SOLVING LOW IDLE

Been having a low idle issue around 700rpms or so. When it gets up to 195 degrees it will get to 1k, earlier in the year I had a High idle . So Just checked my 1-4 bank at idle, 12 degrees at 1K and approx. 34Deg at 3500-4K Best I could do with my young copilot holding the throttle. 5-8 was 14 deg at 1k and around 35deg at 3500-4K.
I noticed that the timing marks jump around and difficult to get on the pointer. Iam using a Digital advance timing light. I would like to be sure about this before I go into resync of carbs.
Thx in advance,, Pun intended

Btw just pulled all the plugs yesterday to mark both PM marks and both +7 marks on flywheel and pressure plate. Interesting that number 4 and number 8 plugs were a little wet. Plugs have always been super clean prior. Ignition is XR700, with Bosch blue coils

 

Are the advance values ok ? I do I need to actually bring the motor to 5k ?
Also what would cause the marks to jump around?

 

Thx Steve. Interesting I thought that more advance at idle will give more grunt? The car runs great other than this new idle issue. I think ill run it up to 5k rpms and report back on total advance. Im using a advance timing light and using the PM marks. The cross talk did cross my mind. I checked the Carb flow at idle yesterday for fun and things are a little screwy. Rear most bank is pulling 5.5kg across both carbs, the front number 5 and 6cyl are pulling 3kg. Cyl 7 is pulling 3kg and number 8 is pulling 2kg. So not all cylinders are equal. Im gonna re check everything today.

 

BTW engine was all gone through in 2016 and wasn't installed in the car till 2017. All tuning done by an Indie shop

 

Yup. Why I posted the findings. I’ll check total advance first and make sure it’s not way past 36.

 

That carb Probably kicks in at high temp.

 

Ok so with untangled wires I’m more in the 7-9 range at idle on both banks and the marks are jumping around less. But I’m at approx 40adv at 5k rpm.
Idle is around 800 or slightly higher

 

Understood on the kg. I think the diszzy advance curve isn’t correct. Probably ok to move on to the carbs next.

 

Hmmm too much advance is bad. But I’ve never heard any detonation

 

Yea but it feels like Death Valley in the cockpit

 

So I didn’t finish up the carbs. But can someone explain best lean idle? 3 turns out is the starting point on the idle mix screws then keep turning out till it starts to run faster and as you keep turning out it will run slower and then turn in 1/4- to1/2 turn back in according to Birdman. Sounds like best rich idle to me. Lol.

 

Yea cool I like the idea of best lean. And yes I’m aware of the tapered and stepped screws.

 

Thx Steve I’ll post back tomorrow. Appreciate you

 

All Air bypass screws closed. Each carb had one screw open.im assuming once I dive in and the idle changes I’ll need to adjust timing at 1k rpms?

 

I have a feeling the carbs were not synced front to rear. I observed that turning the forward most idle screw slightly had no effect on idle. If I hold the rear carb side to side linkage and pull on the forward carb idle stop arm slightly the rpms will rise And no movement on the rear carb. So something is up with the front to back linkage

 

Image Unavailable, Please Login Front on top rear on bottom notice the front isn’t lifting the 7-8 carb which has the lowest kg notice the adjuster is almost bottomed something wrong with the spring? Image Unavailable, Please Login

 

Ok sone progress I got the 7-8 carb to come up. There was enough adjustment in the screw. I check with engine running and flow meter installed. I used a needle nose to squeeze the adjuster ka bob to see if it would raise. It did so then I adjusted the screw

 

Ok now all 4 are at 6-6.5 kg at 1500