WillieB's 1275 Engine Rebuild

Started by MiniDave, October 30, 2020, 04:22:55 PM

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94touring

Do you have #2 vented or capped?

Willie_B

Vented long hose to beneath engine.

Willie_B

Put the old carb on and it still did not want to start. Put a NEW set of plugs in and that made it happy enough to start. Let it idle while I checked the timing and look for anything leaking. All looks good, as expected. Got a rattle or two to chase down. One I think is the rad shroud.  4.gif

Willie_B

Out for a short drive to the gas station today. Stumbles bad from a stop till the revs are up. Need to lower the idle and tune on the carb some. Had to change the plug wires to fix an erratic idle. Runs good when running except for the off idle stumble.

Also need to raise the front. New cones dropped 1/2" just in a few miles. At least I have the old style RipSpeed Hi-Lo's so I can adjust them from above with a long allen wrench.

My difficulty with the clutch not completely disengaging making it hard to get into first seems to gone. Shifts great now. Of course I have not had it above second yet. Brakes a little squishy so another bleed soon too. Then drive, drive, drive to be ready for the Hill Country.

94touring

You have a BCE needle in there?  Really need that wideband or dyno tune.

Willie_B

Put a bung in so I can use my wideband now. Also have a Gunson's gastester to play around with.

94touring

Perfect.  Let us know what you find.

LarryLebel

BCE is completely useless. I would say BDL at a minimum, maybe even a BDK.

94touring

#183
Quote from: LarryLebel on April 01, 2021, 05:10:46 PM
BCE is completely useless. I would say BDL at a minimum, maybe even a BDK.

All 3 of those are close.  BCE is slightly richer down low and more matched to his cam per Keith Calvert. 

94touring

For reference. Should be around one of these.  Wideband will make it easy to decide.

Willie_B

Adjusted the carb using the Gastester. Set the Co at 3%. Next is put the wideband in. Scheduled for an alignment Thursday. The only problem I have now is lack of traction mostly in first gear...... Damn this thing pulls hard and I don't even have the carb dialed in good yet.

94touring

Quote from: Willie_B on April 12, 2021, 08:15:18 AM
Adjusted the carb using the Gastester. Set the Co at 3%. Next is put the wideband in. Scheduled for an alignment Thursday. The only problem I have now is lack of traction mostly in first gear...... Damn this thing pulls hard and I don't even have the carb dialed in good yet.

Sounds about right with traction given your build specs vs mine. Without my race tires I couldn't grab at all in 1st.

MiniDave

Too much HP? Damn, I guess I'll have to stop that....  71.gif
Complete failure at retirement

1989 Cooper Racing Green
2009 Clubman S
2014 Audi Allroad

94touring


94touring

Brad, I have a dozen plugs headed your way! 

Willie_B

Thanks Dan.


Got the wideband installed. The readout is app based so easy to see while under the bonnet. Have not driven it yet but it seems to go rich (10-11) when opening the throttle. After a bit of stumbling it evens out to 14.5-15. So if I am thinking about this right the dashpot is going up too fast? If so, then check what spring is in it and maybe thicker oil?

Going for an alignment later today so will see what is doing while driving then.

MiniDave

It's not just a function of where the needle is, when you open the throttle the increased airflow over the jet draws more fuel too......even if the needle is not moving up quickly. But changing the oil and spring are the two easiest things to try, so I would go there first - one thing at a time tho.
Complete failure at retirement

1989 Cooper Racing Green
2009 Clubman S
2014 Audi Allroad

94touring

#192
You'll have to drive it under load to really know.  But, the faster the piston moves up the leaner it will be.  The slower the richer.  While cruising if you're lean and stumbling, you'll want more weight on the piston.  So either a heavier spring OR use some big washers to add weight.  If it's too rich in cruise you want less weight.  This is of course assuming the needle you have works perfectly at wide open throttle at around 12:5 to 13:1. For best power keep it between 12:1 and 13:1. Leaner than 13:1 at full throttle can cause detonation depending on other factors.  Lean stumble at cruise when initially giving it throttle means you need a thicker dashpot oil to slow the initial movement of the piston.  I found I get the most peppy feel at cruise with it dialed in around 13:5 to 14:1.  Best lean fuel economy will be upwards of 17:1 but I just didn't like how it felt.  You need vacuum advance to cruise that lean too or it will be a dog.

Willie_B

Ok, got some drive time in. Idle is at 12.5 to 13.5. Cruise is 16-17 range. Drops to very lean when accelerating. So I have a lean stumble. Just got the WinSU program too so lots to work with.

MPlayle

The vast majority of needles have the same idle value.  Changing to a richer needle should preserve the idle ratio while attempting to solve the too lean cruise and acceleration.


94touring

What Michael said.  Which needle do you have in there?  When you say lean when accelerating, do you mean a WOT pull or just at cruise when giving it a little extra throttle?

Willie_B

At cruise and accel, not to the floor but not very light on the pedal either.

94touring

Gotcha.  Once you get that cruise down in the 14s that acceleration lean stumble will probably go away.

94touring

Get any more tuning to report to us?

Willie_B

#199
Swapped the carb needle to a BDL. That is the needle that the WinSU program suggested and I happened to have. It still was not quite rich enough, 16-17 in cruise,  so filed a bit off one side. Will see in the morning if it was a bit right or a bit too much.

Before I did that it did feel better and the stumble was much less but still 18-19 when getting on the gas. When it picked up enough to get down to the 14 range it really goes well then.