2021 DLX 250 EFI to Carb Conversion

[John Holifield]

Is it possible to convert an EFI Hawk DLX 250 to Carb? Ever since I purchased this bike it has run extremely lean (bad) with no way to fix this issue. Since this bike has a lot in common with the standard 250, how difficult would it be to convert it to carb?

[Thumper]

Originally Posted by John Holifield

Is it possible to convert an EFI Hawk DLX 250 to Carb? Ever since I purchased this bike it has run extremely lean (bad) with no way to fix this issue. Since this bike has a lot in common with the standard 250, how difficult would it be to convert it to carb?

The whole point of EFI has always been to reduce emissions. But you have no control over fuel-air mixture (jetting!). You should be able to disconnect the EFI module and replace the carb with a standard PE28 and rejet it properly. It will run better. Oh, and if you take it into the mountains, you may need to rejet down to reduce fuel input, but you will be 100% in control.

[JFOlivier]

I doubt that it would be as easy as fitting a carb to the intake, there is also the matter of the ignition system which is run by the ECU. So I think besides the carb you will also have to put in a sepparate CDI or else the ECU will just shut you down if all its signals do not compute within its working range.

[TominMO]

And what about the fuel pump in the gas tank? Will gas just come out of the EFI setup's petcock via gravity as it would on a carby?

[Mudflap]

May be unrelated but my EFI scooter was running lean until I put a 100 ohm resistor in series with the cylinder head thermistor. I suspect that fools the computer into thinking the engine is colder than it is so it squirts in more fuel. Made a big difference. Might give it a try.

[Thumper]

Originally Posted by Mudflap

May be unrelated but my EFI scooter was running lean until I put a 100 ohm resistor in series with the cylinder head thermistor. I suspect that fools the computer into thinking the engine is colder than it is so it squirts in more fuel. Made a big difference. Might give it a try.

Based on these comments, seems like the best answer is to work on modifying the EFI. A full conversion to carbed system is possible, but doesn't sound easy. Good luck. I know some people are lucky with EFI systems, but when it doesn't work, you are left scratching your head for answers.

[Teklock]

Doesn't this bike have the Delphi MT05 ECU? If so, it can be tuned pretty easily.

[Thumper]

Motocheez has a video on youtube using something called HUD ECU hacker. Looks a bit complicated, but he gets through it. It is called

"Tuning the Hawk DLX Dlephi EFI computer with HUD ECU Hacker and a test drive. Broken speedo"

And there is another called
"Yoshua's Hawk DLX 250 EFI Mods and upgrades, personal touches and ideas."

[JFOlivier]

ECU hacker seems to hit a brick wall with the lifan ECU's, all you can see is the running information and cannot download a bin file.

[John Holifield]

I appreciate the replys! I found motocheez YouTube vid yesterday and am gonna try that first. I'll keep everyone updated

From my understanding I would:
1) have to purchase and install a carb plus tune it
2) purchase the CDI box
3) replace the fuel pump for whatever the carbed 250 uses along with the petcock valve
4) most likely the wiring harness for everything to work

I'd rather use a tune that motocheez has used and see if that will just make this pos run correctly. I'm not interested in doing 100 mph just being able to rely on this pos to run correctly

[robertj1984]

Hey I accidentally burned my $500 ecu up on my hawk 250… soooo yes I ordered one of those wire harness kits off of Amazon so I would have connections… and yes hooked my 11 pile stator to a 6 point cdi and ran the lights and signals etc off of the fused power wire put a 34 mm carb.. I believe it runs better than it ever did when fuel injected.. I have shave the head .75 ported and polished intake and exhaust.. took the cat out well spark arrest… I have a muffler though sort of lol… I have hit 85mph .. and drive it from lake Cumberland my to Cincinnati Ohio.. it needs an oil cooler I change oil often… 500 miles .. I’ve put over 3k on it…

[robertj1984]

I hooked the stator to the rectifier .. to charge battery.. and the pulse coil to cdi along with batttery and kill switch.. if you have a basic understanding of circuits.. you should be able to pull it off…

[robertj1984]

I ordered a 3.5 gallon tank from Amazon and a different seat.. all together 300 dollars

[Icj2]

Would you share a link for the gas tank you were able to fit? I'm doing the same conversion and was trying to gravity feed with the original tank that have the gas pump. But I can't get a good stream

[alex_in_az]

Originally Posted by robertj1984

Hey I accidentally burned my $500 ecu up on my hawk 250… soooo yes I ordered one of those wire harness kits off of Amazon so I would have connections… and yes hooked my 11 pile stator to a 6 point cdi and ran the lights and signals etc off of the fused power wire put a 34 mm carb.. I believe it runs better than it ever did when fuel injected.. I have shave the head .75 ported and polished intake and exhaust.. took the cat out well spark arrest… I have a muffler though sort of lol… I have hit 85mph .. and drive it from lake Cumberland my to Cincinnati Ohio.. it needs an oil cooler I change oil often… 500 miles .. I’ve put over 3k on it…

the speedo might have said 85, but you'd need about 20bhp at the rear wheel to do 85