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

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Hi

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.... I dont currently have the filter on the end either?

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

HELP PLEASE!!!!!!!!
 
To begin with, if they are stock jetting, the bike will be so lean that you are lucky it runs at all with just bare carbs.

Are you running pods, stock air box, has the bike been rejetted. Give us something to work with? I'm good, but I ain't psychic. You have to give us some information.

Did you set the float levels when you had the carbs apart?

If you run it with no filters, and have not rejetted, you WILL fuck up your engine. Burned exhaust valve or holed piston are a couple of the things that can happen.
 
she runs fine, once she going, and she will start all day long, its seems to be when she left overnight.... maybe not having any filters on is affecting it
 
I am still in the process of putting her back together, i have not been riding her, just starting her now and then for a min of so
 
That sounds about right. (I never jetted this particular bike.)

When you cleaned the carbs, did you remove the plunger for the enrichener circuits? Then, after a soak in carb cleaner, blast it out with carb cleaner, then compressed air.

It sounds like you may have clogged enrichener circuits. They have some really small passageways. You may not have gotten them cleared out. Did you remove the pilot jets during the cleaning process? Sometimes you have to poke them out with music wire. The pilot jets have really, really small openings in them.
 
Hi..

I sent them away to be cleaned, i just got them back and put them back together.....

so i asume they did all that....

its driving me mad.....
 
Was it that guy on eBay who brags about how many thousands of carburetors he has rebuilt and how he is the fucking carburetor god?
 
Also, when she is ticking over, the pressure i can feel at the back of the pipes is very diffrent on each side.... is this to do with timing? or something else? the one with the lower back pressure, sometimes coughs alittle out the back of the carbs
 
All I can say is that I have had customers come to my shop that I have had to re-do their carbs because the carburetor god on eBay fucked them up. Float levels were way off, idle air mixture screws were set at 1/2 turn out, synchronization was way off.

The uneven exhaust is caused by the carbs being out of sync. You can sort of set it by ear and feel on a twin. Just adjust the sync screw in the middle link between the two carbs until the two cylinders idle evenly. I use a manometer, but it can be done reasonably well by ear. That can cause the one cylinder to hesitate/pop/lag a little when you come off idle.
 
Well you are the dog bollocks... ok. I plan on fitting new points, setting the timing as a start off. Then i will try to sync the carbs as you say... Also, is it 1 and a half turn back, from all the way in on the mixsture screw, or from when it bites as you screw it in?

Thanks for all the help :)
 
Screw all the way in until gently seated, then 1 1/2 turns out. That is a pretty good starting point. Should be within half a turn or so either way for best idle. Mandatory that the carbs be synced first. And of course, having your ignition timing and valve clearance all set.
 
can i sync my carbs by eye? i could prob make up a very simple device to see if both throttle butterfly valves open at the same time, as i twist the throttle?
 
No. Do it with the engine running. Sometimes you have to remove the gas tank to get to the adjusting screw. How do you have the engine running without the gas tank? :)

I have made temporary fuel bottles from 1 litre beverage bottles. What I have now it a 1 qt metal acetone can that I soldered a 1/4" X 3/8" brass pipe bushing into near the bottom. I screwed a 1/4" ball valve into that with a hose barb in it. I soldered on a wire bale at the top so that I can hang it like an IV bottle.

Set up a fan blowing on the engine while you do this. It could take 10-20 minutes of idling to get it synced, and the engine will get pretty hot.

Refer to the service manual for the carb adjustment procedure.
 
yes. i have a remote fuel bottle.. :)

Ok, i will get her running, and buy a carb sync tool, to get her set up.

Once done that, i will do the emission screws
 
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