So so running 912

[buckeye1049]

Hi All, My 1969 912 is in mothballs for the winter and I'm tackling several projects. It was a non running barn find with lots of cooling tin missing and a flat cam lobe. I went through the entire motor, new piston rings, rod bearings and reworked the heads. The car runs well but has a spitting (backfire up through #1) at idle intermittently. Off ide and driving it is very strong and I'm happy with the outcome. I thought this winter I would rebuild the carbs (Dellorto DLRA36) and replace the points/condensor with a petronix unit...I have a .050 distributor.
Does anyone disagree with this move?....Does anyone know what port on the DLRA36 is the vacuum port for my vacuum advance?


Thanks,
Toby

[Jaems]

Make sure that you do not have any exhaust leaks. Also if you can afford it. Get rid of the 050 it was never meant for the 912 engine. A 022, 031, or a RS0012 would be your best fit. The RS0012 will be the cheapest of the three. Most that have it rave about the improvement in engine performance.

[WFBowen]

Toby:
I'd check for a vacuum leak at the base of the carb or around the throttle shaft on that cyl. Then check your idle mixture adjustment on that cyl. If nothing improves, you might have something blocking a jet. If there's still no improvement,check the valve clearances on that cyl, the spark plug and its connection on that cyl. As for the vacuum port, it'll be one that takes vacuum from above the throttle plate (i.e. momentary.) Is this the way the car has always run since you've owned it? Are you sure there are no open or leaking vacuum ports?
Bill.

[buckeye1049]

Thanks for the responses, I've checked for vacuum leaks and found none. I know I'm do for my first valve adjustment as I've logged 1,000 miles since the rebuild...But the problem is intemittent and only at idle or just off idle. I think it's carb related and they are the only thing I left untouched in the rebuild. I read up a bunch on idle mixture and no matter where I adjust the idle mixture screws it runs the same. I think pulling and rebuilding them will get me a whole lot familiar with them and I'll have better luck adjusting/tuning. It runs very strong off idle and smooth.
I'd like to remove the points and condensor just because there is a reliable alternative available..


Thanks

Toby

[Scott Douglas]

I'd recommend adjusting the valves first. If it's been 1k miles since you did them last on a new rebuild they will surely need it. Don't ask how I know. =;>)

[1968/1976 912]

I have a similar problem... cylinders 3&4 are chirping through the carburetors... and when I give it gas, they blow back and chirp and backfire... I did the timing, and checked the gap on the valves... any ideas here??? The other side of the engine (1&2) are fine... Help?
Thanks a lot, New to Pelican Forum.

[WFBowen]

Might be time for a compression check on that side. Since you've owned it, did the motor ever run well? Are you dead-sure your plug wires aren't crossed?

[1968/1976 912]

Thanks so much. I'll do a compression check. It's never really run right... there was a re-build, and I don't think it's been to a professional mechanic since. Do you know the firing order? 1,3,4,2? I'll check that too. I did a TDC and found #1, and that's passenger side front, 2 is passenger back, 3 driver front, and 4 driver back... right? I really appreciate your help here...

[WFBowen]

Firing order is 1 4 3 2
Your cylinder numbering/location's correct.