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Post by shapiror06 on Sept 30, 2012 17:50:33 GMT -5
On my '86 Honda Elite 150, I recently tore down and cleaned the carb, installed new #38 and #110 jets, and installed a new inline fuel filter since there was not one from the factory. I noticed today after about a 20 minute drive, averaging some higher speeds like 55mph, the engine started choking at higher speeds, so I slowed down and returned home. I looked at the fuel filter, and it was empty.
I could be wrong, but here's my logic: since the fuel petcock is vacuum operated, and vacuum goes down at higher RPMs, If there's a large amount of air in the line or the filter, when the vacuum goes down at higher speeds it won't be able to open the petcock and allow fuel to get to the carb. However if I can bleed the air out of the line and filter, when the vacuum goes down at higher speeds it will be easier to pull fuel from the petcock through the line and into the carb.
So, how do I get the air out of the line and filter?
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Post by tz250racer on Sept 30, 2012 19:33:05 GMT -5
check your gas cap air vent
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Post by Blueboy5000 on Oct 1, 2012 5:51:55 GMT -5
Either you need a new gas tank vent (gas cap) or much more likely, a petcock/fuel pump. If you loose fuel at higher rpms, I'm betting it's the petcock.
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Post by carasdad on Oct 1, 2012 7:24:33 GMT -5
On my '86 Honda Elite 150, I recently tore down and cleaned the carb, installed new #38 and #110 jets, and installed a new inline fuel filter since there was not one from the factory. I noticed today after about a 20 minute drive, averaging some higher speeds like 55mph, the engine started choking at higher speeds, so I slowed down and returned home. I looked at the fuel filter, and it was empty. I could be wrong, but here's my logic: since the fuel petcock is vacuum operated, and vacuum goes down at higher RPMs, If there's a large amount of air in the line or the filter, when the vacuum goes down at higher speeds it won't be able to open the petcock and allow fuel to get to the carb. However if I can bleed the air out of the line and filter, when the vacuum goes down at higher speeds it will be easier to pull fuel from the petcock through the line and into the carb. So, how do I get the air out of the line and filter? Also DO NOT use the fuel filters you see in auto parts stores or the lawn n garden section. They are too big and only seem to fill half full....never seen one work right....they just don't flow fast enough without the pressure of a fuel pump. Filter should not be much larger than your thumb. Doesn't seem like a petcock or filter problem to me..cause if you have gas in the filter at the bottom....it also means you have it in your carb float bowl...or at least trying to get in there unless float is sticking. Btw vacuum goes up with engine speed. To prove this....puff lightly on your vac line.....then give a good suck on it...you will see increased vacuum = increased flow....and engines are basically 'air pumps'...so vac goes up as engine increases in speed...cause the engine is...well...an 'air pump' so to speak. If the vac got lower at high RPM's...we would all be running out of fuel above 30 mph...  Willing to bet your filter is too big...and you used an automotive or lawn tractor type as they are most readily available... |
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Post by Lukain on Oct 1, 2012 16:51:03 GMT -5
another thought is that the vac lines are poor quality and are collasping and need to be replaced.
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Post by shapiror06 on Oct 1, 2012 20:03:24 GMT -5
i think the next step is to remove the tank, and thoroughly clean the screen on the petcock and the petcock itself with carb cleaner. I did use a filter from the auto parts store, but it is as big if not smaller than my thumb, it's not a very large one.
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Post by cygnus on Oct 1, 2012 20:28:47 GMT -5
never had an issue with a filter that didn't completely fill with fuel. I like big filters because they have more surface area, and can flow more fuel than filters with less surface area... Plus they can catch more poo before they clog.
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Post by jlee on Oct 1, 2012 20:56:10 GMT -5
never had an issue with a filter that didn't completely fill with fuel. I like big filters because they have more surface area, and can flow more fuel than filters with less surface area... Plus they can catch more poo before they clog. Agree. I've always used the biggest inline filter that would fit on all my bikes - from the auto parts store. Never had an issue. You did install it between the tank and the petcock, didn't you? If you put it on the carb side, then raw gunk can flow into the petcock and block it... |
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Post by jlee on Oct 2, 2012 0:36:47 GMT -5
Here's another thought, since the fuel filter is a recent addition. If your system is gravity fed (I don't know the Honda Elite - ignore this if you have a fuel pump), make sure the outlet side of the filter is below the inlet side. If it's not, and you start sucking gas faster than gravity can feed it, you'll immediately suck air as soon as the filter starts to empty. If the outlet is at the bottom, then you won't suck air into the line unless the filter completely empties first.
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Post by carasdad on Oct 2, 2012 0:56:23 GMT -5
Here's another thought, since the fuel filter is a recent addition. If your system is gravity fed (I don't know the Honda Elite - ignore this if you have a fuel pump), make sure the outlet side of the filter is below the inlet side. If it's not, and you start sucking gas faster than gravity can feed it, you'll immediately suck air as soon as the filter starts to empty. If the outlet is at the bottom, then you won't suck air into the line unless the filter completely empties first. Excellent point... |
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Post by shapiror06 on Oct 2, 2012 16:58:01 GMT -5
Here's another thought, since the fuel filter is a recent addition. If your system is gravity fed (I don't know the Honda Elite - ignore this if you have a fuel pump), make sure the outlet side of the filter is below the inlet side. If it's not, and you start sucking gas faster than gravity can feed it, you'll immediately suck air as soon as the filter starts to empty. If the outlet is at the bottom, then you won't suck air into the line unless the filter completely empties first. The Honda Elite's are gravity fed, and I made sure the filter is more vertical than horizontal so the inlet of the filter is above the outlet. The petcock screws onto the bottom of the tank so there's no way to put the filter between the petcock and tank, it HAS to be installed after the petcock and before the carb. |
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Post by jlee on Oct 2, 2012 21:52:31 GMT -5
The Honda Elite's are gravity fed, and I made sure the filter is more vertical than horizontal so the inlet of the filter is above the outlet. The petcock screws onto the bottom of the tank so there's no way to put the filter between the petcock and tank, it HAS to be installed after the petcock and before the carb. Ok, that's copastetic. Was just trying to eliminate as many variables as possible, but it sounds like you've got it covered. |
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Post by someoneinnc on Oct 2, 2012 22:20:50 GMT -5
im putting my money on a leaking vacume to petcock or bad petcock itself....
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Willing to bet your filter is too big...and you used an automotive or lawn tractor type as they are most readily available... 