Choke It

[Timbone]

I am still learning about the 2-stroke engine.

At the end of last Summer, I rejetted my HT to a #65, and I have had nothing but awesomeness at full throttle. But starting was always an issue. I figured the learner configuration messed everything up. As the weather got colder, I'd have to pedal more an more to get things up to speed.

I use the delortto clone carb (RT) that has the semi-automatic choke option. That thing has never worked for me because as soon as the engine popped, it released. So I just ignored it. My most recent starting technique was to pedal and pop the clutch with no throttle, keep pedalling until some engine heat would build, then I could gradually work in the throttle until I got continuation.

Full throttle application made starting worse, so I figured the mixture was too lean and more air made it worse.

Also, I noticed an occasional problem when motorbraking after a fast, high RPM run. When starting from zero after, the engine would act (to me, at least( as though the fuel wasn't feeding through. Not always, but often enough to be a pattern. It was very similar to my slow startups.

For whatever reason, I simply covered the intake to impede airflow with my left hand as the engine chugged at low RPM and - ZIPP! - the thing took off. All I ever needed was a touch of choke! I get a bit of fuel spitback on my fingers but that's nothing.

I am slow to learn sometimes, but I can learn.

 

[bakaneko]

Yeah, I feel like my 4-stroke HuaSheng 49cc performs better at half choke than at open. I am going to try it at 1/2 to 3/4 choke. You know if modifying the choke during operation becomes a necessity. I imagine we could use a bike cable and Mac Guyver up a level on the handlebar to adjust the choke while riding.

 

[crassius]

needing to be choked to run right is usually due to an air leak at intake

 

[Timbone]

needing to be choked to run right is usually due to an air leak at intake

The bike runs great without choke. The variable choking (done by my hand) is needed only during a cold start situation.

The only other situation I've had is in this scenario: I am driving WOT and I am forced to drop the throttle (traffic, red light, etc) and I get in the brakes without clutching i.e motorbraking. Every now and again, this will cause the engine to ask for choke after a start from zero. Choking the intake a tad allows for rapid run out.

 

[Timbone]

Yeah, I feel like my 4-stroke HuaSheng 49cc performs better at half choke than at open. I am going to try it at 1/2 to 3/4 choke. You know if modifying the choke during operation becomes a necessity. I imagine we could use a bike cable and Mac Guyver up a level on the handlebar to adjust the choke while riding.

Adjustable on the fly choking would be nice! That could be conquered...

 

[bluegoatwoods]

Adjustable on the fly choking would be nice! That could be conquered...

I've done it twice. The first time worked well. That was some years ago.

The second time was on my current bike. It didn't work as well. Largely, I think, because this bike has an odd frame and I just couldn't get everything lined up right.

But....anyway..... on the first one I used a stem mount shifter as my lever. It ran down to an L-bracket that I had fastened to the seat tube so that the horizontal leg of the L was right above the choke lever. An inch and a half or so above it. Drilled a tiny hole in it for the cable to pass through. Plus a tiny hole in the choke lever. In between I used a section of that little clutch return spring, cut to size.

The shifter pulled the choke lever up and the spring returned it down. The stem mount was handy since it meant that I could adjust the choke with either hand.

And it was very handy in the winter, in particular, when you need more on and off choke.

I'll do it again.

 

[Frankfort MB's]

That would mean it's running to lean in the low RPMs is what I was always told, you could get a walboro carb that's used on chain saws that run off of pulses of the crank.... It actually has adjustable jets for low RPMs and then a separate adjustable jet for high RPMs... Plus also since they are chainsaw carbs so you could run your China girl upside down

 

[Hello Moto!]

I have one of those Runtong HP carbs. It has a semi automatic choke release that's supposed to disengage when you open the throttle up. It never worked right. I'd push the choke lever down and it wouldn't hold in the choke position. There's a little screw inside behind the air filter that you can adjust the tightness of the lever action. So I tightened it but could never find the sweet spot to utilize the throttle open disengagement. It would either not hold in the choke position at all or it was to tight and I had to manually release the choke lever. This is what I ended up doing. Manually releasing the choke lever after a quick start. This type of carb only has full choke and run position. There's no adjusting the amount of choke you can use like on a stock carb. As for the performance, it is a little more snappy I would say. I also have a pull start on my bike so starting and releasing the choke is very easy off the bike.

 

[45u]

I have the SHA clone as well and not matter the weather it has to be choked to start many times even when warm. If the choke is not working correctly take the slide out and made sure you have the arm for the choke installed properly. My choke works great once started blip the throttle wide open and the choke cuts off.

With out being able to adjust the low speed makes it a real pain and will never be correct this is why on my next build I will be running a Mikuni VM series round slide 18mm clamp mount.

 

[Frankfort MB's]

On some bikes you don't have to use the choke... All of mines you just have to use a little bit of throttle and they start right up