non starter

[philwright]

Removed the carbs on my 88j yesterday with the intention of changing the o rings in the carbs and fitting a new throttle cable, anyway to cut a long story short the screws holding the carb rubbers are all solid and I couldn't be arsed to try and get them out for the moment, so I fitted the new cable and put the carbs back on, connected fuel pipes and vacuum pipe set fuel cock to prime and pressed the starter ,it cranks over like a good'n but just wont start ,it doesn't even cough,  pulled the plugs to make sure theres a spark and there is a strong one on all plugs, but they are all bone dry, looks like no juice is getting to them, took the tank off and theres fuel in the pipes, took pipes off tank and turned cock to prime and theres just a trickle out of one of the stubs and nothing out of the other, i expected fuel to be pissing out of both...the bike was running fine apart from slightly hanging  revs before I stripped it down, acratching my head,am I missing something?...any advice welcome.

[Captain Chaos]

fuel tap is fucked if it does not flow on "prime".

With the tank off, put it on "on" or "res", and suck the vacuum pipe with your mouth. Fuel should flow.

If it does, install and connect the tank, suck the vacuum pipe before connecting that, to let fuel in the carbs. Bike should start now. Fuel tap is still fuct but at least you'll have a running bike.

[philwright]

Thanks , just a bit strange that bike was running ok before stripping carbs, i didn't touch the fuel tap at all, i guess  empty carbs and a dodgy prime setting has brought it to light. i'll have another look at it tomorrow time permitting.

[jonny1bump]

Ive seen 10 bhp gain just by pressing on fuel tap on dyno.  Thet really are rubbish.

[philwright]

Got the bike to run this morning in a fashion, revs are all over the place revving its tits off and up and down on its own without me touching the throttle...somethings wrong somewhere, must have fucked up re -fitting the carbs ?... starting to wish i'd left the thing alone in the first place...any advice please?

[E T]

Sounds like its drawing air, check the carb to mainifold joints 

[jonny1bump]

As above does sounds like air but first what did you actually do to the carbs and what's carbs are they.

[philwright]

Carbs are BST36SS, i removed the carbs and fitted a new throttle cable ,also changed the far left carb top for a good spare one  i had lying about cos it had a small crack on one of the corners ,turned the carbs upside down in order to fit new cable and all the petrol left in the bowls spilled out and that's it...did have a struggle fitting the far left airbox rubber onto the carb body ,and i did check that the fitment onto the manifold rubbers was a good one and made sure all the screws were tight.

[jonny1bump]

When you changed the carb top you did make sure the small tiny o ring was located. Also the diagram itself located correctly. 

If they were any crud in petrol turning it upside down would also fill jet with all this crud quite nicely not in a good way.

[philwright]

Thanks for the advice, will have another look at things next weekend i will remove carbs again and clean jets ,also check whether little o ring is there and do a double take on everything, fingers crossed, i'm a carb novice!.

[jonny1bump]

Just take your time..

[nopokewithoutsmoke]

I've just spent a fair amount of time trying to sort the carbs on my 600 Srad.

My advice would be: make sure you've got somewhere clean to work with plenty of light, a torch, magnifying glass (yes, really), clean containers for carb parts, penetrating spray for stuck screws and jets, carb cleaner, brake cleaner, nylon wires for poking down brass jets, take photos along the way, ask if you're not sure, and don't rush.

Oh and it might be worth checking that your tank isn't rusty too...

Good luck!

 

[philwright]

Thanks...I've never stripped a carb bank down before but I guess checking all seals , making sure the jets are all clean and the floats are working properly will be a start, i'm sure i'll be back on here looking for further pointers in due course.

[jonny1bump]

Don't strip them to component bits, take jets and emulsion tubes out and blow with compressed air and through passages they screw into. Make sure diaphragm on slides until top cover not perished and are located correctly along with the small o rings in the carb tops.

[philwright]

Removed carbs off bike again this afternoon, took float bowls off, inspected the seals and all are Ok, took mains and pilot jets out and blew them through, a couple of the mains were partly blocked with muck, took carb tops off and all diaphragms are ok, again tiny 0 rings are all in place, silly novice question...which are the emulsion tubes I need to be blowing out?...and thanks.

[jonny1bump]

Take main jets out and carefully push emulsion tube up out towards top of carb. When 're inserting be gentle lining tenon with slit in tube to carb body.

Hope that makes sense.

[Captain Chaos]

when pushing the emulsion tubes out (use a longer bolt with the same thread/size as the main jet for this), don't be surprised if the white plastic slide holder comes out with it. Good opportunity to replace the O-ring on it around the emulsion tube.

[philwright]

Managed to push out emulsion tubes and blown everything clean ,o rings look ok so I've left them alone,Is there anything else I should be looking at before I reassemble carbs and refit them on the bike?...thanks .

[jonny1bump]

Make sure floats and needle seat is are ok you can rattle floats make sure no fluid inside them. The seats is more about having the correct fuel level inside the fuel bowl. 

[philwright]

Checked everything, just ordered a new set of o ring kits of Eblag to be on the safe side, they should be here in time for the weekend when i'll attempt to get the bike running so that its rideable!...fingers crossed.

[wsn03]

Connect a remote tank.up and flood test your carbs on a bench

 If carbs dont piss fuel out after 20 mins all is good.

If they do order new needle float valves either from Mikuni USA or try Wemoto...some here say they're good. Do not risk other patent parts

[philwright]

Whats the best way to clean/unblock the tiny holes in the emulsion tubes, just bought a can of compressed air and some carb cleaner, I was going to leave the tubes soaking in the carb cleaner for a couple of days then block one end off and give them a good blast ...is there a better way anyone can recommend?...thanks.

[Fula28]

Try profi fuel max additive, it will clear all known blockages, pricless stuff.

[Guest YoshiJohnny]

16 hours ago, Fula28 said:

Try profi fuel max additive, it will clear all known blockages, pricless stuff.

except air jets :-)

[wsn03]

Leave overnight in thinners...never fails. Wash off thoroughly in WD40 afterwards, must not come into contact with any rubber

Edited October 14, 2018 by wsn03