1 reply to this topic

[DougMayfair]

Hi All.

Im looking to get my mini on the road in the next few weeks. I completed an engine rebuild, and a restoration. I'm ready for the mot, but there's a problem.

The engine drops power when i want to pull away.

 

the engine starts with no issues with a bit of choke and ticks over. When I put it into 1st and start to pull away, the engine power drops. I then have to feather the accelerator with clutch off(not engaged) to get the revs back up. I manage to get it to pull forward, but its not anywhere near good enough to drive. 

I've played around but I feel like I'm going around in circles, and not ticking off areas before moving onto he next, so I'm not fixing the issue.

 

The engine has had the head and block skimmed for clean level, and a copper gasket

I stripped, cleaned and rebuilt the dizzy, with new points, condenser and cap. it has vacuum advance with a new vacuum hose.

New ht leads new plugs

The Carb (HS4) has also been stripped, cleaned and rebuilt with a rebuild kit.

all gaskets are new,

I have added a fuel filter to the system at the tank end. with fresh fuel.

The fuel pump is the same as it seems to work ok,

 

So far I've researched online and looked at timing by the slight adjustment of the dizzy.

I've also tried slackening and tightening the needle nut of the carb and looked at the carb adjustment screw. this hasn't solved the issue.

I've had the plugs back out, as far as i remember, they were a cakey brown colour, but I've adjusted quite a bit so this me different now.

 

The engine runs with choke out. and is sitting at 2500 revs. if I push the choke in once warm, it will drop down and eventually die, I cant get the engine to idle under 1500 to 2000 yet alone 1000. Obviously the pull away issue is still there when the engine is warm too.

 

Any advice is welcome as I try to get over this last hurdle. And learn something at the same time.

Should I / can I reset the carb to default?

should i remove the air filter? do i check the float level of the carb?

 

Happy to give more info if needed. I'm hoping to jump back on this on Sunday.

 

Thanks in advance chaps

 

 

 

 

 

[evoderby]

Compression, ignition, fuel.

 

Check the tappets (0.012) to be set correctly with all valves moving freely, then run a compression test at wide open throttle and all spark plugs removed. If everything checks out ok, go to the next step….

 

Check all plugs to be firing followed by checking ignition timing by hooking up a strobe, if everything checks out ok go to the next step….

 

Check fueling. A colortune spark plug can already give some very insightful info at idle conditions, showing whether your mixture is rich or lean. Wide band lambda is much more of an investment with the added benefit of covering the entire rev and load range under driving conditions of course.

 

Chances are you’ll find issues to rectify when running the above tests, such as valves not closing, incorrect ignition timing, mixture woes caused by vacuum leaks, incorrect float level wrong jetting…you name it. Being methodical is what it takes, ruling out one potential cause after the other until the underlying issue manifests itself. If everything mentioned checks out ok there’s one thing left….cam timing. Good luck!

Edited by evoderby, 24 February 2023 - 06:18 AM.