650 poor/not running

[Soichiro]

Hi chaps, I'm having bother with my 650 and could do with suggestions.
I've only done 4 trips (75 miles) since it's back on the road. Firstly, it's always a pig to start - usually needing to be jumped off the van battery.
Once started it'll run OK.
Trip 1: ran great for 40 miles
Trip 2: after 5 miles, after starting again it went on 2 pots. 1 and 2. 3 and 4 were stone cold.
Trip 3: ran OK, took ages to start though
Trip 4; same as trip 2 - went on 2 pots. Limped home being overtaken by mopeds.

I've eliminated poor compression because it runs OK sometimes, not ignition either because 3 and 4 not working (instead of 1,4 or 2,3)
Thinking there may be blockages in the carbs, I stripped them, blasted all the channels with compressed air and fitted new jets etc.
Yesterday it refused to start. 15 mins or so of cranking with the occasional DUF as the engine overtook the starter motor. I didn't even get a DUF DUF or DUF DUF DUF. Sparking OK, air filter not blocked.

The petrol hasn't gone off bacause the 400four started 1st prod with older petrol.

I'm thinking it may be the carbs need to be ultrasonically cleaned but I've run out of ideas really.
Where do I go from here?

[sparki]

valve clearances all ok?

[Soichiro]

I assume so. When it's running, it goes great. Doesn't sound tappety at all, even when cold.

[sparki]

could explain poor starting however...

[fossie]

Choke cable, disconnect it and pull the bar out by hand, make sure it goes back all the way, never reattach it!

Fuel filter in tank, is bike left on side stand.

[johnr]

when you rebuilt it, did you clean out the tank? is it rusty inside? have you ultrasonic cleaned the carbs or just sprayed them? have you a fuel filter fitted? it does sound like a fuel problem rather than ignition because the coils feed 1+4 snf 2+3 so if it were ignition, then these pairings would be failing. if its been stood and the fuel had gone stale or else theres rust in the tank, it could cause the problems you describe.

[Soichiro]

I'm thinking it's a fuel issue too. When I stripped the carbs for the second time, there was some shite in bowls 3 and 4, although there was the same amount of fuel in each bowl. The float valve filters were all clear though. The inside of the tank looks ok but I'll flush it out to make sure. Using the compressed air may have forced some shite further up some channels causing more problems, although I did check the fuel passages weren't blocked. I always pull the choke rod out anyway because it works better than the choke knob.
I'll also borrow the HT caps from my other bike because they're known good ones.

[johnr]

empty your tank, take it outside, put your fag out, put your bike gloves on, squirt in a bit of washing up liquid, and then pour in a couple of kettles full of boiling water, and get shaking, this will remove all the residue, and fuel deposits, after youve given it 5 mins shaking, get a length of light chain, the sort of chain they hang sink plugs on with, as long as youcan get , chuck it in the tank, and shake it for as long as you can take it, the chain will dislodge any loose rusty bits and scale in the tank. after youre satisfied, get the hosepipe into it, give it a good swill and shake out. then bring the tank indoors and put a hairdryer or hot air paint stripper on low heat into the filler neck with the tap removed, you need to dry it out quickly, so if you want to, swill more boiling water round then dump it out whilst still hot and pop the hoover pipe in the neck, this will create air flow to dry it out.
now, its possible that your tank could have been sealed in the past with petseal, but petseal cant cope with modern unleaded and is dissolved by it causing all manner of problems. so, buy some acetone from ebay, ( you can get it by the gallon) and use this to dissolve the petseal in the tank.
once the tank is clean you need to either fill it with fuel or seal it with an ethanol resistant sealer, i use por15 and havent had an issue, but there are others available.
finally, get a petrol filter, nothing fancy, just a small square one with flat sides, then get a neodymium magnet from ebay and araldite it to the side of the filter. the reason is that when a tank rusts, the fine dusty rust that forms gets dragged down into the carbs and clogs them up. but this dust is so fine that it will go right through a fuel filter, but this fine rust is magnetic, and the magnet will hold it in the filter and keep it from your carbs. you can also stigk the magnets under the bottom of your tank though this can cause long term problems if there is ever any water in your fuel tank.

[Soichiro]

Cleaning the tank is on my to do list. I think it's fairly clean inside bacause It's been emptied for respraying. The filter/tap was clean when it came out (unlike some I've seen). The shite in the float bowls was when the sprayer painted inside the neck of the filler and the petrol lifted the paint. I've since cleaned all that up.
Can't do much on it while it's monsoon season.

Meanwhile.. I'm bidding on a 2litre ultrasonic cleaner so I can immerse entire carbs.

[bobster]

Or I can sell you a brand new 650 tank for £250 posted..lol