Help With a Simple Modification

schwinnsidewinder · Jun 19, 2009

It's been a long while since I've been here but I have now got my bike set up almost perfectly.

Just in case you want to know what I've built, (otherwise skip to the next paragraph) I had a 2006 Schwinn sidewinder bicycle which has been converted into a motorcycle (yes, that's right, motorcycle, not motorised bicycle! r.ly.

) using a 66cc two-stroke, mid-mouted chain-drive with a homemade gearbox (2-speed). Everything has been painted and all of the parts in the kit that are junky by nature (bolts, studs, etc) have been replaced. It has been given the full motorcycle treatment as well (two mirrors from an old HD, a headlight, taillight and analog speedo/odo from a moped). The frame is reinforced and the wheels were pulled from a 26'' dirtbike. Spark and sparking cable from an old British two-stroker, and all cables from mopeds. Small 1-litre reserve tank under the main tank and a full toolkit inside a bag mounted on the bars. 0-30mph about 25 secs, top speed 37. Due to the extremely modified nature of this... thing... I've built, it had to be classified as a "vintage motorcycle". Therefore I don't need registration and can travel with it wherever I want, but a policeman can pull me over and issue a ticket.

The little motorcycle runs very well and pulls nicely, corners well, has no vibration problems and is very stable.

But there is one more thing before it's perfect... a frontal-intake (forced induction) mod. In other words something like the mod Cabinfever did here: (apparently I can't post links... sorry) I need to do this seriously on the cheap- I have spent my entire budget down to the last $5 (but I still feel the need to do it... laff

). Is there any reliable way to make one of these without spending anything? For example, a rubber boot from a dirtbike suspension lead, a piece of black PVC pipe and zip ties?

Thanks alot for any help (and listening to me ramble on about my little vehicle

)

Norman · Jun 20, 2009

want real ram air then turn your cylinder around puts the intake into the air stream but your not going to get any forced air until your up to a speed over over 60mph or faster. I did the backwards engine thing and it will work fine just some grinding on the cylinder transfer ports and a custom intake and exhaust. A land speed record bike was built this way I'm told. cooling isn't a problem either.
Norman

Cabinfever1977 · Jun 20, 2009

i would have liked to turn my engine around but my way was cheaper,easier and less time.
i used a rubber boot from a bike front fork shock,any one that will stretch over the end of the carb will do. and i used a 6" aluminum pipe, but plastic will work too.
i stretched the rubber boot over the end of the carb and slid the other end of the boot over a pipe and taped together with black tape and swiveled the pipe around the engine to point toward front of bike and used a plastic tie tied to clutch cable. and if you want you can put a filter on the end of the pipe,but i didnt yet.i am getting faster acceleration and overal top speed.

im thinking of putting a filter between the pipe and rubber boot.

rsdoherty88 · Jun 20, 2009

If there is any difference in power it's due to the length of the intake pipe. By making it so long and narrow it increases the velocity into the carburetor. You're not going to be getting any ram air effect until well over 60mph. So, don't think you're forcing air into the engine. It sucks in air in a lot faster than you going 35mph.

Cabinfever1977 · Jun 20, 2009

well then lets forget about the ram air effect,its getting plenty of air for sure which helps with faster acceleration and speed.it also helps to quiet the engine down.

its faster than when i was using the stock air filter plastic thingy because the air filter in stock location used to get clogged with alot of gas/oil blowback.so just moving the filter away from the carb will keep it from getting clogged as much.

xlite · Jun 21, 2009

I noticed that temporarily taking the filter off sometimes results in noticeable increase in power but throws the mixture off (lean). However I don't think forced air works with these carbs unless the entire carb is enclosed in the ram chamber which is impractical. On surplus engine forums several people tried fan induced intake pressure and the results were never beneficial.

weekend-fun · Jun 21, 2009

dude, what motor did you use? was it a shop motor, or from ,like, a old applaince ( lwan mower, rider mower? dirt bike?) i am using a chainsaw but want one that go go like a motor bike without over heating :-||

Cabinfever1977 · Jun 21, 2009

my engine came from gasbike.net and its a engine kit for a bicycle.

im not trying for forced air,i just wanted to make a airbox and move the filter.
and when i store bike in my living room, i cover the gascap and put a cork on end of pipe to keep the gas smell and fumes out of my living room.

schwinnsidewinder · Jun 23, 2009

I have made the mod- I used the rubber dirtbike lead for the enclosure/bend and a PVC for the pipe. Zip tied together. It sets off a little bit easier, which has nothing to do with any "forced induction" (maybe the length of the pipe? I don't know.) and it performs better at higher speeds. I've been riding alot lately and my engine's power has increased- top speed in 1st is 35 and top in 2nd is 43.

Fairly fast for something made from bits of whatever was lying around

.

By the way, where would I post my bike? I finally have pics of it.

Cabinfever1977 · Jun 23, 2009

i added another 6" of hose and a airfilter on the end of my pipe and tied it to my bike frame. i will post pictures after i take the bike for a ride.

update: i will be takening this hose and airfilter off,it worked better with just the rubber boot and pipe,maybe i will put a thin filter on end of pipe.

Retmachinist · Jun 23, 2009

Since you are on the subject of air flow. I have tried several variations of air breathers. I found with the K&N style breathers you can buy at the Auto parts store you are actually restricting air flow a little more than the stock air breather. It' s because of the small 20 mm bore in the breather. You can either open the bore up to 1 1/4" or build a velosity stack.
I attached a couple pictures of the velosity stack. I would have liked to make it a little larger, but you can see by the pictures I was out of room on this bike. ( OCC Chopper)

John

Cabinfever1977 · Jun 23, 2009

Ret i like that airfilter and housing you made.

xlite · Jun 24, 2009

I experimented with K&N (borrowed from Rotax airplane engines) and found they worked good on the bike as long as you kept them clean. You are supposed to use their special cleaner but it is very expensive. And they were very diffcult to mount on my bikes.

Ultimate solution was to simply cut off the bottom half of the stock air filter cover. Still hold the foam in, protects from dripping water, but gives performance close to no filter at all. Noticeable increase in power. On some engines had to move the c-clip up 1 and wondering if I should rejet.

restapukin · Aug 9, 2009

Brilliant stuff, Cabinfever. I'm - wait a minute - yeah I'm holding a rubber shocker gaiter now from a honda xr i used to own. I'd actually angle-cut the carby end of it when i came across your post.

I'm motivated solely by noise reduction considerations, by the way.

Just a couple of thoughts, my dear fellow-experimenter....

Your design already incorporates one of the most fundamental methods of air-filtration; to whit - make the airflow change direction...

(Jes' like yer nose...)
(Jes' like mercedes benz airfilters for various truck and other motors over the years)

maybe you could get more aircleaning by coating the early sections of your setup with a tacky oil... or grease may be even better... and giving the whole bizzo a good clean-out every so often...

perhaps we should be thinking of aircleaning rather than filtration here.....

oh yeah... beware of sourcing your air from an area too near the 'throw' of either wheel... wheels throw up a lot of abrasive particulates

anyhow, great stuff, well done & blah & bore & goes on and on & on........ ZZZZZzzzzzzz

restapukin
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Help With a Simple Modification

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