Nikki Carb Question

[Twinky]

I've looked through the Nikki carb guide and it does not mention anything about a certain part of the carby.

On the underside of the carb, in between and off centre of the two throats there is a bolt with a hole going through the centre of it.

It sort of looks like an port or source of vacuum for the carby.

This bolt/hole looks the same as the one on the stock Aisan carb.

 

The question is, what purpose does this have for the carby? The 4k carby mounting plate actually has a hole cut out

for this port on the carby.

 

Why this is of relevance to me is that to mount this carby you need to double stack the mounting plates. I am using a different mounting

plate that has this port blocked off. The reason I am using this specific plate is that it is slightly thinner than a standard 4k carby mounting plate

thus retaining the original mounting studs. If this port is significant on the nikki carby then I will have to use the 4k carby plate and get longer studs.

 

The reason for all of this is that I'm having a bit of trouble with setting the idle below 1600 rpm. Apart from the idle the carb works superbly.

 

Cheers

[altezzaclub]

Nice photo of it....

 

ooohh... look what I found

 

http://www.gemswa.com/phpBB3/viewtopic.php?f=29&t=2419

Edited October 29, 2012 by altezzaclub

[Twinky]

Thanks for that altezzaclub, my net has been extreemely sluggish today (worse than dialup) let along looking at or uploading any pictures.

I do usually google before I post but this time is a special occasion.

 

According to that picture it is simply a bolt.... But why then does it have a hole going through the middle of the bolt? That's what the picture

still can't explain. I've looked at the 4k Carby and it has the same thing but no description or reference in the book. Either way I suppose

I'll swap the plates around so that the mounting plate with the hole shall be on the top and I'll see what happens from there.

 

Cheers for your time!

[Boosted]

Blow some air into it, see if it comes out anywhere. I thought it might have been the port for the power valve, though the pic altezzaclub has linked to shows that it's taken from a seperate port in the base of the carb.

[Twinky]

I drilled a hole out in the mounting plate and put it all back together. Not really any noticeable difference. Found out all of my issues were to do with the dizzy.

[altezzaclub]

ohh... ...and what dizzy issues were they??

[Twinky]

Well I'm not so sure in my ability to set points.

I was looking over everything I could think of to try and figure out why I can't get the car to idle low and I thought to check the spark gap. When I checked it the gap was almost non existant and had the volcano-crater issue meaning that the points were melting/welding. So I got a new set and thought my troubles would have been over. I used the feeler gauge to set the points to a .45mm gap. Checked and re checked. Re set the timing to 8 degrees and still no bingo. Wouldn't idle low.

 

I bought maybe the points weren't seated correctly so I took them out to check if there was any buildup underneath and as I pulled them out I could see the volcano/crater thing developing again.

 

So at that point I gave up on mechanical ignition and installed my electronic ignition which funnily enough I had issues as well. I had it set to 10 degrees but when I went for a test drive it had no power and carny was making popping noises. After another hour of tinkering and no success I was going to throw the towel in when I remembered something I read about the effect of retarded ignition timing and the reading you get on a vacuum guage. My gauge had been reading quite low at around 15inhg. I thought that indicated a vacuum leak at first but after looking into that it turned in no results. A low reading could also mean diluted oil or worn rings but I had only just changed the oil and my compression reads 150ish on all cylinders. So I thought ok maybe my ignition timing somehow magically changed itself.

 

Alas when I checked the ignition timing was still at 10 degrees. I thought wel I don't have anything to loose and advanced it another 10 degrees! Not to my surprise the engine speed picked up quite a bit so that it was idling at 2200rpm. I tinkered with the the throttle and idle mixture screwed and BINGO it now likes to idle at 1000rpm! After more setting and re setting I got it to idle around 850rpm. At this point I was no longer using the timing light and tuning it by sound and constant road testing. So I'm not actually sure where the timing is at now but the car is fantastic now.

 

The acceleration is smooth all the way along the rev range and there are no flat spots. I've still got to do some more fine tuning but I'm happy with it now.

[altezzaclub]

Ahh... not the same electronic igntion I had to re-curve?? Mine felt very dead when I fitted it so I just kept advancing it until it got up and went, and dropping the idle speed at the same time.

 

When I put a timing light on it I had 18deg of advance at idle!

 

That's when I stareted changing the springs.

 

The burning of the mechanical points gets worse when the condensor is old and leaky. The points are set more accurately with a dwell meter, so the volcano surface doesn't matter, but its not that crucial, the problem of worn points is the way they retard the ignition timing.

 

Grab your timing light & draw up an advance curve, and compare it to mine.