stuck in a bog

OK so it's a 2 stroke I'm asking about and it will bog a little when I start it up cold and bring up the throttle to keep it from dying.

But when it's warmed up nice it's fine, no problems. I had to turn the air screw on the carb IN a full turn (OEM says start with 2 full turns out) to make that happen. I haven't tried more than that.

I want to remember the bogging is about the bike running lean, but my youtube training uses the term "chop" to describe the throttle action and I don't really know what "chop" means in english except that it implies a quick movement.

My question is, is everything okay if the bike's warmed up or do I need to make the fuel mix richer, period?

Thanks!
Johnny Blaze(less)

[ame="https://www.youtube.com/watch?v=OrjmeGKoR1E"]Napoleon Dynamite - I don't understand a word you just said - YouTube[/ame]

Hahaja don't be scared JMZ I can't hurt anything but your expectations

The radiator fan actually seems to run less often now when I ride, but that's my only temp sensor for anything engine related.

Maybe the fan doesn't come on as much because it is not as hot these days. Don't know, just a wild guess [emoji15]

Signatures? We don't need no stinking signatures!

Hard to say for sure, but in general all carb adjustment should be done when the engine is warmed up.

As the air temps drop the density of the air increases so more air in the same space. It is normal to need to richen the the fuel as the weather cools.

Thanks y'all. Yeah the weather's cooler but I haven't ridden the 300 since springtime so I didn't think about that. That'a a good point.

It can't be that I'm riding faster that's for sure lol

I think I picked up the "chop" from a Slavens video, but I haven't watched any of those in a while. Too many Jarvis videos to gawk at now and I'm still way behind. But I am waiting for a break in the rain to suit up for the Emma trail so maybe I should try to find it again.

When you start it up cold - the engine will be lean(er) - colder engine, colder air... if you blip the throttle hard and it sounds like its going to die instead of rev - it's sorta normal at that point.
- use the choke a bit, or ride it around gently with the choke off to bring the engine up to temp.

Once the engine is fully warmed up - you can set the idle.
If you blip the throttle hard and it bogs now - you're lean. you can try to adjust the air screw, but it may need a jetting change (richer) with colder air if the air screw cannot accommodate enough.

It might be good to pull the jets out just to see what's in there currently as a baseline.

StrokedNBored said:

When you start it up cold - the engine will be lean(er) - colder engine, colder air... if you blip the throttle hard and it sounds like its going to die instead of rev - it's sorta normal...once the engine is fully warmed up - you can set the idle...
If you blip the throttle hard and it bogs now - you're lean. you can try to adjust the air screw...]

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Thanks SnB that's what I was hoping. The bike originally came with some other jets but I put the OEM jets and needles back in that came with the bike (the specs in bold from your scan, which should be spot on for today's weather)...but like I said I did have to bring in the air screw a full turn to eliminate the bog when hot.

I did put in a Vforce 4 reed just to play and make the bike more mine. That may be why I had to cut the air some. I might go down the chart another 20 degrees next time I play with the carb and give it a little.more juice.

Way back when I was running smokers, I had to re-jet one. If I remember correctly (and I might not), I ran it to warm, then in third gear, at the beggining of the power band for a few seconds, then abruptly yanked the clutch and cut the motor. Pulled the plugs, and check for condition. Then it was a guessing game of how much to change jets/needle settings. I'm sure there's a better way - I just didn't know it.

I also believe the jet settings are best checked at WOT, and the needle adjusted at idle, or near to it. Depending on the taper, the fuel curve will change as you twist the throttle.

Not too long after that, I got a little tool that acts like a spark plug, but has a clear top. You install it in the plug hole, fire it up, and watch for color changes in the burn to set the air screw. Again, memory is vague, but I think the rule was, if you're more then 1/2 turn from stock, the jets need changing.

Thoughts?

[ame="https://www.youtube.com/watch?v=zVzqqpgviyI"]How to Tune/Adjust KTM 2 Stroke Carburetors - YouTube[/ame]

Johnny Blaze said:

Thanks SnB that's what I was hoping. The bike originally came with some other jets but I put the OEM jets and needles back in that came with the bike (the specs in bold from your scan, which should be spot on for today's weather)...but like I said I did have to bring in the air screw a full turn to eliminate the bog when hot.

I did put in a Vforce 4 reed just to play and make the bike more mine. That may be why I had to cut the air some. I might go down the chart another 20 degrees next time I play with the carb and give it a little.more juice.

Click to expand...

Why did you change the jets the original owner had installed?