Bandit spitting back

[jimbob43]

Recently bought a bandit, it was spitting back through the carbs below 2000 revs, carbs were worn badly, so i had a set of fcr,s that i fitted and its still doing it, changed plugs and leads (taylor leads), as these looked shot, green dyna coils look ancient, it was lumpy as hell below 2000rpm with the CV,s, to the point where it sounded like it wasnt running on four cylinders, lot better with the fcr,s, but still spittng back below 2000rpm, its a mk 1, but mark 2 engine fitted, said engine has done less than 3000 miles, its running the mk1 cdi?

[KATANAMANGLER]

Spitting back through the carbs would suggest a lean idle circuit. Have you tried richening the idle circuit? Could also be caused by an air leak have you checked all the boots for leaks?

[jimbob43]

I,ve squirted washing up liquid around the boots and everything looks ok, it did it with the old engine, but i,ve fitted a different set of inlet rubbers, and tried different carbs

[Oliekoel]

maybe farfeched but couldn't it be that the outlet valve is too tight causing the backspitting?

[Scara]

I would take carbs off. Check all float levels, check pilot screw positioning check the individual slides, and E Clip positions,  paying particular attention to any worn parts that should be refreshed, and balance the carbs. ANY Vacuum issues are going to show up on the gauges.  Next ensure when you are setting carbs, you dont run the risk of allowing the engine to get too hot, you would again run the risk of setting it lean again.  Everything except checking your exhaust system to me points back to carbs.

This whole process shouldn't take more than 3-4 hours if you have the tools in front of you. Do you happen to know when the last time was it had the top end valve clearance done by chance ?   Would also run a compression test for shits and giggles regardless of being less than 3000 miles. Prolonged lean running burns out valves,

However, that does not account for a shorting CDI system. Do a primary and secondary coil test on each of the Dyna units. Also double check the stator is sending out the correct amount of voltage between idle and 2000 rpm, you never know.

If you have full exhaust flow, balanced clean and functional carbs, needles, jets, good emulsion tubes, mains all good, timing is correct and fully operational, no vacuum leaks, it has to start and it has to function. Once you have those elements right, and your timing is spot on, the engine is out of excuses not to operate properly. 

I have on more than one occasion found If you follow a pattern in your process, akin to the process of elimination - you cannot go wrong and you will find the culprit, I promise. 

Let us know how you go, would be keen to hear your results.

 

EDIT: Just did a read somewhere on the say what now!? forum US. Guy had a similar issue, turned out to be coils not delivering and over fueling through poor emulsion tubes straight into the exhaust, subsequently burning fuel in gas system, just  a thought. 

Edited July 13, 2015 by Scara

[jimbob43]

Cheers for that scara, i,ll start the working through that

 

[wraith]

Car't much more that scara says, or I somtimes put it it's got a gremlin ;)

[canamant]

First check inlet valve clearance - make sure there is some .