Bucking and pilot air restriction jets

[Alan H]

Never use tescos (ask Scotch!) Just on a nice Auchentoshan and a few of its friends......

[GTSteve]

Can you tell me what the Fuel Level (height) should be on a GT550?

[Alan H]

Yup..

[GTSteve]

Thanks Alan.

[GTSteve]

It may be of interest for those with bucking kettles to know that the kawasaki 750 H2 suffers with exactly the same problem. I'm thinking that perhaps 750cc's is just too many for a 2 stroke.
I was advised to thorougly clean the carbs, reduce the pilot jet size and balance the carbs precisely. This enabled me to drop the tick-over to a smidge above 1k revs. Having done this the bucking either disappeared or was very minimal.
Also the tickover tended to change up and down from one day to the next!
steve r

[Davidcumbria]

Been browsing threads around my bucker and before I fit the restrictors I wonder if the problem is with too high idle. It sits at a about 1250 on the tacho and if unscrew the adjuster a good part of a turn or so it doesn't reduce much but then Starts to shake a little thenstops abruptly.. Engine only has 500 miles once rebuild so may be al little tight. I have to say it is a nice smooth and even idle at 1250 and the engine picks up quickly and smoothly without hesitation on the throttle. Does seem comparatively to my other two strokes a bit slow to rev down but I wonder if that is just how they are. Is the high and difficult to reduce idle at the root of my overrun bucking problem and what should I be looking at to get it idling slower ?

[Alan H]

Recently sold a boat with a 1.7 litre V4 2 stroke and didn't have those issues, but there's always this one.
https://www.youtube.com/watch?v=EmnsXTMLzCE
https://www.youtube.com/watch?v=RoiWpJLokEc
https://www.youtube.com/watch?v=mrhsUXnodfw

or
https://www.youtube.com/watch?v=lRKeuHyI0lw

[yeadon_m]

David,
1250rpm is too high and can on its own provoke bucking. I wonder if your idle is set too lean? if yours are BS40 carbs, what number of turns out are your fuel screws at the front? try opening another 1/4 turn or so.
Possibly you also need to carefully balance the carbs, per the manual.
Cheers,
Mike

[Davidcumbria]

I found the fuel screws were all set at one half turn only. Set to3/4 turn and bike will now hold idle at 1100rpm and bucking seems better. Will check balance and find out if any pilot air restrictors are currentlyfitted. Heading in the right direction now.

[Davidcumbria]

Still playing around and getting slight bucking but not all the time. A few pointers it doesnt buck at all and seems to accelerate faster with the choke on and the engine at working temperature which suprised me - is that normal? Tempting to ride with choke on all the time but probably not a good idea. Possibly related I had a plug oil up and stop working today. new plug when checked after a run ( no choke ) not oily at all. Getting a smears of oil running down sides lower exhaust cans ( delkevic) and can see wetness and oil dripping from end of all cans. Oil pump is set to line. Bucking is not too bad but choke on performance is completely smooth on overun and I would have thought this was achievable without choke. will idle at 1100 but slowly die if not blipped occasionally which i gather is normal. It feels like perfect smoothness is within reach. Also It seemed to buck less on the 98 octane than the 95 I have just put in.Any and all input appreciated.