Honda Spree and Elite 50 Forums

So if I don’t ride much which I don’t I always end up having to pull the vacuum line off the carb, apply negative pressure, then the bike fires up as it should and runs fine. Problem with this is when the side panels go back on its not exactly reliable.

What I’m considering doing is adding one of those primer bulbs immediately after the petcock under the seat, so I can self prime the carb with the side panels on using a primer bulb similar to whats on like a chainsaw or weedeater. Not entirely sure whether the vacuum will break when the motor stops though. Any ideas on whether that will work or not? Seen some similar posts on triumph forums but nothing with pictures or actual results.

Originally was thinking of adding it directly to the vacuum line to create the suction that I manually have to do. Just not sure it would allow the normal vacuum operation after it starts. I’d be using it to create the initial vacuum until running and not have to crank over the motor so much.

Greetings:

I did this some time (11 years?) back. A "T" fitting and a 1-way valve is needed. The 1 way valves were a feature on old Dodge Ram vans, vacuum-operating the ducts for Defrost, Dash and Feet. I'm not sure if autoparts stores still stock them. Tap into the vacuum line with the T. Then install the 1-way valve on on the vacuum line, making sure it faces the right way. Then run a short length of line you can park under the saddle somewhere. The end needs to be capped securely so no extra air gets in from the end you suck on to prime the carb.

They have primer pumps made for like snowmobiles and I guess jet skis for this purpose but the carbs have a secondary input. Wouldn’t just using a primer bulb or pump inline on the vacuum line work? Assuming air would continue to flow through the primer bulb but not entirely sure.

Adding the bulb to the end of the line would work but yeah then the input to the bulb would need to be capped everytime. Should be a way around this

Wheelman-111 wrote: ↑Fri Dec 31, 2021 7:21 pm Greetings:

I did this some time (11 years?) back. A "T" fitting and a 1-way valve is needed. The 1 way valves were a feature on old Dodge Ram vans, vacuum-operating the ducts for Defrost, Dash and Feet. I'm not sure if autoparts stores still stock them. Tap into the vacuum line with the T. Then install the 1-way valve on on the vacuum line, making sure it faces the right way. Then run a short length of line you can park under the saddle somewhere. The end needs to be capped securely so no extra air gets in from the end you suck on to prime the carb.

Greetings:

Primer bulbs are inline, and a squeeze on the bulb results in fuel being pumped through the bulb and along the line to the engine. Gravity-fed scooter carbs really don't need this, but DO need the vacuum petcock to open and allow fuel to drop into the evaporated carb bowl. I don't see how a primer bulb on the fuel line side would accomplish this, but may be worth a try. Otherwise, see above.

Wheelman-111 wrote: ↑Sat Jan 01, 2022 9:57 am Greetings:

Primer bulbs are inline, and a squeeze on the bulb results in fuel being pumped through the bulb and along the line to the engine. Gravity-fed scooter carbs really don't need this, but DO need the vacuum petcock to open and allow fuel to drop into the evaporated carb bowl. I don't see how a primer bulb on the fuel line side would accomplish this, but may be worth a try. Otherwise, see above.

Yeah I was thinking of using the primer bulb on the ‘vacuum’ line to open the diapraghm after sitting for awhile to allow fuel to flow to the carb. Similar to how you would pull the vacuum line off the intake manifold and apply negative pressure to test the petcock functionality. Normally yeah it would suck fuel from the gas tank and send it to the carb but thinking that same suction could be put on the vacuum line to open the petcock and immediately get gas to the carb to help with cold starting.

Yeah I was thinking of using the primer bulb on the ‘vacuum’ line to open the diapraghm after sitting for awhile to allow fuel to flow to the carb...

I'd have same questions as you:
1) The vacuum loss to operate valve during full throttle (or starting w/o primer bulb) may be too large to open the petcock.
2) The primer bulb may not release vacuum in a timely manner after engine shutdown.

I'm certainly curious to find out if primer bulb works.

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Years back a member used a mower type primer bulb to pressurize the carb bowl.

As long as there's still some fuel in the bowl, it forces fuel up the emulsion tube and into the carb venturi. Beyond adding the primer bulb, the member also plugged the bystarter circuit.

Link: viewtopic.php?f=3&t=26542

Yep that thread in the link you attached is exactly what I’m thinking would work. As long as it breaks siphon after shut down as to not flood the case, should be a winner. When the weather warms up I’ll start working on em again and try it.

Tried connecting a plunger/primer to the vacuum line this afternoon. If I remove the vacuum line from the carb and cover the end with my thumb the primer will open the petcock and allow fuel to flow. However, when the vacuum line is connected to the intake the primer doesn’t open the petcock. Any ideas?

It won't work hooked to the vacuum line. period.

Yeah didn’t work. I’ll be trying a tecumseh primer connected the the vent line next. If that doesn’t work, I’ll swap the vacuum one with a regular on/off valve.

Update: Removed the vent line and connected a tecumseh primer bulb via hose going up to where the petcock is for easy access. Drained the bowl then primed using the primer bulb, does not work. Maybe the user in the other thread had a different primer bulb or they are made differently now but this one does not send fuel to the carb when pushing the primer bulb connected to the vent line.