Sym DD50 cold start issue.

[islandscrub]

Aloha!

     The used Sym I picked up a couple months back has developed a starting issue. It refuses to start up nice when cold, and I often have to hold the throttle open to get it to 'catch' and idle on its own. I noticed after getting it running and let it sit, the idle got real nice and smoother after the point where I assume the enrichener fully extended. So I did a little experiment, I fed 12v to the enrichener for a while and then tried to start the bike while cold, it started immediately and idled nicely. So I am guessing its just an idle balance that's out of whack, the engine idles and runs great when warm. The bike has a Keihin carb, and I am not sure how the enrichener works on this one, does the it let in more air and fuel, just fuel, or just air? What would I need to look at in each case (pilot, idle mix, jet?) Any input appreciated!

[gsx600racer]

Have you checked the compression with a gauge and spark ? You need a minimum of 90 psi

Any idea what the main jetting size is ? Not sure of the pilot on the Sym DD50, but they are similar to the Honda Elite 50 and Kymco ZX50 and I know both of them have fixed pilot jets(stock).

Air screw should be about a 1 turn to a 1 1/2 turns out.(good starting point)

As for the enrichener, it lets more fuel in when cold.

My thoughts on the hard starting when cold, possible intake leaks, leaking crank seals, or o-ring on oil pump would be worth checking. Doing a leak down test with find them. Ifs it hard to start, Im thinking there might be leaks till things warm up and expand and then the leaks might be going away.

[islandscrub]

There is spark and I don't own a gauge, I should get one sometime.

The only thing I've really tried was warm up the enrichener (apply 12v) before starting, and it started immediately with no problem. I let it cool off again and then it had trouble starting. My guess is maybe it's too much fuel, but not sure how to reduce it.

[gsx600racer]

Nov 8, 2017 12:33:32 GMT -5 islandscrub said:

There is spark and I don't own a gauge, I should get one sometime.

The only thing I've really tried was warm up the enrichener (apply 12v) before starting, and it started immediately with no problem. I let it cool off again and then it had trouble starting. My guess is maybe it's too much fuel, but not sure how to reduce it.

Try cleaning/washing the foam air filter, or try starting it cold without the air filter. 

[islandscrub]

I think it's fixed. Just gave the carb a good cleaning and made sure the intake connections were solid. Starts up after sitting 2 days, will see if it can go 3+ since I'm trying to alternate bikes weekly.