now (if you have them and they fit) and try it again.
Try one mod at a time starting simple. If it runs stock, try the pipe, if it still runs, try the carb, etc.

If it doesn't run stock, look for detail problems first, noting time as a factor such as blocked fuel flow. So check fuel flow, if it is poor, look at filters, valves, tank outlet, carb inlet.

I hope this helps you solve not only this problem, but any that come up in the future.
Please keep asking and tell us what worked or didn't so we learn too.

Steve

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  #3  
Old 01-23-2016, 11:27 AM
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Agreen Agreen is offline
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Location: Southeastern GA
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Default Re: building my motor up-need help

After installing a pipe on mine I got the same issue. It ran good for a bit, but after about 10 or so minutes of full throttle riding it lost power. It felt like it had a rev limiter. It would speed up, hit a wall, slow down, repeat.

The issue for me was that I had too small of a jet in the carb.

Simple fix. Buy a kit of micro drills and a pin vice. If the engine does a "machine gun" noise when it loses its power, it's running too rich. Mine didn't machine gun, it just bogged down. That means it's too lean.

Depending on the rich or lean condition, you either need to solder and drill smaller, or just drill out larger respectively.

There are diy tutorials here on how to do so.
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  #4  
Old 01-23-2016, 03:33 PM
brywink04 brywink04 is offline
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Location: new york
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Default Re: building my motor up-need help

thanks for the replies. but i went back to the stock carb after my first ride. it ran alot worse.i will try going back to the stock pipe. i seem to be having the same problem as the previous reply about it hitting a wall then reving. just like a rev limiter/
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  #5  
Old 01-23-2016, 04:46 PM
ru14real ru14real is offline
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Location: warrenville
Posts: 42
Default Re: building my motor up-need help

I am a newbie here so I am not an athority on the subject.

Where do you live? Carbs usally have been set to an inbetween elevation. No dout they will react differently depending on your evelation. I am near sea level so i need it to run lean, I think. Anyway I did an adjustment just to fine tune it and no problems. I use the stock NT carb, but thinking aobut upgrading. Also replace those stock sparkplugs. It could not hurt, but make sure you get the right NKG plug. Everyone recomments them on this site.

Keep us posted with updates.

Last edited by ru14real; 01-23-2016 at 04:51 PM.
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  #6  
Old 01-23-2016, 05:53 PM
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Agreen Agreen is offline
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Default Re: building my motor up-need help

I use the stock NT carb on a 48cc engine. I hit over 40 mph constantly. It's all in how you tune it.

If I'm not mistaken, I believe the NT and RT jets are the same. So you can take the spare jet and drill it. Then swap it out in your carb that's on the bike (takes like 1 minute) and if it's not right, drill the one you just pulled out. That way you're not having to wait to get the jet out of the carb before drilling it.

I found the size 61-80 micro bits and pin vise at a local hobby store. You can find them on the internet just as easy.

Should you need to solder it shut, clean the jet with rubbing alcohol first. Heat the jet with either a propane torch or a soldering gun. Touch the solder to the hole in the jet. Don't add too much, just enough to close the hole. Then carefully drill the desired size.
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  #7  
Old 01-23-2016, 05:55 PM
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Agreen Agreen is offline
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Default Re: building my motor up-need help

And the ngk b5hs spark plug is the one to get.
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  #8  
Old 01-23-2016, 05:57 PM
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sbest sbest is offline
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Location: Nova Scotia
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Default Re: building my motor up-need help

Hey Brywink04, I think going back to the stock pipe is a good idea, until you get the bugs out. Do not confuse "running bad" with "less power". They are 2 different things. Isolate what your symptom is and chase it. It was originally power fading with time.

There is a thread where I described how to tell if your carb is running rich or lean at;
http://motorbicycling.com/showthread.php?t=60467
It also describes some ways to adjust.
You will need at least one new plug to be able to read the mixture.

Power fading with time is usually poor fuel supply or CDI or engine overheating.

Steve
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  #9  
Old 01-24-2016, 10:26 AM
brywink04 brywink04 is offline
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Location: new york
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Default Re: building my motor up-need help

okay. once it warms up a little bit i will definetly go and switch back to the stock pipe. i had to take the old carb off because it leaked air really bad causing a vacuum leak. the new car fixed that problem. the plug is very black. but im assuming thats becasue im stillrunning the 16-1 ratio. once i get a better plug id like to run ams oil. ive always had good luck with that oil even running it at a 100-1 ratio in my 2002 rm 85.
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  #10  
Old 01-24-2016, 10:29 AM
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2door 2door is offline
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Default Re: building my motor up-need help

The OP hasn't said how many miles he has on the engine but it sounds like not many.
All too often I see a new builder asking how to make his engine run better and wanting to make modifications and add go-fast parts when his engine isn't close to be broken in.

Before I'll suggest changes I'll tell him to put two to three hundred miles on a stock engine before worrying about top performance. The little Chinese 2 strokes are like a good wine. They need to 'mature' before they are ready to be enjoyed

Tom
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