RPS hawk 250 idle issues

Harmlesssphinx · 04-19-2021, 04:33 PM

From the start I have not been able to idle the bike without choke. I replaced the carburetor with the mikuni clone and I'm still running into the same issue. I'm not a mechanic so I'm hoping to find some tips and tricks to help me troubleshoot. Thank you in advance.

Bruces · 04-19-2021, 04:58 PM

What carb did you buy ?what jets does it have in it ?

Skyd · 04-19-2021, 05:01 PM

When you say you bought the mikuni clone, did you simply buy it and install it? Or did you tune it first? Proper Jetting and adjusting your idle mixture screw are for sure gonna help you out here. I'm not a carb guru, I know the basics but it's not my strength only because I haven't done alot of tuning but the basics aren't that hard.

For idle I believe your pilot jet and the mixture screw are your main points of interest.

**JerryHawk250** · 04-19-2021, 05:08 PM

Before you drive yourself nuts trying to tune the carb. Take the time and adjust the valves. They are know for being set with little to no gap from the factory. Read through the stick at the top of the dual sport section. It will have all the info you need for guidance with a new bike.

Skyd · 04-19-2021, 05:49 PM

Ahhh Good point Jerry - I always forget about that. Tight valves will make it hard to start too if you happen to be having that issue.

They should be checked and adjusted regardless of if you need to tune the carb or not so I'd go with what JerryHawk said first.

Harmlesssphinx · 04-19-2021, 07:47 PM

Thanks everyone, I'll check the valves, fingers crossed! It would make sense if an aftermarket carburetor provided the same issue.

grumpyunk · 04-20-2021, 11:12 AM

One other thing to check is open ports. Some have vacuum ports that could be disconnected "back there where you can't see...". If so, you could have excessive air being let into the intake and cause a too-lean mixture that would likely cause an unstable idle.
tom

Harmlesssphinx · 04-30-2021, 08:56 PM

So I adjusted my valves to .003 and .005 with no luck. So to be more descriptive. If I turn it off choke it sounds like it popping and it bogs down after half throttle.

Megadan · 04-30-2021, 10:02 PM

Quote:

Originally Posted by Harmlesssphinx

So I adjusted my valves to .003 and .005 with no luck. So to be more descriptive. If I turn it off choke it sounds like it popping and it bogs down after half throttle.

So, let me start with... Are you sure you are turning OFF the choke? The VM26 clones have a choke that works backwards from the stock carb. Believe it or not, this is a more common mistake that you would think.

Also, you never did answer a very important question asked by another...

What jets are in it?

Piglife · 05-01-2021, 01:08 AM

Completely agree.
1) Adjust your valves
2) Confirm choke is off (down position on Mik clone VM 26)
3) Elevation has a lot to do with jetting, you can google a jetting calculator for specific jet sizes. Your pilot jet is responsible for idle - 1/4 open throttle
Inspect your spark plug to get an idea, you want a “golden brown” color, not black (to rich) and not to lean either. If your not sure it’s safer to be a little rich than lean.
*Im at ~6700’ and am running a 98 main and 42 pilot if that helps you at all. I’m also (as of yesterday) running a NIBBI PZ 30 (connected to box not AirPod) it’s a good carb, did a little more than 100 miles on it today with no problems but for the cost difference I can’t say that it’s a ton better than the Mik clone-took a while to dial it in to.

Piglife · 05-01-2021, 01:17 AM

Quote:

Originally Posted by Harmlesssphinx

So I adjusted my valves to .003 and .005 with no luck. So to be more descriptive. If I turn it off choke it sounds like it popping and it bogs down after half throttle.

Mid throttle sounds like a needle adjustment (assuming it’s a carb issue)

...maybe? It’s definitely worth ruling out and simple enough to check.

04-19-2021, 04:33 PM	#1
Harmlesssphinx Join Date: Apr 2021 Posts: 3	RPS hawk 250 idle issues From the start I have not been able to idle the bike without choke. I replaced the carburetor with the mikuni clone and I'm still running into the same issue. I'm not a mechanic so I'm hoping to find some tips and tricks to help me troubleshoot. Thank you in advance.
	0

04-19-2021, 05:01 PM	#3
Skyd Join Date: Mar 2021 Location: New Hampshire Posts: 242	When you say you bought the mikuni clone, did you simply buy it and install it? Or did you tune it first? Proper Jetting and adjusting your idle mixture screw are for sure gonna help you out here. I'm not a carb guru, I know the basics but it's not my strength only because I haven't done alot of tuning but the basics aren't that hard. For idle I believe your pilot jet and the mixture screw are your main points of interest. __________________ 2020 RPS Hawk 250 - Build thread can be found here: http://www.chinariders.net/showthread.php?t=28374 "Do Wheelies and Forget your Feelies" "If vegetarians eat vegetables, what do humanitarians eat?" -unknown
	0

04-19-2021, 05:08 PM	#4
JerryHawk250 Moderator Join Date: Oct 2016 Location: Houma, La. Posts: 11,738	Before you drive yourself nuts trying to tune the carb. Take the time and adjust the valves. They are know for being set with little to no gap from the factory. Read through the stick at the top of the dual sport section. It will have all the info you need for guidance with a new bike. __________________ 2024 Linhai 300 ATV 4x4 2023 Lifan Lycan 250 Chopper 2023 Venom Evader 2022 Lifan KPX250 2020 Kawasaki Vulcan S (Sold) 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
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04-19-2021, 05:49 PM	#5
Skyd Join Date: Mar 2021 Location: New Hampshire Posts: 242	Ahhh Good point Jerry - I always forget about that. Tight valves will make it hard to start too if you happen to be having that issue. They should be checked and adjusted regardless of if you need to tune the carb or not so I'd go with what JerryHawk said first. __________________ 2020 RPS Hawk 250 - Build thread can be found here: http://www.chinariders.net/showthread.php?t=28374 "Do Wheelies and Forget your Feelies" "If vegetarians eat vegetables, what do humanitarians eat?" -unknown
	1

04-20-2021, 11:12 AM	#7
grumpyunk Join Date: Jul 2018 Location: nw of atlanta Posts: 169	One other thing to check is open ports. Some have vacuum ports that could be disconnected "back there where you can't see...". If so, you could have excessive air being let into the intake and cause a too-lean mixture that would likely cause an unstable idle. tom __________________ vertical and above ground - my daily goal
	1

04-19-2021, 04:58 PM	#2
Bruces Join Date: May 2018 Posts: 1,656	What carb did you buy ?what jets does it have in it ?
	0

04-19-2021, 07:47 PM	#6
Harmlesssphinx Join Date: Apr 2021 Posts: 3	Thanks everyone, I'll check the valves, fingers crossed! It would make sense if an aftermarket carburetor provided the same issue.
	0

04-30-2021, 08:56 PM	#8
Harmlesssphinx Join Date: Apr 2021 Posts: 3	So I adjusted my valves to .003 and .005 with no luck. So to be more descriptive. If I turn it off choke it sounds like it popping and it bogs down after half throttle.
	0

05-01-2021, 01:08 AM	#10
Piglife Join Date: Apr 2021 Location: New Mexico Posts: 24	Completely agree. 1) Adjust your valves 2) Confirm choke is off (down position on Mik clone VM 26) 3) Elevation has a lot to do with jetting, you can google a jetting calculator for specific jet sizes. Your pilot jet is responsible for idle - 1/4 open throttle Inspect your spark plug to get an idea, you want a “golden brown” color, not black (to rich) and not to lean either. If your not sure it’s safer to be a little rich than lean. Im at ~6700’ and am running a 98 main and 42 pilot if that helps you at all. I’m also (as of yesterday) running a NIBBI PZ 30 (connected to box not AirPod) it’s a good carb, did a little more than 100 miles on it today with no problems but for the cost difference I can’t say that it’s a ton better than the Mik clone-took a while to dial it in to. Last edited by Piglife; 05-01-2021 at 01:13 AM. Reason: Elevation*
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