Bingo!

work on the main body to get that flat. Any warpage in the air horn may be taken up with the gasket. Ideally that should be surfaced to . follow the instructions I gave in the earlier post about making a surface plate with some holes/slots in it to accomodate the bit hanging off it.
Good luck. I could post a pic of the plate if you like.

hi thanks i meant to say that its so rich that when the choke is applied it runs too rich and the engine stalls jets and balls are in right position!

i took of the top carb cover and i see what u mean the screw holes have lifted up while the rest is fine in middle which leaves a visible gap in the middle!

the carb body was fine might just go over with fine stine and kerosene!

the top cover to get even will be a challenge with the float arm and power valve in the way!

Thanks again!!!

I am not sure exactly what you are saying in relation to the operation of the choke.

Have you check to see what the fuel level is in the bowl?

Did you remove the jets ? If so , are they in the correct positions ?

In answer to your question about the rich condition being cured by re-surfacing the mating surface, the answer is yes.

I also query if you have the little ball valve in the accelarator pump and the corresponding pump discharge needle both in place? If that check needle is missing then fuel can be drawn at all time through the discharge nozzle.

Have a look at these things and make sure they are all there and doing their job.

hi thanks fredeuce i just tried tuning the engine and its running rich that the manual choke wont even work just dies and and when you lean the mixture the engine dies because not enough fuel!

is this the same problem you had?? did fixing the warpage help?

thanks!

Had a similar problem a while back. The problem with those little Hitachi carbs is that they are getting old . Being old they have been on an off a few times and stripped downn etc.

What happens is the main body warps as does the air horn.That causes an internal vacuum leak between the body and the air horn. When that happens the power valve remains open at all times and produces the rich running you are experiencing.
Run a straight edge over the two mating surfaces and look for a gap. Make sure you place the straight edge on the ears where the screws are inserted. They are particularly prone to warpage.
What you need to do is strip the body down to the bare body and run the top surface over a surface plate with some 180 wet and dry and some kero . That will bring it back to a flat surface.

Similarly with the air horn you can to the same thing. However this is a bit trickier as you have the lugs for the float and the spring loaded plunger for the power valve in the way . What I did was to make a surface plate out of a piece of 100mm by 8mm plate about 150mm long and made some slots in it so that I could move the air horn back and forth about an inch. I then simply place a piece of similar wet and dry over the plate, punched holes in the wet and dry and then sat the air horn on it, aligning the dangly bits with the holes and started rubbing until it was flat. That should sort it out.

the bakalite 'spacer' you mentioned should never be removed. it acts as the insulator, to prevent heating the carb. try reface it, and readjust. see what happens. maybe you need to find another unit if filing doesnt help.

yes i used gaskets i will try to file it down and see if it helps!

Thanks!

There should be no gaps between spacer and manifold or spacer and carb. Removing it will not help as the linkage will foul on the carb. Did you put the paper gaskets in-between the spacers and the surfaces? Might just mean you need to file the spacers down flush. Then retune them

hi,

yes sykine has offered to tune it for me but he lives quite far from me!

i use standard plugs for a12 engine over the counter so i think heat range is fine i will try gapping it smaller!

also the carby has a spacer in between the manifold i noticed when the spacer sits on the manifold in the middle were (between the two circle ports) the spacer doesn't sit flat so there's a gap!

could this cause this problem? maybe i will try without a spacer just to see?


thanks!

what plug gap you use? try 0.8mm. if misfire happens, reduce it by 0.1mm until there's no misfire.. also, what heat range? using plug colder than it should be tends to foul the plug itself as it is too cold for the application.


i recommend NGK BP5ES with 0.8mm plug gap.