Xl125k2 conversion?

[Arch stanton]

I am currently playing around with a Xl125k2. Which has no engine.
But i have a Xl185 engine, which i will try to fit into the 125 frame.
But whilst comparing parts. I noticed the throttle slide in the 125 carb.
Is much larger than that in the 185 carb. This i found surprising.
Can anyone explain. Why the extra 60cc would need a smaller carb slide?
Sean.
 

[Bryanj]

Gas flow different, i put a Morgo 750 onto a Triumph T110 many years ago and had to fit smaller mainjets as it ran rich

[Laverdaroo]

Not that this helps in the slightest and didnt mean to swerve but I had an ancient XL 185 when I was at school at my mates farm. Now, there's shagged and theres shagged out.......this particular bike was WELL shagged out It ran so well though and all it had was teenage abuse from several yoofs that used to come and faff about at the weekend.

In its final field repair as a result of a spirited attempt and spectacular 'off' trying for the 'holy grain' and getting it into 4th on the rear wheel, (if the tyre stayed on that long); it ended up with a section of rusty tower scaffold leg bent and welded and fitted as the replacement exhaust which angled down towards your left foot which subsequently kept yer welly red hot!
Ace in the winter, not so great when ragging across the stubble fields in August several hot left wellies were holed on that gear lever over the years I can tell you 

It never really had much mechanical sympathy spent on it but at 13 or 14 you didn't care, I think the most we ever spent on it was on gaffer tape to tape the cushion (we'd nicked off Darrens Mum ) to the area as there was no foam. Looking back it was an utter, utter death trap, but what a bike, I've loved them ever since.

It only didn't start once which was when the HT lead came adrift and was lost during a 'medium speed off' into a ditch when my pal over took me and pushed me with his left hand .......Those were great bikes although I've never found one without a rattly cam chain. My mates 'oop Norf' have just finished a 250 back to OE, its a great little thing and gets attention all over the place but even that has a rattly chain

[Arch stanton]

Hello Chaps.
Firstly. Thanks to bryan. I knew it had to be something to do with the dark art of carburetion.
Thank for the tales of youth on the po old XL.
Funny how the mid sized trailies always proved the best.
I've had the 185 engine for years. And just been given a barn find rolling k2 chassis. So if they go together. Thats good. But if not. I have a complete
Nos Cb125 engine still in its box. That i can use.

[Laverdaroo]

Your garage sounds ace!!

[Arch stanton]

Its a shitty shed. Full of shit!
Its an eclectic mix of bikes i have stumbled across & restored, over the last
30yrs. There is no common thread to it. Hondas,suz,yam, even a Kawasaki.

[Laverdaroo]

It's sounding better all the time

[Arch stanton]

I see you have a 550f. They sound fantastic with the original 70,s Marving
4 into 1 pipe & Bell mouths.

[Rozabikes Tim]

Talking of lack of sympathy in younger years. Fond memories of the 185. First bike I could Wheely of the throttle without clutch.

Crakin motor - use it if you can.

[Laverdaroo]

I see you have a 550f. They sound fantastic with the original 70,s Marving
4 into 1 pipe & Bell mouths.

I'm just starting it now, albeit slowly. Don't really know what it might have on it in the end, I'm still open to suggestion but read a great deal about the Marving pipes. Ideally I'm trying to save the headers in their original form if I can as it just make the bike for me but summut'll happen and things will change no doubt. They always do

[K2-K6]

"Can anyone explain. Why the extra 60cc would need a smaller carb slide?
Sean"

Probably raised gearing on the 185 to use less rpm and relying more on lower down torque compared to the 125, for which it doesn't need such a big carb bore.

[Arch stanton]

I wouldn't use a modern day Marving. They rust terribly.
And they are completely different to the original.
I have an original Marving on my 750k1. But the 750,s never sound as good as the 500/550.

[Laverdaroo]

INteresting, thanks f rthe input, like I mentioned, still dont know what to do but I'll have a more of in inkling once a second hand set turns up after the weekend which I've bought.