Jota 180 Missing ?

[jotajoe]

I've noticed a symptom or maybe a characteristic on my Jota 180.

When I'm riding along if I for instance forget to go down a gear when slowing up and then open the throttle in slightly too high a gear she seems to miss spark for a second and then pick up quite nicely as the revs increase. She never misses when revving it's just when I am in slightly too high a gear. Almost like what they call in aviation a " lean cut" ..The rush of incoming air weakens the mixture and she misfires as a result.

I just wondered if I have an issue of some sort going on here or is this a normal characteristic of Dellorto's

Thanx in anticipation..

Ciao

joe

 

[Haggis]

Hi Joe

How fast are you opening the throttle when this happens?

 

[Dellortoman]

Try some new spark plugs. My Jota did exactly that last year, new plugs fixed it.

Simple things first 

Cheers,
cam

 

[Grant]

Check also HT lead to spark plug cap condition. Trim 1cm or so off the HT lead and screw it into the cap again.
In fact maybe replace plug caps while you are in there.
I have had this sort of stumble with the motor/carbs over the years and if the carbs are in balance then the culprit is usually something simple like I mentioned.

 

[jotajoe]

Thanks Guys,

Firstly apologies for posting in the wrong section  :-[

I'm not opening the throttle too rapidly. It happens under gentle accelaration too.

I'll clean the Splitfire plugs which are almost new and look into the HT leads/caps too.

I did notice the other day that centre carb dripped a tiny bit o fuel when parked up so there could be a little bit of overfilling going on there. I'll check that out too. This might be the fuel admittance valve or a heavy float ? I had heavy floats on my R90/6 and couldn't stop em dripping until I put brand new floats in. I understand that over time the plastic absorbs fuel and becomes weightier.

I do promise not to fiddle with the carb settings at this stage ; )

joe

 

[3patC]

I thought someone had pinched your bike for a moment Joe 

 

[jotajoe]

That's a cracker Pat lol

The little sprogs round here only go after scooters ..They wouldn't get too far on a Jota lol

 

[Grant]

Throw away the Splitfire plugs now. Replace with Champion or NGKs (my preference, but others swear by Chumps)

 

[cwis]

I second this! Mine ran like a big of poo with splits in. Back to NGK's and all OK.

Throw away the Splitfire plugs now. Replace with Champion or NGKs (my preference, but others swear by Chumps)

 

[jotajoe]

Ok Guys..Wildo..That's what I call " Champion" advices 

 

[Grant]

If high comps in your Jota go for B9ES and if low comps then B8ES.
If possible use the EV plugs instead of ES (gold palladium and tiny electrodes). I use them when I can get them and they are better (IMHO).
Don't use Iridium plugs

 

[jotajoe]

Thanks Grant..Yes High comp pistons and 4c cams on board. I also do motorway work and relatively high speed at times so I'll take your advice.

cheers

joe

 

[bclark]

As mentioned on a reply to a different post, you could use a timing light on each plug lead to see if any cylinders are misfiring due to lack of spark. Connect up, start the strobe and rev - frequency of flashes should increase without any missed flashes - if there are missed flashes it is either the a problem with the spark plugs themselves or the supply to the spark plugs. If not break in flashes, the problem is elsewhere.

 

[CLEMTOG]

are you on osch ignition Joe?
it might be the advnace step doing its switch.
CLEM

 

[Laverdalothar]

Might be the acceleration jet of the carb just p***s out the spark?

 

[jotajoe]

Hi Clem, It is Bosch ignition. It happens when I open the throttle fairly quickly and yes it does feel as though the candle has been snuffed out for a second or so. I'll take a look at the plugs and see wot's wot..

joe