Hi.
I have a Honda Vision50 and replaced the Engine with a AF18E engine. It runs great but the problem is that fuel seems to get cut off after running the highway at 50kph for about 5 mins. I use transparent hose for the fuel supply so I can clearly see no more gas flowing after several minutes of running at moderate speeds (50kph for about 5 mins).
It uses the old vacuum petcock of my Honda Vision to draw fuel from the tank. I already replaced the old petcock with a brand new one, still fuel cuts off at said speed.
What could be the problem and what can I do to solve the problem?
Here's the photo of the engine at carb side.
If you're seeing that the fuel flow from the tank to the carb is not keeping up then it seems like you would want to check your in tank filter and make sure your gas cap vent is open.
If you replaced your petcock, you probably checked the fuel strainer in the tank...
I already removed the strainer completely when i replaced the petcock, though it was not that filthy when i took it off. Good point on the float and gas tank cap.
Can I just drill a small hole in the center of the gas cap? Isn't it gonna vent gas out?
The vent in the fuel cap is to vent air in to allow fuel out. if no fuel is flowing from the tank and it flows after 5 min that gas cap could be the gremlin. Next time it goes dry just pull the gas cap and see if fuel flows.
Do the af18s Have the Vacuum nipple near the oil plug, and what about the oil pump? I can see that its still on the motor by the starter motor. IS it being used and if it isn't is it sealed? Hope all of our advice helps you bro!
That also used to happen to me when I Was using the Stock carb and airbox when I Was running a 66cc Though.I had to up the jetting since my bowl would completely empty out and wouldn't refill fast enough.
@patthesoundguy - of course the cap vent is to let air in and gas down, everyone knows that sir. i mean am i gonna loose gas through the hole if i am gonna drill a small one through? you loose gasoline through evaporation right?
@Dakine - i used the vacuum nipple just below the starter motor. connected it to the vacuum side of the petcock. so yes its sealed otherwise you'd expect the engine to run like crazy.
graphite9 wrote:that petcock needs constant vacuum. Thats what holds it open. The crankcase cycles from positive pressure, to negative. Thats causing that diaphram to open-close-open-close-open-close.
Ok. So maybe this is where i got it all wrong. I used the vacuum nipple in the crankcase. Is this why I dont get enough fuel at higher speeds? AF18s don't have vacuum nipple between the reed and carb. Where else can I get constant vacuum?
Theres no vacuum nipple on your manifold? The very bottom of the manifold? I just looked at my stock carb and I have a nipple on it. Maybe you don't though...
Oh and im sorry but What are the specs on your engine if you don't mind me asking? Is EVERYTHING completely stock?
So your on the Highway holding the throttle at a constant speed of 50kmh.. If you let go of the throttle for a little while and just baby it, throttling slightly here and there does the fuel continue to come down and the bike not shut off?
^Meaning.
If your holding the throttle as far as you can and once you hear the bike starting to bog, you let go of the throttle and just play with it VERY little bit. Does the bike still shut off and fuel not come down the line?
Oh and what is your compression at? Compression good and no leaks what so ever? Seals?
The AF18e came from a Dio and Dios have their tanks in floorboards. And no, Dios don't have vacuum nipples in the manifold. And yes this engine is all stock down to bore.
graphite9's idea of clipping the hose to hold the vacuum applied then make a test run already crossed my mind. That means clipping the vacuum hose in the crankcase as well. but is it not the same as using a gravity fed petcock? Because i already drilled a hole in my old petcock to make it free flowing, made a test run and still same problem came up.
Already lost that's why I came here. I think I have tried everything. Even attached a makeshift free-flowing tank to the carb. Same problem. That's why I came here.
"I get this question all the time so finally decided to post the answer here for all to see. Maybe some of the 808 crew can chime in.
1.) af18 right side case has the pulse generator at the front
2.) af18 uses the '87 elite se50 flywheel and stator
3.) af18 left side case has a vacuum nipple at the front (this is to faciltate the fuel pump for floorboard mounted fuel tanks)
4.) af18 uses a different right side fan shroud because of item number one listed above
5.) af18 intake tract openings are hollowed out more below the reed block
6.) af18 boost port is barely larger than an af16 (I've examined five bone stock af18 motors to confirm this and have one virgin left side case straight from the factory parts warehouse in Japan)
7.) af18 utilizes a different airbox
8.) af18 has different part numbers for the crank, piston, cylinder head and jug
9.) af18 uses a different exhaust (Dio ZX used an upgraded Goshi exhaust)
10.) af18s on ZX scoots have larger diameter pulley sheaves
I have never bothered to find out if the carbs are different, but I'm assuming they are. If you are using a gravity fed fuel system there's no reason to run an af18 over the af16 as-long-as you use an after market cylinder kit. That's all I know.
Victor"
Since graphite has the manifold. I also have the Carb and Airbox which is different then yours I think.
if no fuel is flowing from the tank and it flows after 5 min that gas cap could be the gremlin. Next time it goes dry just pull the gas cap and see if fuel flows.
