XMOTOS CRT 250 (DF250RTT) NIBBI PE28FL swap

NathanTC · 04-03-2022, 09:13 PM

ok so with the bike 100% like it comes, it can get the front tire off the ground in first only. Any other gear you would have to dump the clutch or force a wheelie.
The bike with my 230lb 6'5" self sitting up right would hold 60 mph into the wind up hill. So there is room to grow for sure

With the valves adjusted at 0.10mm and the frame cut, carb installed with a 40 pilot and 120 main, needle set one step up from the lowest point (lower into the carb) and NO AIR FILTER. EGR deleted the bike now will torque wheelie in 2nd, has some bog off idle but im sure i can tune it out once my filter gets here. This seriously woke the bike up. Now in 2nd on loose dirt you can spin the bike right out from under you, could not do that before hand.

Re-routed the crankcase vent as well... Below is a photo dump of my progress so far. Waiting on my 45* pod filter.

NathanTC · 04-03-2022, 09:14 PM

photo of the bike for reference, not much info on these at all out there, especially not the street legal one like this.

XLsior · 04-03-2022, 10:43 PM

that intake manifold looks familiar.

NathanTC · 04-03-2022, 11:25 PM

Quote:

Originally Posted by XLsior

that intake manifold looks familiar.

It's the one that came with the bike. For whatever reason they designed this bike to put the carburetor on the opposite side of the port on the head. So it's opposite of the hawk 250

XLsior · 04-04-2022, 12:01 AM

I believe it is to keep the airbox away from the exhaust side. Just got around to getting a very similar intake manifold modified for my XL185 frame clearance.

unfortunately for you that frame cross brace was an unavoidable conflict. I guess something had to give.

NathanTC · 04-04-2022, 06:34 AM

Quote:

Originally Posted by XLsior

I believe it is to keep the airbox away from the exhaust side. Just got around to getting a very similar intake manifold modified for my XL185 frame clearance.

unfortunately for you that frame cross brace was an unavoidable conflict. I guess something had to give.

Fortunately the frame is braced directly above and directly below that crossmember. So I don't believe it's going to harm anything the way it is now. When I test drove the bike I got about 3 ft of air on a jump and ran it pretty hard. Double checked to be sure that nothing moved. Should be fine just felt weird taking a sawzall to a brand new bike. Either way the improvement was worth the sacrifice.

ghostdancing · 04-04-2022, 06:50 AM

There are many alternative intake boots available on aliexpress for the nibbi pe..i would try one of them before cutting the frame..

XLsior · 04-04-2022, 08:19 AM

I don't think any alternative intake manifold options would avoid hitting that cross frame bar.

perhaps a little bit brutal/excessive on the material removed for clearance...but If that's the only tool available for the job and the user is fine with it then yo gotta do what you gotta do.

I'd agree it's still pretty strong...could always weld in a gusset/back plate later on if required.

NathanTC · 04-04-2022, 10:52 AM

The original carburetor had only 1/16" between that bar and the float bowl. I thought the NIBBI PE28FL would be a direct swap, and it would have been, but the shape of the bowl is different just enough. The bar would have had to been crushed flat to clear, bending it would also cause it to become shorter, pulling the two outsides of the frame to each other. The two gussets going to the engine case could be braced if one felt the need to. That said its rock solid and not going anywhere. I will be using this like a dirt bike, jumping and being rough on it. It will be off road much more than on. I was hard on it with my test ride and my micrometer showed absolutely no movement before and and after the ride so im sure its going to be just fine.

NathanTC · 05-10-2022, 08:59 PM

FINALLY got this carb acting as awesome as fuel injection. NO BOG at any point in the throttle and starts cold in an air conditioned garage with no help, choke anything, and even cold runs flawless.

3 different pod filters, 3 different results. None were perfect. Then i got to thinking about some of the hot rods i've built and had an "ah ha" moment.

It needed a velocity stack. Yet it needs a filter.

So the answer was a 2"-3" 45* silicone turbo boot, and a 3" ID spectre air filter. This kills the turbulence in the carb, and creates the "constant velocity" the carb requires. Something a normal pod filter alone cannot do. The jetting changed drastically with this set up as well.

With the best running pod filter (ran the same with NO filter) it used a 42 pilot and a 115 main with the needle in the # 5 position. float set dead on at 18mm. This Gave me very good throttle response and awesome power to get the front end off the ground with my 15t-40t sprocket set. The down side is i lost all power above 5,000 rpm killing my top end.
With this new set up, jetted at 42 pilot, 145 main (anything lower than 140 and there is bog from 3/4 throttle to wide open), and needle still in the #5 position, float still set dead on at 18mm, I kept the awesome throttle response and can now rev instantly to 10,000 rpm. Way to high, in neutral it revs like a 2 stroke now. Now i can hit 80mph with the wind at my back at 8500 rpm. Again, revved to high but it will do it. The vibrations above 60 mph are annoying, above 65mph the vibration is awful but seems to smooth out after 70. Harmonics maybe????

Anyway it now hangs neck and neck with my friends Honda 300L. Except i have a better 1st gear for wheelies and trail riding. His first gear sucks.

The very over sized pod filter actually fits under the plastics. .

rjirvin06 · 05-22-2023, 10:22 AM

i just got a df250rtt and i was wondering what i should look at for the exhaust. I cant find parts anywhere.
thanks,
rj

GypsyR · 05-22-2023, 01:56 PM

Nice bike. An interesting mod for the carb there. Pretty sure I would have modified the intake myself. It looks like milling it down at the flanges a bit and enlarging the bolt holes a bit so the carb would no longer sit perfectly level would do it. But that's just me looking at a couple of pictures and estimating.

I've seen enough bikes with stock and unmodified frames that broke and cracked welds I'd have to do something to replace that missing piece of frame. Whether you think it appears to have any structural value I kind of bet it does. Long term.

04-03-2022, 09:13 PM	#1
NathanTC Join Date: Mar 2022 Location: Lumberton TX Posts: 36	XMOTOS CRT 250 (DF250RTT) NIBBI PE28FL swap ok so with the bike 100% like it comes, it can get the front tire off the ground in first only. Any other gear you would have to dump the clutch or force a wheelie. The bike with my 230lb 6'5" self sitting up right would hold 60 mph into the wind up hill. So there is room to grow for sure With the valves adjusted at 0.10mm and the frame cut, carb installed with a 40 pilot and 120 main, needle set one step up from the lowest point (lower into the carb) and NO AIR FILTER. EGR deleted the bike now will torque wheelie in 2nd, has some bog off idle but im sure i can tune it out once my filter gets here. This seriously woke the bike up. Now in 2nd on loose dirt you can spin the bike right out from under you, could not do that before hand. Re-routed the crankcase vent as well... Below is a photo dump of my progress so far. Waiting on my 45* pod filter.
	0

05-22-2023, 10:22 AM	#11
rjirvin06 Join Date: May 2023 Posts: 1	df250rtt i just got a df250rtt and i was wondering what i should look at for the exhaust. I cant find parts anywhere. thanks, rj
	0

04-03-2022, 09:14 PM	#2
NathanTC Join Date: Mar 2022 Location: Lumberton TX Posts: 36	photo of the bike for reference, not much info on these at all out there, especially not the street legal one like this.
	0

04-03-2022, 10:43 PM	#3
XLsior Join Date: Aug 2020 Location: Australia Posts: 1,298	that intake manifold looks familiar.
	0

04-04-2022, 12:01 AM	#5
XLsior Join Date: Aug 2020 Location: Australia Posts: 1,298	I believe it is to keep the airbox away from the exhaust side. Just got around to getting a very similar intake manifold modified for my XL185 frame clearance. unfortunately for you that frame cross brace was an unavoidable conflict. I guess something had to give.
	0

04-04-2022, 06:50 AM	#7
ghostdancing Join Date: Jul 2021 Posts: 62	There are many alternative intake boots available on aliexpress for the nibbi pe..i would try one of them before cutting the frame..
	0

04-04-2022, 08:19 AM	#8
XLsior Join Date: Aug 2020 Location: Australia Posts: 1,298	I don't think any alternative intake manifold options would avoid hitting that cross frame bar. perhaps a little bit brutal/excessive on the material removed for clearance...but If that's the only tool available for the job and the user is fine with it then yo gotta do what you gotta do. I'd agree it's still pretty strong...could always weld in a gusset/back plate later on if required.
	1

04-04-2022, 10:52 AM	#9
NathanTC Join Date: Mar 2022 Location: Lumberton TX Posts: 36	The original carburetor had only 1/16" between that bar and the float bowl. I thought the NIBBI PE28FL would be a direct swap, and it would have been, but the shape of the bowl is different just enough. The bar would have had to been crushed flat to clear, bending it would also cause it to become shorter, pulling the two outsides of the frame to each other. The two gussets going to the engine case could be braced if one felt the need to. That said its rock solid and not going anywhere. I will be using this like a dirt bike, jumping and being rough on it. It will be off road much more than on. I was hard on it with my test ride and my micrometer showed absolutely no movement before and and after the ride so im sure its going to be just fine.
	1

05-10-2022, 08:59 PM	#10
NathanTC Join Date: Mar 2022 Location: Lumberton TX Posts: 36	FINALLY got this carb acting as awesome as fuel injection. NO BOG at any point in the throttle and starts cold in an air conditioned garage with no help, choke anything, and even cold runs flawless. 3 different pod filters, 3 different results. None were perfect. Then i got to thinking about some of the hot rods i've built and had an "ah ha" moment. It needed a velocity stack. Yet it needs a filter. So the answer was a 2"-3" 45* silicone turbo boot, and a 3" ID spectre air filter. This kills the turbulence in the carb, and creates the "constant velocity" the carb requires. Something a normal pod filter alone cannot do. The jetting changed drastically with this set up as well. With the best running pod filter (ran the same with NO filter) it used a 42 pilot and a 115 main with the needle in the # 5 position. float set dead on at 18mm. This Gave me very good throttle response and awesome power to get the front end off the ground with my 15t-40t sprocket set. The down side is i lost all power above 5,000 rpm killing my top end. With this new set up, jetted at 42 pilot, 145 main (anything lower than 140 and there is bog from 3/4 throttle to wide open), and needle still in the #5 position, float still set dead on at 18mm, I kept the awesome throttle response and can now rev instantly to 10,000 rpm. Way to high, in neutral it revs like a 2 stroke now. Now i can hit 80mph with the wind at my back at 8500 rpm. Again, revved to high but it will do it. The vibrations above 60 mph are annoying, above 65mph the vibration is awful but seems to smooth out after 70. Harmonics maybe???? Anyway it now hangs neck and neck with my friends Honda 300L. Except i have a better 1st gear for wheelies and trail riding. His first gear sucks. The very over sized pod filter actually fits under the plastics. .
	0

05-22-2023, 01:56 PM	#12
GypsyR Join Date: Feb 2023 Location: Upstate SC Posts: 276	Nice bike. An interesting mod for the carb there. Pretty sure I would have modified the intake myself. It looks like milling it down at the flanges a bit and enlarging the bolt holes a bit so the carb would no longer sit perfectly level would do it. But that's just me looking at a couple of pictures and estimating. I've seen enough bikes with stock and unmodified frames that broke and cracked welds I'd have to do something to replace that missing piece of frame. Whether you think it appears to have any structural value I kind of bet it does. Long term.
	0