Engine runs kinda "lurchy"

[Nomad]

Thanks to everyone for the replies to my questions on the other thread, I appreciate the input. I have been "shaking out" the motorbike and adjusting here and there, I believe I will have it secured and properly adjusted in a year or two

I have noticed that my engine feels like it's lurching at low speed almost as if it is only firing on every other revolution, it seems to smooth out if I open the throttle more, I did fix my chain with a solid link and some light work with a dremel, and a hammer and dolly bar behind the chain so I could "peen" the little studs over, works good.. I understand that this is still a "bicycle" so I don't want to fly around at wide open throttle, putt putt, is cool with me... I live in a retirement community and alot of the people stand there with their hands on their hips wondering what the "farg" just went by.... any help on this lurching issue?... ;thanks
Bob

[Large Filipino]

You may need to gear down a bit by getting a larger rear sprocket. This will bring up your RPM a bit higher eliminating that lurching. It seems to me you aren't running fast at all as it is. If you have a 44 tooth in back get a 48 tooth.
Is this a China 2 stroke?

[Bikeguy Joe]

How fast are you going when it's lurching?

Could it be "four cycling" and running rich so it IS only firing ever other stroke?

[Nomad]

Thanks Large Filipino, yes it is a China 2 stroke, I think I would rather eat crushed lightbulbs than to start changing the rear sprocket 2 days after I built it.... that sprocket was a real pita...
BikeGuy Joe, I am going really slow, just a little above idle, putt putting along, I'll say probably about 5 - 8 mph. I thought maybe my chain was to slack.. so I moved the tensioner, I still can't figure out how to bend that danged muffler pipe out of the way of my left pedal crank, I tried bending it in a vise ,even heated it with a propane torch... that sucker is hard to move at all..... any suggestions?

Thanks
Bob

[misteright1_99]

Originally Posted by Nomad

Thanks Large Filipino, yes it is a China 2 stroke, I think I would rather eat crushed lightbulbs than to start changing the rear sprocket 2 days after I built it.... that sprocket was a real pita...
BikeGuy Joe, I am going really slow, just a little above idle, putt putting along, I'll say probably about 5 - 8 mph. I thought maybe my chain was to slack.. so I moved the tensioner, I still can't figure out how to bend that danged muffler pipe out of the way of my left pedal crank, I tried bending it in a vise ,even heated it with a propane torch... that sucker is hard to move at all..... any suggestions?

Thanks
Bob

Mine was the same way. I dont want to go fast. I put on a 50t and I love it, top end is about 22mph, but I can ride at idle now. I bent my exhaust (when I had it) by bolting it to the workbench, heating it up at the bend (red hot) and pulling it to where I needed it....

[Nomad]

Well thanks gentlemen, that looks like a consensus to me. I will look into getting a bigger sprocket, but I gotta run it around for a week or three.

Thanks
Bob

[pedalpower]

porting the exhaust helped the lower speed/rpm smoothness a little. but going below 10 mph impedes the minimum rpm for 2 cycle operation because my idle is higher operation than what I'm asking it for. seems you are looking for the centrifugal clutch feeling found in those automatic moped thingys I see around. feather the clutch, or pulling it in and pedal-nothing about these little fireboxes want to go slow.

[Nomad]

Originally Posted by pedalpower

porting the exhaust helped the lower speed/rpm smoothness a little. but going below 10 mph impedes the minimum rpm for 2 cycle operation because my idle is higher operation than what I'm asking it for. seems you are looking for the centrifugal clutch feeling found in those automatic moped thingys I see around. feather the clutch, or pulling it in and pedal-nothing about these little fireboxes want to go slow.

Hi and thanks Pedalpower, I will trim the exaust gasket before I put the muffler back on.... I like the last line, "nothing about these little fireboxes wants to go slow"

[Bikeguy Joe]

I would think 5-8 is a little slow for the stock sprocket!

Yes, order a 48-50T and you'll smile again.

[Large Filipino]

I know there's a consensus as far as using a boost bottle but it made my china engine run smooth down at the low end. Maybe you can give it a try.

Boost Bottle Industries

I got the 63 to 65cc to compensate for the tube.