Author Topic: WillieB's 1275 Engine Rebuild  (Read 5052 times)

Offline 94touring

Re: WillieB's 1275 Engine Rebuild
« Reply #175 on: March 24, 2021, 02:35:54 PM »
Do you have #2 vented or capped?

Offline Willie_B

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Re: WillieB's 1275 Engine Rebuild
« Reply #176 on: March 24, 2021, 03:29:03 PM »
Vented long hose to beneath engine.

Offline Willie_B

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Re: WillieB's 1275 Engine Rebuild
« Reply #177 on: March 24, 2021, 07:38:44 PM »
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

Offline Willie_B

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Re: WillieB's 1275 Engine Rebuild
« Reply #178 on: April 01, 2021, 02:20:22 PM »
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.

Offline 94touring

Re: WillieB's 1275 Engine Rebuild
« Reply #179 on: April 01, 2021, 02:25:02 PM »
You have a BCE needle in there?  Really need that wideband or dyno tune.

Offline Willie_B

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Re: WillieB's 1275 Engine Rebuild
« Reply #180 on: April 01, 2021, 02:40:10 PM »
Put a bung in so I can use my wideband now. Also have a Gunson's gastester to play around with.

Offline 94touring

Re: WillieB's 1275 Engine Rebuild
« Reply #181 on: April 01, 2021, 02:41:12 PM »
Perfect.  Let us know what you find.

Offline LarryLebel

Re: WillieB's 1275 Engine Rebuild
« Reply #182 on: April 01, 2021, 07:10:46 PM »
BCE is completely useless. I would say BDL at a minimum, maybe even a BDK.

Offline 94touring

Re: WillieB's 1275 Engine Rebuild
« Reply #183 on: April 01, 2021, 07:21:47 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. 
« Last Edit: April 01, 2021, 07:23:58 PM by 94touring »

Offline 94touring

Re: WillieB's 1275 Engine Rebuild
« Reply #184 on: April 01, 2021, 07:45:57 PM »
For reference. Should be around one of these.  Wideband will make it easy to decide.

Offline Willie_B

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Re: WillieB's 1275 Engine Rebuild
« Reply #185 on: April 12, 2021, 10:15:18 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.

Offline 94touring

Re: WillieB's 1275 Engine Rebuild
« Reply #186 on: April 12, 2021, 10:19:18 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.

Online MiniDave

Re: WillieB's 1275 Engine Rebuild
« Reply #187 on: April 12, 2021, 10:48:13 AM »
Too much HP? Damn, I guess I'll have to stop that....  71.gif
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Offline 94touring

Re: WillieB's 1275 Engine Rebuild
« Reply #188 on: April 12, 2021, 11:14:15 AM »
Time for stickier tires!

Offline 94touring

Re: WillieB's 1275 Engine Rebuild
« Reply #189 on: April 13, 2021, 02:41:31 PM »
Brad, I have a dozen plugs headed your way! 

Offline Willie_B

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Re: WillieB's 1275 Engine Rebuild
« Reply #190 on: April 15, 2021, 11:42:12 AM »
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.

Online MiniDave

Re: WillieB's 1275 Engine Rebuild
« Reply #191 on: April 15, 2021, 12:44:44 PM »
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.
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Offline 94touring

Re: WillieB's 1275 Engine Rebuild
« Reply #192 on: April 15, 2021, 01:20:37 PM »
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.
« Last Edit: April 15, 2021, 01:23:10 PM by 94touring »

Offline Willie_B

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Re: WillieB's 1275 Engine Rebuild
« Reply #193 on: April 15, 2021, 03:50:08 PM »
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.

Offline MPlayle

Re: WillieB's 1275 Engine Rebuild
« Reply #194 on: April 15, 2021, 04:10:17 PM »
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.


Offline 94touring

Re: WillieB's 1275 Engine Rebuild
« Reply #195 on: April 15, 2021, 04:13:08 PM »
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?

Offline Willie_B

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Re: WillieB's 1275 Engine Rebuild
« Reply #196 on: April 15, 2021, 04:24:00 PM »
At cruise and accel, not to the floor but not very light on the pedal either.

Offline 94touring

Re: WillieB's 1275 Engine Rebuild
« Reply #197 on: April 15, 2021, 04:26:14 PM »
Gotcha.  Once you get that cruise down in the 14s that acceleration lean stumble will probably go away.