r/carburetors

Hey everyone,
My Yamaha XT350 has an odd issue at idle and I’m running out of ideas.

Symptoms:
- rhythmic “plop” / pop every few seconds at idle
sometimes the pop is strong enough to stall the engine
- runs better at higher RPM
- fresh 98 fuel
- new spark plug
- new air filter
- carb cleaned
- intake manifolds replaced

I attached a video with the sound.
Any XT350 or dual sport carb experts here? Thanks!

I dont think it is running good maybe carb or firing but idk. Please help. It is straight piped

What i have here is a piaggio typhoon 50cc 2 stroke, it has a 19mm dell’orto phvb carbarateur

With the original piaggio filterbox, together with a malossi red sponge filter inside, the scooter does not do a thing, unless i spray brake cleaner into the filter’s intake

When i remove the filter completely, so the carb’s intake is open air, the scooter does work when i hover my hand over it a bit and cover it a little every once in a while, i can feel my hand getting wet from the fuel while doing that. It does not want to stay running and completely bogs down once i remove my hand

Demonstration:
https://share.icloud.com/photos/0aaOltE2kJF7DNoyK5uygApRA
(At the start the throttle cable wasn’t in correctly)

Now when i put a little cloth over the open air intake of the carb, and attach it with elastic bands:
https://share.icloud.com/photos/0cfiYQSeiOBxXCwG7nHk79A6g

It suddenly runs completely fine, no issues. Maybe a tiny bit unstable as you’re usually not meant to use a cloth as an air filter, but it doesnt stall or just bog down for no reason at all, video here:
https://share.icloud.com/photos/09fUB36RDfWGbeSL5RlmGQ4Kw

Does anyone know why the f my scooter is acting so damn weird? I already tried installing a bigger jet, originally it’s 72, went up to 84, did not change anything to the open or filtered setups, just made the cloth setup run a bit rich
I did also remove the restrictor plate before the membrane, but that did not change a thing, only became more powerful when using the cloth

I am genuinely confused by this and just want to get to driving this thing

By the way, i am new to 2 stroke scooters, first one i have ever owned, did have 4 4 strokes in my past, all of which i have bougt broken doen, and fixed myself, so i do have some experiences with engines, just not specifically 2 strokes

Ill admit I got impatient. Gasket had the block glued on so i tried to gently pry with a screwdriver, forgetting how soft the aluminum can be. The rest is good, but will that mark cause any issues?

I know I’ll get roasted, and I am ok with that.

Put my card back together and I cannot figure out where these go. They are T-25. Fairly certain they are not external. Any help is appreciated!

Don’t how what carb it is all I know is that it’s a Holley 4 barrel and it has an electric choke

2019 Suzuki DR-200s, less than 2k miles
New carburetor
New petcock (fuel filter included)
New battery
New spark plug
Fresh oil change
Scoured gas tank
Cleaned air filter
Cleaned muffler
Ethanol-free gas with no additives

Runs fine for about fifty miles (about a week’s worth of commuting, not a single trip) then does this for a bit. Backfires, rough starts, dies under throttle, only idles with choke out) After sitting for a couple weeks it goes back to normal for another fifty miles.

I've got an old motorhome with a Ford 460 in it. It'll run off propane or gas.

The circled part has broken, the hose isn't attached to the plate any longer. It goes up into the carburetor. I just need to know what it's called so I can order a new one.

Thanks in advance!

This truck hasn’t ran in a good while, new fuel cell, lines, pump, filters, my question is why it’s breaking up/ backfiring through carb when I hit WOT. Otherwise it’s runs good until the secondary tries to open. The carb is hooked up only to the drivers side valve cover and the distributor and both bowl levels are setting in the sight glass 6-7 psi

So the guy i sent my carbs to ultra sound clean them lost what i think is called an air jet , it sits under a metal plate , he lost the idle-slow one and i cant find a replacement. Is there anything that works 100% as a replacement since OEM isn't listed anywhere (im willing to change em on all 3 carbs if i have to )

Thanks in advance everyone :)

note 1 : all internal fuel jets have been changed with oem ones (pilot screw etc included)

note 2 : if you dont know please atleast upvote this so the right person sees it cause on Facebook groups no one seems to care to help me :(

thanks again everyone

It’s a 1983 Mastercrsft with a 351 Windsor motor in it. Holly 4160 carb. Just put new gaskets on the bowls after I found it leaking thinking it would fix it. It definitely slowed down but still leaking

Also how could I get the idle down screw is almost all the way out if I put it out any more it stalls when I put it in gear

I just got this 2nd gen camaro that im told has a 383. The block is a 327, has aftermarket aluminum heads, headers, msd hei, and an edelbrock 650. I set the timing to 16 degrees btdc and got the highest vacuum I could while tuning the carb. Im new to the whole carburetor world and am trying to learn. From what Ive read my issue seems to be with the carb or the carbs accelerator pump. I tried putting the linkage in the top, middle and bottom spots on the accelerator pump linkage and it didn't make a ton of difference. I also tried revving the throttle arm at the carb with the throttle cable, kickdown and return spring disconnected and it behaves the same. I'm hoping someone might have some suggestions or advice for me on this issue. Thanks in advance.

Fresh 350 SBC in my 1978 Firebird formula with a TH350 auto. Running a brand new Edelbrock AVS2 650 carb and HEI distributor. Looking for advice on where to go next diagnosing a high idle issue because I feel like I’ve narrowed a lot of things down already.

Here’s the full timeline/details:

Motor fired up and ran pretty good initially during first starts. Was working on getting coolant burped, timing dialed in, and carb adjusted. At one point I had timing too advanced and the engine started acting crazy:
- idle shot up to 2000-3000+
- occasional backfire/fireball out of open headers
- RPM would keep climbing

Since then I’ve done a TON of testing and adjustments:

What I’ve already checked/done:
- Retarded timing multiple small adjustments clockwise and the engine behavior improved a lot
- Starts cleaner now
- No more violent runaway RPM
- No more major fireballs/backfires
- Idle now starts around 1200-1500 and slowly climbs/stabilizes around 2200-2400 instead of endlessly racing
- Mechanical advance in HEI seems free and springs back normally
- Vacuum advance disconnected/capped
- Brake booster line capped
- PCV disconnected/capped for testing
- All carb vacuum ports capped for testing
- Sprayed carb cleaner around carb base/intake/vacuum connections with basically no major change
- Mixture screws reset to baseline (1 turn out each)
- Choke adjusted 2 notches leaner
- Fast idle cam does not appear to be hanging up or moving weird
- Pushing throttle linkage closed by hand does NOT lower RPM
- Primary blades visually look barely cracked at idle
- Secondary blades appear closed too
- Covering the carb opening with my hand DOES immediately drop RPM / almost kill engine

The confusing part:
At this point the engine no longer acts dangerous or violently runaway. It just seems to settle into a very high idle that I can’t get down enough to properly check/set initial timing because it’s idling around 2200-2400.

Throttle blip after warming up does not lower idle either.

So my questions are:

1. Where would you go next from here?
2. Could this still be carb throttle blade/transfer slot/secondary stop related even if everything visually looks closed?
3. Is this still potentially a vacuum leak or does the hand-over-carb test mostly rule that out?
4. Would you pull the carb at this point or continue diagnosing on the car?

Trying not to randomly crank adjustments anymore and want to diagnose this correctly before I make things worse.

Are these my idle mixture screws screws?