250-500cc Hard starting after warming up?

My 12 wr300 w/38mm Lectron has always started hard cold and is getting worse. I'm pushing 100 hrs on the original top end and my new compression gauge says only 160 psi. Have you actually tested the compression?
I had this idea previously, but just remembered to try it and the bike started easier. Try turning the idle screw 1/4-1/2 lean or more when cold starting. It's not a solution IMO, but gives another clue.
I finally bit the bullet and ordered a new CDI and a set of rings too.

Actually the lectron was a lot better than the mikuni at first. It started well in 1 to 5 kicks. I'm going to give it a good cleaning and address the choke not staying up. The choke serms loose to me.

Did you get another ducati ignition? I've heard that the ducati CDi can be flacky. My bike seems to run great once I warm it up. I'm just wondering if my spark is slightly weak causing hard starts on a cold bike? Once the wr300 is warmed up it rips, so the ignition seems to be working fine in normal operating temps.

I am interested in your results with a new CDi unit. Does anyone know if the earlier pre-ducati ignition is available and will fit on a 2012 wr300?

Yeah, I just got it a couple of days ago and haven't installed it yet. Been sick for a week or more and not interested, but worked on the 144 and rode around a little today.
Mine rips once it's warm and restarts easy too, though it does have an annoying miss/stutter I haven't been able to tune out. It also spooges more than it should no matter how it's tuned. Pull the plug and watch the spark. Mine looks weak. Will do the new CDI this weekend and let you know.

Ducati CDI is digital, older ones are analog, so you have to replace everything. There's some threads discussing it.

Took apart lectron today and noticed that the choke plunger is a little chewed up. Basically the rubber piece that pushes down to stop flow to the choke circuit looks like it might leak thru a little. Calling Lectron in the morning. I remember it getting stuck up once and having to work it to get it to come back down.

My bike is doing this too - 14 model . Starts ok cold and then hard to start . I kick it hard sitting but not hard enough . I need to lean against a tree to stand up and give it a huge kick and lots of throttle .
Normally 2 or three kicks . Pain in the butt

I did a few rides with the new CDI and don't notice an obvious difference. Starting didn't improve Doing rings now, but realized someone sent me a 125 oring instead for the 300, so waiting on parts. Next, adjust timing I guess.

have you tried leaning the airscrew or pilot a touch?

it was running a 40 pilot I am now on 30 - same with both . Idle improved with air screw further in so I think I will go back to a bigger pilot
If its a weak spark I am thinking the fix may be a decompression head to be able to give a very strong kick from sitting . I may try thicker base gasket first .
Nothing worse than not being able to start the bike

Jus get in the gym Ash!

I do ...

Shouldn't be that hard

My two cents worth, hope it helps.

Over the years I have noticed many big two strokes like to be started by first bringing the piston to TDC. Then , kick it like you mean it.

For my 09 WR300, with 36 Lectron, cold starts require around three slower kick/push through' s of the kick starter with the choke on, then the above big two stroke starting method. Hot, TDC then just kick, no choke. Hot or cold it starts first kick 99% of the time, if not it is almost always because I'm kicking from an awkward position.

About the easy start cold, hard/no start hot symptom. Firstly, if the bike has been running well from a jetting point of view, especially with a Lectron, then it suddenly changes, this is unlikely to be a "jetting" problem. The symptom you describe of easy cold, hard hot starts is very symptomatic of an electrical fault, particularly some type of coil, either High tension or Pick up coil.
I suspect your 09 WR300 has the Kokusan ignition like mine. I would thoroughly check all connections to and from the HT coil to the spark plug. Then check the HT coil for continuity " while it is hot". (Hot air gun etc).
If the HT coil checks out ok (make sure of it) then check the pulse coil of the stator the same way, cold and "hot".

If indeed the jetting has suddenly changed ( given the same atmospheric conditions) then it would point to something becoming loose in the carb, so adjusting only treats the symptom, not fix the cause and will likely continue to cause problems.

I've had buddies try too start my bike and failed due to improper technique. I watched one friend kick at it about 10 times with no luck, I got back on it and it started one kick. I made a video a while back on how I start my 300. I would assume if you're under 6 foot tall , it might be more difficult. Being a fat bastard and having a little weight on the kicker helps a little too.
View: https://www.youtube.com/watch?v=vZkhnaIFdbg