My engine si sputtering when I am at full trottle, only at top end speed. Anyone know what could be causing this? I notice that the gas in the line entering the carburator is vibrating violently. Could this be an issue? How could I fix this? if I back down a bit it runs fine.
Losing power at full trottle
- Thread starter kkalan
- Start date
Get rid of the rubber. It will NOT eliminate vibration but only transfer it to the engine mounts and fasteners. Much has been written here about that issue. Every experienced builder will tell you the same. Solid mount the engine to the frame.
How many miles/gallons of fuel does this engine have on it? The Chinese 2 stroke will not be fully broken in until somewhere in the two to three hundred mile range. Don't expect it to perform to full potential until then. What fuel to oil ratio are you using? Disregard the instructions that say 16:1. That's too much oil. Start at 24:1 then move down to a 32:1 mix after a few tanks of fuel.
What is the spark plug gap? You'll want .024 to .028.
What size rear sprocket? Hilly terrain or flat ground?
What carburetor do you have?
Tom
How many miles/gallons of fuel does this engine have on it? The Chinese 2 stroke will not be fully broken in until somewhere in the two to three hundred mile range. Don't expect it to perform to full potential until then. What fuel to oil ratio are you using? Disregard the instructions that say 16:1. That's too much oil. Start at 24:1 then move down to a 32:1 mix after a few tanks of fuel.
What is the spark plug gap? You'll want .024 to .028.
What size rear sprocket? Hilly terrain or flat ground?
What carburetor do you have?
Tom
I think it is the rubber, The fuel was slashing around in the tubing. The engine has about 150 miles running 24:1 ration. I just installed it on a new bike and was running great before I sitched bikes. I think it is the rubber. 44t rear sprocket, hilly and flat terrain, stock carb. What do you think about a high performance carb? Someone told me they were a waste of money, just look cool. Spark plug is gapped correctly.
Bring a plug wrench with you on your next ride. When it starts to cut out on you at full throttle, kill the engine and pull the plug. Look at the color. Make sure its not running to lean. Just a thought.
Get it running right before investing money in go-fast parts. If it isn't running to your satisfaction now, adding parts will only muddy the waters. You need a basis for comparison before installing performance equipment.
If you feel that fuel starvation due to foaming is a problem you can confirm that by checking spark plug color. It will show in a light tan to white porcelain meaning a lean condition. If the plug is dark brown to black, you're too rich.
Just because you see bubbles in the fuel line doesn't mean the fuel in the carburetor bowl is foaming and that's where it counts. Bubbles in the line is more normal that abnormal. It is not a cause for concern.
Tom
If you feel that fuel starvation due to foaming is a problem you can confirm that by checking spark plug color. It will show in a light tan to white porcelain meaning a lean condition. If the plug is dark brown to black, you're too rich.
Just because you see bubbles in the fuel line doesn't mean the fuel in the carburetor bowl is foaming and that's where it counts. Bubbles in the line is more normal that abnormal. It is not a cause for concern.
Tom
Is the engine mounted at the same angle on this bike as it was on the other? If not the float level may be wrong.
It could be 4-stroking too- ie, running rich.
I would ride it for a while, then before another ride, pull the plug. If it's black, you're rich. White, you're lean. Brown, pretty much perfect.
I would ride it for a while, then before another ride, pull the plug. If it's black, you're rich. White, you're lean. Brown, pretty much perfect.
Thanks for all the input. I removed the rubber and put a few zip ties on the fuel line and it is running great! I think the rubber was making it vibrate to much and choking the fuel. Now I have noticed my chain tensioner keeps moving, I think becuase my frame is round and I can get a good grip. Can anyone recommend a good chain tensioner?
The chain tensioner can be a problem. Some members have removed the tensioner drilled and taped a hole for a set screw, or welded on a nut if the mount is too thin to tap. I haven't had mine move, I found that if I located the tensioner a little farther forward it puts less pressure on it to move. I haven't tried the set screw but think its a good idea. The picture below is of my o /p cruiser tensioner.
http://motorbicycling.com/album.php?albumid=259&pictureid=4457
http://motorbicycling.com/album.php?albumid=259&pictureid=4457
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Chain tensioner is moving? That's a common issue. You need to get one that connects to two points on the frame. You'll NEVER have to worry about it! (I found mine on ebay).
KKalan,
Be very cautious until you find a way to secure that tensioner bracket. There is the potential for it to rotate into the rear spokes and turning itself into a very effective brake. Something you don't want at 25 to 30 MPH.
There is a lot of information here regarding the tensioner. It is probably one of the most discussed subjects. Use the search feature, keyword 'tensioner' and read what has been written about this trouble prone aspect of motorized bicycles and the many ways to deal with it..
Tom
Be very cautious until you find a way to secure that tensioner bracket. There is the potential for it to rotate into the rear spokes and turning itself into a very effective brake. Something you don't want at 25 to 30 MPH.
There is a lot of information here regarding the tensioner. It is probably one of the most discussed subjects. Use the search feature, keyword 'tensioner' and read what has been written about this trouble prone aspect of motorized bicycles and the many ways to deal with it..
Tom
I am surprised no one has used Plasti-Dip on the tensioner bracket to hold it place. I am making a long board touring cruiser. I am going to attach a board to the rear frame with conduit clamps. Without the Plati-Dip, they hold loosely when tightening with a bolt. But 2 coats of Plast-Dip and they cannot be moved when tightening the clamps with a bolt.
Here's a picture:
http://motorbicycling.com/attachment.php?attachmentid=55970&stc=1&d=1359605338
Good Luck,
Chris
AKA: BigBlue
Here's a picture:
http://motorbicycling.com/attachment.php?attachmentid=55970&stc=1&d=1359605338
Good Luck,
Chris
AKA: BigBlue
Attachments
I run without a chain tensioner, best thing I ever did for my bike was toss that thing aside... You can't get away with this on EVERY bike, sometimes the chain will rub on stuff depending on the shape of the frame, but if you can get your chain on from front to back sprocket without rubbing anywhere it may be worth a try.
Some will tell you that you need the tensioner to adjust when the chain gets slack, if you run a cheap kit chain this may be true, but I weigh over 200lb and haven't had my #41 chain go slack after almost 2000 miles. This industrial chain can stand up to the job without wearing enough to effect the tension.
When I first built my bike I spent more time messing with that tensioner and broken (kit) chain than I did riding! Finally I got fed up and bought industrial #41 chain and removed the tensioner and haven't had to touch it since, best $10 bucks I ever spent (which got me enough chain for 2 bikes). With the tensioner gone and the #41 chain in place the chain noise is much less, and the resistance when pedaling is WAY less also. Now I can pedal the bike again without feeling so much drag from the motor and don't have to listen to my motor chain making a bunch of mechanical noise as a pedal, it was a big improvement on my bike...
Some will tell you that you need the tensioner to adjust when the chain gets slack, if you run a cheap kit chain this may be true, but I weigh over 200lb and haven't had my #41 chain go slack after almost 2000 miles. This industrial chain can stand up to the job without wearing enough to effect the tension.
When I first built my bike I spent more time messing with that tensioner and broken (kit) chain than I did riding! Finally I got fed up and bought industrial #41 chain and removed the tensioner and haven't had to touch it since, best $10 bucks I ever spent (which got me enough chain for 2 bikes). With the tensioner gone and the #41 chain in place the chain noise is much less, and the resistance when pedaling is WAY less also. Now I can pedal the bike again without feeling so much drag from the motor and don't have to listen to my motor chain making a bunch of mechanical noise as a pedal, it was a big improvement on my bike...
Nightcruiser - thanks for that advice. Tonight or tomorrow I am finally getting around to adding the hub adapter to my new wheel I received recently (with Shimano 110 hub). I've got a 41 chain that I ordered on ebay (was that a mistake?). Anyway, I'll give it a shot - no tensioner - and post the results once it warms up enough to try. Thanks.
I guessing pretty much any #41 chain you buy will do the job well, whether from ebay or whatever. One thing you might have overlooked (like I did), most regular chain tools will not be large or tough enough to break the links on the #41 chain, so you will need to get a tool that is made to break the #41 chain or you'll have to do it with hand tools. I ended up using a hammer and center punch with the chain set on a vise open enough for the pin to go down in when I hammer it out. I was able to break and mend the #41 chain with these tools and get a smooth chain, but it would definitely have been much easier with a chain tool designed to work on #41 chain....
The kit chain (or any bicycle chain) will have the same LENGTH links as the #41, they will be much wider and stronger on the #41 chain. When sizing the chain for the bike without the tensioner you need to get it just right since you no longer have the tensioner to remove slack. I found it best to use the kit chain for sizing since it is much easier to break and mend, once I got the size just right I counted the links and then made my #41 chain have the same amount. If you can't get the chain size just right to tension properly there are half links available that you can use, or you can adjust the rear wheel position (if possible on your frame) or adjust the way you mount the engine slightly to change the required chain length a little bit.
I think you will find the #41 chain is much more forgiving than the bike chain with the tensioner... good luck....
