Header on Cylinder 1 is not getting hot like others!

If it's broken or just needs tweaked

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Raiken1
Posts: 1
Joined: Mon Sep 25, 2017 9:47 pm

Header on Cylinder 1 is not getting hot like others!

Postby Raiken1 » Wed Sep 25, 2019 10:19 am

I just finished most of my tune-up/rebuild of my 1981 CB650 and have started having a new issue. It seems like one issue goes away and a new one starts. Previously the bike would idle well and then when given throttle it would hang at high rpm. All 4 pipes were heating up the same amount. I decided to take the advancer out and clean it then lube it with engine oil. I reinstalled it and put the timing back where it was before. Now, the bike will not take any amount of throttle without dying. The header on Cylinder 1 is only getting warm after 3-5 minutes of idling as well. I pulled the plug and it arcs off the engine head. I still need to do a leak test and carb sync, which were next, but this cylinder 1 issue has started. What should I look at next?

Here is what I have done thus far:

-Professional carb rebuild bike a vintage bike shop- Ultrasonic bath, pilot jets cleaned with guitar string, new seals and other jets etc are new (All parts from K&L carb rebuild kits) - Stock jet sizing 120 mains - Carbs were bench synced
-Brand new Vacuum tees between 1-2 and 3-4
-Rebuild kit for accelerator pump
-New Carb boots
-New Plugs and wires
-Set pulser gap to .3mm
-Set valve clearances
-New filter (I have a stock paper filter and a uni foam filter) - original airbox
-Mac 4 into 1 exhaust with megaphone muffler (Original exhaust was rusted)
-Checked static timing
-New fuel filter (Although testing without it - Auxiliary fuel container)
-Cleaned inside of fuel tank
-Set mixture screws to 1.5 turns out
- Lubed and cleaned advancer
-Oil change

User avatar
GeorgeSweety
Posts: 462
Joined: Tue Aug 08, 2017 11:47 am
Location: UK.

Re: Header on Cylinder 1 is not getting hot like others!

Postby GeorgeSweety » Fri Oct 11, 2019 3:30 pm

Hi Raiken and welcome. You don't mention doing anything to the wiring harness on this bike, I have found in the past that a lot of problems can be solved by starting with what you already have, but seem to be neglected when it comes to a refurbishment of a nearly 40 year old bike.
Most people assume that the wiring worked once, the wires aren't broken so it should be ok, the chances are that it won't, trust me. To eliminate any stupid little inexpensive wiring problems first I recommend going through every single electrical connector on the bike.
Get yourself some fine emery paper, scissors, electrical contact cleaner, a small flat blade screwdriver (or scalpel) and if possible access to a compressor or compressed air. Cut some of your fine emery paper into 6 mm strips around two inches long and then fold in half so that you end up with a double sided 3 mm wide x two inch strip of emery.
Take each connector apart and insert your emery strips into each female connector and lightly sand, if you cant get the emery in then gently open up the connectors with the fine screwdriver/ Scalpel blade until you can. You only need to brighten up the contacts.
Once you are happy with the female contacts, lightly sand the male contacts and spray both male and female contacts with electrical contact cleaner, leave to flash off for a few seconds then blow out the connector with compressed air. Repeat with contact cleaner then blow out again. Use your fine flat blade screwdriver to slightly bend the crimps on your female connectors back down so that when the male side is inserted it is tight with no play. Leave each connector for 10 minutes before reconnecting just to make sure any contact cleaner evaporates.


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