1981 honda cb750 exhaust #2 is cold !!!

[jamthebamm]

I helped local mechanic to clean the carbs last month( New spark plugs , new air filter, new fuel filter , new Petcock +filter )  and didn't ride the bike much be cause of the cold shity weather here in Brooklyn till today and today after starting the bike up was getting back fire around 4000 , 5000 rpm and  I noticed exhaust #2 is way colder than the other ones !!
I would appreciate any sort of help .

[TOOLS1]

You need to figure out if it is a carb problem, or an ignition problem. Try switching the plug wire with the No# 3 wire. If it stays cold, you have a carb problem, if it gets hot, you have an ignition problem. However my money is on a carb problem.
TOOLS

[jamthebamm]

Thanks tools ,I havn't check it yet but lets say if it's ignition problem then what parts should be replaced ?
Ps congrates with your kawazaki , just saw the pics . She's a beauty .

[TOOLS1]

If it is the ignition, it would be either the plug wire, or the coil. However both can be tested with an Ohm meter.
TOOLS

[jamthebamm]

I started the bike today and noticed #4 is cold too , I turned the bike off and turned it back on and smoke and gas popped out of number 4 . as you said it was carb issue . I took the bike to the mechanic who cleaned the carbs last month , he said the boots went loos and need to readjust them again ! any suggestion mr tools ?
I also checked the Ignition system ( coils and connectors ) , seems to be ok .

[TOOLS1]

Find a REAL MECHANIC.
TOOLS

[LukeM]

Agreed.  You need a more reliable/experienced local resource for this problem.

That being said, here is how I would approach this issue:

The main elements for a working 4 cycle engine are: Suck Squeeze Bang Blow.

Verify your compression is good in all 4 cylinders. In an ideal motor, all 4 should be within 10% of each other.  However, a "bad" cylinder can be off by 30% and it will still work.  If you have good compression, it will help with steps 1, 2, and 4.

Next, check the ignition.  The coil wires are actual wires, and not the kind used for noise supression in modern cars.  The caps for the spark plugs have a point on them, that engage the wire with the boot when pressed into the wire.  If it's not a good contact, the spark will be weak or non-existent.  If the ignition is working, it helps with step 3.

Next, check the fuel deliver system.  As you might have read on other postings, sometimes it takes more than one disassembly of the carbs to make sure they're totally clean inside.  I had to pull my CB750 carb bank at least 3 times, and my Shadow 700c 4 times before the carbs worked reliably. If you don't have an inline filter for the gas line, get one.  Paper, bronze, either one. It will save you time and aggravation.  If the fuel delivery system is working, it helps with steps 1, 2, and 3.

Sorry to be so long winded, but these engines will work even if one or two systems are not working at top efficiency.  When all 3 are working well, it's a very flexible and strong engine indeed.  To follow up on TOOLS's comments, check your compression, then check your spark plugs, then check your carbs.  Hopefully, it's something simple and easily resolved.

PS: be careful riding your bike in NYC. I worked in LI for 18 months, and MC riders were treated with considerable disdain.  I can only imagine it's worse in the city.

(Edited the posting a bit: corrected 1-% to 10%.)

I hope this helps.  Keep us in the loop with your progress, and we'll help if we can.  Good luck!
Luke M

[jamthebamm]

thanks lukeM  wow it was so efficient and well said . I'll go step by step as you suggested and most definitely will watch out for taxi drivers here in NYC .

[LukeM]

Just thought of a shop that might be able to help.

Liberty Vintage in Philly.

Here's the link.

I love this guy's attitude.  It's less about the bikes as much as it is looking to your fellow human, and making them better as well.  Granted, the guy knows his stuff, and his bikes are very cool.

Don't know how you would get your kinda not working bike over there, but I leave that up to you.
Luke M

[TOOLS1]

I can guarantee that guy will not be cheap. Why not just study up on how to rebuild the carbs with all the information available here on the forum, and do it yourself?
TOOLS

[jamthebamm]

Mr tools I started doing some research to learn about carbs from here , youtube etc , well it takes time to get them perfectly done and  I'm sure I might need to redo them several times to get perfect results but I'm willing to do that happily with all the info that I can find here and your precious helps . as we all know a good mechanic doesn't come cheap and it would be so costly for a student/bartender here in new york  plus I would love to learn new things .

[TOOLS1]

TOOLS

[jamthebamm]

Mr lukeM that website was fantastic , the guy is such character and his bikeshop is like a luna park for me but not kind of practical way for me to go down to Philly right now but soon .Two places on my check list in Philly 1: liberty vintage 2: Pat's or Geno's or both at the same time

[jamthebamm]

Ok this is what I've been up to these last two days

I don't know how bad it is but I soaked and cleaned them with carb cleaner and also soaked the jets and needles in a jar for 10 min ( not the washers or the diaphragm or any plastic material part )

pulling them back together was kinda easy but being patient is a must , I also bench synced them , well I'm gonna borrow my friend's Emgo Carburetor Synchronizer to sync the carbs more properly

and here it becomes a serious pain in the neck , taking them off was kinda hard but put this harlot back together was almost impossible specially with new boots but after spending hours and sweating blood out , finally put them back on the bike , tight and nicely ( I guess )

Cleaned the dark wet spark plugs , all 4 of them were nasty  

borrowed a compression tester and this is what I got , all 4 cylinders were almost in same range which I don't know if its the right place that they should be or not .
But here it becomes kinda disappointing , when I put the gas tank back on and turned the petcock to on position , I noticed after a few second gas is coming out of #1 nipple , I guess I must have screwed up the float or it's pin or .. I really don't know !! SOS please !!
 So as much as I wanted to turn the bike on and hear it's voice , I didn't .Obviously something is wrong with it and it can be dangerous , anyhow at this point I really don't know how the bike would Idle or if the carbs are properly installed or if the new boots leak gas or not !!  
Tomorrow I'm gonna try and see if I can reach the float without taking the crabs apart  , if not , have to do the whole process again
ps after the whole carb issue if the weird noise that was coming out of the engine( in neutral) is not gone I think I have to adjust the camshaft too .

[jamthebamm]

Ok after cleaning all the carbs and putting new boots on , the bike is still shooting fire . I checked the spark plugs , # 1 and 3 are clean but 2 and 4 are wet !?!? almost same problem like before ! in short note , I changed the regulator and starter solenoid fuse 2 weeks ago , and the problem started showing up almost 1 day after . is shooting fire related to electrical malfunctioning ? can it be bad gas ? I tried to switch the coil wires but they were too short , so I'm gonna take them of the bike and test them with an ohmmeter tomorrow .

[TOOLS1]

Do you have the plug wires crossed? Shooting fire is a symptom of this.
TOOLS