Few questions - CSC TT250 setup

danfandango · 11-01-2020, 10:31 AM

Bought my CSC TT250 just to play around with early in Covid-19. Rode it a few hundred miles over the summer and recently listed it for sale due to lack space and time primarily. May now be hanging onto it for a bit longer so I am thinking about enhancing the riding qualities a bit both for my own enjoyment and in the event that I put it back on the market next year.

To that end, I have a few questions:

I have a high idle that the bike has had since new approximately 1700 RPM and sometimes creeps up over 2K. Also, when cold, sometimes the bike won't idle with the choke on unless I bump the revs and start riding.

Is the TT250 jetted really lean out of the box and is that is that what could be causing the issue? I am due for valve checks and I figured that might be a good time to rejet, if necessary.

The pickup feels a little lackluster with "chunky" acceleration and I think a sprocket change would be warranted (possibly also compounded by bad carb setup). I don't really care about top end speed over 45MPH. What would be a good low end acceleration oriented gear setup that works with the stock chain?

The ride is a little rough in the rear - the rear shock is adjustable correct? If so, what should I set that to for 170 pound rider? I don't want to adjust any of the suspension components too much because I understand stripping is a concern on the hardware.

Thanks,

Dan

BTW, I have read through some of the stickys and apologize if I missed directly pertinent information. I know there is a lot on the sprockets, but I have never changed those out on a bike before.

danfandango · 11-02-2020, 09:05 PM

I adjusted the valves on Sunday and that seems to have helped with the idle. Planning on just changing the rear sprocket out to a 49 tooth so I don't have to modify or replace the chain and getting a jet kit directly from CSC. Think that covers it.

grumpyunk · 11-05-2020, 01:16 PM

A cold engine will likely not idle well, especially if you had to choke it to get it to fire. It will be lumpy for a minute or so, until it warms a bit. The rpms will also likely be slower than when it is warmed up. You can start with full choke, and almost immediately push the lever down to the middle detent, once started. You may have to buzz the throttle a few times to keep it running. Totally normal for a carb'd air-cooled machine.
Once warmed the idle should be solid, not lumpy, and you can adjust the rpms to what you want. When you next restart cold, it will likely idle too slow, and you'll have to mess with it to keep it running as above.
tom

NinjaSICKthirtysix · 11-07-2020, 06:23 PM

DAN - i just got my 2021 tt250 4 days ago and i too have been asking questions regarding the "chunky" and lackluster acceleration. How many milesbhave you got on it?

I am attributing these symptoms to the carb. I live in NY ans its cold here now and mine is a real bitch to get and keep started. It feels like choke does nothing. I just put the choke all the way on, quarter throttle it and hit start, then drop choke to midway about 30 seconds in and still hold the throttle to around 2 grand for about 1.5 minutes then turn choke all the way off and gently let go of the throttle. Then let it warm up another 2 to 4 minutes.

As for your idle you need to adjust your idle screw on the carb. Go to the side of the bike where the fuel petcock is and look at the carb. You see that long screw sticking out, that is your idle adjustment. Take a screwdriver and while the bike is on (and already warmed up - IF the bike is still idling high when the choke is all the way off AND the bike is warmed up already) turn the scree gently and slowly counter clockwise and u will see and hear the idle drop. Adjust it to the 1400 to 1500 rpm level.

As for the rear shock, i too thought it was adjustable but its really not. Atleast not in the sense i thought it was. All you are able to do is make the shock stiffer or softer. Same thing like the idle screw, there is a screw on the side of the shock, which i believe is on the right side (exhaust side). Take a screw driver and turn to the right to make it harder or left dor softer. It will only turn fully about 1.5 revolutions i believe.

I can tell my bike needs to be rejet and dialed in as well as a 47tooth sprocket to wake it up a bit. But i think the jet kit i got will help alot because not only does the accel feel chunky but it hesitates in the higher rpms. I literally know nothing about carbs or tuning them but i do all my own work on everything especially my Kawi Ninja so i am going to do the jet kit exhaust and sprocket on the tt250.

Ill keep you posted. You do the same please.

danfandango · 11-09-2020, 10:40 PM

Thanks for the feedback guys. I just got a jet kit in the mail so I am going to simply try swapping out the jets and see if that improves anything as far as power curve, acceleration, etc..

I have adjusted the idle down to about 1400 RPM just based on it seeming happy enough at that speed once warmed up. I may bump it up a bit if it doesn't idle well at that speed on the next ride or two.

Ninja, I am at about 600 miles presently. I was expecting the character of the engine to change a little more after break-in, but it seems pretty similar to what it was before. Since this is a single cylinder 250 cc thumper, I am assuming everything is going to be in the tuning.

I previously had a Triumph Speed Triple with the carbed 885 and a ZRX1200r, I never tuned those because there was so much power to spare.

Also, when I adjusted the valves they were at basically zero gap as I could not get a gauge in between the valve stem and the rocker. I set the gap at .06 and now I feel like I am getting some valve float at 6500 RPM. You may want to check yours before 500 miles, especially if you are going to pull the tank for any reason like jetting the carb.

grumpyunk · 11-10-2020, 12:41 PM

If you read a bit about these engines .. CG250... there are words to the effect that the aluminum expands more than the Fe. That means that the valve clearance will GROW as the engine heats up, not shrink as most other engines that I am familiar with do.
So... Checking your clearance, you may want to close it up some. Mention was made on another post about the VW method. Gently close the clearance to zero, while twisting the push rod... When you tighten and can no longer rotate the push rod, loosen just enough to let it twist. Tighten the locknut(jam nut).
A test of this would be to do the VW adjustment, ride until the engine is hot, and then check the clearance.
Are you setting to .06" or to .06mm? Inquiring minds...
tom

danfandango · 11-10-2020, 10:30 PM

I will go back and double check my feeler gauge, but I believe I set it to .06 millimeters (factory spec per the TT250 manual is .04-.07MM). They recommend that you set to .07MM and the gap should close over the 2500 mile service interval. Supposedly if it gets too tight, the valves hang open and get burnt.

I ran a .06 inch to mm conversion and it was like 1.5MM so I don't think there is much of a chance I set the gap that wide. Not sure the valves would even open with that much gap.

grumpyunk · 11-11-2020, 08:51 AM

Whether the gap opens or closes over the 2500 mile interval depends on which parts wear more, the valve seat and valve face or all the operating linkage. One would think the pivot for the cam follower arm, the cam follower surface, the pushrod cup, the tips of the pushrod, the rocker arm cup, the rocker arm pivot, and finally the tip of the rocker arm would add up to more wear than the valve seating meeting surfaces. But it may not. I do not know.
My point was more about the heating and temperature affecting valve lash during operation. That would cause more noise when warmed up, an unusual circumstance.
tom

danfandango · 11-11-2020, 09:55 PM

Thanks for the clarification. I would note that the there was a good amount of clatter when the engine was cold right after the adjustment, but it quieted down after heating up a bit. I may try to check the clearance hot per your method and see if I can get a reading of the valve clearance at close to operating temp. Maybe when I install the new jets in the carb.

I also think the tight valves were causing excessive resistance on the engine so I am hoping the whole motor is moving a bit less restricted now. Who knows? I am not putting this thing on a dyno anytime soon

TheChairman · 11-12-2020, 01:27 AM

Check, set, and recheck valve clearance with the engine stone cold. It needs to sit overnight. These don't have huge clearances so the expansion of the parts will close up the gap once the engine heats up.

You should hear a little clatter on start up, then it should quiet down once the engine gets heat in it, the oil heats up and gets closer to 40 weight, and the parts expand a bit. Once it's good and warmed up, it should just have a healthy tick. An occasional rattle is normal too. It's a pushrod engine after all. It should not have clatter all of the time.

.076mm seems to be the common theme.

danfandango · 11-15-2020, 04:55 PM

That is what I did when I set the valves and also bumped it over a couple times to make sure that I was on the base of the cam lobes.

I also ended up making some idle adjustments that seem to have made everything operate a bit better. It seems pretty happy with an idle around 1600 rpm so I am leaving it there for now.

The valve noise on this is absolutely nothing compared to my Triumph 885. They described those as running correctly when it sounds like a washing machine full of nickles. I think the valves are good now but will check again in a few weeks to confirm.

Since adjusting the valves and the idle, I seem to have picked up a couple of top end MPH as well. Seemed to top out at about 54-55 before and now it is is getting up to 57-58. Seems to be revving a lot better in the high end of the RPM band from about 6-8K. I wonder if that is just a function of the engine finally breaking in fully?

motochutuya · 11-21-2020, 06:11 PM

danfandango,

Quote:

"The pickup feels a little lackluster with "chunky" acceleration and I think a sprocket change would be warranted (possibly also compounded by bad carb setup). I don't really care about top end speed over 45MPH. What would be a good low end acceleration oriented gear setup that works with the stock chain?"

keep the 50t, you might even go higher if you dont care about top speed, look at what kind of ratios you can achieve with a front tooth lowering too.

Ditto on what others have said, a little rough idle cold is too be expected - mine needed a steady hand on the throttle + half choke for a minute or so

after installing the jet kit, it just needs a little blip + half choke and its happy

Quote:

Is the TT250 jetted really lean out of the box and is that is that what could be causing the issue? I am due for valve checks and I figured that might be a good time to rejet, if necessary.

CSC admits themselves that its very lean when you pick it up from the store. resetting feels necessary to get the intended performance. Personally I haven't gotten "faster", buts its smoother, idles lower, no bogging and less popping from the exhaust

danfandango · 11-23-2020, 08:46 PM

motochutuya, what jets did you change and to what size? I ordered the CSC kit, but haven't installed yet.

Also, what is your elevation/climate?

motochutuya · 11-24-2020, 07:40 PM

danfandango,

I bought the kit from CSC, im in centeral texas ~500~1,000ft. and i only tried the 112 main + idle jet that came in the kit.

i have no bogging at 7krpm, previously when I hit high speeds i would immediately bog which was not fun. No bogging, and less popping from the exhaust now on decl.

The biggest issue with the CSC jet kit is the idle mixture screw - its impossible to adjust once mounted on the bike. I actually just spent a few hours on it ...:(

i cant find a stubby idle mixture screw anywhere...

motochutuya · 11-24-2020, 08:01 PM

gonna go to homedepot early am and see if I can find a snub screw driver that fits. hopefully I'll have some success and can at least report on which one to buy

11-01-2020, 10:31 AM	#1
danfandango Join Date: Oct 2020 Location: Atlanta, Georgia Posts: 14	Few questions - CSC TT250 setup Bought my CSC TT250 just to play around with early in Covid-19. Rode it a few hundred miles over the summer and recently listed it for sale due to lack space and time primarily. May now be hanging onto it for a bit longer so I am thinking about enhancing the riding qualities a bit both for my own enjoyment and in the event that I put it back on the market next year. To that end, I have a few questions: I have a high idle that the bike has had since new approximately 1700 RPM and sometimes creeps up over 2K. Also, when cold, sometimes the bike won't idle with the choke on unless I bump the revs and start riding. Is the TT250 jetted really lean out of the box and is that is that what could be causing the issue? I am due for valve checks and I figured that might be a good time to rejet, if necessary. The pickup feels a little lackluster with "chunky" acceleration and I think a sprocket change would be warranted (possibly also compounded by bad carb setup). I don't really care about top end speed over 45MPH. What would be a good low end acceleration oriented gear setup that works with the stock chain? The ride is a little rough in the rear - the rear shock is adjustable correct? If so, what should I set that to for 170 pound rider? I don't want to adjust any of the suspension components too much because I understand stripping is a concern on the hardware. Thanks, Dan BTW, I have read through some of the stickys and apologize if I missed directly pertinent information. I know there is a lot on the sprockets, but I have never changed those out on a bike before.
	0

11-05-2020, 01:16 PM	#3
grumpyunk Join Date: Jul 2018 Location: nw of atlanta Posts: 169	A cold engine will likely not idle well, especially if you had to choke it to get it to fire. It will be lumpy for a minute or so, until it warms a bit. The rpms will also likely be slower than when it is warmed up. You can start with full choke, and almost immediately push the lever down to the middle detent, once started. You may have to buzz the throttle a few times to keep it running. Totally normal for a carb'd air-cooled machine. Once warmed the idle should be solid, not lumpy, and you can adjust the rpms to what you want. When you next restart cold, it will likely idle too slow, and you'll have to mess with it to keep it running as above. tom __________________ vertical and above ground - my daily goal
	1

11-10-2020, 12:41 PM	#6
grumpyunk Join Date: Jul 2018 Location: nw of atlanta Posts: 169	If you read a bit about these engines .. CG250... there are words to the effect that the aluminum expands more than the Fe. That means that the valve clearance will GROW as the engine heats up, not shrink as most other engines that I am familiar with do. So... Checking your clearance, you may want to close it up some. Mention was made on another post about the VW method. Gently close the clearance to zero, while twisting the push rod... When you tighten and can no longer rotate the push rod, loosen just enough to let it twist. Tighten the locknut(jam nut). A test of this would be to do the VW adjustment, ride until the engine is hot, and then check the clearance. Are you setting to .06" or to .06mm? Inquiring minds... tom __________________ vertical and above ground - my daily goal
	1

11-11-2020, 08:51 AM	#8
grumpyunk Join Date: Jul 2018 Location: nw of atlanta Posts: 169	Whether the gap opens or closes over the 2500 mile interval depends on which parts wear more, the valve seat and valve face or all the operating linkage. One would think the pivot for the cam follower arm, the cam follower surface, the pushrod cup, the tips of the pushrod, the rocker arm cup, the rocker arm pivot, and finally the tip of the rocker arm would add up to more wear than the valve seating meeting surfaces. But it may not. I do not know. My point was more about the heating and temperature affecting valve lash during operation. That would cause more noise when warmed up, an unusual circumstance. tom __________________ vertical and above ground - my daily goal
	1

11-02-2020, 09:05 PM	#2
danfandango Join Date: Oct 2020 Location: Atlanta, Georgia Posts: 14	I adjusted the valves on Sunday and that seems to have helped with the idle. Planning on just changing the rear sprocket out to a 49 tooth so I don't have to modify or replace the chain and getting a jet kit directly from CSC. Think that covers it.
	0

11-07-2020, 06:23 PM	#4
NinjaSICKthirtysix Join Date: Oct 2020 Posts: 56	DAN - i just got my 2021 tt250 4 days ago and i too have been asking questions regarding the "chunky" and lackluster acceleration. How many milesbhave you got on it? I am attributing these symptoms to the carb. I live in NY ans its cold here now and mine is a real bitch to get and keep started. It feels like choke does nothing. I just put the choke all the way on, quarter throttle it and hit start, then drop choke to midway about 30 seconds in and still hold the throttle to around 2 grand for about 1.5 minutes then turn choke all the way off and gently let go of the throttle. Then let it warm up another 2 to 4 minutes. As for your idle you need to adjust your idle screw on the carb. Go to the side of the bike where the fuel petcock is and look at the carb. You see that long screw sticking out, that is your idle adjustment. Take a screwdriver and while the bike is on (and already warmed up - IF the bike is still idling high when the choke is all the way off AND the bike is warmed up already) turn the scree gently and slowly counter clockwise and u will see and hear the idle drop. Adjust it to the 1400 to 1500 rpm level. As for the rear shock, i too thought it was adjustable but its really not. Atleast not in the sense i thought it was. All you are able to do is make the shock stiffer or softer. Same thing like the idle screw, there is a screw on the side of the shock, which i believe is on the right side (exhaust side). Take a screw driver and turn to the right to make it harder or left dor softer. It will only turn fully about 1.5 revolutions i believe. I can tell my bike needs to be rejet and dialed in as well as a 47tooth sprocket to wake it up a bit. But i think the jet kit i got will help alot because not only does the accel feel chunky but it hesitates in the higher rpms. I literally know nothing about carbs or tuning them but i do all my own work on everything especially my Kawi Ninja so i am going to do the jet kit exhaust and sprocket on the tt250. Ill keep you posted. You do the same please.
	1

11-09-2020, 10:40 PM	#5
danfandango Join Date: Oct 2020 Location: Atlanta, Georgia Posts: 14	Thanks for the feedback guys. I just got a jet kit in the mail so I am going to simply try swapping out the jets and see if that improves anything as far as power curve, acceleration, etc.. I have adjusted the idle down to about 1400 RPM just based on it seeming happy enough at that speed once warmed up. I may bump it up a bit if it doesn't idle well at that speed on the next ride or two. Ninja, I am at about 600 miles presently. I was expecting the character of the engine to change a little more after break-in, but it seems pretty similar to what it was before. Since this is a single cylinder 250 cc thumper, I am assuming everything is going to be in the tuning. I previously had a Triumph Speed Triple with the carbed 885 and a ZRX1200r, I never tuned those because there was so much power to spare. Also, when I adjusted the valves they were at basically zero gap as I could not get a gauge in between the valve stem and the rocker. I set the gap at .06 and now I feel like I am getting some valve float at 6500 RPM. You may want to check yours before 500 miles, especially if you are going to pull the tank for any reason like jetting the carb.
	0

11-10-2020, 10:30 PM	#7
danfandango Join Date: Oct 2020 Location: Atlanta, Georgia Posts: 14	I will go back and double check my feeler gauge, but I believe I set it to .06 millimeters (factory spec per the TT250 manual is .04-.07MM). They recommend that you set to .07MM and the gap should close over the 2500 mile service interval. Supposedly if it gets too tight, the valves hang open and get burnt. I ran a .06 inch to mm conversion and it was like 1.5MM so I don't think there is much of a chance I set the gap that wide. Not sure the valves would even open with that much gap.
	0

11-11-2020, 09:55 PM	#9
danfandango Join Date: Oct 2020 Location: Atlanta, Georgia Posts: 14	Thanks for the clarification. I would note that the there was a good amount of clatter when the engine was cold right after the adjustment, but it quieted down after heating up a bit. I may try to check the clearance hot per your method and see if I can get a reading of the valve clearance at close to operating temp. Maybe when I install the new jets in the carb. I also think the tight valves were causing excessive resistance on the engine so I am hoping the whole motor is moving a bit less restricted now. Who knows? I am not putting this thing on a dyno anytime soon
	0

11-12-2020, 01:27 AM	#10
TheChairman Join Date: May 2020 Location: Philadelphia Posts: 115	Check, set, and recheck valve clearance with the engine stone cold. It needs to sit overnight. These don't have huge clearances so the expansion of the parts will close up the gap once the engine heats up. You should hear a little clatter on start up, then it should quiet down once the engine gets heat in it, the oil heats up and gets closer to 40 weight, and the parts expand a bit. Once it's good and warmed up, it should just have a healthy tick. An occasional rattle is normal too. It's a pushrod engine after all. It should not have clatter all of the time. .076mm seems to be the common theme.
	0

11-15-2020, 04:55 PM	#11
danfandango Join Date: Oct 2020 Location: Atlanta, Georgia Posts: 14	That is what I did when I set the valves and also bumped it over a couple times to make sure that I was on the base of the cam lobes. I also ended up making some idle adjustments that seem to have made everything operate a bit better. It seems pretty happy with an idle around 1600 rpm so I am leaving it there for now. The valve noise on this is absolutely nothing compared to my Triumph 885. They described those as running correctly when it sounds like a washing machine full of nickles. I think the valves are good now but will check again in a few weeks to confirm. Since adjusting the valves and the idle, I seem to have picked up a couple of top end MPH as well. Seemed to top out at about 54-55 before and now it is is getting up to 57-58. Seems to be revving a lot better in the high end of the RPM band from about 6-8K. I wonder if that is just a function of the engine finally breaking in fully?
	0

11-23-2020, 08:46 PM	#13
danfandango Join Date: Oct 2020 Location: Atlanta, Georgia Posts: 14	motochutuya, what jets did you change and to what size? I ordered the CSC kit, but haven't installed yet. Also, what is your elevation/climate?
	0

11-24-2020, 07:40 PM	#14
motochutuya Join Date: Nov 2020 Posts: 47	danfandango, I bought the kit from CSC, im in centeral texas ~500~1,000ft. and i only tried the 112 main + idle jet that came in the kit. i have no bogging at 7krpm, previously when I hit high speeds i would immediately bog which was not fun. No bogging, and less popping from the exhaust now on decl. The biggest issue with the CSC jet kit is the idle mixture screw - its impossible to adjust once mounted on the bike. I actually just spent a few hours on it ...:( i cant find a stubby idle mixture screw anywhere...
	1

11-24-2020, 08:01 PM	#15
motochutuya Join Date: Nov 2020 Posts: 47	gonna go to homedepot early am and see if I can find a snub screw driver that fits. hopefully I'll have some success and can at least report on which one to buy
	1