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Carb issues
M0WBY:
Hi
OK guys... I have been reading up on issues relating to my Layla (81 CB650C US import). Basically it only runs on choke and only on two cylinders!
I am going to go and buy a compression tester on monday to test the compression. It is not running on cylinders 3 and 4. I am suspecting that, since it only has 25K miles, and due to it standing since 2003 that the piston rings are stuck. The received wisdom as far I can tell is to not worry about it and get a few miles on the clock and they will free up of themselves.
The only problem is I need to get it running right first. All indications are that I have carb issues that need sorting! Now my bike had VB44A carbs but two of them were scrap. I don't know what was in them but it was nasty! Like black paint stripper! I have a set of VB54A carbs off a french CB650 on it at the moment. But the jets and air screws are off a set of VB54B carbs. The jets are #90 they are smaller that the ones from the VB44A as originally fitted which were #120. I may have a go with the VB54B carbs and see what that does. I have a problem though. The VB54A and VB54B carbs both have two air pipes on them that I don't know what they are for! Or where they should connect to! Are they just harmless air vents or am I missing a trick here or what?
http://www.flickr.com/photos/discoclover/sets/72157631764843253/
I have tried winding out the air screws until they are nearly falling out and it still won't run with the choke off!
Help!
Cheers
John
M0WBY:
Hi
My compressions readings on a warme up engine (well running on 3 cyl with choke for 10 mins) are...
cyl 1 left 120PSI
cyl 2 left inner 120PSI
cyl 3 right inner 120PSI
cyl 4 right (not firing) 110PSI
I tried to down another test with a tea spoon of oil added but I could not find a way to get it into the middle cylinders. I need a pipette or something!
I have to admit that my 12mm adapter was not very good so the results are not quite what they should be.
So what do I know now... I am confused!
Help!
Cheers
John
tom400f:
Hi John
The internet is your friend (of course you may have already found these...)
Compression:
http://www.hondacb650.com/viewtopic.php?f=4&t=1369
http://forums.sohc4.net/index.php?topic=15840.0
so it seems that can be left for now at least.
With the basic stuff like valve clearances and ignition timing checked you will have to get your carbs sorted. You are off to a difficult start with the hybrid affair you have got. Something must connect to those pipes you showed because they have clips on them. Here's a manual:
http://cosky0.tripod.com/
but not the same carbs as yours though.
Promise of other manuals here but you'll need to join the group: http://autos.groups.yahoo.com/group/Honda_CB650/?yguid=178049669
I reckon it will continue to cough and splutter until you strip, clean, service and adjust them properly.
tom400f:
More info about those mystery tubes, possibly. May be they just vent:
http://forums.sohc4.net/index.php?topic=100351.95
UK Pete:
slow running jets blocked is my bet
pete
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