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Discussion Starter #1
I'm fairly sure that my bike is running with the choke on most of the time, but need to check something

What is the part highlighted by the red arrow please
Capture.JPG

Is it the rubber seal fitted inside the plunger or a separate part as appears to be the case from the picture

Cheers
 

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Hey Tris

It is the rubber plug inside the plunger :)

Why do you think your running with the choke on?

Charlie
 

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Discussion Starter #3 (Edited)
Thanks Charlie

Bike is new to me and I've found:-

a) never needs the choke to start
b) the spring inside the choke is not original and barely closes it. I need to double check the length now that I know that's not a extra bit that's missing ;)
c) Idle pilot screwed nearly fully home
d) Revs high idle and then drops randomly. OR revs normally at idle and then stays high if I pop the throttle a little and relase

It feels like something is moving unexpectedly and the choke seems to the the prime candidate at the moment!
 

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If this is the single cable carb someone mentioned earlier on a 125, everything is suspect - if this is indeed the case, then you do not have any valid "starting point" on which it would be reasonable for us to comment

Not trying to duck your question {which is perfectly reasonable}, but without walking up to your bike and poking around a bit [or a lot}, it's gonna be guess work at best

My [guess] would be that you have an incorrectly jetted knock off Chinese carb on there that someone has done God knows what to in order to get it running - as such, anything we can add would only be to the confusion you now face

TW125's in the UK are fairly common, and your best bet is to source an OEM second hand carb [still not cheap] - or we'll all be coming to you for advice on carb issues on 125's once you've become an expert …..
 

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Discussion Starter #5 (Edited)
Hi Purple thanks for replying

Yes it is a single cable carb and as far as I can tell its an original one but I do acknowledge your point!

The jets I could read appear to be correct for the bike and it has the heater fitted that functions. Do the Chinese carbs have the heater pocket?

Whats puzzling me is that it starts super easily and idles well but then randomly (but not repeatably of course:() the revs change either up or if already up, then down

Its like a step change - feels like something is moving due to heat or vibration perhaps rather than jetting

I've think I've sorted the choke, and the throttle slide moves freely, so I'm wondering if the float is sticking

However, does anyone have all the basic starting parameters for the standard TK carb - Jet size, float height/fuel level, No. turns for idle mixture, etc., etc.
All I've been able to find so far is those for the 200cc bike

Both valves were 1 1/2 to 2 thou tight when I checked them yesterday. They aren't now ;)


Tris

PS "... you've become an expert" ...... I'll be happy to be just lucky at this point:D
 

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As far as I can tell, the 200 manual is good for the 125 as well. There may be a few slight changes, but you are largely good to go

You are correct – the Chinese carb does not have the electrical heater, so yours is possibly an original. Float height will be the same as the 200, the jets you can work out from performance and the plug colour. Pilot jet is usually happy at one and a half to two turns out on these bikes

What mileage does the speedo say ?
 

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Discussion Starter #7
Cheers P

Its "allegedly" done 10K ish and "allegedly" had a re-bore and new valves recently - Looks like I can see the edge of some new gaskets on the engine so that bit might be correct!

I need to borrow the boroscope from work and poke it through the plug hole and see if any honing marks are visible and give it a compression test

I'm away on holiday tomorrow so the next exciting episode of this saga will be delayed
 

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Lol – well the 125 was often thrashed due to lacklustre performance (we would never dream of doing this on a 200 of course), but in the case of the 125, usually by “one careless owner” – the fact that it is now on its second (re-bored) engine should tell you all you need to know

Nonetheless, the knowledge gained from trying to keep this thing going will stand you in good stead should you stumble across a 200 or 225 in the future (they do exist in the UK, though they don’t come up often at the right price)

Meanwhile, I see you have another bike to play with – used to have a G5 myself (till I wrote it off, nearly totalling myself in the process) – however, onwards and upwards ……
 

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About that random idle change, I recently had a bout with that on my 200 and it turned out it was the air filter had literally gone to pieces. Also check your carb boots for cracks and a tight fit. I’m assuming the 125s have air boxes and not pod filters.

If your choke doesn’t have a tight fit with clicks for each position, it probably needs to be addressed.
 
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Discussion Starter #11
An interesting ride over the weekend!

Throttle decided to stick wide open due to a sticky cable that was free but sticks sometimes at WOT I've now discovered, so might be the cause of my perceived choke problem!

Still I managed to score a NOS throttle cable for a tenner so we'll see if I can kill 2 birds with one stone!

Cheers All

Tris

PS - It made me laugh all the way round and I'm really looking forward to riding it once I get the niggles sorted
 
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