direct air and duel exhaust...

[Cabinfever1977]

my c-clip is second from the top on slide.
my engine is a 48cc dualstart dualclutch starfire gt-2 grubee from gasbike.net.
with the stock filter and black plastic thingy i could do around 28mph or so.
with a rubber boot and a 6" aluminum pipe pointed forward or backward plus filter i can do around 35mph. so i belive that that just having a airbox or air pipe is like air on demand and it helps to keep the filter clean by having it farther from the carb due to gas/oil blowback. and it may be operating like a vacume cleaner.

 

[drhofferber]

I was just warning about the dangers of running with no filter at all.

If you still have the original foam then there is no risk. No dust is getting in and it hasn't leaned out much. But I doubt there is any ram effect due to that filter and the small opening up front.

I think if one had a really wide mouth (i.e. 12") pointing forward and no filter then ram effects could occur at high speed. This would cause major leaning which might be harmful. Just speculation.

2 strokes are funny. Turns out changing the length of the inlet tube can have surprising effect on power. I haven't experimented with this myself and don't know if the stock inlet is optimized. I believe adding tubing like you did could increase power if the original path was too short. I don't know what effect having the foam still in place would have on this.

FYI Moving the clip has little effect on mixture at full throttle. To really change ratio you'd need to drill out the jet. If the foam is still there I don't think it's necessary to do that. These are a little rich from the factory anyway and IMO those covers with the 4 tubes pointing down are too restrictive (you had the type w/louvres). They act like a choke. Maybe the louvres are less restrictive.

Getting rid of that stupid plasic cover with the tubes is a good idea. I replace the cover on some of mine with safety wire to hold the foam in. On others I cut off the bottom half with the tubes. The remaining top part still holds the foam. This gives barely noticeable increase in power. Not much, a little over 1mph average. And my plug shows slightly leaner.

PS I discovered this trick accidently because the engine will not fit a Magna Glacier Point with that stock cover on. Took it off, put it back, took it off again, put it back... There was no doubt, a little more power.

woow...very scientific...yes my intake has been altered...straight and 3 1/2 inches...i've moved the clamp down one notch on neddle...it used to choke out, now smooth but it takes a higher speed for trootle to kick in, in other words i'm feeling the lean condition at lower speeds, but this creates higher rpm's and a smoother condition at lower speeds...and still at higher speeds the trootle functions well and it smooth with no coughing...i'm not to worried about speed or i'd put my large expansion pipe back on....i took it off for respect for my neiborhood...i will keep experimenting but right now smooth is in...clean power instead of coughing to get there...this 50cc has never been smooth, now it is...my 80cc is smooth and power...30mph cruiser...37 top still in break in...about 150miles...like i said if the 50 goes i'll buy a 70 or 80 and replace it...this bikes mounts are setup so easy a hour and new engine...well ok your information is greatly appreciated...thank you and i'll keep you posted, thaks...Dennis

 

[drhofferber]

my c-clip is second from the top on slide.
my engine is a 48cc dualstart dualclutch starfire gt-2 grubee from gasbike.net.
with the stock filter and black plastic thingy i could do around 28mph or so.
with a rubber boot and a 6" aluminum pipe pointed forward or backward plus filter i can do around 35mph. so i belive that that just having a airbox or air pipe is like air on demand and it helps to keep the filter clean by having it farther from the carb due to gas/oil blowback. and it may be operating like a vacume cleaner.

so you have a fork boot..2 1/4inch dia...what size pipe?...no filter?...just went thru that with xliter...i'm hearing good things about grubees...speed is not the issue here...i have my other bike that cruises 30mph...80cc...so far 37 is top...it will top out at 40 one of these days but 30 cruising is fine...the 50 , 25mph cruise...is fine but it goes faster...but Y....ok thanks for the help, i'll keep you posted...Dennis

 

[Cabinfever1977]

rubber boot is 5 1/2" long x 1 3/8" dia with end stretched over carb end.
aluminum pipe is 9" long x 3/4" id 7/8"od dia.
stock filter is on end of pipe.

i built this not for speed either since i like to ride around 25mph. but i built it to keep my filter clean and to quiet the engine down like a intake silencer. it takes off faster and has higher top speed(35mph) is just a bonus i guess.

 

[drhofferber]

rubber boot is 5 1/2" long x 1 3/8" dia with end stretched over carb end.
aluminum pipe is 9" long x 3/4" id 7/8"od dia.
stock filter is on end of pipe.

i built this not for speed either since i like to ride around 25mph. but i built it to keep my filter clean and to quiet the engine down like a intake silencer. it takes off faster and has higher top speed(35mph) is just a bonus i guess.

here is a site on ebay...jpxsales...boots...2 1/4 inch...will fit over carb...Dennis...heres a cool bike also...the flying pegion from china...ha

 

[Cabinfever1977]

thats a cool bike.

 

[drhofferber]

thats a cool bike.

ya...they were selling them for 200 on craigslist...san diego...didnt last long...now portland and la. .not craigslist...you have to put it togeather yourself...just google flying pegion and it will come up...i.m going to give you another pic...hard to find this one...the pegion is my next bike..i'm getting ready to put my new chain tensioner on the bike...you might like this...how did you like that boot..i'm going to get one and try something else...i decided to lower the clip one more notch...i'll let you know...wait tell you see this tensioner...i'm sure you'll like it...i'll send you a pic...i'll keep in touch...the bike is a forza...Dennis

 

[Cabinfever1977]

those rubber boots are great,they keep the gas/oil blow back from leaking out of the carb.

 

[skyliner]

has anyone informed you that your fuel filter is on backwards they tend to get clogged reall easy like that nice idea with the ram air dual exhaust ??? does that really help or is it for looks

 

[drhofferber]

has anyone informed you that your fuel filter is on backwards they tend to get clogged reall easy like that nice idea with the ram air dual exhaust ??? does that really help or is it for looks

skyliner...ya if it was on backwards that be hard to do...looks...well i'm just a 63 year old fart...trying new things...and having a good time doing it...isn't that what this hobby is all about....have you ever been to rock port, tx....i here thats a fun place...thanks for the reply...good luck and have fun...Dennis

 

[skyliner]

just tryin to help you from it getting clogged if you look on your fuel filter it has an arrow on it to let you know the direction the fuel should flow in

 

[drhofferber]

just tryin to help you from it getting clogged if you look on your fuel filter it has an arrow on it to let you know the direction the fuel should flow in

skyliner...the parts from the carb are in the pic...the only thing that is not there is the louvers...what else i'm i missing...anything that will help will help...about rock port...have you been there...looks like a nice place to retire....ha...Dennis

 

[skyliner]

no im talkin about the fuel filter going from your gas tank to your carb on your fuel line THE FUEL FILTER is on backwards and will eventually clogg i had the same problem

 

[Pablo]

My goodness.

 

[drhofferber]

no im talkin about the fuel filter going from your gas tank to your carb on your fuel line THE FUEL FILTER is on backwards and will eventually clogg i had the same problem

skyliner...yes i see what you are talking about....that could be a problem...for what i paid for them i could change them every month...i got 5 for 11.00 thats with shipping...there old style VWbug gas filters....the way its setup is a quarter inch tube on top and 3/16 on the bottom...if you turn them upside down i'd have problem with the tubing...just bought a new nt carb from spookytooth...than i think i could turn it...that bottom inlet with the old nt in hard to get tightened up...thanks for the info...hopefully my pit cock filer is doing its job...hey what about rock port????Dennis

 

[xlite]

IMO direction of fuel filter don't matter. SIZE matters. Those tiny chainsaw filters have very short life. Automotive G2 etc. last much longer. 2 bucks at Walmart.

 

[skyliner]

i dont know anything about rockport but i get my fuel filters from west marine 2.50 a peice work good and i ve had problems with putting them on upside down

 

[Ghost0]

Here is an attempt to explain why filter orientation does make a difference.

 

[Ghost0]

Now onto "Ram Air". Having worked on Formula and GT racing cars as well as having experience in wind tunnel testing here are a few facts on air intakes. To get an advantage from an air intake it needs to be designed similar to the attached photo. Notice that the inlet is of relatively small diameter and leads to a very large box. The effect here is to turn velocity into pressure. As air flows into the small intake at high speed and transitions into the larger portion of the box the flow slows down but the pressure increases. Increased pressure is what you want so that as the carb opens there is air pressure forcing air into the carb.

It is also necessary to have an air filter that will not impede the air flow. The foam filters will negate any effect of this increased pressure. No filter would be the best but not practical. A large K&N type however would work as it has the needed surface area and virtually no restriction to air flow.

On these engines at these speed there would be little to be gained by doing this. With the properly designed air box at speeds above 35 mph there may be a small gain but then we need to properly jet the carb.

 

[Cabinfever1977]

the stock air filter plastic housing leaks a little oil/gas from blow back after shutting off.
so i now use a rubber boot hose that fits tight around the end of the carb and it hooks to a aluminum pipe with a filter on the end,i have this pointed toward the rear of bike.
with this setup the engine is more quiet,the airfilter stays clean longer and still performs great.