6 replies to this topic

[bikewiz]

Motor specs 1293 mild cam (not entirely sure on cam spec) HIF44, BBW needle, LZX2085 damper red spring, 65D distributor, MED stub stack with ITG foam filter, LCB RC40 SS DTM exhaust, new mechanical fuel pump, inline filter just before carb. New cap,rotor, and plugs.

So I had a leaking float bowl so I while I had it apart I replaced the jet and float bowl gasket, set everything to spec float height, jet height etc. Had 94 octane non-ethenol gas in it. Fired right up and ran great, idle at 850-900 rpms.  Drove around 200 miles put 93 octane gas in, ran fine for another maybe 50 miles. Started the car Saturday ran like shiite, rough on choke, wouldn't idle off choke. Checked oil in damper OK (SU damper oil 20w) Checked vac advance for cracks, sprayed carb cleaner around pivots and manifold to check for leaks no change of idle. Checked the manifold bolts everything is tight.

 

Subsequently fooled with the jet height (richer) and had it running really nice, stable idle, pulls from 2000 rpms in 3rd, after doing a few plug checks they appear near perfect. The car sat one day and wouldn't idle and ran rough so I removed the vacuum chamber and sprayed carb cleaner down the jet to see if it would change anything (like maybe something was blocking the jet?) after fiddling with the idle adjustment screw once it was fully warm (190 degrees) I got it to idle around 900-1000 but then would rise to 1500 and wasn't consistent.

What should I check? Vacuum advance? Just give up and install a new carb? Lower or high viscosity oil in the damper? Just set the idle higher?

[beardylondon]

Have you taken it to a rolling road to be set up?

My 1293 ran like crap until I had mine rolling roaded.

[sonscar]

In my experience barring mechanical maladies like cable sticking,not enough free play or return spring etc unstable idle is usually too lean.Other things like sticky distributor springs or advance mechanism can be culprits.Is the vacuum can leaking?Just some thoughts,Steve..

[bikewiz]

No rolling road/dynos available here, even if there were I doubt I could find one that could tune an SU or be small enough for a mini.

 

By the looks of the plugs I don't think it's too lean but I don't have a O2 sensor in the system so I'm just going by the plug color.

I have new vacuum advance can  I will try. I may also try it without the vacuum attached and see what happens.

[StefanMini]

It's not a solution for now, but invest in a wideband kit (AEM). It helped me a lot to set up the mixture right. As above a low and inconsistent idle can be a lean mixture.
I don't know the compresion ratio but 93 octane is a bit low. Here in Europe I only put 98 octane in my Mini. Try a higher octane fuel as well.

[bikewiz]

It's not a solution for now, but invest in a wideband kit (AEM). It helped me a lot to set up the mixture right. As above a low and inconsistent idle can be a lean mixture.
I don't know the compresion ratio but 93 octane is a bit low. Here in Europe I only put 98 octane in my Mini. Try a higher octane fuel as well.

The octane rating between the US and Europe is different. Our rating is (R+M)/2 or RON + MON divided by 2, I believe Europe is the RON number only, which equates to  4-6 octane lower.

 

I plan on installing a wideband but it's a ways down the to do list.

[croc7]

Sounds like you’ve done a fair bit of troubleshooting. Disable the temp compensator of the HIF44 before you spend good money on a new carb. A search on this forum will detail the mechanics for you.