full throttle hesitation, only downhill

[burnt_toast]

gotcha, open filter will never run right on the stock carb

maybe, but feel im close

Results of auxillary fuel tank w uninhibited fuel flow ==> Fail! same symptoms.
At least this rules out a defect in the petcock, so that's a positive note.

Next up, is to source 96+ jets and go bigger on main. my final attempt

[kjkenney]

If you're stuck on the pods I say Godspeed sir. May get it to where you want it on a flat, but situations like the downhill will be hard to account for when tuning. But hey all this trial and error is half the fun of scooter tuning right?

[burnt_toast]

Guys come on. You can run the stock carb with the stock pilot and up-sized main jet. It runs fine. If your running a 47-48mm a good main jet is 100-102. A 50mm is a 105 main. You can either mod the stock air box with 3 one inch holes in the air filter box cover and add 1 inch uni breather filter plugs. You don't have to use the uni plugs if you don't want to. The air will still pass thru the filter. Or you can use a uni free flow sponge filter. Either way it runs great. Plug chops are the proof.

Taz

quote from Taz, on this thread:
viewtopic.php?f=4&t=32553

open filter has def been done with success in the past. but alas as mentioned, if there is no improvement im my case w/ bigger main, will likely retune to stock box. final verdict by tonight hopefully

[patthesoundguy]

Could be an atomizer issue. I have heard about carbs having the wrong atomizer causing issues like that. I'm wondering if when you are going downhill its not under load and its going on the rich side. My af18 with the 28mm carb behaves kind of like that. I wonder if you get a different carb the issue will go away

[MrJumps]

I would get the pod and tape it until it matches stock airbox and stocks doing that nonsense. At least you dont have my issue, no matter how fat the jetting is or the other way it stalls at wot.

[burnt_toast]

I would get the pod and tape it until it matches stock airbox and stocks doing that nonsense. At least you dont have my issue, no matter how fat the jetting is or the other way it stalls at wot.

have actually considered something like this. had one jog setup where i put an empty metal can on pod, with some success.

i saw your other post, that totally sucks. hopefully you can trace air leak if that's what it is. i hear you on the chore part, not enjoying the hassle of this problem either.

small update, no upjets avail locally anywhere so I filed up one more. was ~98 new one is ~100main. sucking/hesitation at WOT/downhill seems a bit better, so going to try even bigger. however i'm at end of my jet files, so hard to gauge now. filed out another to ~102 but ran out of daylight to test.

[MrJumps]

I bet if you taped a fikter it would disapear I did that on a spree with a pod filter. Use eltrical tape then over that duct tape.holds good

[MrJumps]

I mean if you tape the pod right it should be fine. Your only letting the same amount or air through as stock. But g9 is right about the wot and anything under that being lean. Rember also its not about how much air, I know a lot of people say that, but its about how well the engine can be fed and its exhaust of air. You can have a ct on a good pipe, but if your running open fikter, stock intake and carb, your sucking probably roughly 30% more air and it goes into the bigger bore then is forced into a smaller pipe. The pipe causes your temps to go up, the small carb with open air causes your temps to go up when under wot due to piolet restriction.

[Wheelman-111]

Greetings:

Actually an increase to 72cc from 50 is a 44 percent displacement increase. If the pilot is not richened by that increment, watch out for off-throttle heat spikes. The stock airbox is calibrated to reduce intake air pressure to a vacuum, which sucks more fuel through the small PA pilot. A pod eliminates that negative pressure and the mixture goes lean, as Graphic pointed out. What is the point of a Pod if you have to tape it up?

[tazland001]

To pod or not to pod that seems to be the question. I have good results running BBK's with a pod on a stock carb but in Vegas we don't have a lot of hills in town so maybe that is why. Most of the time I used the stock box with the uni breather tabs. I do have bigger pilot jets for the stock carb. The stock pilot is 34. I have 34 and 38 pilot jets. I have never tested this theory so I can't say. Im surprised more people don't use the neg pressure from the stock airbox and just go up a few sizes. I have seen people on here who have done this with great success. Just a thought.

Has any one ever copied the jet sizes from say a polini carb set up. They run pretty small jets. You could copy the jets in that and apply it to the stock carb and see what happens. You can drill the pilot out a little bigger. There are some threads on here that offer the drill bit sizes to match the correct jet sizes. Just a thought.

taz

[benji]

To me the only reasons to use a pod filter is for looks and to replace a missing airbox. I wish I could use a factory airbox on either of my bikes but the aftermarket intake kinda stops that from happening.

[burnt_toast]

small update:
stock pilot, main to ~102, needle clip -1 (richer), still using pod

monitoring CHT today on ride to work. didn't get to play much with part throttle settings, but tried to get WOT baseline. long stretches of WOT temps were at 200F creeping to 230F, then spiking to 250-280F when letting off. back to 240-250F when back on it WOT. seems reasonable for a malossi sport cast, at WOT anyway.

on ride home, will try some hard WOT to heat up, then monitor part throttle cruising and see how she goes.

[burnt_toast]

CHT at part throttle confirms heat spikes between 0 to 1/4 throttle, jumps to 260-280. then half drops to 240-250, wot to 200-230.

not much surprise as its been mentioned this could be the case, but good to confirm what's going on.

looking into drilling pilot. decided to extrapolate some data from the wiki links in this thread:
viewtopic.php?f=1&t=32950

keihin main vs drill bit in.JPG (94.92 KiB) Viewed 7162 times

plotted data, and got this linear equation:
Y = 2500(X)+5

Where Y is main size, and X is drill bit diam in inches.
However, I'm not sure the relationship between main and pilot sizing is same..

from noiseguy on that thread, a .009" bit is a 22pilot
yet equation nets 27.5

only local option for micro drill bits is Harbor Freight, with smallest bit of .5mm, .0197"
which is a jet size 54 using equation, or a size 48 using proportianal comparison w/ noiseguy's #'s.

if stock is 34, 54/48 sounds like a considerable jump. debating trying it anyway, ordering drill bits online, or just leaving as is. YES i still want to keep pod
could all be waste of time, if anything at least this equation can be useful for someone drilling custom main jets!

[MrJumps]

Okay try something out for me Toast, what size is the hole for the air intake, use paper to protect the foam from tape and mock up a prefilter out of paper that woukd match the stock air intake size and enlarge it (insert %of bbk added to the stock bore ) and make the filter off. Duct tape the paper as not to accidently tape the fikter and slide the paper "resistor" onto the pod. Now use a rubber band around it to hold it on and try that out. It will need a jeting change but it should give the back pressure of a stock airbox and fool around with either adding or taking material away from this paper-taped pre filter until it runs good. Then make a permanent prefilter restrictor out of duct tape taped to itself still to kep the filter from getting torn up and hold that on with rubber bands. Then search for a cone filter that macthed the size or custom order one from k&n and then your stock carb will enjoy its intake flow. From how I understand the stock carbs are very good carbs, but suck for modificaci├│n.

If this dosnt work then I woukd address a piolet, but thats a ton of work to adjust a piolet on that carb as it is pushed in correct?

[MrJumps]

Okay another post

The stock jet is a 36 if I rember from the other post correctly

Taz sells a sa style idle at 38 2 sizes up from stock sa jetting. Well if we know the bit size for the other jet size and then know the bit size for this guy http://m.ebay.com/itm/Honda-Spree-NQ50- ... nav=SEARCH

You could make a graph of the scaling to make a drill bit refrence sheet to every size of pilots via drill bits.


Or you could order that jet, find what size drill bit it is and step up the stock drill bit in your current carb slowly until it runs right and post what size drill bit you used for other people using a 72cc cast kit.

( I feel smart )