A15 running standard points dizzy, standard Hitatchi carb. In a 1000 with a 1000 coupe engine loom.



Well i thought i had it all sorted! But no, no i didnt! It wouldnt start because the plugs were caboned up. Clean the plugs and hey presto she lives. But at around 4500rpm it would slutter and fart and die in the ass. Under 4500 and feathering the throttle it would be smoother but still lurchy. Adjusted timing to no avail. Seemed sluggish under 4500 to what it was before too
So then i cleaned the WHOLE fuel system out. Blew out the lines, stripped the carb, new filter etc.
It was a bit better. But still ####! So i swapped the main jets for a bigger set. It kind of cleared, then went beautifully! So i thought i would put the elecy dizzy back in. Didnt run very well at all with that! very roughg revving and was just ####... ok back with the points dizzy, in the exact same spot... runs like #### again! So i went and got another carby(Cheers Richard!) and stripped/cleaned it and put it on this morning.
Cleaned the carboned up plugs(for about the 5th time) and she fired up. Ran like ####. It seemed like it was running out of fuel after you give it about 5 good revvs, but the float bowl never went under 1/2.
Then it started doing its trick of blowing all the fuel out the carb, like a big backfire(no flames or BANG). Its just like a mass of compressed air pushed back out the caby. blowing fuel out the top and out the top gasket. It does it like every rev of the engine too... like the valve overlap is too big and its pushing the exhaust out the inlet???

Any ideas this time

i would check your valve clearences.

if your cleaing plugs all the time u dont want bigger jets. The standard jets should be fine...

it mite be in the coil or something.

did u take the ballast resistor out when u put the elec dizzy in?
if you didnt it wont work properly...

sounds like the spark is a bit weak or (as u mentioned) the valves are too loose and the A/F mixture is getting out of the chamber/ not burning correctly

standard jets are in.
never had a balast resister on it, i have the points dizzy in it atm anyway.
tappets are spot on (rechecked on friday)

It seems fuel related to me. I re-cleaned the original A12 carby and found a little more #### in it(pulled EVERYTHING apart this time). I put that on. Fired up and it ran and revved. Then it seemed to run out of fuel and then do the backfire thing. So maybe it is the fuel pump still? (new electronic 'facet' located just under fuel tank). Seems to flow well tho and the fuel bowl seems to be full all the time. But now even when i goto try to start it, whenever it tries to fire it pushes the fuel back out the carby, and with a bit or force too coz its blowing through the top gasket.

what fuel regulator are you running?

maybe pressure is too high (sounds like it if fuel is being pushed out the gaskets)

no no no

if you read i say it pushes the fuel out thru the gasket when it backfires. when under normal conditions, fuel bowl fills, valve shuts off flow, no leaks.

went out for another play. when i retard the ign more it stops the backfiring thing... but acts as if its too retarded, i can barely keep it alive.

ALSO, when i had it running the timing mark would be around 30btdc. even 20btdc would make it run like ####. but the timing mark is spot on when you check cam timing???

Exhaust system is partially blocked
Too much backpressure

cant see how unless somebodys broken into the garage and stuffed a potato up the pipe... 2" system with 1 straight thru muffler under 6months old.

might explain it though???

ok ill leave you all with this final comment(for now)

Cam timing???

Mark on balancer is spot on TDC(checked with screwdriver in plug hole)
But 'ran' at about 35btdc. It would start running very poorly at 20btdc and stall not far after when retarding ignition.
Without touching dizzy, would run worse and worse. start 'cracking' thru exhaust. Then pumping fuel/air the wrong way thru the carby(i dont beleive its a back'fire'). Then sometimes fix itself and be driveable and then run fine again.

Loose cam chain? Adjustable came gear with loose bolts? Stripped sprokets?
What makes a engine run great(idle and revv to 6k+) at 35btdc?

Thats the current thought. Me and dad(im a 3rd year mechanic, dads fully qualified) sat down and thought it out and that was our conclusion. Something internally is drastically wrong!