Tips/Hacks to Make Carb'd Bike Easier to Start After Sitting?

[unL33T]

My daily is a 2009 Aprilia RS125 which is a carb'd 2 stroke. If I don't ride it for about 2 weeks, it becomes very hard to start. But if I try (and often fail) and then let it sit for awhile and come back, it starts instantly.

I presume this is from the fuel evaporating from the float bowl and then it takes some time to refill once the turning engine pulls a vacuum to open the petcock.

Are there any tips or hacks I can do to prevent this? Maybe install a fuel pump or something? It's kind of annoying.

Happened just on Friday. Hadn't ridden in about a month. Wasted about 10 minutes trying to start it. Eventually the battery was so low the starter wouldn't engage. Went back inside, changed, took the car, ended up way late for work. When I got home I hit the starter and it started incredibly quickly (basically the instant I hit the button).

 

[Scuba Steve]

My daily is a 2009 Aprilia RS125 which is a carb'd 2 stroke. If I don't ride it for about 2 weeks, it becomes very hard to start. But if I try (and often fail) and then let it sit for awhile and come back, it starts instantly.

I presume this is from the fuel evaporating from the float bowl and then it takes some time to refill once the turning engine pulls a vacuum to open the petcock.

Are there any tips or hacks I can do to prevent this? Maybe install a fuel pump or something? It's kind of annoying.

Happened just on Friday. Hadn't ridden in about a month. Wasted about 10 minutes trying to start it. Eventually the battery was so low the starter wouldn't engage. Went back inside, changed, took the car, ended up way late for work. When I got home I hit the starter and it started incredibly quickly (basically the instant I hit the button).

Here what works on my 2t dirt bikes. If you lean them way over or lay them on their side fuel will start to come out the overflow once it does stand it back up, then they start right up.

Sent from the future

 

[Ash]

You should be able to replace the vacuum petcock with a manual one.

Or this part description suggests that a hard-start condition can be caused by a faulty petcock, so maybe $20 on an OEM one would fix you up:

This vacuum fuel tap is a standard wear item, and does need to be replaced periodically. Replace your fuel tap if you Aprilia has mysterious bogging, or is especially hard to start after longer periods of sitting.

OEM Aprilia Vacuum Fuel Tap -#8201824

OEM Aprilia Vacuum Fuel Tap -#8201824

www.af1racing.com

 

[Mad Mike]

My daily is a 2009 Aprilia RS125 which is a carb'd 2 stroke. If I don't ride it for about 2 weeks, it becomes very hard to start. But if I try (and often fail) and then let it sit for awhile and come back, it starts instantly.

I presume this is from the fuel evaporating from the float bowl and then it takes some time to refill once the turning engine pulls a vacuum to open the petcock.

Are there any tips or hacks I can do to prevent this? Maybe install a fuel pump or something? It's kind of annoying.

Happened just on Friday. Hadn't ridden in about a month. Wasted about 10 minutes trying to start it. Eventually the battery was so low the starter wouldn't engage. Went back inside, changed, took the car, ended up way late for work. When I got home I hit the starter and it started incredibly quickly (basically the instant I hit the button).

I second the petcock as the issue. Vacuum petcocks open when there is engine vacuum, this lets fuel flow to the carb bowl. Over time the rubber in the petcock hardens and will not let as much fuel thru, particularly with low vacuum condition during cold starting. A running engine produces lots of vacuum, so once started and warmed up the problem should disappear.

If your bike sits for weeks, fuel evaporates from the carb bowl, the petcock is not likely flowing fast enough to fill the bowl for a cold dry start.

There are 2 options:

1) Replace the petcock with an OE. A stock replacement should clear the problem for a few years.

2) Use an aftermarket high flow manual petcock. This will delete the reserve function and you may need to add another shutoff downstream if you can't access this one easily. Look at places like Treatland or Moped Army for sources.

malossi purple knob style petcock - no thread - 8mm fuel line

malossi twist knob style petcock. this cock has no thread and is for plastic tanks or other applications like that where you don't got threads. comes packaged with malossi carb kits for increased fuel flow with large carbs using 8mm fuel line. 6511990B

www.treatland.tv