hitachi carb problems

[LenRobertson]

Yeah, there is a point where you have to give up on something that isn't fixable. I fiddled around a lot with the Hitachi on the 510 and couldn't make it better. I finally pulled it off and seriously was headed toward replacing it with a Weber. But then I got stubborn and decided I didn't want it to beat me. So I've torn it all down and soaked the parts in carb cleaner. Now to put it back together and see if anything improved or not. 50-50 chance I think. At least now the inside of one of these isn't a total mystery anymore.  But that may not mean I can actually fix one. If it does end up better, I really won't know what was bad, other than guessing a plugged passage in the body. The screws holding the bottom section to the upper section weren't very tight. Not loosey-loosey, but not tight either. I suppose there could have been a small air leak through that gasket, but don't know what that would do to the function of the carb.

 

Len

[devilsbullet]

ya, i seem to have that too. the top of it will move a very, very small amount. blew carb cleaner around it while it was running to see if there were any vacuum leaks and it didnt seem to have any so i'm not overly worried about that.  new flloat seems to be working, we're just fine tuning now. no more liquid gas coming out of the tailpipe, dead spot seems to be going away somewhat. hopin once we get this tuned back to where its not flooding the carb it'll be running sweet and cherry again.

[ggzilla]

New float is a waste of time and money unless there is a hole in it.

 

Overflow is caused by mis-adjustment, bad needle-and-seat, or sunk float (all of which you can see throught the sight glass, as the fuel level will be too high). Sometimes when guys remove the float bowl cover they lose the tiny spacer for the float pivot.

 

When it is idling, where is the fuel level?

[zah_chronicler]

Glad to find this thread.  Sounds similar to  a problem I have been dealing with.  I have a 1974 L18 620 with stock hitachi carb. 

 

My troubles began over a year ago now.  I had gotten this truck running from nothing to running like a dream.  I was using it daily with only some minor fiddling necessary to keep it happy.  One day while getting of the interstate it basically stopped wanting to accelerate at all.  I was able to limp it along in idle letting the clutch out slowly.  I have not since been able to get it to run smoothly.  I have been worried that an internal engine part broke but can't seem to diagnose what.  The best i can tell is that the engine is running incredibly rich.  All the spark plugs were fouled out with thick black soot.  I had already done work on the internals of the engine and rebuilt the carb when I first got it.  Everything worked fine for over a year so i don't think any of that work was a direct cause of this.  I have since tried to thoroughly check and clean systems of the engine.  It now will idle but not smoothly accelerate.  There is a white smoke in the exhaust that smells sometimes like gas.  when I do accelerate I can get the engine to rev as high as I want but get a lot of black smoke.  Not getting back firing.  plugs are getting black and wet now, seems to be gas and maybe some oil.  Now that it will idle I am also noticing a gassy smell to the oil. 

I have taken the carb off cleaned it thoroughly, I have checked the entire electrical ignition system,(previously put the pertronix induction system on instead of the original points) found a resistor was only allowing about 9 volts into the main ignition coil, got that taken care of and now have 12v.   The cleaning and new part has helped but still getting really bad combustion. 

I am wondering if it may be the carb still or if I should look at other parts.

 

A compression test showed equal pressure on all cylinders but I don't know that the actual pressure should be.

 

I want my datsun to rise from the ashes again.

[devilsbullet]

it was full everytime we got it to go, wayover what it was supposed to be. still not sure what was wrong with it, but its running now, with a weber 32/36 :thumbup: .  still have the old one and at some point in time i may go thru it. or i'll sell it and let whoever know what was happening and they can go through it. thanks for all the help guys!

[zah_chronicler]

My gas level seems to stay right at the etched line on the sight glass.  I even pinched off the fuel line at the filter watched the level slowly fall then then let go and it returned to normal.

 

 

 

I can start a new thread if that would be better

[ggzilla]

Start a new thread for what?

[zah_chronicler]

wasn't sure if this forum group wanted to keep each problem more seperated.   

Sounds like Devilsbullet baught a Weber,  I am thinking of doing the same but am not entirely sure where my problem is.  Carb or something worse like worn rings

[zah_chronicler]

was thinking about shutting off parts of the carb that try to make it more environmentally friendly so that it is a simpler system to trouble shoot is that a good idea.  If so what are some easy reversible ways to do so

 

for example the BCDD

[ggzilla]

yes, start a new Topic