Carb Problems

[mono]

I've opened the float bowl and the first thing that i noted that was obviously different was that the idle jet on the new carb stands proud of its location tube.... whereas the idle jet on the old carb sits deep inside the tube so it shrouds the jet (maybe this is why I was having idling problems me thinks? - maybe with the jet being shrouded it was struggling to get a good and regular supply of gas?)

Nope, it's just a different design... (unless it isn't and they just didn't turn it into place all the way, of course  )

With the actual passage being only .35mm diameter or so, it definitely won't struggle for gas... The .35mm opening is the limiting factor by design... Any shrouding around it will relatively be such a small hindrance to the flow that it's completely negligible...

[fabio]

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The replacement carb has landed in the post today - so hopefully tomorrow I can get it fitted.

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Right! - that's done it !!!

I fitted the replacement carb after swapping the jets out of my old carb (MJ is a 85, IdleJ is a 35) and using the old auto-choke, and after tweaking the air/fuel mix and the idle speed I've got it to settle down to a fairly even idle at about 1800 rpm, so I'm quite happy. I'm guessing that it was the old carb itself that was at fault - total cost for the replacement carb was £6 inc postage so I'm even more chuffed.

Next job is to get the transmission cover off and replace the rollers (well lighten them any way - what I did with the vespas that i was modding was to drill out the spare material of the rollers a bit at a time to get down to the right weight, then I've already got some stiffer clutch springs and a stronger contra spring both of which aren't specifically for a 139Q engine but I think will be close enough to be suitable

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[streido]

For the price of a set of rollers and having less hassle its easier to just buy a new set. Stock is 6,5g, i found 5.5g work well for me, also like 5.1g or 5.3g for acceleration but i did lose a few mph top end so went back to the 5.5's for now.

[fabio]

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I must admit I think I've already got some 5.5g rollers in the garage with all my scooter bits somewhere - I just need to put my hands on them.

Until I find them I'm not so sure of the physical dimensions though, if i remember they were 19mm wide and the outer diameter 16mm, I'm not too sure until I get the variator off what the stock physical dimensions for the Agility are.......

I know that the ones currently fitted are stock because the previous owner had them renewed when he had a service done not so long ago - the invoice says 6.5g rollers fitted.

On the MJ front - the stock one I had was an 80 and I bought an 85 - do you think this may be too big? I haven't done any plug chops as of yet but when I popped around the block on it earlier this evening it sounded a bit flat as if it was a touch rich.



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[wordslinger]

..all kymco 50cc rollers are 16 X 13...


..a50 oem wts are 6.5...

..some 5.5s will work well...

..i never tried any dr pulley sliders in my a50s, but i love them in my s9!

[wordslinger]

..i'd put my money on an 82 mj being closer to optimum...

[fabio]

..i'd put my money on an 82 mj being closer to optimum...

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Yes good!!, I've just ordered an 82, I re-read a few older threads on KF and found out that 82 was prob the best for the UK.

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[fabio]

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Ok - the transmission cover is off....I've got a "waz-hammer" so the variator and clutch nuts came off without too much hassle.......

The variator is off and the boss is the de-restricted smooth one....but the rollers have sizeable flat points on them (probably one of the reasons why the acceleration is total pants). I've weighed them and they're 6.5g. I've ordered 5.3g Narakua ones.

I've removed the clutch and undone the clutch holding nut and released the torque spring, cleaned up the plates and replaced the spring with the one I'd already got, its a white one which felt a touch stiffer than the slightly rusty one that came off.

The springs that I'd got in mind for replacing the current 3 clutch springs were not quite right so I'm going to order a set of 3 strength Naraku ones (9 springs in total, they are in 1000, 1500 and 2000 rpm strengths) so I can trial and error a bit.

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[mono]

Stiffer contra spring AND lighter rollers ?  You'll probably run the poor machine right into the revlimiter all the time 

Better try to change only one thing at a time, CVTs are a bitch to get right otherwise...

And take small steps only, from 6.5g to 5.3g sounds like a lot to me. My experience is that a difference of 0.25g is already noticeable in most cases (unless you're running into the revlimiter, but then it gets hard to tell any difference anyway...)

[matthew_addison]

A new carb for £6?! Where did you find this I can only find ones on eBay at around £36 this must be the problem with mine the idle is mega high then it just drops and dies and will only start with a little throttle then as soon as I go for any throttle again the revs just drop.

[fabio]

Stiffer contra spring AND lighter rollers ?  You'll probably run the poor machine right into the revlimiter all the time 

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Yes I'm probably being a bit too severe there aren't I ?

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[fabio]

A new carb for £6?! Where did you find this I can only find ones on eBay at around £36 this must be the problem with mine the idle is mega high then it just drops and dies and will only start with a little throttle then as soon as I go for any throttle again the revs just drop.

Ebay - new old stock - http://www.ebay.co.uk/itm/121020873883?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649&clk_rvr_id=427017325959

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[JC]

Forgive me but just so I'm clear, I need M5 threads for my stock carb jets? Flame away

[fabio]

Forgive me but just so I'm clear, I need M5 threads for my stock carb jets? Flame away

Hi JC

Yes M5 (I think that its best to use Keihin threads cos they are slightly a different pitch to normal 5mm threads) - I ordered the Keihin variety ..... Keihin M5/5mm

Fabio

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[Edited for more clarity of information]

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[matthew_addison]

Damn they haven't got any more of those carbs left looks like im gonna have to pay £36 for a new one