New Hawk Owner! Carb issue.

aaw611 · 06-20-2020, 06:38 PM

Hey folks, excited to be part of the Hawk community. Good thing I like to tinker. I got my Hawk assembled in the last day or two and got it running. I got the idle set where I want it but every time I revv it, the motor will race up and stay there at a few 1000 rpms. I thought that it may just be the lean nature, but it was pretty significant. I pulled the spark plug and it was fouled up (carbon from new engine?) and at the lower end of the gap range or under. I opened up the gap thinking there bay be incomplete combustion happening. I was getting black smoke out of the exhaust when revving after idle. I don't know if this was junk inside the muffler burning off, or unburned fuel. So, after this didn't fix it, I pulled the intake boot and wiped some grease around it and tightened up the carb to the intake manifold. Still didn't fix it. Is it the lean jetting, the junk plug not burning all the fuel, or some other vacuum leak? I've had lean running Japanese bikes before and they never raced at idle this bad...

Anyways, if anyone has some insight, it would be appreciated. Glad to be here!

Albert

aaw611 · 06-21-2020, 12:20 AM

May have solved the issue! I went to autozone and got a good ol' fashion NGK DPR8EA for a couple bucks and was able to take it around the block a few times! I also ditched the factory hose clamp on the intake boot and put on a new one that was more true; the factory hose clamp looked nice but it didn't put even radial pressure on the carb/boot.

aaw611 · 06-21-2020, 02:55 PM

So if anyone is following this, it is still doing it to a certain extent, but it's running better. I took it out for a few mile ride today and it wouldn't go past 30 mph with the choke off. Would make it a little bit through the rev range before sputtering and hesitating. On half choke, I was able to get up to 50+. I have a jet kit on the way!

discochris · 06-22-2020, 02:09 AM

Have you checked the valves? They're probably really tight.

Rocket tests · 06-22-2020, 04:12 AM

After checking your valve lash pull the slide from the top of your carb and make sure the needle is seated properly at the bottom of the slide and held in place with the "V" retainer clip. Also make sure the needle is straight and true. Check for binding of the throttle cable, they often get pulled out of the boot and hold the slide open a bit.

aaw611 · 06-22-2020, 12:28 PM

Yep, I did the valves and no improvement, but they were wayyy tight. Pulled the carb, shimmed the needle with a small nut, and put it back together. Runs like a champ now. I took it out for a ride on some forest service roads and she did great!

CaesarVis · 06-22-2020, 06:04 PM

I was going to suggest shimming the needle but you got it covered. I use 2 nylon washers that are about 1mm each for a total shim of 2mm. You sure your nut isn't too big?

What size is your main jet? I know the stock Hawk one is super small and should get bumped to at least 105.

aaw611 · 06-22-2020, 08:00 PM

I was a little worried the nut would be too big, but it's running pretty well. It's a very small nut for a little machine screw so it's pretty tiny. Maybe 2mm; less than 1/8 inche surely. I got a set of kehein type main jets, but they ended up being the longer hex type instead of the slotted screw type. I think the thread size is the same but they are longer than the stock jets. Will see if they work.

06-20-2020, 06:38 PM	#1
aaw611 Join Date: Jun 2020 Posts: 48	New Hawk Owner! Carb issue. Hey folks, excited to be part of the Hawk community. Good thing I like to tinker. I got my Hawk assembled in the last day or two and got it running. I got the idle set where I want it but every time I revv it, the motor will race up and stay there at a few 1000 rpms. I thought that it may just be the lean nature, but it was pretty significant. I pulled the spark plug and it was fouled up (carbon from new engine?) and at the lower end of the gap range or under. I opened up the gap thinking there bay be incomplete combustion happening. I was getting black smoke out of the exhaust when revving after idle. I don't know if this was junk inside the muffler burning off, or unburned fuel. So, after this didn't fix it, I pulled the intake boot and wiped some grease around it and tightened up the carb to the intake manifold. Still didn't fix it. Is it the lean jetting, the junk plug not burning all the fuel, or some other vacuum leak? I've had lean running Japanese bikes before and they never raced at idle this bad... Anyways, if anyone has some insight, it would be appreciated. Glad to be here! Albert
	0

06-22-2020, 06:04 PM	#7
CaesarVis Join Date: Mar 2019 Location: New Orleans, LA Posts: 54	I was going to suggest shimming the needle but you got it covered. I use 2 nylon washers that are about 1mm each for a total shim of 2mm. You sure your nut isn't too big? What size is your main jet? I know the stock Hawk one is super small and should get bumped to at least 105. Last edited by CaesarVis; 06-22-2020 at 06:04 PM. Reason: More info
	0

06-21-2020, 12:20 AM	#2
aaw611 Join Date: Jun 2020 Posts: 48	May have solved the issue! I went to autozone and got a good ol' fashion NGK DPR8EA for a couple bucks and was able to take it around the block a few times! I also ditched the factory hose clamp on the intake boot and put on a new one that was more true; the factory hose clamp looked nice but it didn't put even radial pressure on the carb/boot.
	0

06-21-2020, 02:55 PM	#3
aaw611 Join Date: Jun 2020 Posts: 48	So if anyone is following this, it is still doing it to a certain extent, but it's running better. I took it out for a few mile ride today and it wouldn't go past 30 mph with the choke off. Would make it a little bit through the rev range before sputtering and hesitating. On half choke, I was able to get up to 50+. I have a jet kit on the way!
	2

06-22-2020, 02:09 AM	#4
discochris Join Date: Apr 2020 Location: Minnesota Posts: 35	Have you checked the valves? They're probably really tight.
	0

06-22-2020, 04:12 AM	#5
Rocket tests Join Date: Mar 2020 Location: Pennsylvania Posts: 87	After checking your valve lash pull the slide from the top of your carb and make sure the needle is seated properly at the bottom of the slide and held in place with the "V" retainer clip. Also make sure the needle is straight and true. Check for binding of the throttle cable, they often get pulled out of the boot and hold the slide open a bit.
	0

06-22-2020, 12:28 PM	#6
aaw611 Join Date: Jun 2020 Posts: 48	Yep, I did the valves and no improvement, but they were wayyy tight. Pulled the carb, shimmed the needle with a small nut, and put it back together. Runs like a champ now. I took it out for a ride on some forest service roads and she did great!
	2

06-22-2020, 08:00 PM	#8
aaw611 Join Date: Jun 2020 Posts: 48	I was a little worried the nut would be too big, but it's running pretty well. It's a very small nut for a little machine screw so it's pretty tiny. Maybe 2mm; less than 1/8 inche surely. I got a set of kehein type main jets, but they ended up being the longer hex type instead of the slotted screw type. I think the thread size is the same but they are longer than the stock jets. Will see if they work.
	0