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Carb balancing bad starting?

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myvision
Scooby Slapper



Joined: 26 May 2016
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PostPosted: 10:25 - 09 Jul 2017    Post subject: Carb balancing bad starting? Reply with quote

I'm having a couple of problems with my Hornet which I think is down to the carbs needing balancing rough idle and runs shit at low revs.

Would the out of balance carbs also cause a starting issue when cold?

Are these kits any good for a first time?
https://www.amazon.co.uk/BIKE-IT-VACUUM-GUAGE-CYLINDER/dp/B003370YWQ/ref=sr_1_1?ie=UTF8&qid=1499588642&sr=8-1&keywords=Carbtune

Thanks.
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Teflon-Mike
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Joined: 01 Jun 2010
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PostPosted: 11:27 - 09 Jul 2017    Post subject: Reply with quote

If you read the paynes manual, or even the instructions in a carb-balence kit; they will tell you that carb-balencing is a 'final' fine tune adjustment, and should be performed after ALL remedial repairs or normal service items; it is not a 'fix' for pre-existing problems.

So, even if you got a balence kit; you would have to start at the top of the list; make sure carbs are clean; air-filter clean or new; sparkplugs clean or new; valve clearances in spec; bores & rings not loosing compression or letting oil be burned etc etc etc...

Good chance that when that lot has been worked through, you wont 'think' carbs need balencing.... and if you do anyway, the 'difference' will be quite subtle, in so much as it will show itself in a slightly crisper thottle response and better mpg. It WONT sort out bad starting or bad idle.. that should have been remidied before you start a balence, and if not, you likely wont get a good balence, and balencing wont make much difference to it.

Essential principle of a balence is that you are syncronising each carb, so that each pot is pulling its own weight, and none of them are trying to race ahead or hold back the pack, anywhere theough the rev-range; consequently you get best power and best economy, and best throttle response from them all working together... little else.

Now; how many miles is on the motor? When should it have had its tappets tickled? When did it last get a set of plugs or an oil change; what state's the air-filter; and are the carbs properly serviced, clean and in tol flor float height etc?

You probably have absolutely no need of a carb-balencer, and trying to use one, would likely make little or no difference; is one likely the most effective / ecconomic way to tackle the issues you suggest?

Your call.

As to the kit? They are dial guages; many will contend that they aren't as accurate as mercury U-tube manomoter type, and are probably right; but consistency is more important than accuracy in this job, and operator error is likely the biggest discrepancy for the job; and not employing the damping valves, or having damping valves open, doing bog all or shut, stopping a reading; lack of suitable screw-driver to get at the indiviual butterfly adjusters; trying to do the job 'tak-on' or tank half on!!! Rather than on a Medi-Drip, will likely make far more difference to how successfully you might be able, or as likely cock-up the bank-syncro.... They 'do' for me, I will say; but only get used at about once a year, for 'final fettle' on a newly restored multi-carb bike, that has probably had at least a top end rebuild, let alone carbs USC'd; they come out maybe once ever three years or so, on the bikes ';in service'.. if that, as part of a 'super-service'... and even then; all other service items 'done'... cleaned, and serviced,factory set carbs are rarely very far off... even on an old hulk like my quarter century old Seven-Fifty with worn choke spindles!

Fun to play with... B-U-T... NOT really a 'go-to-tool' to 'fix' stuff.

A pair of £40 gauges isn't going to 'fix' an out of tol valve shim or three; or a worn slide needle, or gummed up pilot jet, or a sticking or worn float valve; all it will do is let you wast a lot of time, finding you 'cant' get the thing to balence up; and that 'something' else, like a carb service, or tappet tickle, has to be forked out for, and you are down £40 on available funds to get that sorted.

My advice; get the thing properly serviced; get the tappets checked; give it a good thrashing, to get the battery charged up and wash the carb jets with some nice new fuel.... ponder what's what after that.

A-N-D, if its an older bike, with non-stock can; £40 for a set of vac-guages, to sit in the shed for years unused, would go a long way to a proper rolling road set up, and do far more to get it in tune and on song than a throttle sync.... your call.
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myvision
Scooby Slapper



Joined: 26 May 2016
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PostPosted: 13:59 - 09 Jul 2017    Post subject: Reply with quote

Bike is now on 46k
Here's when thinks were last done
Valve clearances 36k
Plugs and air filter 40.5k
New coolant 43k
Oil and filter less than 300 miles ago.
I'll take the plugs out and have a look at them failing that anything else I should be looking for?
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myvision
Scooby Slapper



Joined: 26 May 2016
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PostPosted: 11:42 - 17 Jul 2017    Post subject: Reply with quote

I took the air box out and tightened everything up that i could now get to.
Then put the airbox back and whacked some carb cleaner in the tank and took it out and thrashed it around for two full tanks and can honestly say it's now spot on.
Must have been a loose connection on one of the carbs.
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