Am i way over Jetted?

Ok I have a puch maxi luxe 1.5 hp and i recently installed a new cylinder kit on it as mine was trashed. The carb was previously jetted for the hight torque settup while now i have a regular cylinder i recieved from ikes bike thats not high torque its just the regular puch cylinder. My moped starts up great first kick and idles great as well. Whenever i attempt to give it any gas it bogs incredibly and smokes, and is not even rideable. The jet in it was a 62 and i am thinking the problem could be that this is way to big for my new cylinder. I did a plug chop and my plug was completely black and oily. My mixture is around 50:1 so i dont think thats a problem.

Please help with any suggestions or comments on what to do?

Re: Am i way over Jetted?

you could take off some restriction on your air box,like the grey tube that goes into the frame.or go down to a 50 or 52 jet

Re: Am i way over Jetted?

Mike,

Probably the smartest thing to do, is look up the stock jet size in a manual, and if it's different than yours, change it out. At least then you will be working from a known-good reference point.

Re: Am i way over Jetted?

Jason Luther /

62 isnt all that big. at least not enough for the symptoms you describe. are you sure you put the jet back in there? sounds like it either fell out (which happened to me) or its not there at all. is the carb flodding over at all?

Re: Am i way over Jetted?

Jason Luther /

oorrrr are you sure the piston is in the correct way?

Re: Am i way over Jetted?

I have a 1.5 hp onmy Newport and it calls for a 50 jet stock...

Make sure the found plug is in the back of the airbox and downjet and you will be fine!

Re: Am i way over Jetted?

Mike Gleick /

Jason im pretty sure the piston is in right because i installed it already mounted in the cylinder and theres only one way i could put the cylinder on so i think thats fine. The jets in there and didnt fall out, but you said something about the carb overflowing out the top, and mine is somewhat doing that as well as coming out the air intake a bit as well

Re: Am i way over Jetted?

Sounds like a stuck float.

Grey

Live to ride, Ride to work

Re: Am i way over Jetted?

_Whenever i attempt to give it any gas it bogs incredibly and smokes, and is not even rideable_

This symptom does point to too rich a mix, but it's something other than the main jet.

Although the main jet might actually be way too large, main jet size has little or no effect on air/fuel mixture except right near wide open throttle.

Check for fuel leaks of some sort, improper float level, etc, as others have suggested.

Re: Am i way over Jetted?

I have the same setup... those engines are very sensitive to overjettting... and will die when you open the throttle if the jet is too big... unless the round plug has been removed from the back of the airbox... and you are running a Biturbo it is critical to have the plug in the airbox and a #50 jet or it will not run right... unless you have a Biturbo ...the then jet should be 58 with the plug in or 60 with the plug out... any variation from this will make that ped choke out...

I have tried like 30 combinations of jets/12/14/15 mm carbs and intakes... and it is tricky...

Re: Am i way over Jetted?

oh... if it is only dripping a little... even out of the intake... it's probably the bowl gasket.. unless you have tried to bend the float level it should be fine.. those carbs sit in at an angle and if the float was stuck it would gush out of everywhere... even out of the primer button

Re: Am i way over Jetted?

Mike Gleick /

Fratbone you seem to know what you are talking about with this puchs and there jetting and everything but why would the jetting with a biturbo be lower than without one. I would think that you would upjet when you put a biturbo on. The ideal setup you described with the 58 jet is what i am running and it bogs incredibly. I think it has something to do with my rebuilt engine cause i think i have a different cylinder maybe the 1hp or something. thanks for the responses

Re: Am i way over Jetted?

sorry for my punctuation... you mis read my post...

it is critical to have the plug in the airbox and a #50 jet or it will not run right… unless you have a Biturbo …the then jet should be 58 with the plug in or 60 with the plug out…

Re: Am i way over Jetted?

Mike Gleick /

Ok that makes sense now i was hoping to hear a suggestion like that because thats what i was thinking my self. Thanks a lot for the help and ill let you know how it turns out after i order and try few jets around #50

Thanks

Re: Am i way over Jetted?

let me know how how make out!

Re: Am i way over Jetted?

jetting and air/fuel mixture is somehow related to air pressure and air temperature right?

Re: Am i way over Jetted?

Yeah.. air temperature and atmospheric pressure affect how much fuel and air is delivered. (so does humidity.)

Fuel is not really sucked up through main jet, into the intake manifold and into the engine. It is pushed up by atmospheric pressure.. pushed by the weight of all the air above you.

Carburetors float bowls are vented to the atmosphere. When there is lower air pressure in the intake manifold (a "vacuum") than there is above the fuel surface in the float bowl, fuel is pushed up the jet. More atmospheric pressure means more fuel will be pushed through the jet. This means the mix gets richer with more atmospheric pressure.

Run the bike on top of a mountain where air is "thinner" and atmospheric pressure is lower than down at sea level. Less pressure is pushing on fuel in the bowl. This would make the mixture lean.

However, since the air is thinner on the mountain, there are less air molecules per cubic foot of air. This makes the mixture rich.

Air temperature also matters. Cold air is more dense than is hot air. Denser air means more air molecules per cubic foot and leans the mixture.. (more air, less fuel)

Humidity is water in the air. If a cubic foot of air contains lots of water there is less room for air. High humidity means less air which means a rich mixture.

All these opposing forces make it very difficult to accurately tune a bike.. Race tuners do it right at the track according to the immediate weather conditions, altitude, etc. They have special tools that simplify things a little.

Plug chops and accurate plug reading is about the best the average person can do.

Re: Am i way over Jetted?

Altitude makes a huge difference, and I've found that this is one place where CV (vacuum-piston) carburetors really shine.

Many years ago, I took my BMW R-80/7 up through Powder River Pass, which has an elevation somewhere around 12,000 feet. The higer I climbed, the slower the traffic became. At full elevation, most of the cars were crawling at 10-15mph.

The BMW (Bing CV carbs) pulled a steady 45mph all the way up, it was totally awesome. I passed hundreds of cars on the way, just blew by them.

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