Starting Point For Idle And Main Jets

[Hellion]

I've been eying the 6 or so inch long curved ones. Any advice or recommendation about that?

How much of a curve? There’s a few guys trying to run the U shaped ones (to where the carb is above the engine and out of harms way) but it does something funky to the A/F mix and the charge. Requires more tuning and Excedrin.

 

[Wicked_Daddy]

The issue with the curved manifolds is that they are 22mm. At least the one I have is. So it seemed a mismatch/waste to fit a 22mm manifold on a 24mm carb. The Nibbi manifold is made for the carb. That said, the intake port is about 20mm but the intake valve is 25mm. I ported my intake with a Dremel to match the manifold and taper it into the 20mm remaining distance to the valve. In theory, this would cause a venturi effect that will speed the flow of mixture into the chamber and provide the associated increased burn rate of the flame front for more complete combustion - thus my lean condition until I provided a richer mixture.

 

[OneTimeUser]

How much of a curve? There’s a few guys trying to run the U shaped ones (to where the carb is above the engine and out of harms way) but it does something funky to the A/F mix and the charge. Requires more tuning and Excedrin.

The ones I've been looking at are a bit less than 90 degrees and horizontal. "Some" say that the extra distance is better for atomizing and performance.

I'm over my head at this point 'cause I only understand the basics of carburetors.

 

[Whitetrashrocker]

Yes, long intake runners have better low end torque.

 

[panchothedog]

WTR,

You were spot on. I had leaks at both ends of my cheap Amazon manifold. The rubber gaskets are junk. I fixed one by tightening, but the other remains despite some torque and some gasket sealer.

It is better over all, but I'm now on the hunt for a new manifold.

I've been eying the 6 or so inch long curved ones. Any advice or recommendation about that?

Thanks again.

Yes. Don't buy the Amazon cheapie. We usually get what we pay for.

 

[Edwin Spangler]

Welp, I went to a 48 idle jet yesterday on the 212. I feel like that needs to be said after my previous comment.

 

[Edwin Spangler]

Yes, long intake runners have better low end torque.

I have found that they help the cheap carbs run better also.

 

[Edwin Spangler]

Yes. Don't buy the Amazon cheapie. We usually get what we pay for.

GPS sent me a manifold with both faces bowed. Light shown thru both sides.

Since then, I have resurfaced all intake mating surfaces that I mess with. Just glass and 220-400 sandpaper.

Trying to "tighten the leak out" has been the cause of several intake stud re-tappings.

 

[OneTimeUser]

GPS sent me a manifold with both faces bowed. Light shown thru both sides.

Since then, I have resurfaced all intake mating surfaces that I mess with. Just glass and 220-400 sandpaper.

Trying to "tighten the leak out" has been the cause of several intake stud re-tappings.

This.

I torqued to the max (calibrated wrist) and plan first to resurface as you mentioned and find new orings for both ends. Chinese rubber parts seem to be especially bad. Bellows boots on things like master cylinders and cable ends seem to last about 6 months.

These days I see the same Chinese-made items on Amazon, and also often at Lowes, Tractor Supply, and even some auto shops.

 

[Edwin Spangler]

Chinese rubber parts seem to be especially bad.

Yes! Ive noticed its affected by gasoline MUCH worse than rubber from Nibbi or something.

Removing the bowl for example. If I get gas on the o-ring of one of the Chinese carbs, its a huge hassle to get it to fit again. The Nibbi on the other hand, I just remove that bowl full, gas all over the o ring, no problems.

 

[OneTimeUser]

Yes! Ive noticed its affected by gasoline MUCH worse than rubber from Nibbi or something.

Removing the bowl for example. If I get gas on the o-ring of one of the Chinese carbs, its a huge hassle to get it to fit again. The Nibbi on the other hand, I just remove that bowl full, gas all over the o ring, no problems.

I've had the same experience. Come daylight I'm going to hand lap the cheap Amazon manifold and go in town to the air and pump guy who has a seemingly endless assortment of orings (and other such things). I think with a bit of hand lapping and a new oring I can solve my immediate problem leak while I do some more research about a new, longer, and curved, manifold.

I'm just about done building this cart. A new center-mounted solo seat will finish the job.

FWIW I'm very pleased with the electric start Tilliotson 212. It's stronger than the Predator I had and quieter too (go figure--because it has the same exhaust on it that the Predator had). They were on sale for a while for about $350. I snagged a couple of 212 predators when they were on sale for $99. They are spares that will most likely end up on the log splitter or a generator when the time comes.

I'm resisting the urge to hot rod the Tilliotson with a cam and stuff 'cause it's plenty fast for me now and I don't want to compromise it's reliability.

 

[Hellion]

Hey we could all benefit from a pic or link of the cheap a amazon manifold(s). Show us what you’re working with. O.T.U. or E.S., don’t matter who

 

[Edwin Spangler]

Hey we could all benefit from a pic or link of the cheap a amazon manifold(s). Show us what you’re working with. O.T.U. or E.S., don’t matter who

PWK 24mm and 34mm.

 

[Edwin Spangler]

View attachment 164569View attachment 164570



PWK 24mm and 34mm.

Also, I DO NOT recommend these things. Theyre terrible. You have to be SO GD precise with tuning. Ive been thru several now with various engines and I havnt found one that runs acceptably whereas the name brand equivalent runs smoothly even with poor tuning.

If at all possible, avoid and get name brand.

 

[Wicked_Daddy]

Pics:
- Nibbi on a curved Amazon manifold (22mm) - worked good, no leaks. I was also concerned about the vibration being amplified by the manifold and ultimately weakening the threads in the head.

- Nibbi on a Nibbi manifold - held together with a rubber sleeve (comes with it). This one is on a 196cc that I built and currently doesn't have a home. (searching for a minibike roller I can refurb).

- Nibbi on a Nibbi manifold - all bolts. This is my current Kart engine and it screams. The picture is just a zoom in so, excuse the clarity.