New carb and cold start problem

[Shane-O]

I am new here and searched as best as I could but I couldn't find answers to these two questions. First off I recently bought a 86 Aero 50 and after replacing the carb and new spark plug, air filter and fuel filter it runs well once warmed up.

#1: When I try to start it cold it will not start easily. I have to hold the throttle almost all the way open and after it starts I have to hold it open until it warms up and will idle on its own. Is this a bystarter problem or is it loading up on leaking fuel? The carb does not leak that I can see. The port on the carb with the small rubber hose, should that go into the air box, or just open to atmosphere?

#2: I bought this carb: http://www.ebay.com/itm/250833763594?ss ... 1497.l2649 and it has one extra port that looks like it goes right into the barrel. My carb I took off did not have that, so at the moment I have it blocked off, but is there something it should be hooked up to? Or should it be left open?

And heres a pic for those curious, the black panels all need a repaint, so I am debating repainting stock, or flat black and having my buddy stripe them rat rod style.


Thanks!

[mousewheels]

...1) The port on the carb with the small rubber hose, should that go into the air box, or just open to atmosphere?...
2) ...it has one extra port that looks like it goes right into the barrel. My carb I took off did not have that, so at the moment I have it blocked off, but is there something it should be hooked up to? Or should it be left open?

1) It is a vent, open as it is is fine
2) That port should be plugged, It is for Oil input line for scooters with no tap on the intake itself. Left open, it becomes an air leak.

OilInjectionInlet.JPG (26.13 KiB) Viewed 3315 times

When I try to start it cold it will not start easily. I have to hold the throttle almost all the way open and after it starts I have to hold it open until it warms up and will idle on its own. Is this a bystarter problem or is it loading up on leaking fuel?

I've had a clone carb that ran too rich when cold - although not quite as bad. It did take throttle babysitting. For that and other reasons, the clone got replaced with a rebuilt OEM when one became available.

I've never tried this but - If you have an OEM carb bowl and it fits your clone, it may help. There is an orifice between the main bowl and the tube supplying fuel to the bystarter. It is a metering point for the circuit, and the clone may be different.

[Shane-O]

Thanks!

I have the original carb, so I think I will rebuild it and use the new carb for any parts I need.

[Shane-O]

Well still no luck, still have the clone carb on it, in the process of rebuilding the original carb. I did replace the carb o-rings on the block and the carb to make sure it wasnt an air leak. Didnt help, so I think a compression test is in order. Anything else I need to check, will the reeds effect cold starting?

Thanks,
Shane-O

[devenex]

Another sweet new aero on the board!

Bad reeds would typically cause poor starting all the time and reduced lower rpm performance.

As mouse alluded to, the clone carbs vary in quality and it could very likely be the cause of your problems. Having said that, the first thing you want to check with poor cold starting is the bystarter. Theres a couple ways to do this depending on what equipment you have, so read up and decide which way works best for what you have.

[maddog]

I am not a fan of by starters, there is an o ring that the by starter fits into if its worn change it otherwise try another one.

[JJ Joseph]

Bystarter carbs have to be started with the throttle CLOSED. With throttle open, the bystarter doesn't richen the mixture. Also, 2-strokes are hard to start if compression is low, so it's a good idea to check the compression. Above 80psi, it should start with minimum difficulty, but below 60psi you'll never get it going. Over 100psi it should light off with a bang!

[Pete M]

JJ J is on the $