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intake manifold question

8553 Views 46 Replies 6 Participants Last post by  derrick
so i got the engine in the other day, it should have been sent with a 26mm carb but they sent a 22mm, waiting for an email back on that.. anyway the intake part on the intake manifold where the carb and manifold comes together measures 26mm but the on the side where the manifold meets the engine the manifold measures 22mm, should i grind this side open to be 26mm aswell? or is that side supposed to be a little smaller?
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another thing i was looking for information on was this home made head breather, iv seen this in a few threads but never any instructions on how to make one.
You can go with a small hole to big hole but not the other way it usually creates turbulence and what I did was use the stock 110 manifold and port it to the correct size I needed with a drill and carbide bits or you can use a dremel tool as well

use the gasket that fit The head and use it for a template to open up the hole or order one in the correct size manifold I mean

And the stock intake port is what size

Aldo when you measure a carb you measure where the slide is for mm the smallest opening in the carb
its lines up like that tho. the big hole is to the carb and the small hole lines up with the engine. its deff a 22mm carb tho if thats what you were saying. it says 22 on the side and it doesnt line up with the manifold gasket at all. so its okay if i open it up so its 26mm all the way through?
I would not do anything till you find out why you got a 26mm manifold and a 22mm carb on your engine. I don' think you can bore the 22 to 26, you have a O ring that still has to seal. Someome might have just grabbed the wrong size carb when they shipped it to you. You would be better to have a 22mm manifold and carb, than a 22 on a 26mm. The intake port on the head is small and anything big will just be restricted entering the head.
yea im sure they just shipped the wrong carb, the intake manifold and manifold gasket are both 26mm. im just asking should i port the outlet of the manifold to 26mm? so it would be 26mm carb, to a manifold thats 26mm on the intake side and 26mm on the outlet side. or leave it 26mm on intake side to 22mm on outlet side. idk if you ment bore the 22mm carb to a 26mm carb, thats deff not the plan. just should i make the intake manifold 26mm all the way through?
well i just found some stuff on a pitbike website saying to make it 26 all the way through. and all the intakes for sale iv seen were 26 all the way through.
How heavy are them mufflers you got, I might get one for my 110cc ZX1 extreme dirt bike, friday when I get paid. Hugh at SD Scooters is a good dude. He knows more about this stuff than I do,lol.
id guess between 2.5 lbs and 3 lbs each, i dont have a good enough scale to just weigh the muffler by its self but im 2.8lbs heavier while holding it..
@EPR - thanks, i try.

@derrick - The pitbike info is a good rule of thumb for a general use performance engine.

derrick, you can use the bigger manifold, ya its not the best way to route the mix but it will work
when i had my 22mm carb it came with a manifold that was 26mm on the carb side and 22mm on the head side i think
you would lose a little velocity where it goes from 22 ro 26 id think, not the best but not a no-go either
when you get into high compression is when those things matter alot more
its not supposed to be a 22mm carb, nor will i be using the 22mm that came with it. im pretty sure ima have to buy a 26 sense the seller isnt emailing me back.. im gona get a 26mm carb and have it go into a manifold that has 26mm ids on both openings. but the manifold came with the 26mm and 22mm ids, was wondering if there was a reason why. like should it get smaller as the air/gas goes through it? or shouold i open it up to 26mm all the way through. thanks
oh i couldnt use this carb with this manifold if i wanted to because the gaskets dont line up.
How big is the intake hole in the head?? I just bought a PZ25mm for $28 and $9 S/H for my 125cc ATV, it came with a 20mm and no air idle. Now I can put the 22mm on my 110cc X18 again. I have a new 26mm Mikuni w/ lever choke, made in Japan sitting around here and a 27mm China carb and manifold also.
26mm intake on the head.
I'd look up something on velocity porting. I really don't remember the dynamics of it. But It's like going from a big opening tappered down to a smaller. Causing more pressure and it's suppose to flow more. I think this is the idea also behind tappered bore carbs.
They say porting is an art and some time if something is ported wrong. It can cause more harm than good. I don't know what kind of carb you got. But I prefer spigot mount carbs. With a radiator hose from an auto I can make up my own intake. So far I have had great success and no one can dispute the results. Just something to think about
I will trade you my 26mm Mikuni for your 22mm carb?? I had it on my 110cc X18 and had gummed up gas that keep clogging the pilot jet, and it was alittle big for this engine, so I took it off. I am putting my 22mm re-jetted carb back on the X18 and could use a 22mm for my 110cc dirt bike.
Just bought a 25mm or PZ25 for my 125cc ATV engine last night, the 20mm has no air idle screw.
yea i looked it up, they where making the area around the valves smaller.. idk i could think of way that could work and why it cant... seems like the same thing applies to this manifold, and yea i started to open it up but then i figured one the geniuses from pbp would pry have some info on weather this is a good idea or not. but i could see it with a smaller opening on the end of the manifold. like in the head before the gas goes past the valves it makes this low pressure area that has to suck the gas out of the manifold making it all flow faster. does that sound like a real thing to anyone else?? cuz if it was all the same size it would just flow, but because its smaller on that end its being sucked into the engine..?maybe?
Then your talking about match porting the intake. Which I think is always a good thing. I would go ahead and do it. You can't hurt anything there,matching intake inner dia,gasket dia to intake port on the head.
yes thats exactly what im taking about. okay ill deff fo it then when i get some new dermal stuff, i didnt realize how much grinding on the frame id have to do to fit a 140 in there, any bigger im sure i would have had to cut the frame apart...
It be such a big deal though for the power gain of big block. Like say a 150 or a 184cc to much fun..lol
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