New tt250 help

[Bobertj]

So bought new tt250 nice bike but having one issue basically when you try to give it 1/2 throttle or more the bike misses as it climbs through the rpm range if you feather it all the way through no missing only half throttle
Or more csc has been helpful sent me coil and new computer for the coil still same problem my
First thought was fuel and I’m still leaning towards this being
The issue any ideas? New to the forum thank you so
Much

[NzBrakelathes]

Have you checked valves? This might help a little
Second thing is tune the carb or look into carb check jetting that’s actually in it
I do have a set listed in my eBay store for first tune, this might be useful to you.
So you changed the CDI and coil? Any color smoke when it plays up?

[NzBrakelathes]

Do you have a timing light? See if it’s loosing spark when it plays up etc

[JerryHawk250]

Also try a new plug. The one that came on the bike may be defective or cracked. I agree, valve lash would be one of the first things to check.

[Bobertj]

Thank you both for response so the valves are due in the next 40 miles so I’ll be doing them this weekend yes replaced both under warranty and also spark plug was the first thing I did to see and no improvement with all three those parts replaced. Changed the oil already bike is about to hit 500

[Bobertj]

Also idk what size jets are in it that’s was my thought maybe needs a different main
Jet since it’s only 1/2 throttle or more
I’m not to well with carbs but I’m
Decent with cars etc so

[JerryHawk250]

Try adjusting the idle mixture. It may be set to lean. Once you have the idle mixture set and it still does it then you can raise the needle up one notch.

[NzBrakelathes]

Also idk what size jets are in it that’s was my thought maybe needs a different main
Jet since it’s only 1/2 throttle or more
I’m not to well with carbs but I’m
Decent with cars etc so

DO check my eBay store for some stuff that might help you etc
Valve adj set, first tune set, carb air screw adjuster all could be useful to you
I’m in the USA Saturday and have some products with me or it be 2ish weeks before I’m back
If you’re lucky I might be passing thru your area if you’re west coast lol
I have some items to drop off to customers already and it’s not the first time I’ve deluverrd in person

[Bobertj]

Ok I’ll check it out. Do I have to take the carb off to change the idle mixture ? Think the older models don’t have screw but I believe mine does

[Ariel Red Hunter]

So bought new tt250 nice bike but having one issue basically when you try to give it 1/2 throttle or more the bike misses as it climbs through the rpm range if you feather it all the way through no missing only half throttle
Or more csc has been helpful sent me coil and new computer for the coil still same problem my
First thought was fuel and I’m still leaning towards this being
The issue any ideas? New to the forum thank you so
MuchMy first thought is "too lean."...ARH

[Bobertj]

Ok yea I agree that’s its probably to lean do I need to take the carb apart to fix that ? And if so do
I just move the needle or change the jets thank you all for the responses just trying figure out the best way to go about it when I take the bike apart

[JerryHawk250]

Ok I’ll check it out. Do I have to take the carb off to change the idle mixture ? Think the older models don’t have screw but I believe mine does

The stock carb does have an idle mixture screw. It may be covered by with a plastic or brass cap that can be drilled out. It will be hard to adjust while on the bike but can be done. You want to adjust the idle mixture after the engines up to running temperature.

[Air_male]

and please make sure the choke is off

[Megadan]

I actually agree with the choke comment. Make sure the choke is all the way off (open). If you only have it in the half choke position it will behave almost exactly as you describe.

[Azhule]

This might also be helpful if you have to actually open up the CSC carb for cleaning or needle adjustments

https://www.cscmotorcycles.com/check-out-our--tt250-carburetor-maintenance

[Bobertj]

Thank you every one for response yea me and the gentleman at csc went over the whole choke thing it’s been off I live in hot climate don’t use the choke he even had me ride the bike at half choke didn’t help anything guess I’m
Going have to go into the carb. Just never worked on carbs before but doesn’t seem to complicated

[NzBrakelathes]

https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.com%2Fulk%2Fitm%2F30 3077495104

Take a look as this might be useful
I’m in the USA Saturday I can ship 1-2 things while I’m there etc

[NzBrakelathes]

Thank you every one for response yea me and the gentleman at csc went over the whole choke thing it’s been off I live in hot climate don’t use the choke he even had me ride the bike at half choke didn’t help anything guess I’m
Going have to go into the carb. Just never worked on carbs before but doesn’t seem to complicated

Worst case send them back your carb? Let them test it on another bike in Cali

[Megadan]

A full tear down and clean can't hurt. Sometimes junk, swarf, and other nasty stuff can get trapped in the small passages. Even from new.

Take the carb apart completely. remove every jet, the floats, the float needle, out of the carb including the idle mixture screw - with spring, washer, and O ring (might need a small pick to get it out). Take all of your rubber seals and O rings out so they don't get hit with carb cleaner and set them aside in a safe place. Use the straw on the can of carb cleaner and blast it through every hole and passage you can find. clean out the bowl and the inside of the carb body as well. Then, if you have some compressed air, blow through those same passages to clear them. Do the same with the jets, and if you have any jet cleaning wires you could use them. Then re-assemble.

This is a good time to check your float height. If the carb has the flat bottom floats then the float height setting is 14mm to the top edge of the float with the carb inverted. This is measured from the bowl flange opposite of the float needle.

I would do this and try it out before any jetting changes.

[NzBrakelathes]

Yes you need to see why it runs so bad
I also doubt it’s wrong jetting unless the factory by mistake used wrong jets.
I’m guessing about 34/36 pilot and around 98-103 main as the stock set up.

The stock jetting is more fuel efficient scale rather then power

[Bobertj]

Ok thanks I will have to get into it this weekend and report back it has to be something with the carb idk what else would make it run like that cus other then that the bike runs good and still gets me doing 60 or more fairly easy minus the misses along the way

[elkhunter338]

Also try a new plug. The one that came on the bike may be defective or cracked. I agree, valve lash would be one of the first things to check.

I would second new spark plug. I had that happen in my honda car, new spark plugs, 10 miles later one failed. Replaced it and running good now for 40k+

Valve lash would be good check, mine were tight at 400 miles (I hope I did not damage valves) Bike runs great.
Dad's valve lash was spot on at 100 miles.

[Ariel Red Hunter]

I would second new spark plug. I had that happen in my honda car, new spark plugs, 10 miles later one failed. Replaced it and running good now for 40k+

Valve lash would be good check, mine were tight at 400 miles (I hope I did not damage valves) Bike runs great.
Dad's valve lash was spot on at 100 miles.You make a good point here about damaging valves. If you ride at 60 mph for an hour at 6500 rpm, that means that the engine has fired 3250 times in one minute, to cover one mile. To put it simpler, that poor exhaust valve has been assaulted by 500+ drgree heat and flame 3,250 times in order to cover a mile. I think people should adjust the valves before they even start it for the first time. I know, I know. You want to declare "IT LIVES!!!" as soon as possible, but patience, patience!..ARH :cry:

[elkhunter338]

You make a good point here about damaging valves. If you ride at 60 mph for an hour at 6500 rpm, that means that the engine has fired 3250 times in one minute, to cover one mile. To put it simpler, that poor exhaust valve has been assaulted by 500+ drgree heat and flame 3,250 times in order to cover a mile. I think people should adjust the valves before they even start it for the first time. I know, I know. You want to declare "IT LIVES!!!" as soon as possible, but patience, patience!..ARH :cry:

You would think the factory could set the valves right, makes me wonder what else they screwed up.
Had I known I would have set the valves from day 1. But another bike my Dads. tt250 was perfect, set on the loose side of the spec.

I removed the side plate to rotate the engine, 1 out of the 3 screws was significantly tighter. Hmm they don't have a torque tools for assembly?

[Ariel Red Hunter]

You would think the factory could set the valves right, makes me wonder what else they screwed up.
Had I known I would have set the valves from day 1. But another bike my Dads. tt250 was perfect, set on the loose side of the spec.

I removed the side plate to rotate the engine, 1 out of the 3 screws was significantly tighter. Hmm they don't have a torque tools for assembly?I've worked in plants that use air operated torque wrenches, and I can tell you that every operator gets a different result with those wrenches. For example, your sideplate issue. The first screw is applied to hold everything in alignment, and to make sure nothing moves the first screw has the torque wrench applied longer. Then the other screws are run in just tight enough to make the hammers in the torque wrench make that B-r-a-p noise, and the job is done...ARH :clap: