z 650 carbs

[johno]

Been out on the B1 today done about 80/90 miles its been fluffing and missing at low revs I have had the carbs off half a dozen times ultra cleaned. the last time it's doing my head in now what to do next try changeing carbs? dyno kit? you would think the pilots were blocked but the carbs are spotless the only other thing is that its a bit of a pig to start from cold once started its on the button all day any help would be appreciated
john

[000zeds]

Johno you posted this in wrong section !

Should be in Bike Help !

[johno]

oops !! how do i delete it?

[000zeds]

Hopefully one of the moderators will spot this and move it

[Ginger Bear]

I'll move it.

[z1bman]

possibly a bad ignition coil or low compression

[Crofty]

the 650 is a notorious cold starter.
Mine starts better on Dynas s coils and ignition.
Be sure not to touch the throttle when starting (in fact closing it against the springs helps the starter circuit pull more fuel due to increased vacuum).

If its fluffing when warm, it could be ignition as already mentioned by Z1b man

[johno]

Thanks for that ginger bear.
Cheers for the input guys its had new coils, leads, plugs, points, condencers, checked gaps and comp's no air leaks all good don't want to give up on the old girl might try to get hold of another set of carbs just to see

[z1bman]

don't be fooled into thinking new parts are good. even new parts can be faulty. leaving the ignition switched on for long periods of time without the engine running + with the kill switch in the run position will damage the coils

[Charlie]

What exhaust are you running and what air filter set up do you have - stock or aftermarket ?

I had to up jet (mains AND pilots) quite heavily just for a 4-1 exhaust

[johno]

Thanks Bman the ignition info is a new one on me I wont forget it !!
charlie I have a std. air box and std. zorst but I am going to run a nice little Marving 4into1 while I tidy up the std one what size jets do you reckon for the Marving??

[Charlie]

There are no set rules.

I fitted a V&H 4-1 with the standard airbox and genuine air filter and ended up using #17.5 pilots (1 size up from std) and #107.5 mains (2 sizes up from standard). I am currently running a Predator 4-1 and the same settings work OK on that too.

All bikes are different though. I ended up where I did through trial and error. Initially I had a fluff on the first 1/8th throttle - altering the pilots cured that, then it misfired and ran out of steam at 3/4 throttle. Going up one main jet size sorted some of that - but it took 2 jumps to get it right. As you will know, getting the carbs on and off (particularly back ON) can be a pain in the arse too....I found using a hair dryer on the inlet/airbox rubbers to soften them up temporarily made the job a LOT easier ;) I was very surprised that just an exhaust change, warranted those jet changes - the manufacturers usually say no jetting upgrade is needed....but it most certainly was on mine.

I run Dyna coils and ignition too - much better than stock ...

[zedrider]

i too have a z650 b1 an old guy once told me if you think its carbs its normaly ignition . and visa versa . funny enough most of the time he was quite right .

[johno]

yeah cheers Charlie will go for jetting I see there is a dyno kit available £62 wonder if that might be the way to go?

[Charlie]

Dunno mate.

Personally, I went the genuine Mikuni jet route. I've had bother with after market jets and carb stuff before.

I KNOW that genuine Mikuni is exactly what it says it is. ;)