23 replies to this topic

[AndrewT]

I'm not sure there is a definitive answer re oil type.

20w50 is way too thick in my HIF44 and it takes a fair bit of pressure to push the piston up. It then takes 7 seconds to fall back down. Swapped it for 3-in-1 and it's perfect.

On my HS4 20w50 was just right so I guess it depends on damper fit and wear to some extent.

It's easy enough to whip the dashpot off and empty oil out so try a few different types of whatever you have to hand until you get a drop rate of about 1 second. It won't be the last word in carb setup but may be enough to solve your current problem.

[Quinlan minor]

Unfortunately I dont have 20/50 any more as my mini is automatic so no need for the classic stuff. 

 

Whereabouts in Surrey are you? I could, perhaps,  drop a little round.

[steeley]

I always use su carb oil, it’s less than a tenner on eBay and it may save a lot of messing around

[JCmini]

Thanks for the offer.i'm actually near Gatwick. I will have to wait for the cable before I can resume but will keep you guys up to date. 

 

*update*

I thought I would start the car without the cable. It starts fine and idles fine. I gave it some  throttle and it really starts to bog down. similar to if it was running really lean or really rich to the point if I held it any longer it would stall.  I tested the damper with my finger and it goes up fine when i blip the throttle with some pressure and drops down slowly as suppose to shooting down. 

 

I went full throttle and the damper went all the way up and the car was just bogging to the point it wanted to stall.

 

Does this help?

I also had another idea. The o ring I replaced. How important is the size as I used a generic o ring from my halfords box of o rings that fitted over the fuel tube?

thanks.  

Edited by JCmini, 10 December 2020 - 05:05 PM.

[Dusky]

Might be the wrong material o ring blocking the fuel partially.
The speed the damper goes up is important. It's our acceleration pump.
Synthetic isnt thinner than co conventional either. You can try ATF, but the proper su oil is the best starting point.

[sonscar]

The oil and damper is to stop the piston rising too quickly when the throttle is opened.This speeds up the airflow over the jet and sucks more fuel in to overcome the initial lean spot.The damper then rises to catch up with the motors need for air.I would start from new,check the spring in the dashpot,change the oil in it,and also as a long shot ensure that you have replaced the gasket for the elbow the correct way round not blocking the air holes.You did refit the vacuum line?Have fun,Steve..

[AndrewT]

It starts fine and idles fine. I gave it some  throttle and it really starts to bog down. similar to if it was running really lean or really rich to the point if I held it any longer it would stall.  I tested the damper with my finger and it goes up fine when i blip the throttle with some pressure and drops down slowly as suppose to shooting down. 
 
I went full throttle and the damper went all the way up and the car was just bogging to the point it wanted to stall.

You shouldn't need to push the piston up when you blip the throttle so it does sound like it could be over-damped. You say it drops slowly. How slowly? With the engine off push the piston to the top and then let it go. It should take one second to drop down with a light 'thunk'. Much faster or slower than that and you'll have richness problems.

Also, what happens if you press the accelerator really, really slowly? If you can get the engine to rev up this way then again it suggests that your piston is moving at the wrong speed.

[AndrewT]

Just to add - have you reconnected the vaccuum advance and checked that the carb is correctly re-seated with no air leaks?

It's possible that something else has coincidentally failed but as you have only touched the carb then it is almost certainly one of the above.

[JCmini]

UPDATE-Fixed. 

 

Hi all.

Stripped the carb out. turns out it was a very small black crumbs/dirt in the jet somewhere. I blew the the tube at the float chamber end and could feel resistance. I then sucked and a small piece flew in my mouth.So this little piece was letting enough fuel in for idle but when I accelerated it wouldn't allow enough fuel through  to match the air/fuel ration hence bogging down. 

 

I also changed the dash pot oil from 5w40 to ATF which was 75w/90.  Its made the piston more stiffer so not sure if its better or worse but i'll just leave it.

 

Now just need to re tune it all again as I noticed it was running too advanced as I can hear pinking. 

 

thanks again for all your suggestions.