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DIY Carburetor conversion- anyone done one?

Roy Gavin said:
Carbed bikes had no evap system, only tank vent was through cap.
Injected bikes were meant to vent through the evap system, so if you vent the cap the evap line can be sealed at the tank..
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Someone please help me understand why just disconnecting the tank to evaporate system line would not vent the tank to atmospheric without drilling holes in the fuel cap !
 
Landsurfer74 said:
Someone please help me understand why just disconnecting the tank to evaporate system line would not vent the tank to atmospheric without drilling holes in the fuel cap !
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You still have a hose to atmos to locate, OEM poor quality and prone to kinking and blocking, a pain to install. and has no baffle.
Unless you want the vent /OVERFLOW discharging fuel over the engine and electric, which some might consider undesirable.
Vent in cap has a labrinth to help return a little neat fuel, is quick and easy to do, removes the troublesome vent hose under the tank, and is the way the factory do it!
And you don't have to drill holes, just remove a spring and diaphragm.
 
Roy Gavin said:
You still have a hose to atmos to locate, OEM poor quality and prone to kinking and blocking, a pain to install. and has no baffle.
Unless you want the vent /OVERFLOW discharging fuel over the engine and electric, which some might consider undesirable.
Vent in cap has a labrinth to help return a little neat fuel, is quick and easy to do, removes the troublesome vent hose under the tank, and is the way the factory do it!
And you don't have to drill holes, just remove a spring and diaphragm.
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All good stuff and thank you Roy … but … I’m an Engineer so here we go …🙂 …The reason for venting the tank is to fit a carb ..which has a float bowl that will vent fuel over the engine / electrics or under the bike if there are any issues with the floats …rare but not that uncommon in my experience of carbs ..? … Would it be true that disconnecting the evaporator at the bash plate would leave a breather in place and with the spring and diaphragm removed would give parallel vents …. .. genuinely interested, not just being Mr. Awkward … 👍👍🇬🇧
 
Landsurfer74 said:
All good stuff and thank you Roy … but … I’m an Engineer so here we go …🙂 …The reason for venting the tank is to fit a carb ..which has a float bowl that will vent fuel over the engine / electrics or under the bike if there are any issues with the floats …rare but not that uncommon in my experience of carbs ..? … Would it be true that disconnecting the evaporator at the bash plate would leave a breather in place and with the spring and diaphragm removed would give parallel vents …. .. genuinely interested, not just being Mr. Awkward … 👍👍🇬🇧
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No, the Ucal float bowl overflow , and bowl bowl drain screw , discharge through a hose connected to the bottom of the bowl which goes to a low point same as the drain from the overflow channel at the tank cap
Mikuni's have a vent point too, which some folk like Guzzi put on a hose to take it a long way from the motor, but as you say some folks put either a short hose of nothing at all.
But if you have spent weeks trying to sort out a poor running Guzzi only to find the vent hose was kinked and blocked you might understand why!
 
So did you try to start the bike with the fuel cap open? If it starts easily you know where the problem is and if it doesn't start you know it isn't the problem. Seems an easy place to start before drilling holes.
 
OK chaps; my bike now starts and runs. I hesitate to say that I fixed it- you know how mysterious things can be. But I can say that after I raised the float in the carb by a fraction of a smidge, things appear to be O.K. Starting, running, that sort of thing.

I read the on-line instructions of a carb conversion marketed by a well-known Enfield business. To my surprise, all that's necessary is to unplug and tape up the electrickery attached to the fuel injection and away you go. They even show you how to disconnect the Malfunction Indicator Light, which remains on otherwise.

The carb cost AUD$56.95 (eBay), $18.23 the air filter (eBay) plus some fuel tube, a filter and a tap from the mower shop.

I used the original fuel pump mounting plate (minus pump); I had to put some spacers behind the r/h cubby hole to prevent the air filter touching it. That's all. All up less than $110.00.

The result so far is a little more grunt when climbing hills/accelerating and so on. I never go flat out, so I can't comment on top speed. No doubt I shall try different jets (currently main 122, pilot 32) in future- any advice would be welcome.
 

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I fitted the ThreeLetterAcronym carb conversion kit to my 2014 B5.
I didn’t mess with the fuel filler cap and left the tubes on the underside of the tank connected. The Amal wouldn’t carburate correctly when transitioning from the idle onto the main circuit. You could slowly open the throttle and about 2,000 rpm it would instantly die from fuel starvation.
The cure was to fit a much richer slide cutaway. Something to bear in mind if you suffer a similar problem. The Bike was able to run a rock steady idle at around 500rpm - as a very occasional party trick! The usual inlet cam mod of repositioning it by one tooth out from stock undoubtedly helped as well as offering a noticeable gain up at the top end.
 
momentmal said:
OK chaps; my bike now starts and runs. I hesitate to say that I fixed it- you know how mysterious things can be. But I can say that after I raised the float in the carb by a fraction of a smidge, things appear to be O.K. Starting, running, that sort of thing.

I read the on-line instructions of a carb conversion marketed by a well-known Enfield business. To my surprise, all that's necessary is to unplug and tape up the electrickery attached to the fuel injection and away you go. They even show you how to disconnect the Malfunction Indicator Light, which remains on otherwise.

The carb cost AUD$56.95 (eBay), $18.23 the air filter (eBay) plus some fuel tube, a filter and a tap from the mower shop.

I used the original fuel pump mounting plate (minus pump); I had to put some spacers behind the r/h cubby hole to prevent the air filter touching it. That's all. All up less than $110.00.

The result so far is a little more grunt when climbing hills/accelerating and so on. I never go flat out, so I can't comment on top speed. No doubt I shall try different jets (currently main 122, pilot 32) in future- any advice would be welcome.
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That looks like a PWK flat slide clone, my hands down favorite carb to put on Pre Unit Enfield Bullets.
 
Hello all also looking for advice.

I would like to do a carb conversion on my 2018 himalayan bs4.

Would look to use a 32mm clone carb from aliexpress. With a pod type filter.

What do you use for the inlet rubber? The one that is already part of the efi set up?

Also re fuel tap has anyone gutted the fuel pump but left the outlet in place and just fitted an inline tap?

You might of guessed looking to do as cheap as possible conversion😀

With an eye on doing a 477 big bore at some point

Cheers Dean
 
The fuel pump lower housing, sometimes called a bowl, isn't suitable for a carb conversion.
There are pre made aluminum block off plates drilled and tapped to accept a fuel shut off that take it's place

Making one from a scrap piece of steel or aluminum plate would take a couple hours but it would be fun and satisfying.

The budget friendly carb conversion way is identify what carb Hitchcock's is offering for their Himalayan conversion kit and poach a used one off the web.
 
Well, well, I have to say that after a few hundred kms, I got fed up with the fact that although the grunt factor increased noticeably, fuel consumption more or less doubled! I went to have lunch with a pal about 110 kms distant, and found I'd used nearly half a tank. So back to the efi. Not defeated, just educated, and perhaps learning to be appreciative of things as they are, not as I wish they were..
 

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momentmal said:
Well, well, I have to say that after a few hundred kms, I got fed up with the fact that although the grunt factor increased noticeably, fuel consumption more or less doubled! I went to have lunch with a pal about 110 kms distant, and found I'd used nearly half a tank. So back to the efi. Not defeated, just educated, and perhaps learning to be appreciative of things as they are, not as I wish they were..
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Something is definitely wrong. It should go twice as far on that amount of fuel.

What does the spark plug look like ?
Is there soot inside the tailpipe?
 
Roy Gavin said:
I have a good 411 factory CV you can have for postage.
Rumer has it that the were the same as fitted to some Bullets.
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That's kind, Roy, but I think I've done enough experimentation! Everyone I've spoken to says, 'Why on earth did you do that?'
I have read that early UCE Bullets had carburetors, but I'll stick with the EFI for now. Not so bad, after all.
 
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