Yamaha XS250 Cafe Racer build CVH Carbs PLEASE HELP ME!!!

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Hi People...

I know I dont have an XS400, but I do have a XS250.... really need some advice

I have just stripped and cleaned my XS250 CVH carbs, it runs ok, once i get her running, but if i leave her over night, I struggle to start her, unless I pop my hand over each carb inlet, turn it over, till it sucks on my hand, then she will fire... and start on the button for the rest of the day....

Is this a diaphram issue, or float hight issue? or something else?

HELP PLEASE!!!!!!!!!
 
Have you tried using the enrichener?

Have you tried starting the bike without touching the throttle?
 
bcware said:
Have you tried using the enrichener?

Have you tried starting the bike without touching the throttle?
Click to expand...
Yes i have tried the choke too... yes i did twist the throttle... but nothing, until I put my hand over each inlet, while cranking, then we are off and running...
 
I know that it is labeled a choke, but that is to not confuse people unfamiliar with CV carbs. Yamaha correctly calls it a start enrichment circuit. On a cold start, open it fully for maximum enrichment. If you open the throttle, you will defeat it, so don't touch the throttle when trying to start!

If the bike won't start like this, then I'd suggest pulling the carbs again, checking the float levels and the plungers for the enrichment's. The plungers have rubber seats and if they are worn or cracked they will constantly enrichen the idle mixture. This may have lead you to set the pilot screws too lean in an effort to lean out the idle mixture, resulting in a lean condition during a cold start.

Also check for vacuum leaks on the carb mounts.

Let us know what you find!
 
Hi I have fitted new carb mounts. To be honest, i was doing the throttle same time as choke. next time, i will try with just the choke.

i am going to sync the carbs first, as i noticed when she was running, the pressure diffrence felt at the exhaust was a lot diffrent from one side to the other.
 
no yet. but i will install some, before i start. I have re jetted and i will be running cones
 
A good oiled uni filter will work the best on cv carbs. The emgo or pleated ones cause air flow turbulence plus poor filtration unless you have real K&N chargeable filters.
 
Hi, I also have a xs250 which is currently in pieces just starting the rebuild now actually, anyways I read that you've rejetted? This is something I'm gonna have to do as I'm fitting pod filters and shorty mufflers can I ask what size jets you went for so I've got an idea on where to start as I've no idea! :)
 
Yes I do, mine is finished. Where are you based? you can call me if it helps, quite a lot to explain...

171278476259
 
Jonesy154 said:
Hi, I also have a xs250 which is currently in pieces just starting the rebuild now actually, anyways I read that you've rejetted? This is something I'm gonna have to do as I'm fitting pod filters and shorty mufflers can I ask what size jets you went for so I've got an idea on where to start as I've no idea! :)
Click to expand...
135 jet. I made my own filters. Get the jets from NRP carbs. Mine runs mint with these settings. If you take a look on Eaby, you will see my bike. I am happy to talk it through with you, let me know, and I will send you my number.

:)
 
Nice build love the rear end with them lights, I might build a cafe racer after the bobber is done. I've got the same mufflers as you by the looks of it so I'd hope my carbs just need setting the same as yours if yours runs good? So the main jet you've got is 135 did you change any other jets or settings?
 
Hi

Yes it does. I made my filters from some filter foam. I bought some cheap 42mm rubber to fit over the intakes, then made my own this way.

Dont buy cones, as they will affect the performance of the air that enters the carbs. Yes, 135, and NRP carbs do them. You will need to balance the carbs after, and ajust the tick over, but it wont take long. Make sure your Choke circuits are all blown out too.

If you need any other info on the XS, let me know

Cheers
 
Was gonna buy some ram air foam filters from eBay, did you change any pilot jets? Thanks for your help I think you may have saved me a heap of time! :)
 
Yes, the Ram air are ok. But I made my own, as it was cheeper... No! not the pilot jet. Just one of the main jets that sits in the float bowl. The brass 10mm that that sits under the the bottom of the float bowl, undo that, and it sits in there.

:)
 
Ok thanks mate, do just change the main jet, in each carb? Sorry if I sound stupid just like to be totally sure before I start tearing things apart
 

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