Brozz 250 refuses to go over 6500rpm. Thoughts appreciated!

Marc Hufnagel · 07-26-2021, 10:36 PM

Ok I have a 2020 Brozz 250 with about 65 miles on it.
Stock carb ,Stock exhaust, stock airbox. Came with a 98 jet.

I'm at 500 ASL. I did a 100 jet drilled out to 110, needle in 2nd position.

valves .003/.005 in/out choke fully off and warmed up.

I can get up to 18 or so in 1st, 6500 is the wall for the engine. Just refuses to rev in N over that, or over 6500 out on the road no matter the gear.

Thoughts on where should I start? A local guy who does a lot of work on bikes says he thinks it's ignition related. Plug replaced with a fresh NGK, gapped properly.

gwowzer · 07-26-2021, 10:40 PM

Make sure you do a proper valve adjustment with a cold engine, your choke is in fact off after getting the bike running, and then get back to us. Nobody can help until you've made sure that is a completed job.

Marc Hufnagel · 07-26-2021, 10:44 PM

Quote:

Originally Posted by gwowzer

Make sure you do a proper valve adjustment with a cold engine, your choke is in fact off after getting the bike running, and then get back to us. Nobody can help until you've made sure that is a completed job.

Yes .003 and .005 in/out. Choke is indeed off. Updated post.

Bill Hilly · 07-27-2021, 09:11 AM

They must have changed carbs, or at least carb set up during the 2020 year. Mine came with a 105 main jet, and a needle that was non adjustable except by shimming.

TxTaoRider · 07-27-2021, 09:41 AM

Maybe replace the main jet with a mikuni 110 instead of the drilled out one. They are only a few bucks.

franque · 07-27-2021, 11:33 AM

What's the air filter look like? It could be if it's a bit clogged that it's limiting the engine's ability to breathe.

herbie · 07-27-2021, 11:58 AM

65 miles is nothing, give it a little time to break in, most recommend 500 miles. The carb main jet should have come with a 105 like Bill Hilly said, if indeed it does have a 98, I would buy a jet kit and put a 105 or 110 in it. What's your top speed as indicated on the speedometer? It should do around 69-70 which is GPS about 64-65mph.

2LZ · 07-27-2021, 12:00 PM

Quote:

Originally Posted by herbie

65 miles is nothing, give it a little time to break in, most recommend 500 miles..

Zakkly. These things are super-tight out of box.

stewbrash · 07-27-2021, 05:14 PM

I have almost 400 miles on the BSR and I have never had a problem 'revving' it up - noticeably so after I installed my tach, I regularly take the rpm's up to 7500 if I'm accelerating out of the way of approaching danger! (Big Trucks, People Texting etc...) I did have a bad CDI on my Z50 that wouldn't let it rap out. Here is a pic of just blipping the throttle. If you could put on an inline spark tester and see if it is still sparking at 6500, that would be a big help in determining whether it's fuel or spark related.

https://www.harborfreight.com/90-in-...0aAsqrEALw_wcB

Marc Hufnagel · 07-27-2021, 08:24 PM

OK all, here is something to maybe work with. A local cycle shop guy substituted a drilled-out (10) holes in the lid for my solid one. It seems to run much better.

So getting more air makes it run lots better; but this bike was made to run all stock with a solid lid. What do I need to be looking at to allow me to go back to my own lid and have it run like it is at the moment with the 'holey' lid.

110 jet, stock primary. Not sure on mixture screw setting.

franque · 07-27-2021, 10:44 PM

It sounds like you're jetted rich, or there's a restriction in the airbox, like maybe the snorkel is crushed?

herbie · 07-28-2021, 10:24 AM

Somethings just doesn’t sound right to me; a 98 main jet, jet needle in second position when there is no adjustment on the stock needle, drilling holes in the air box lid when it has a removable snorkel that leaves a big hole when removed

stewbrash · 07-28-2021, 03:04 PM

If you have eliminated the 'spark', or a bad CDI then it must be a fuel related issue. 3 things come to mind, 1 - a partially clogged fuel delivery system, either a clogged filter, or something in the tank blocking gas to pass through the on/off valve. 2 - a particle stuck in your main jet, limiting the amount of fuel. 3 - a mis-adjusted float-bowl, closing at too low a setting to supply enough fuel at 6500 RPM. I'm sure there could be other reasons.

07-26-2021, 10:36 PM	#1
Marc Hufnagel Join Date: Jul 2021 Location: Southern Illinois. Posts: 33	Brozz 250 refuses to go over 6500rpm. Thoughts appreciated! Ok I have a 2020 Brozz 250 with about 65 miles on it. Stock carb ,Stock exhaust, stock airbox. Came with a 98 jet. I'm at 500 ASL. I did a 100 jet drilled out to 110, needle in 2nd position. valves .003/.005 in/out choke fully off and warmed up. I can get up to 18 or so in 1st, 6500 is the wall for the engine. Just refuses to rev in N over that, or over 6500 out on the road no matter the gear. Thoughts on where should I start? A local guy who does a lot of work on bikes says he thinks it's ignition related. Plug replaced with a fresh NGK, gapped properly.
	0

07-27-2021, 09:41 AM	#5
TxTaoRider Join Date: Oct 2020 Location: Flower Mound Texas Posts: 904	Maybe replace the main jet with a mikuni 110 instead of the drilled out one. They are only a few bucks. __________________ 2021 Tao Tbr7 - "Lucille" Mods so far- Brozz swingarm, 21" front rim (Bridgestone Tw302 rear/Dunlop D606 front tires), Digital gauge cluster, pz30b pumper carb, after market hand guards, aftermarket brake and clutch levers, round fold away mirrors, Fly handlebars shortened slightly, 13t front sprocket 2009 Q-link Legacy 250 1982 Suzuki GS1100ES - "Jolene"
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07-27-2021, 11:58 AM	#7
herbie Join Date: May 2019 Location: Illinois Posts: 864	65 miles is nothing, give it a little time to break in, most recommend 500 miles. The carb main jet should have come with a 105 like Bill Hilly said, if indeed it does have a 98, I would buy a jet kit and put a 105 or 110 in it. What's your top speed as indicated on the speedometer? It should do around 69-70 which is GPS about 64-65mph. __________________ 2022 Venom KPR 200 Red- the fastest color 16t and 46t sprockets, NGK Iridium CPR8EAIX-9, aftermarket full exhaust system. Top speed 81GPS 2023 Venom SS3 KP mini 150– Nibbi carb, Nibbi air filter, aftermarket muffler, decat 2022 Venom Ghost chopper 250 1997 Honda GL1500 Goldwing 1978 Kawasaki KL250 https://youtube.com/@herbiesgarage681
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07-28-2021, 10:24 AM	#12
herbie Join Date: May 2019 Location: Illinois Posts: 864	Somethings just doesn’t sound right to me; a 98 main jet, jet needle in second position when there is no adjustment on the stock needle, drilling holes in the air box lid when it has a removable snorkel that leaves a big hole when removed __________________ 2022 Venom KPR 200 Red- the fastest color 16t and 46t sprockets, NGK Iridium CPR8EAIX-9, aftermarket full exhaust system. Top speed 81GPS 2023 Venom SS3 KP mini 150– Nibbi carb, Nibbi air filter, aftermarket muffler, decat 2022 Venom Ghost chopper 250 1997 Honda GL1500 Goldwing 1978 Kawasaki KL250 https://youtube.com/@herbiesgarage681 Last edited by herbie; 07-29-2021 at 07:10 AM.
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07-26-2021, 10:40 PM	#2
gwowzer Join Date: Aug 2019 Location: Central Ohio Posts: 297	Make sure you do a proper valve adjustment with a cold engine, your choke is in fact off after getting the bike running, and then get back to us. Nobody can help until you've made sure that is a completed job.
	0

07-27-2021, 09:11 AM	#4
Bill Hilly Join Date: Feb 2021 Posts: 948	They must have changed carbs, or at least carb set up during the 2020 year. Mine came with a 105 main jet, and a needle that was non adjustable except by shimming.
	0

07-27-2021, 11:33 AM	#6
franque Join Date: Nov 2017 Location: Marseille, France -> Conakry, Guinea Posts: 1,481	What's the air filter look like? It could be if it's a bit clogged that it's limiting the engine's ability to breathe.
	0

07-27-2021, 08:24 PM	#10
Marc Hufnagel Join Date: Jul 2021 Location: Southern Illinois. Posts: 33	OK all, here is something to maybe work with. A local cycle shop guy substituted a drilled-out (10) holes in the lid for my solid one. It seems to run much better. So getting more air makes it run lots better; but this bike was made to run all stock with a solid lid. What do I need to be looking at to allow me to go back to my own lid and have it run like it is at the moment with the 'holey' lid. 110 jet, stock primary. Not sure on mixture screw setting.
	0

07-27-2021, 10:44 PM	#11
franque Join Date: Nov 2017 Location: Marseille, France -> Conakry, Guinea Posts: 1,481	It sounds like you're jetted rich, or there's a restriction in the airbox, like maybe the snorkel is crushed?
	0

07-28-2021, 03:04 PM	#13
stewbrash Join Date: Oct 2016 Posts: 405	If you have eliminated the 'spark', or a bad CDI then it must be a fuel related issue. 3 things come to mind, 1 - a partially clogged fuel delivery system, either a clogged filter, or something in the tank blocking gas to pass through the on/off valve. 2 - a particle stuck in your main jet, limiting the amount of fuel. 3 - a mis-adjusted float-bowl, closing at too low a setting to supply enough fuel at 6500 RPM. I'm sure there could be other reasons.
	0