81 Low Rider front cylinder running hot
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Cruiser
Joined: Feb 2018
Posts: 191
Likes: 9
From: Texas
81 Low Rider front cylinder running hot
Front cylinder is getting around 300F back is 190F. It spits and sputters & runs real rich. Starts super easy too. Any one have any ideas?
Plugs are showing a rich condition as well all soothed up after 2-3 min of run time. It was leaning out due to manifold vacuum leaks before and overheating. Pipes ended up all blued. Also had a front exhust gasket leak at the head. (No leaks at intake or exhust now)
I checked the timing with a strobe and I see the dot. It has a New 38MM Mikuni (dirt bike style) and I dropped down to a 280 main jet from a 330, I have a new coil, new wires, new plugs in it. No new vacuum or exhust leaks I can find. It just seems out of sync.
Orig. electronic ingnition, volt reg, & stator. All seem okay, but I am leaning toward that ingnition module or maby that coil is goofy.
Any ideas?
Plugs are showing a rich condition as well all soothed up after 2-3 min of run time. It was leaning out due to manifold vacuum leaks before and overheating. Pipes ended up all blued. Also had a front exhust gasket leak at the head. (No leaks at intake or exhust now)
I checked the timing with a strobe and I see the dot. It has a New 38MM Mikuni (dirt bike style) and I dropped down to a 280 main jet from a 330, I have a new coil, new wires, new plugs in it. No new vacuum or exhust leaks I can find. It just seems out of sync.
Orig. electronic ingnition, volt reg, & stator. All seem okay, but I am leaning toward that ingnition module or maby that coil is goofy.
Any ideas?
Thread Starter
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Cruiser
Joined: Feb 2018
Posts: 191
Likes: 9
From: Texas
I guess I can do a compression check and cylinder leak down test. It seems like it has good compression. I am still leaning towards the timing and or something related to that part of the system due to the fact it is all the original 37 year old electronic ignition components. Most of the wires that connect them seem hard and a bit brittle, and that could be an issue.
I am leaning on trying the Ultima Single Fire Programmable Ignition Coil Kit Harley Evo Big Twin & XL for $160 and put the Standard Motor Products Custom Electrical Switch 3In Hg Mc-Vos4 Voes 3 21010258 for $39 on it.
I am leaning on trying the Ultima Single Fire Programmable Ignition Coil Kit Harley Evo Big Twin & XL for $160 and put the Standard Motor Products Custom Electrical Switch 3In Hg Mc-Vos4 Voes 3 21010258 for $39 on it.
Seasoned HDF Member
Joined: Nov 2009
Posts: 15,705
Likes: 22,718
From: Farmington ,MS
No way the timing would make one cylinder run hot
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Cruiser
Joined: Feb 2018
Posts: 191
Likes: 9
From: Texas
What do you think it could be? I put a bore scope in there yesterday, and except for a little vertical wear marks in the bore, I did not see anything extreme though it looked was getting hot. the carbon was all shiny in there.
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Seasoned HDF Member
Joined: Nov 2009
Posts: 15,705
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From: Farmington ,MS
It is that or compression..."seems to have compression" is not on my compression gauge.
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Cruiser
Joined: Feb 2018
Posts: 191
Likes: 9
From: Texas
PER NGK - carbon fouling, is often caused by an overly rich condition, and the problem may lie with your air cleaner (clogged) or carburetor. Other possible causes could be low compression, vacuum leak, overly retarded timing, or improper spark plug heat range.
Setting the timing on this bike was a PIA, and I got a feeling I messed it up. It almost takes two people to do it right. I got to get a new a new compression tester to confirm compression & I will do that. ( but, if it is bad compression on one cylinder, wouldn't it show up in different conditions between the plugs?) Both plugs show a rich condition.
I sprayed all around the intake with brake clean and I could not detect any leaks. I have no visible blow by or oil leaks around the head or head gasket area, looks good. No goofy sounds either.
I may have set the timing up incorrectly by adjusting it to the rear cylinder advance timing mark Lower (DOT) in stead of upper dot. The chart in the manual is confusing, and I may have inadvertently set it to the rear cylinder advance timing mark. It is almost impossible to see that mark when its running at 2000 RPM when its hot, I actually started to melt the plug. I used a standard timing light set at zero advance. Any thoughts on checking timing would be helpful.
Also it says to check the timing every 2500 miles? I never did that and I owned the bike since new from 1981... So that kind of tells me too, that it might be time to upgrade that component anyways,,,,,
Setting the timing on this bike was a PIA, and I got a feeling I messed it up. It almost takes two people to do it right. I got to get a new a new compression tester to confirm compression & I will do that. ( but, if it is bad compression on one cylinder, wouldn't it show up in different conditions between the plugs?) Both plugs show a rich condition.
I sprayed all around the intake with brake clean and I could not detect any leaks. I have no visible blow by or oil leaks around the head or head gasket area, looks good. No goofy sounds either.
I may have set the timing up incorrectly by adjusting it to the rear cylinder advance timing mark Lower (DOT) in stead of upper dot. The chart in the manual is confusing, and I may have inadvertently set it to the rear cylinder advance timing mark. It is almost impossible to see that mark when its running at 2000 RPM when its hot, I actually started to melt the plug. I used a standard timing light set at zero advance. Any thoughts on checking timing would be helpful.
Also it says to check the timing every 2500 miles? I never did that and I owned the bike since new from 1981... So that kind of tells me too, that it might be time to upgrade that component anyways,,,,,