9 replies to this topic

[mikemate]

I have fully rebuilt a HIF38 carb for my mini 1000
It's had a engine rebuild and isn't a standard 1000
I've put the HIF38 on because it's a slightly better carb than the SU4
But I've noticed the dash pot is emptying like every day or two!
I'm using power steering fluid as I was told it's the best for all round year use.. But it's vanishing! Could it be due to over filling?
Or should I be using thicker fluid? Like 10w40? Or 20w50

It does go like stink ..but when it starts to run out of oil it don't like ticking over lol

Any comments would be appreciated!

Edited by mikemate, 13 March 2014 - 12:03 PM.

[KernowCooper]

I use 20/50 in mine and this would have the effect of making it richer on initial acceleration, it does not need to be fill to the top as when you insert the damper it overflows and get drawn downwards. Just so when the damper is inserted its covered by oil

[Dan]

Is it completely emptying? How high are you filling it? Did you drop test the piston when you built the carb?

[mikemate]

I use power steeringg fluid as it doesn't get thinner when warm or thick when cold
I've only been filling the bit where the plunger goes
But if I leave the plunger out and leave it a couple mins it vanishes but then drives fine
After a while the carb is empty and the damper/plunger has some oil on it
But when empty won't tick over if cold outside with out almost stalling I put more in and it's fine!

It seems to be completely empty
Piston moves fine (no Judders or snagging) if that's what you mean
And due to the cam it has to be driven at 2600 rpm + to get optimum performance (kent 266)

[mikemate]

Piston wasn't dropped at all all mint condition was 2nd hand

[mikemate]

Piston wasn't dropped at all all mint condition although was 2nd hand

[Scott@minispeed]

I would remove the needle and needle carrier and shine a light down the tube and see if it has a hole in it letting the oil out. It shouldn't have but I have seen it on HIF carb pistons where there is a tiny core plug in the bottom that can come adrift and cause the problems you are experiencing.

[mikemate]

What happens if there is? Can it be fixed? Or could the oil just be to thin?

[mikemate]

right, ive just took it all apart, the dash pot, when i put oil into it doesnt seep out the level stays the same.. i think infact i was overfilling it.. and due to the weather being warmer its just been blowing the oil out the lid

 

ive also emptied the oil out the damper, and tried blowing down it, and it wasnt letting any air through

 

i will try some 10w40 and 20w50 to see if it solves the problem

[Dan]

Drop testing a piston means checking how long it takes to fall in the chamber to see how well it fits. Each piston and chamber are a matched pair and the fit is critical to the function of the carb. If they are too loose air will flow through and you will loose more oil as well as the piston not moving properly. The level should be about 1/2" below the top of the tube in the top of the piston where the damper fits, even if you overfill it though it should only fall to the proper level fairly quickly and stay like that for several months.