WOT on first start of Hawk 250

Maadcat · 05-22-2019, 09:29 PM

Well,

I got the bike finally the way I wanted, with the upgraded Minkuni with a 115 jet and the new chain and sprocket, changed out the oil. Otherwise it is stock. On my first start with no choke I got what seemed like wide open throttle. I quickly shut it down. I turned the idle screw on the carb all the way in. Next start did the same thing. I checked the throttle cable and plunger and it seems like I am getting a full return on the throttle. Any other thoughts on what to check next? I don't want to blow the engine right out of the blocks....

I did search around before I posted and didn't find anything obvious..sorry if I missed a previous thread.

ChipToothy · 05-22-2019, 09:41 PM

Twist the top of the carb off and make sure the needle/spring isn’t bundled up in some way. My v26 clone has done it at least 3 times.

Megadan · 05-23-2019, 05:56 AM

racing idle on a cold start is a solid symptom of a lean idle mixture/pi;ot circuit. I see you mention a 115 main jet, but did you change the pilot jet? The proper mikuni clones come with a 20 pilot, which is too lean for these bikes. If you combine that with a too lean idle mixture setting you can end up in this scenario.

Other possible cause is a vacuum leak causing said lean condition. Throttle slide cap seal may be bad, intake seal is bad, or a tear/crack in the rubber.

My recommended Mikuni setup on an otherwise stock bike is a 25 pilot, 105 to 110 main and needle in the 4th notch down. Pretty bulletproof starting setup for a stock CG250 below 4000ft.

**JerryHawk250** · 05-23-2019, 07:29 AM

First check that the slide is closed all the way. Is there enough slack in the throttle cable to let the slide close? also check that the slide is not in backwards. (turned 180*)

2LZ · 05-23-2019, 10:24 AM

Agreed. Sounds like something isn't right with the slide. Also, check to make sure the cable sheath seats all the way down into the slide cap

Sport Rider · 05-23-2019, 11:12 AM

remember to also hold your left nut when you start it. people always seem to forget that.

Dan...Idle screw at 1 1/2 turns? 1 3/4?

Maadcat · 05-23-2019, 02:47 PM

Thank you all for the responses. In summary, I'll pull the carb and check the slide to make sure it is actually seating all of the way and the needles setting is correct. If that doesn't work it sounds like digging further into the carb and maybe changing out the pilot jet. Oh yeah, grab left nut while holding in the clutch and starting....That will be tonight's project.

2LZ · 05-23-2019, 03:25 PM

Quote:

Originally Posted by Maadcat

Thank you all for the responses. In summary, I'll pull the carb and check the slide to make sure it is actually seating all of the way and the needles setting is correct. If that doesn't work it sounds like digging further into the carb and maybe changing out the pilot jet. Oh yeah, grab left nut while holding in the clutch and starting....That will be tonight's project.

Jetting wouldn't create a WFO situation. I'm betting something's up with the slide. We actually had a member here, who was mechanically inclined, accidentally put one in backwards. Things happen.........

Maadcat · 05-24-2019, 08:44 AM

Last night I got it running! I think it was either total incompetency on my part or a combination of things. I pulled the carb, pulled the slide entirely, swapped the slide for the clone (I just left the stock slide/needle on it before), and carefully reassembled everything. However, in the process of pulling everything apart I suddenly realized that the idle adjust screw works in the reverse of how I was thinking of it. When everyone said run the screw in all the way and then back it off 1 1/2 turns, I assumed that all the way in was closing an idle air/fuel channel. I didn't realized until I looked at the slide and throat that all the way in was holding the slide open....DUH! So I ran the screw out all the way, made sure the slide was closing all the way. And give it a go. Sure enough the bike turned over and putt..putt....turned the screw in a little further....putt putt putt. A little more and the bike fired right up and idles great. So now for the burn in cycles and I'm on my way. Thanks again for everyone's help. I bought this bike to force me to learn these things. So far so good.

**JerryHawk250** · 05-24-2019, 08:50 AM

That is the idle speed screw you have been playing with on the side of the carb. The idle mixture screw is on the bottom of the carb hidden under a plastic or brass plug that you will have to remove on the stock carb. That is the screw everyone is talking about setting from seated 1 1/2 turns.

Maadcat · 05-24-2019, 10:26 AM

Quote:

Originally Posted by JerryHawk250

That is the idle speed screw you have been playing with on the side of the carb. The idle mixture screw is on the bottom of the carb hidden under a plastic or brass plug that you will have to remove on the stock carb. That is the screw everyone is talking about setting from seated 1 1/2 turns.

Yep!

Megadan · 05-24-2019, 12:56 PM

Quote:

Originally Posted by 2LZ

Jetting wouldn't create a WFO situation.

I've seen a minute vacuum leak create a racing idle (5000rpm). Might not be "WFO" but when you just start an engine and it shoots the revs up that high instantly...

05-22-2019, 09:29 PM	#1
Maadcat Join Date: May 2019 Location: Holland, MI Posts: 14	WOT on first start of Hawk 250 Well, I got the bike finally the way I wanted, with the upgraded Minkuni with a 115 jet and the new chain and sprocket, changed out the oil. Otherwise it is stock. On my first start with no choke I got what seemed like wide open throttle. I quickly shut it down. I turned the idle screw on the carb all the way in. Next start did the same thing. I checked the throttle cable and plunger and it seems like I am getting a full return on the throttle. Any other thoughts on what to check next? I don't want to blow the engine right out of the blocks.... I did search around before I posted and didn't find anything obvious..sorry if I missed a previous thread.
	0

05-22-2019, 09:41 PM	#2
ChipToothy Join Date: Apr 2018 Posts: 819	Twist the top of the carb off and make sure the needle/spring isn’t bundled up in some way. My v26 clone has done it at least 3 times. __________________ Bashan Storm: Ebay steel exhaust wrapped, folding shift lever, seat mod, vm26 carb, air pod, dual led scrambler headlamps, windshield mod, led brake/tail light, secondary led brake light (swingarm), Ebay 295mm rear shock, back up CDI (racing unknown), oil cooler, digital gauge cluster,
	1

05-23-2019, 05:56 AM	#3
Megadan Join Date: Apr 2017 Location: Omaha, NE Posts: 8,028	racing idle on a cold start is a solid symptom of a lean idle mixture/pi;ot circuit. I see you mention a 115 main jet, but did you change the pilot jet? The proper mikuni clones come with a 20 pilot, which is too lean for these bikes. If you combine that with a too lean idle mixture setting you can end up in this scenario. Other possible cause is a vacuum leak causing said lean condition. Throttle slide cap seal may be bad, intake seal is bad, or a tear/crack in the rubber. My recommended Mikuni setup on an otherwise stock bike is a 25 pilot, 105 to 110 main and needle in the 4th notch down. Pretty bulletproof starting setup for a stock CG250 below 4000ft. __________________ Hawk Information and Resource guide: http://www.chinariders.net/showthread.php?t=20331 2018 Hawk 250 - Full Mod list here. http://www.chinariders.net/showpost....62&postcount=1 2024 Royal Enfield Shotgun 650 https://chinariders.net/showthread.php?t=34124
	0

05-23-2019, 07:29 AM	#4
JerryHawk250 Moderator Join Date: Oct 2016 Location: Houma, La. Posts: 11,564	First check that the slide is closed all the way. Is there enough slack in the throttle cable to let the slide close? also check that the slide is not in backwards. (turned 180) __________________ 2023 Lifan Lycan 250 Chopper 2023 Venom Evader 2022 Lifan KPX250 2020 Kawasaki Vulcan S 2004 Honda ST 1300 2016 Black Hawk 250 (sold) Keihin PE30 carb,125 main,38 slow.Pod filter,ported & decked head 10:1 CR,Direct Ignition Coil,15/40Sprockets,NGK DPR8EIX-9,De-Cat,Dual Oil Cooler,Digital Cluster 2016 Cazador180 XL 2014 Coolster150 JerryHawk250.com* My YouTube Channel Last edited by JerryHawk250; 05-23-2019 at 08:18 AM.
	1

05-23-2019, 10:24 AM	#5
2LZ Join Date: Mar 2010 Location: Volcano, Ca Posts: 7,092	Agreed. Sounds like something isn't right with the slide. Also, check to make sure the cable sheath seats all the way down into the slide cap __________________ "Light a fire for a man, and you heat him for a day. Light a man on fire, and you heat him for the rest of his life." 2007 Suzuki DRZ400S (SM convert) 2009 Q Link XP 200 1967 BSA B25 250cc Starfire 2022 Royal Enfield Interceptor 650 2023 Royal Enfield Scram 411 1948 Royal Enfield Model G 350
	1

05-23-2019, 11:12 AM	#6
Sport Rider Join Date: Jan 2016 Location: Mooresville NC Posts: 2,041	remember to also hold your left nut when you start it. people always seem to forget that. Dan...Idle screw at 1 1/2 turns? 1 3/4?
	0

05-23-2019, 02:47 PM	#7
Maadcat Join Date: May 2019 Location: Holland, MI Posts: 14	Thank you all for the responses. In summary, I'll pull the carb and check the slide to make sure it is actually seating all of the way and the needles setting is correct. If that doesn't work it sounds like digging further into the carb and maybe changing out the pilot jet. Oh yeah, grab left nut while holding in the clutch and starting....That will be tonight's project.
	1

05-24-2019, 08:44 AM	#9
Maadcat Join Date: May 2019 Location: Holland, MI Posts: 14	Last night I got it running! I think it was either total incompetency on my part or a combination of things. I pulled the carb, pulled the slide entirely, swapped the slide for the clone (I just left the stock slide/needle on it before), and carefully reassembled everything. However, in the process of pulling everything apart I suddenly realized that the idle adjust screw works in the reverse of how I was thinking of it. When everyone said run the screw in all the way and then back it off 1 1/2 turns, I assumed that all the way in was closing an idle air/fuel channel. I didn't realized until I looked at the slide and throat that all the way in was holding the slide open....DUH! So I ran the screw out all the way, made sure the slide was closing all the way. And give it a go. Sure enough the bike turned over and putt..putt....turned the screw in a little further....putt putt putt. A little more and the bike fired right up and idles great. So now for the burn in cycles and I'm on my way. Thanks again for everyone's help. I bought this bike to force me to learn these things. So far so good.
	1