Moped starts but dies at idle? help!

Jeb Zinewicz /

So finally got the Jawa back together with new highflow carb. She starts up at 3/4 throttle with power to the wheel but then dies as soon as I let off. She also starts up and idles just fine with the choke in but then when I open the throttle and release the choke she dies? Any ideas?

Thank you! (edited)

Re: Moped starts but dies at idle? help!

Air leak for sure

Re: Moped starts but dies at idle? help!

Jeb Zinewicz /

jayson sumpter Wrote:

-------------------------------------------------------

> Air leak for sure

Alright. Best way to test for this? I've heard about spraying something and looking for bubbles? or maybe that was for a gas leak? Thanks for the reply.

Re: Moped starts but dies at idle? help!

Andrew Kotcher /

carbs have little holes in them the first hole is the idle hole used with the choke always "on" then some have multiple holes a lil further back these are mid range ports which get fuel from your idle circuit then if you have a mechanical slide carb you have the main jet and jet needle sounds like you are not getting fuel past the idle circuit so check for clogged jets also if you have a non emission carb it will have a circlip and grooves on the needle move the circlip down one notch this will induce a more rich situation and should allow gas to flow also while you are at it make sure the float vent is open and the air inlet ports are clear, have you checked the float level? the lower the float sits the leaner it will be the higher up the float goes the richer it will run, i am in school for motorcycles so this info is still fresh in my mind.

MMI student here!

Re: Moped starts but dies at idle? help!

Jeb Zinewicz /

Damn man, too technical for my newbie butt. It's a brand new Dellorto 14/14 SHA lever choke, has slide with spring. Fires right up with the choke clicked down, soon as I lay on the throttle to release the the choke it dies? Still can't figure it out.

Re: Moped starts but dies at idle? help!

Downhill Harvey (OFMC) /

Re: Moped starts but dies at idle? help!

Jeb Zinewicz /

Yep, definitely air leak around my modified intake. Sprayed carb cleaner on the base and the bike died instantly. Now one of the bolts is rusted and I cant get the damn thing off.

Re: Moped starts but dies at idle? help!

Jeb Zinewicz /

Got it off finally. Gonna try to find some slimmer maybe shorter bolts and maybe file down the shaft of the intake a little more. Maybe a riser would help? Really a tight fit!

Re: Moped starts but dies at idle? help!

Jeb Zinewicz /

Ok, so got the intake clamped on there as tight as can be. Now the bike is firing up perfect without choke but still dying when I open up the throttle, seems like the air is choking it off?

Re: Moped starts but dies at idle? help!

[Radium City] kyle k $ /

did u let it get warmed up a bit? mine will do that on cold starts sometimes

Re: Moped starts but dies at idle? help!

[Radium City] kyle k $ /

well mines not a jawa but maybe

Re: Moped starts but dies at idle? help!

Are you running it with an air filter on it? SHA carbs like some air restriction like the stock air box has. You must tune your carb to the amount of air flow. restrictive filter needs leaner jet, high flow air filter needs richer jet. If your intake tube is smaller than your carb you may not get enough vacuum in the carb.

Re: Moped starts but dies at idle? help!

Jeb Zinewicz /

Running highflow dome air filter like this one - https://www.treatland.tv/60mm-dome-screen-air-filter-p/sha-air-filter-60mm-dome.htm with some UNI foam stuffed behind it and a single stock screen behind the foam. Using a 15mm intake and Dellorto 14/14 carb with shim to fit the intake. Vlado swears by using a highflow on 210's but then he's also doing other mods as well.

Re: Moped starts but dies at idle? help!

Jeb Zinewicz /

What is the stock jet and what range do you think I need to be trying? Thanks for the help!

Re: Moped starts but dies at idle? help!

I'd start at 64 and do plug chops. don't know what stock is. what's in there now?

Re: Moped starts but dies at idle? help!

Jeb Zinewicz /

I'll have to take the bowl off but I thought it was in the low 60's when I first got it and looked.

Re: Moped starts but dies at idle? help!

Jeb Zinewicz /

I lied, it's a 56. Just ordered 60's and 70's from treats. Let's see if this is what the problem is. It definitely has to be something with the air/gas ratio.

Re: Moped starts but dies at idle? help!

Jeb Zinewicz /

Yep, needed to upjet! Currently at 68 and it feels pretty good. 64 and 66 seems like too much air at low throttle. I'll try and figure out how to do this "plug chop" to see if im correct.

« Go to Topics — end of thread

Want to post in this forum? We'd love to have you join the discussion, but first:

Login or Create Account