Yamaha Aerox runs bad when warm!

[davis33]

Hi, 
Ive got a Yamaha Aerox that runs great the first like 2 minutes, but then when it warms up, it doesnt want to run great anymore.

My setup:
Motoforce racing 70cc kit
Motoforce racing crank
Dellorto 21mm carb
Motoforce racing v2 clutch and bell
Polini 90° air filter
Yasuni R exhaust
3.5 gram rollers

Could it be something with my intake like its too small or something?
Anything would help.
Thanks

[aeroxbud]

Did you ever sort out the choke unit?

[davis33]

aeroxbud
i bought a new carb with a manual choke.

[90GTVert]

Cold engines don't process fuel well and they need more fuel. Warm engines don't like so much fuel. This is why we use chokes and enrichers. Anyway, it could be a sign that the tune is too rich. Here are some fuel related symptoms to look for : www.49ccscoot.com/faq/symptoms.html

"doesn't want to run great anymore" also doesn't give us a lot of clues. What symptoms are you experiencing? Is it just slow, does is sound different, etc...?

[davis33]

90GTVert
I dont really know how to explain it. It gets really slow, it only opens up at 50-55 kp/h. I cant go up any hills at all. It doesn't sound any different. I thought that there is an air leak somewhere, so i put some RTV where the intake is on the engine. Also changed the gasket on the exhaust as it was oily around it. Could it be that my main jet is too small as i got my fuel/air mixture turned all the way in?

[davis33]

Heres a video.
It doesnt want to go away quickly and i cant even get past 30 kph up a hill.

youtube.com/shorts/fY8v544Dihs?feature=share

[rtnifty]

What's your jetting on that Dellorto? It looks like your power drop is right at 30kph. Have you done any plug chops to see where you might be too rich or lean? Have you got a temp gauge/rpm for that bike? Highly recommend for tuning. Takes a ton of guess work out and it will save you from burning up the cylinder if you're lean. I'm guessing with that fuel screw all the way in, pilot is likely t0o big, but your problems seem to be further up the acceleration range -needle and main. I would check those. I didn't hear any sputtering, so looks like a bog. Possible that main is too small or needle too lean?

Really though. Get a temp/tach. It will save you some headaches.

Here's a plug chart below
www.lazerhelmets.com/lean-spark-plug-chart/

[davis33]

rtnifty

Sorry for the late response. The jetting is completly stock ( 92 main, idk the pilot). The needle is one clip down from the top one. Quick question, whats a plug chop?
Could you link a fairly priced temp or/and rpm gauge as I cant find one on the site I usually shop.
Thanks for the response!

[rtnifty]

For plug chops and reading info - 49ccscoot.proboards.com/thread/1727/spark-plug-reading-tuning-info

Trail Tech for CHT is pretty standard and very reliable. They sell their Tach and Temp meters separately. If you can find a good quality combo meter (temp and tach), that's really helpful. I've used cheaper meters in the past like Runleaders which you can find on amazon. Word to the wise, they can be hit or miss, so buyer beware on that one.

k- you need to read up on jetting and carb tuning, so you can get the most out of this without messing up your stuff. Just about everything you need to know in order to get started.

www.49ccscoot.com/faq/carbtune.html

[aeroxbud]

You have a bigger carb than the standard one. The jet the new carb comes with will likely not be the right one for your set-up. You need a box of jets to help tune the carb.

[davis33]

aeroxbud
rtnifty

I got the carb jet kit. I went from a 92 to a 95 which ran a bit better but not great still, from a 95 to a 98 with no differnece then i tried my luck with a 100 but it ran the worst. I put in a 90 jet which i think ran the best but it bogged from start. After a long ride  I think it would overheat. IDK what to do now. The pilot is a 60 (if the pilot is the longer one). The needle clip is still one from the top.
+ it sometimes sputters from start.

[rtnifty]

Okay, so here's what you gotta figure out- Were is the issue occurring in the throttle range? You mention that it bogged from start with the 90, but you also mention that it sputters from start. So bog means not enough fuel to air ratio and sputter means too much fuel to air. A bog sound like the motor is going to cut out "BWONG!" and there's a sharp loss of power. A sputter sounds like the bike is blowing a raspberry at you and its sluggish. Doesn't have the sharp drop in power - just does have any oomph to it and often smokes if really bad.

So the 90 ran great on the main. What were you're temp readings? At 60 in the pilot, you might actually be a little big. The sputter from the start might seem to indicate this. Start the bike on stand, let it warm up completely. Then blip the throttle. Does the idle hang (rpms stay elevated after you let go) or do the rpms drop below standard idle (say if normal idle is around 1500, do they drop to like 1200) and the engine starts to stumble? When you blip the throttle, if the idle hangs (elevated rpms above normal idle before coming back down) then the pilot is likely small. If the rpms drop below idle and the engine stumbles, pilot is likely too big.

Again a lot of this tuning comes down to tach and temp sensors. It take a lot of the guess work out of jetting. Also for your main when you do WOT tests the temp sensor will tell you about rising temps so you can cut the bike off before overheat.

To understand more about jetting and carb tuning- make sure you read this guide entirely. www.49ccscoot.com/faq/carbtune.html