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Discussion Starter · #1 ·
As some know Im working on a 1989 CBR600 Hurricane. I did a bench sync of the carbs this weekend. This is what I did....

I used a .009 guitar string to adjust the number 3 butterfly opening. Then followed all the outboard carbs to follow spec using the adjustments between them. Doing number 4, then 2 then 1. After that I turned all A/F screws out to 3 1/2. It is clear that someone else has been in the carbs on cyl 3 & 4 because there are tool marks inside the bowls and number 4 was sealed with RTV. I did my best to clean out the jets but I think some new jets, to match the aftermarket exhaust I will be putting on is in order just for good measure.

However after all my tinkering the bike only fired up on cyl 1 and 2.

I pulled the plugs on 3 & 4 to verify it has spark. Its got great spark and the plugs are new. It also looks like the plugs have never received any fuel. As far as I can tell it *sounds* like it has compression and I will verify this over the weekend with a compression test.

Since the cams are driven from the center how often do they break on the right or left side? Im also thinking that if I drop the engine and take the valve cover off. I can see if the intake cam is broken on 3 & 4.


I also have a quick question. I noticed that there are machine screw holes without screws in them on the intake side of the block... I took pictures and if you follow the red lines you will see what I'm talking about. When I crank the bike, sometimes, it feels like there is air coming out of these but when it is running it doesnt. should I worry?

CAUTION... RUST Take measures to prep your eyes.... lol





Thoughts?
 

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Do you have the service manual for the bike. If not, search for a pdf copy. It is the best tool to use before you do anything else. Did your carbs requure 3.5 turns or was that a best guess
 

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Discussion Starter · #4 ·
Do you have the service manual for the bike. If not, search for a pdf copy. It is the best tool to use before you do anything else. Did your carbs requure 3.5 turns or was that a best guess
I had some bits and pieces that I needed such as a wiring schematic and other systems. The full shop manual is broken down in to several PDFs I just got the whole set of PDFs

Ill look in to the bolts being missing.
 

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sickboy
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spray some brake clean or starter fluid in threw the 3 & 4 carbs. If they start firing, its a fuel problem, check for plugged pilot jets.
 

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Discussion Starter · #7 ·
spray some brake clean or starter fluid in threw the 3 & 4 carbs. If they start firing, its a fuel problem, check for plugged pilot jets.
I have got the bike running and shot starting fluid straight down 3 and 4.... no dice

Are you sure the right leads are going to the right plugs?
Yes I am sure. I have them wired according to the manual. Coil 1 fires 1 and 4 Coil 2 Fires 2 and 3. Im also sure that the plugs on 3 & 4 look fresh and clean like they are straight out the box vs 1 & 2 that have visible signs of combustion.

More and more I think about it it is a broken cam but I wont know for sure till I pop off the cover.
 

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Start with the carbs, since you noticed issues with them when you cleaned them. Soak them in pinesol or carb cleaner. Don't just spray them with carb cleaner. Wire clean the jets, like you did and spray cleaner down them. Assemble the carbs according to the manual. This way you know the carbs are not the issue, then move on to the ignition. Switch the coils, see if the symptoms stay or do they move cylinders.
 

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Discussion Starter · #9 ·
On initial thought to the ignition system I figured I'd swap coils from right to left but since the issue is with half of each coil... lol. Is it possible that even though the wires on the plugs are right the wires in to the coils are flopped?

Checking the ICM possible without specialized tools? I know this is past my own instructions of Think Simple but my head is wondering.

It's a timing issue. I do what it is exactly but timing it is....
 

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Is my bike ok?
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I also have a quick question. I noticed that there are machine screw holes without screws in them on the intake side of the block... I took pictures and if you follow the red lines you will see what I'm talking about. When I crank the bike, sometimes, it feels like there is air coming out of these but when it is running it doesnt. should I worry?
Those are the ports used to synch your carbs. Which means you have a vacuum leak from hell right now. :D Plug those with proper sized hardware and sealing washers first.

In your first post you said that 3 & 4 had spark along with 1 & 2. I wouldn't worry too much about swapping coils and whatnot since you already know you have ignition there.

Sounds like a fueling issue possibly, but those vacuum ports being open aren't going to allow anything to work like it should. Plug those first IMO.
 

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Discussion Starter · #11 ·
Those are the ports used to synch your carbs. Which means you have a vacuum leak from hell right now. :D Plug those with proper sized hardware and sealing washers first.

Sounds like a fueling issue possibly, but those vacuum ports being open aren't going to allow anything to work like it should. Plug those first IMO.
I am going to find a machine screw and rubber O-Ring of sorts to plug those ports. No wonder the damn thing struggles so bad.

In your first post you said that 3 & 4 had spark along with 1 & 2. I wouldn't worry too much about swapping coils and whatnot since you already know you have ignition there.
So I was mistaken, The guy before me, in all of his infinite wisdom, did a "Tune-Up" on the bike with new plugs and he did NOT put the wires back properly. I did my best to follow the wires to the proper cylinders. Bottom line I swapped #3 and #4 wires then gave her hell. Fired up after struggling a while to get fuel. Has to be the carb synch screws missing.

Anyone know the thread size for those?

I managed to fire it up on its own, no sprays or priming of carbs with fuel from a bottle. Ran like crap under 3K, struggling to stay alive but it ran straight up to redline when you open the taps.

I also noticed that it has one hell of an exhaust leak. It seems that the can is held on with a damn hose clamp. Im also sure that with those vacuum ports open it is sounding all sorts of noisy from there too.

Thanks for the help.
 
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