CSC tt250 max. sustained rpms?

elkhunter338 · 08-13-2021, 11:50 PM

The 250 cc Chinese bike from CSC, max. hp at 7,000 rpms. Now that I put the off road jet kit in the bike, 2,200 miles it will rev. to 8,500 rpms.

For cruising down the road what is the realistic max. sustained rpms for a reasonably long engine life?

Mine is geared low for off road use so I sometimes take it out on back roads and to do 45 mph it's running 7k. I normally back it off to 6k.

So far at 2,200 miles the bike is running fine, the gear box is not awesome, it does not down shift unless you are moving, so you can't come up to a stop and down shift once the bike is stopped, it will often lock up and mess with clutch to get the gear box to go down into 1st. It's been like this since new and I was hoping it would get better with some use. Not so much.

franque · 08-14-2021, 02:04 AM

That's how the transmission works, it's not a problem, it's a feature; also, if you let out the clutch just a little bit, it will correctly engage into lower gears. As for rpm, 70-80% of max rpm is seen as a good rule of thumb.

Megadan · 08-14-2021, 12:44 PM

Quote:

Originally Posted by elkhunter338

the gear box is not awesome, it does not down shift unless you are moving, so you can't come up to a stop and down shift once the bike is stopped, it will often lock up and mess with clutch to get the gear box to go down into 1st. It's been like this since new and I was hoping it would get better with some use. Not so much.

It's a sequential transmission. You need to click down the gears while the shafts in the transmission are turning. Even high end bikes won't downshift through all of the gears when stopped and you often have to rock the bike and activate the clutch to get them to click down more than maybe 1 or 2 times.

When rolling to a stop, even if you don't want to rev match downshift through each gear you can simply click down while coasting/braking. This way you will also at least be in an appropriate gear in case you need to get rolling again.

As far as sustained RPM. I have put thousands of miles on CG engines by hammering them on the highway at 7000-8000rpm at near wide open throttle and never had an issue. These engines are tiny, so they aren't under a ton of stress even at 8000rpm.

Even if you eventually killed the rings and lost compression, a new cylinder, piston, and rings costs less than 200 bucks and takes a couple of hours to replace.

Dusman · 08-14-2021, 02:09 PM

In agreement with MegaDan, I also have ran the Hawk at 7-8000 RPMs for up to 2 hours straight without a break at sustained speeds of 60-72 mph on the highway without any problems. I currently run a 17/40 sprocket combination and that brings my RPMs down to about 6500-7000 when running at sustained speeds of 65-70 mph. I do this because I run on the highway more than most Hawk riders and this works well for me. These CG motors can do it. They have proven to be very durable and reliable.

elkhunter338 · 08-15-2021, 01:06 AM

thanks for the feedback and that the transmission is just normal, it works fine shifting down as the bike is moving, glad to hear it's not something that should get worse.
I won't worry about running 7k for 10-20 min in a 45 mph zone. Bike is geared low for trail use, if I recall I am running 16/56, is great from trail riding.

08-13-2021, 11:50 PM	#1
elkhunter338 Join Date: Dec 2018 Location: Oregon Posts: 81	CSC tt250 max. sustained rpms? The 250 cc Chinese bike from CSC, max. hp at 7,000 rpms. Now that I put the off road jet kit in the bike, 2,200 miles it will rev. to 8,500 rpms. For cruising down the road what is the realistic max. sustained rpms for a reasonably long engine life? Mine is geared low for off road use so I sometimes take it out on back roads and to do 45 mph it's running 7k. I normally back it off to 6k. So far at 2,200 miles the bike is running fine, the gear box is not awesome, it does not down shift unless you are moving, so you can't come up to a stop and down shift once the bike is stopped, it will often lock up and mess with clutch to get the gear box to go down into 1st. It's been like this since new and I was hoping it would get better with some use. Not so much.
	0

08-14-2021, 02:04 AM	#2
franque Join Date: Nov 2017 Location: Marseille, France -> Conakry, Guinea Posts: 1,481	That's how the transmission works, it's not a problem, it's a feature; also, if you let out the clutch just a little bit, it will correctly engage into lower gears. As for rpm, 70-80% of max rpm is seen as a good rule of thumb.
	1

08-14-2021, 02:09 PM	#4
Dusman Join Date: Jan 2018 Location: NC Posts: 219	In agreement with MegaDan, I also have ran the Hawk at 7-8000 RPMs for up to 2 hours straight without a break at sustained speeds of 60-72 mph on the highway without any problems. I currently run a 17/40 sprocket combination and that brings my RPMs down to about 6500-7000 when running at sustained speeds of 65-70 mph. I do this because I run on the highway more than most Hawk riders and this works well for me. These CG motors can do it. They have proven to be very durable and reliable.
	1

08-15-2021, 01:06 AM	#5
elkhunter338 Join Date: Dec 2018 Location: Oregon Posts: 81	thanks for the feedback and that the transmission is just normal, it works fine shifting down as the bike is moving, glad to hear it's not something that should get worse. I won't worry about running 7k for 10-20 min in a 45 mph zone. Bike is geared low for trail use, if I recall I am running 16/56, is great from trail riding.
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