Manky's XS650 Yamaha

[Dslam]

OK We have ign timed, compression and it fires when flooded or fuel poured into the combustion chamber. This would imply not enough fuel. You may have a pilot jet blockage (bit of a bugger on these carbs) or too much fuel. Sounds counter intuitive but try flooding the carbs, no choke, open throttle wide and kick. When it fires it will either rev up or die. If it revs up it's pilot or float height. If it pops and farts then dies you have more of a blockage than you think. Either way you are on the cusp of infernal combustion.

[the coppersmith]

Either way you are on the cusp of infernal combustion. 

[hunter]

Is the valve timing and clearances correct.

[BikerGran]

Reminds me of whewn my mate Bob was trying to get my Maestro started after it had stood in a garage foir 2 years without being touched (bearing in mind I know nothing about the XS) - the problem with the Maestro turned out to be the seal in the petrol pump had dried out, after squirting fuel direct into the carbs several times it ran for a little while - then a little while longer - and finally it kept running!

Running like a bag of nails but as Bob said, it's easy to sort that as long as it's actually running!

What about the carb rubbers - are they dry and letting air in?  I remember reading about how to cure that but as I'm an old bint, I don't remember what it was I read!

[Manky Monkey]

No carb rubbers fitted Bobbi. I've swapped the original Japanese Mikuni carbs for old British Amals, basically cos they look cool. Hence the self inflicted problem comment. There's a guy on Ebay who sells cast aluminium manifolds to fit Amals to XSs. Goes by the name of Greensand Foundry if you're interested. I've got a pair of those & set the carb jets & needles up the same as his bike -I did wonder if I contacted him he'd say That's funny, mine doesn't run either!
Valves haven't been touched since I bought the bike. Everything I've looked at seems to be in good condition, so it's either a low mileage engine, or been looked after. So I'm assuming they're O.K
I'm not allowed to play with fire. Or crayons.
Current status:
kick, kick, kick, fiddle with the tickler buttons, tweak the mixture screws & eventually it'll fire, but die after a few seconds. Trying to catch it by blipping the throttle, it just goes bleurgh, bleurgh, bleurgh & still dies. Feels like no fuel.
No chokes fitted.
So no point lifting the needles yet then? Lots of fuel, full throttle, kick?
I may try hitting it with a stick eventually.

[Dslam]

Pretty much Andy. If it persists get it over to mine and put it on the rollers. Two ruddy great GM starter motors and a couple of hundred amps should frighten it into life

[Manky Monkey]

  Went for a walk this evening to walk off my aching ankle after the bike kicked back mid afternoon. May not have been a good idea cos it bloomin' hurts now! Maybe I need to buy a set of rollers myself.
Got to get it to the Basingstoke Transport Festival on Sunday, (got a plan for that), but will take you up on that afterwards if I'm still not having any luck Andy. Thank you.

[fifer]

Andy , go back to basics with the carbs .

{ 1 } Do you have Viton tipped needles in the floatbowl chambers ?
If not , it is worthwhile changing them as it helps towards alleviating vibration bounce . 

{ 2 } Check the float height as per ;
http://amalcarb.co.uk/optimising-mark-1-concentric-fuel-levels 

{ 3 } Check that the needles , jets ,  slides are the same as per ;
http://amalcarb.co.uk/rebuilding-mark-1-concentric-carburetter

{ 4 }  Since you have removed the chokes have you blanked off the the top ?

{ 5 } Did you use a couple of lollipop sticks , nails , biro pen inserts  , etc to check that the slides were opening at the same time ?

[Olds]

Fifer mentioning viton tipped float needle, made me remember that there can be problems using the brass bodied ones as they are heavy and can cause erratic fuel level height, aluminium ones are available from Burlen.
You mentioned in line filters. Are these in addition to the in bowl filters ? Shouldn't cause a problem though.
You could try restricting the bellmouths to see if choke will be needed.

[Manky Monkey]

Yes to most of your list Fifer.
Brass needles with black tips. The problem was flooding of the float bowls rather than not enough fuel in the bowl.
Floats are plastic so I can't bend the tab that holds the needle, to alter the float height, cos it'd break. Checked the Amal site & it says that type are non adjustable.
Needles, jets etc are as per the guy I bought the manifolds from. Work on his bike so should at least run on mine.
Aftermarket cast aluminium carb tops with no choke fittings.
Yes, slides synchronised using lolly sticks under them, (easier to see movement in the sticks than just the slides).
Yup, 2 filters to each carb.

Maybe this can be the challenge at the Basingstoke show at the weekend -see who can get it running

[morrag]

Andy, provided the valve timing has not been interfered woith, we can assume its ok. Similarly, if your ignition timing is set to fire marginally before TDC then it should fire the fuel, even if not ideally and accurately set. Now, fueling, if you inject fuel in to each cylinder, then install a pair of clean, "warm" plugs. it should run until that ful is used, so.... if the motor has been standing the rings might be gummed up, leading to low compression and lack of "suck", so do a compression check, you should see over 150psi, if not bung a mixture of WD & a touch of diesel into each cylinder, let it soak for a day, blow it out with the kickstart, then, inject fuel and....it will run, got to! once thats achieved, set the carbs up, ie. 1 1/2 turns out from closed for your needle valves, throttle abutments to touch slides, plus a whisker! stop the float chambers flooding, and Bingo!........

[Manky Monkey]

Yeah, easy as that!

[the coppersmith]

Just had a "manky moment" my dolomite sprint was reluctant to start, choke cable came adrift, reconnected it and fired up first time ! So you have no choke, gaffer tape across the inlets and poke a pencil size hole through it. Rich mixture by less air equals a choke, what have you (we) got to lose. Hope it works, really hope it works.

[morrag]

Maybe not "simples", but check each cylinders compression, please. Re choke, the "ticklers" are there to enrichen the mixture at starting, so you shouldn't really need chokes, honest, but partially blocking the inlets won't do it no harm, however you have timed the ignition on the firing stroke, haven't you? just a thought ...Morrag

[the coppersmith]

My old Greeves Oulton would never start without a "strangler" once warmed through take the "strangler" off and it would run all day. That was on a Amal TT