Cold start problems

[graeme6]

Hi all,
still not got the bike running how I want it, (RD125LC Mk2), one problem I just can't resolve is very poor starting when cold. Bike needs to be kicked over about 20 times before it starts then just bogs down, splutters and cuts out. I cannot even touch the throttle or it cuts out. After 5 or 6 starts when it's warmed up a bit I can put the choke in and bike revs cleanly all the way to the red line.
Anyone got any ideas?

Thanks in advance

Graeme

[hoist1]

Pilot jet blocked?

[graeme6]

Had it out and clean as a whistle, as is the rest of the carb.

[stusco]

Airscrew?

[mellow]

air correction circuit behind the brass ball?

[wonkywheel]

How good is the spark?

After endless carb stripping, new coil, stator rewind and scratching my balls it was the CDI.

I had similar problems with starting and kicking the shite out of the kickstart.

Hopefully it ain’t CDI, although a faulty CDI can still produce a spark, but weak and probably way off the mark.

[graeme6]

Just fitted a brand new 10W carb, had it in the shed for ages and forgot I had it, probably a Chinese copy, but still having difficulty starting. Spark does appear to be good, starting to think it may be compression, does anyone know what pressure test result should be? Also got a micron on at the moment, thinking of changing back to standard exhaust.

thanks again for all your help and advice.

[museumman]

A recent one of Mine was compression eventually after the left crank seal went with the same symptoms, only got another 100 miles out of it. . An original bike with quite low miles.
DTRs also just stop starting when compression goes. Ive got away with new pistons and rings on a couple of those.

I recently turned a thinnish orange spark into a fatter blue one with a small cut off end of HT lead and new cap on what looked like a mint coil, lead and cap. Low and behold the Cdi went on to fail in a few days with misfiring on kick over

[graeme6]

So, after fitting the new carb was still much the same, trawled the internet for advice and found an article where someone had exactly the same problem. They eventually resolved it by turning down the air screw, had a bit of a play and hey presto - air screw reduced from one and a half turns to one turn and bike starts first time every time. Don't know why but it worked, still haven't had a chance to take the bike out yet to see how it performs, will try and get out this weekend. Also put some fresh fuel in so that may have helped.

[stusco]

Jun 15, 2020 13:44:08 GMT 1 stusco said:

Airscrew?