Re-jetted the 250 Hibird today...WoW

allenr · 04-01-2009, 01:19 AM

I cleaned up the exhaust yesterday; I cut the front pipe in half and ripped all the metal packing out then welded it back together. Got rid of all the smog stuff.( tubing and secondary breather etc.). Next I cut about 2" off the end of the can and cleaned that all out then put the stainless tip back on with self tapping screws.
Next I took the air box out and drilled about 100 3/8" holes in it then lined it with screen. It ran better but still not like a 250.
This morning I took the carb off and pulled the jets. Main was #102 and slow jet was #38. Honda didn't have any; actually he quit paying attention as soon as I said Chinese. Local Lifan dealer wanted to sell me a cruiser but they didn't have any jets. Suzuki/Kawi dealer had a #110 main and a #45 slo jet; not what I would have chosen but the only ones that were even close.(they were Mikuni) I told him they were for a Honda

When I got home, I installed the jets, set the needle clip to the middle notch, set the air/fuel to 2 turns out and installed the carb. I then started it and warmed it a little then smoothed the idle a bit with the air/fuel screw. WoW is all I can say; now it runs like a 250. No hesitation or bogging, throttle response is good all the way to top end. Its easy to get the front wheel up in 1st. a little harder 2nd. but not too hard. Actually I was pretty surprised. I was thinking I should use a #108 and a #40 but I accidentally nailed it first try with the only two jets they had. The only side effect is it will pop sometimes when I get off the throttle. It started doing this when I removed the emissions crap. Sounds kinda cool and the plug is clean so I'm gonna leave it off and try some other things.
Sorry this is so long I just thought I would let ya know what worked for me.

Weldangrind · 04-01-2009, 02:04 AM

Sounds like great progress.

I'd be inclined to go bigger than 110; the popping might indicate that it is still on the lean side. You could continually increase until either the power drops or the plug turns black, and then back off a size.

You'll not likely burn it up if the carb is too rich, but too lean is risky.

Good luck.

allenr · 04-01-2009, 02:54 AM

Thanks for the info Weldangrind. I'll order 3 or 4 more from jetsrus. its obvious that I'm not going to find any local.

You said: I'd be inclined to go bigger than 110

czowner · 04-01-2009, 03:50 AM

The popping noises from the exhaust on the over run is most likley because the pipe has been de-restricted. My MuZ Skorpion (660cc single) with a race can was more like a series of small explosions on the over run.

Jonathan.

forchetto · 04-01-2009, 04:46 AM

I've always been told that popping back in the exhaust was caused either by air leaks somewhere into the exhaust system or an over-lean idle mixture. Try tweaking the idle screw about 1/8 th of a turn clockwise if a slide carb or anticlockwise if a CV type carb.

Leaking exhaust joints can often be felt running a hand around the joints or looking for the tell-tale scorch or carbon marks.

Cal25 · 04-01-2009, 12:28 PM

My hibird 250 came with a 105 main. I did about the same mods as you did and re-jetted the main at 115 to start. Ended up where you are at a 110 jet. Never changed the pilot jet.

It added enough hp to increase the top speed about 5 mph. I was pleased with the results. It felt a little more powerfull at lower speeds but thats subjective with no way to prove or dis-prove the results.

Dragon · 04-01-2009, 12:29 PM

What's your MPG after rejetting?

Cal25 · 04-01-2009, 12:33 PM

Mine remained at 50mpg or pretty close. Not sure why the mileage is so low compred to other bikes. Then again, I live out in the country and alot of my time is spent at close to WOT down Farm to Market roads.

Dragon · 04-01-2009, 12:38 PM

Mine stock Hi Bird 250 gives 70 MPG, based on the odometer. I think it's closer to 55-60 actual MPG.

Cal25 · 04-01-2009, 12:42 PM

Mine was 70 on the stock odometer also. One of the reasons for doing away with it. By my calculations the mileage was off by 40%

allenr · 04-01-2009, 04:02 PM

cal25, mine is way better than before. It ran ok before but now it runs really good. It runs 75 on the interstate without any problem but pulls down to about 60-65 on moderate hills.

clocked 52 miles on the odometer; filled back up and it took 6/10gal.

Cal25 · 04-01-2009, 04:51 PM

Yep, It is for sure a worthwile modification. Are you still usinf the factory speedo? Your mileage figures to about 72.8 mpg. Thats about the same as Snake is getting and I was getting on the stock odometer.

Acording to my temp sensor, the cylynder head temp was a little lower as well after removing the crap in the pipe.

allenr · 04-01-2009, 10:41 PM

Yeah still the factory speedometer. BTW: I messed with the air screw and got rid of most of the popping. Still does it if I get on it hard then let off quickly but not during normal driving.

Yep, It is for sure a worthwile modification. Are you still usinf the factory speedo?

Cal25 · 04-02-2009, 08:05 AM

I have a Trail Tech Vapor installed. Someone on here a few weeks ago pointed out a bike computer on Ebay that does everything but the tach and its lots cheaper.

Weldangrind · 04-02-2009, 10:25 AM

Quote:

Originally Posted by Cal25

Acording to my temp sensor, the cylynder head temp was a little lower as well after removing the crap in the pipe.

I'd like to hear more about your temp sensor; is it a stock item or did you add it? Do you have a photo?

Sorry for the thread hijack...

04-01-2009, 02:04 AM	#2
Weldangrind Join Date: Mar 2009 Location: Sardis, BC, Canada Posts: 25,977	Sounds like great progress. I'd be inclined to go bigger than 110; the popping might indicate that it is still on the lean side. You could continually increase until either the power drops or the plug turns black, and then back off a size. You'll not likely burn it up if the carb is too rich, but too lean is risky. Good luck. __________________ Weldangrind "I figure I'm well-prepared for coping with a bike that comes from the factory with unresolved issues and that rewards the self-reliant owner." - Buccaneer
	0

04-01-2009, 04:46 AM	#5
forchetto Join Date: Jul 2008 Location: Gijon, Asturias,Northern Spain Posts: 396	I've always been told that popping back in the exhaust was caused either by air leaks somewhere into the exhaust system or an over-lean idle mixture. Try tweaking the idle screw about 1/8 th of a turn clockwise if a slide carb or anticlockwise if a CV type carb. Leaking exhaust joints can often be felt running a hand around the joints or looking for the tell-tale scorch or carbon marks. __________________ Jincheng Monkey JC50Q-7 (two of them) Skyteam Dax replica ST110-6 (two of them) Zongshen ZS125-43 Qingqi QM200GY-BA Super Motard Yamaha Virago XV1100 Triumph Bonneville SE Qingqi QM110GY PGO Bug rider 250 Buggy
	0

04-01-2009, 12:29 PM	#7
Dragon Join Date: Nov 2007 Location: Tejas Posts: 834	What's your MPG after rejetting? __________________ Chinabikeless
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04-01-2009, 12:38 PM	#9
Dragon Join Date: Nov 2007 Location: Tejas Posts: 834	Mine stock Hi Bird 250 gives 70 MPG, based on the odometer. I think it's closer to 55-60 actual MPG. __________________ Chinabikeless
	0

04-01-2009, 01:19 AM	#1
allenr Join Date: May 2008 Posts: 22	Re-jetted the 250 Hibird today...WoW I cleaned up the exhaust yesterday; I cut the front pipe in half and ripped all the metal packing out then welded it back together. Got rid of all the smog stuff.( tubing and secondary breather etc.). Next I cut about 2" off the end of the can and cleaned that all out then put the stainless tip back on with self tapping screws. Next I took the air box out and drilled about 100 3/8" holes in it then lined it with screen. It ran better but still not like a 250. This morning I took the carb off and pulled the jets. Main was #102 and slow jet was #38. Honda didn't have any; actually he quit paying attention as soon as I said Chinese. Local Lifan dealer wanted to sell me a cruiser but they didn't have any jets. Suzuki/Kawi dealer had a #110 main and a #45 slo jet; not what I would have chosen but the only ones that were even close.(they were Mikuni) I told him they were for a Honda When I got home, I installed the jets, set the needle clip to the middle notch, set the air/fuel to 2 turns out and installed the carb. I then started it and warmed it a little then smoothed the idle a bit with the air/fuel screw. WoW is all I can say; now it runs like a 250. No hesitation or bogging, throttle response is good all the way to top end. Its easy to get the front wheel up in 1st. a little harder 2nd. but not too hard. Actually I was pretty surprised. I was thinking I should use a #108 and a #40 but I accidentally nailed it first try with the only two jets they had. The only side effect is it will pop sometimes when I get off the throttle. It started doing this when I removed the emissions crap. Sounds kinda cool and the plug is clean so I'm gonna leave it off and try some other things. Sorry this is so long I just thought I would let ya know what worked for me.
	0

04-01-2009, 02:54 AM	#3
allenr Join Date: May 2008 Posts: 22	Thanks for the info Weldangrind. I'll order 3 or 4 more from jetsrus. its obvious that I'm not going to find any local. You said: I'd be inclined to go bigger than 110
	0

04-01-2009, 03:50 AM	#4
czowner Join Date: Sep 2006 Location: North East England Posts: 313	The popping noises from the exhaust on the over run is most likley because the pipe has been de-restricted. My MuZ Skorpion (660cc single) with a race can was more like a series of small explosions on the over run. Jonathan.
	0

04-01-2009, 12:28 PM	#6
Cal25 Join Date: Feb 2008 Location: Terrell and Grapevine Tx. Posts: 1,585	My hibird 250 came with a 105 main. I did about the same mods as you did and re-jetted the main at 115 to start. Ended up where you are at a 110 jet. Never changed the pilot jet. It added enough hp to increase the top speed about 5 mph. I was pleased with the results. It felt a little more powerfull at lower speeds but thats subjective with no way to prove or dis-prove the results.
	0

04-01-2009, 12:33 PM	#8
Cal25 Join Date: Feb 2008 Location: Terrell and Grapevine Tx. Posts: 1,585	Mine remained at 50mpg or pretty close. Not sure why the mileage is so low compred to other bikes. Then again, I live out in the country and alot of my time is spent at close to WOT down Farm to Market roads.
	0

04-01-2009, 12:42 PM	#10
Cal25 Join Date: Feb 2008 Location: Terrell and Grapevine Tx. Posts: 1,585	Mine was 70 on the stock odometer also. One of the reasons for doing away with it. By my calculations the mileage was off by 40%
	0

04-01-2009, 04:02 PM	#11
allenr Join Date: May 2008 Posts: 22	cal25, mine is way better than before. It ran ok before but now it runs really good. It runs 75 on the interstate without any problem but pulls down to about 60-65 on moderate hills. clocked 52 miles on the odometer; filled back up and it took 6/10gal.
	0

04-01-2009, 04:51 PM	#12
Cal25 Join Date: Feb 2008 Location: Terrell and Grapevine Tx. Posts: 1,585	Yep, It is for sure a worthwile modification. Are you still usinf the factory speedo? Your mileage figures to about 72.8 mpg. Thats about the same as Snake is getting and I was getting on the stock odometer. Acording to my temp sensor, the cylynder head temp was a little lower as well after removing the crap in the pipe.
	0

04-01-2009, 10:41 PM	#13
allenr Join Date: May 2008 Posts: 22	Yeah still the factory speedometer. BTW: I messed with the air screw and got rid of most of the popping. Still does it if I get on it hard then let off quickly but not during normal driving. Yep, It is for sure a worthwile modification. Are you still usinf the factory speedo?
	0

04-02-2009, 08:05 AM	#14
Cal25 Join Date: Feb 2008 Location: Terrell and Grapevine Tx. Posts: 1,585	I have a Trail Tech Vapor installed. Someone on here a few weeks ago pointed out a bike computer on Ebay that does everything but the tach and its lots cheaper.
	0