Yamaha XT600E 3TB - cold starting problems

[bernek9000]

Hello !

This is my first post on the forums and I will like to say hello to you guys !

I have the pleasure to ask you a few questions regarding my beloved 3TB from 1993.

There is a small problem starting when cold recently (since the weather dipped bellow 10 degrees Celsius).

The bike turns when I use the electric start it starts after 2-3 seconds and the revs don't climb and it eventually dies out on me. After 2-3 attempts like this the bike eventually starts (the revs climb slowly then a bit faster and reach the rpm it should be with the choke fully engaged) and from there on I have no problems. (I start it once in a week or two)

Things I've tried so far:

- I played with the pilot jet adjustment screw (from 2.5 turns to 4 turns out - no improvement on starting).

- If I try to adjust the pilot jet screw when the engine is warm I sense a small raise in rpm from 2.5 turns out towards 3 turns out the it flattens out (no more increase in rpm) I didn't screw it our further than 4 turns since the bike was running to rich according to my assumptions ...

- I've changed the spark-plug with a new one and charged the battery (it was bought new in summer and my charging system is in working order)

- I've used some carburetor/injector cleaner in fuel with no visible results

- The engine was rebuilt last summer including the following - cylinder honed ,new piston,new valves,new timing chain,etc. The valves were adjusted again after 500 km and they were lapped and checked for leaks when I've mounted them.

In summer I felt it was a little lean at idle and off idle (few pops on the exhaust while decelerating and when fast revving from idle). So I've enriched the idle mixture from 2.5 turns out to 3 turns out and the problems was solved... the bike returned to idle quicker with no popping.

A mechanic set the clip for the needles on middle position on both carbs and I've adjusted the transition mechanism between the carbs. (the transition is very smooth)

The spark-plug that came out soon after the issues became more prominent was black with carbon deposits. I think the bike is too rich on the needle since this guy "had to" move the clips to middle position on both needles but this doesn't explain my problems starting since the needle / main jet is not affecting starting of the bike.

What is the default (factory setting) for the needles and for the pilot jet screw ?

For pilot jet screw I've found on the forum that is 2-2.5 turns out (and Aukeboss says 4-6 turns out which I think would be too rich) and for the needle in the primary and secondary I'm not sure about clip position.

Again the bike turns over 2-3 times and starts but the rpm drops (engine dies) or it climbs very slowly to idle speed that should be with the choke engaged.

Also when the engine is at running temperature if I engage the choke it tends to die then it clears out and the rpm raise ... This sounds too rich ? but hard to start ? A lot of controversy going on in my head right now.

Please help if you have time !

Thanks,

Bernek