little carb help required please!

[johnr]

carbs seem to be the bane of my life, theyre almost a magical black art where the difference between perfect clean running and lumpy backfiring coarseness can be a quarter turn of a screw!
anyhow, ive got a problem with the carbs on the bike that im trying to get my head round. the bikes a kat with a gsxr1100m engine fitted, its got the 36mm carbs from a bandit, but they seem much thee same as the gsxr's stock carbs.
just to fill in the details, theyre 36mm, the needle is in the middle slot, main jet is 150, bike has foam filters and a freeflowing exhaust. the carbs are spotlessly clean and the tank is clean too, sealed with por15, fresh petrol, screws 2 3/4 turns out. new filter vac take offs on the carbs all correct (one for fuel tap, one for scott oiler, 2 blanked off. no air leaks. new plugs. bike fires up on the button instantly and ticks over on all four, choke off and its a level even tickover, so far so good, but when i try to rev it, it boggs down and goes lumpy, popping and banging through the pipe. shut the throttle and it ticks over evenly again.  it just wont rev, so before i take it all apart and start messing with stuff again, any pointers?

[KATANAMANGLER]

 

[johnr]

yeah thanks. thats very helpful. but before i start throwing money at new carbs that will then require setting up, im rather keen to get this done so i can go to germany on it in june...

 

[bluedog59]

What have you got the float heights set at ? From my experience B12 carbs can be very fussy on fuel level in the float bowl. If this is happening when you're just trying to rev it with no load on it, it seems like the next fuel supply up after the pilots is just not kicking in. Even if the needle setting and main jet were well out it should still rev in neutral if the fuel is there.

[KATANAMANGLER]

6 hours ago, johnr said:

yeah thanks. thats very helpful. but before i start throwing money at new carbs that will then require setting up, im rather keen to get this done so i can go to germany on it in june...

 

Sorry John I'm not trying to be smart. That's my genuine answer. If you have the money throw it. The carbs have been running on a B12 so I'll wager they would run on yours as they are. 

 

[Solcambs]

 

I had exactly the same set up on my Kat. The carbs were not bandit but 1100K/L 36mm on pod filters. They popped and banged initially until we set float heights properly. Pretty sure  they were 144 mains - though we would have jetted down for the Harris 4-1 which  is pretty restrictive. 

As you can hear - not exactly healthy on first fire up.

 

Edited May 16, 2018 by Solcambs

[johnr]

This is mine, it starts perfectly and runs evenly, but just off tickover, and without a functioning revcounter I'm guessing here, at a guess perhaps 4k revs it just stops wanting to rev and starts backfiring in the exhaust. What do you reccon?

[johnr]

Arse! That's supposed to be a video!

[Solcambs]

4 hours ago, johnr said:

Arse! That's supposed to be a video!

Lovely picture ... but not a video - you'll need to upload a vid to youtube and then paste the link. It should then display as a video here.

[johnr]

ok, lets try it this way. fingers crossed.
 

 

[Solcambs]

12 hours ago, johnr said:

ok, lets try it this way. fingers crossed.
 

That does seem like float heights or sticking floats ... initially it ran OK, then got worse. If you leave it a minute does is fire and run sweet for a few seconds? Any differences in temp across the headers?

[johnr]

sorted it now. in a roundabout kinda way.......
 

 

[ciderman]

What was the roundabout way you sorted it ?

 

[johnr]

rs38's.

[nokturnal]

watch you don't suck that beard in thar