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  #21  
Old 4 Weeks Ago
Iron Mike Iron Mike is offline
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Nose cone^^ (auto correct)
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  #22  
Old 4 Weeks Ago
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Ferrous Head Ferrous Head is offline
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Quote:
the only way it would run was to leave the enricher on. It generally runs too rich as it is.
I'm not sure why you went away from the carb so quickly without some more thought on the carb.

Quote:
"It generally runs too rich as it is"
So, you put the new Mikuni on and it was running rich after that ?

I would be very tempted to just drop a known good carb on there. You can spend a LOT of time chasing the electrical problems in your carburetor.

Why exactly did you go for a new carb ? Did it have problems with the old carb ?

If not, why not stick that back on for a sanity check ?
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  #23  
Old 3 Weeks Ago
owlsplace owlsplace is offline
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Originally Posted by Ferrous Head View Post
I'm not sure why you went away from the carb so quickly without some more thought on the carb.



So, you put the new Mikuni on and it was running rich after that ?

I would be very tempted to just drop a known good carb on there. You can spend a LOT of time chasing the electrical problems in your carburetor.

Why exactly did you go for a new carb ? Did it have problems with the old carb ?

If not, why not stick that back on for a sanity check ?
Worth considering since I never operated it with the original carb it could be fun!
New coil should arrive soon.
I'll keep you guys entertained with my exploits.

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  #24  
Old 3 Weeks Ago
owlsplace owlsplace is offline
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Originally Posted by The Doctor71 View Post
Understood.

This might help you (or frustrate you further). I dunno.
  • Find TDC on the REAR cylinder
    • remove both spark plugs & rotate the engine until you see the rear piston on the up stroke
    • insert a plastic straw into rear cylinder
    • rotate the engine some more until you hit TDC on the rear. (rock the motor back & forth to confirm you're at TDC)
    • remove the plastic straw
  • FRONT cylinder is now at 45° BTDC
    • the rule is (on an IH) the REAR cylinder is ALWAYS 45° ahead of the FRONT cylinder. (doesn't matter where the flywheel is in the rotation. REAR cyl is always running 45° ahead of the FRONT cyl.)
  • with a Sharpie, paint pen, or whatever, mark the flywheel (thru the timing plug hole) at 45° BTDC. (This is just for reference in case you rotate the flywheel a few times.)
  • slowly rotate the engine (forward) about the width of the timing plug hole
  • the 40° BTDC timing mark should immediately begin to show up in the timing plug hole. Highlight it with a different colored pen, if you wish.
The above should allow you to identify the correct 40° advanced timing mark for the FRONT cyl on a 1000cc motor. If this fails, then I dunno what you got going on for flywheel marks

I'm not a fan of static timing, but for those that insist on static timing...... do NOT try to static time your motor using the above WITHOUT verifying your FRONT cylinder is on compression stroke. aka your front cyl must be on compression stroke.
Quote:
Originally Posted by The Doctor71 View Post
Understood.

This might help you (or frustrate you further). I dunno.
  • Find TDC on the REAR cylinder
    • remove both spark plugs & rotate the engine until you see the rear piston on the up stroke
    • insert a plastic straw into rear cylinder
    • rotate the engine some more until you hit TDC on the rear. (rock the motor back & forth to confirm you're at TDC)
    • remove the plastic straw
  • FRONT cylinder is now at 45° BTDC
    • the rule is (on an IH) the REAR cylinder is ALWAYS 45° ahead of the FRONT cylinder. (doesn't matter where the flywheel is in the rotation. REAR cyl is always running 45° ahead of the FRONT cyl.)
  • with a Sharpie, paint pen, or whatever, mark the flywheel (thru the timing plug hole) at 45° BTDC. (This is just for reference in case you rotate the flywheel a few times.)
  • slowly rotate the engine (forward) about the width of the timing plug hole
  • the 40° BTDC timing mark should immediately begin to show up in the timing plug hole. Highlight it with a different colored pen, if you wish.
The above should allow you to identify the correct 40° advanced timing mark for the FRONT cyl on a 1000cc motor. If this fails, then I dunno what you got going on for flywheel marks
...
Okay, new coil didn't work any miracles so time to address the timing issue.
First photo shows the single line timing mark located using the above proceedure.
At that position the points were open with and without the advance shown in the next photo.
Before this I rode the bike on a seven mile jaunt and just let it bog without using the enrichment lever on the Mikuni.
The plugs didn't look to bad after the run however. I wouldn't ride it like this very long.
So I assume I can use the timing mark above to static time #1 on the compression stroke by centering the mark in the window, engaging the mechanical advance and setting the points to just open. That should get me in the ballpark I presume. I'm assuming I can vary the backing plate while the engine is running to tune by ear if necessary after that. Once that is done I should be able to tweek the cam to even up the point gap between #1 and #2.
I also dug out the original Zenith carb and ordered a cable in case adjusting the timing doesn't solve the Mikuni bogging problem.
Does this sound like a plan?
Is my description of the static timing proceedure accurate? It is from memory and if memory serves the point gap is between .016-.018". It's been a while...



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  #25  
Old 3 Weeks Ago
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Ferrous Head Ferrous Head is offline
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Wait wait wait !

Am I wrong in thinking this is a 80 on engine ? An 81 I thought.

If so, timing mark for front cylinder is a single dot. Vertical line is TDC on these engines.

Easy enough to confirm. Pulll the plug and check if the piston is at TDC with that vertical line showing.
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  #26  
Old 3 Weeks Ago
owlsplace owlsplace is offline
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Get confusing doesn't it. This is the first mark past tdc on the rear cylinder. The pistons are 45 degrees apart so this should be the 40 degree timing mark for #1 I presume.
At any rate it can't be too far off or the engine wouldn't run at all.

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  #27  
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Ferrous Head Ferrous Head is offline
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There is a very simple foolproof way to confirm where you are.

Pull both plugs out. Bring the front cylinder to TDC. This is easy enough to do with something like a pencil (or straw) held loosely in your hand.

Once you have the front cylinder roll the engine backwards a tiny bit.

The measured distance from TDC is 11/16'ths.

At that point you will see whatever timing mark is in the window.

But if the flywheels are stock and the engine is an 81 I am pretty sure front timing mark is a dot, not a vertical line. They changed it to the fot in 80.

Just check and see what marks you do have on the wheel, if nothing else.
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  #28  
Old 3 Weeks Ago
The Doctor71 The Doctor71 is offline
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FH..... you're correct to challenge the marks on this 1981 motor.

owlsplace..... to re-state what FH has already said..... if one believes the FSM, the timing marks changed in late 1980. See Figure 7-29 in your 1979-1985 Service Manual. OR, H-D Service Bulletin 781.... http://sportsterpedia.com/lib/exe/fe...in:tsb0781.pdf

A 1981 motor should have the single dot/circle "o" as the advance timing mark.

BUT, if your observations are correct, this motor seems to have the older style vertical bar "|" as the advance timing mark.

So, before I/we jump to any conclusions, let's do a double check & try to rule out any operator error.

Question(s):
  1. what's the probability the flywheel has been changed / swapped out on this 1981 motor ?
  2. what's the timing mark shown in the timing plug window at TDC on the FRONT CYL ? Use your plastic straw to confirm TDC on the FRONT CYL & post a pic, please.
BTW, the pic of the advance mechanism (in Post #24) indicates the FRONT CYL is on exhaust stroke. The "tell" is that wide lobe on the cam breaker. Rotate the flywheel 360° & the narrow lobe should just be opening the points.... indicating the FRONT CYL is on compression stroke.
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  #29  
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If you have the front cylinder on compression and you have that piston 11/16ths BTDC, then WHATEVER mark is there is the timing mark.
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  #30  
Old 3 Weeks Ago
owlsplace owlsplace is offline
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Quote:
Originally Posted by Ferrous Head View Post
If you have the front cylinder on compression and you have that piston 11/16ths BTDC, then WHATEVER mark is there is the timing mark.
Okay will do today.
I'm guessing the timing is severely advanced and the bogging is being caused by the dual-fire ignition.
I'm a little amazed the engine ran as well as it did in warm weather but cold weather accentuates the problem.
I am one jet size high on the Mikuni currently since we were fooling around with various jets that were on hand.
There may be three marks on this flywheel. I can't remember.

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Last edited by owlsplace; 3 Weeks Ago at 13:12..
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