C20xe running rough

[conza123]

Right my m8 with the viva gt running c20xe is having running issues,

right specs of the car 1st to help,
-standard c20xe
-Yamaha thunder race bike carbs sent off to Boggs brothers and they jetted rebuilt and made manifold
-megajolt kit using ford edis stuff as didn't want to loose heater due to dizzy going threw where heater would be

a month or so ago with it perfectly running fine noticed that the head had become porous so set about whipping it off and had it sleeved between the 2 head bolts and head skimmed etc,

then the problems started, it wouldnt go above 3k when back together it was like it was hitting a limter (3k is ruff rpm as rev counter not wired in yet) and would cut out etc when warm.

so we noticed that the see threw fuel filter was empty so fort the facet fuel pump wasn't doing it's job so replaced that with a new one no joy,

then we fort what could of happened inbetween head being off etc so we checked the engine timing and that was spot on

checked compression as it was free to do and that was perfect

replaced plugs as they where cheap no different,


replaced crank sensor(ford one with trigger wheel) bolted to front of crank pulley which Made it better but still not fixed

replaced coil pack which didn't change anything,

then noticed alternator weren't really charging so replaced that and now it is

and plugged ecu into laptop and that seems to be working as it should.

now we are running out of ideas on what to do next, t's starts to miss and backfire at I'm guessing 3500/4000rpm but sometimes it will almost cut out as soon as I touch throttle so I have to just change gear and let clutch up without accelerating

[Southie]

Firstly double check you've no air leaks as my old bike carb set use to do a similar thing, also have you had the carbs reset back up after rebuilding it?

is the cam shaft and crank sensors okay also?

[conza123]

Carbs have never been setup on the engine just got them from Boggs and bolted them on and ran perfectly fine, I know they could do with setting up propley for best results but it was running perfectly before head was removed, and have checked air leaks and couldn't find any :/

and only has crank sensor which has been checked etc and even replaced with new one

[Southie]

With the engine changing due to the head fix I'd get the carbs reset up, bogg brothers do bike carb setups, that's where I got my old sr done ;)

What colour did the plugs go btw?

Also has the dizzy timing been adjusted at all??

Does the engine rev okay when standing still??

Definitely no splits in the pipes that connect to the manifold and the carbs, also are they tightly fitted???

[conza123]

Plugs went light brown

we cut dizzy off as it's in a rear wheel drive viva so no room for dizzy with pout cutting hole in bulk head were heater is
so it's on megajolt that just uses crank sensor edis unit, coil and ecu

we are gonna strip carbs tomorrow and see if there's anything fallen off or shut in them

[Southie]

Plugs went light brown

we cut dizzy off as it's in a rear wheel drive viva so no room for dizzy with pout cutting hole in bulk head were heater is
so it's on megajolt that just uses crank sensor edis unit, coil and ecu

we are gonna strip carbs tomorrow and see if there's anything fallen off or shut in them
If the it's are a light brown then that's usually ok, I'd still be getting the carbs setup correctly though as they might be slightly under fuelling and need rejetting.

also though does it rev okay though standing still?

[Scottcooper85]

Check the vacuum rubbers aren't split on the sliders in the carbs and the main jets aren't blocked or too small.

[conza123]

Not to sure on revving up standing still as it's to late to try tonight as pretty loud and I think we gonna take a good look at the carbs 1st just strange it was perfect before head off tho :(