Topic: why would pipes #1 & 3 be cool?

[juntjoo]

As I am working with multiple repairs and waiting on parts I want to start getting an idea of what could be going on.

This I noticed after running the engine just recently before taking it all apart again. Felt and sounded great idling and revving.

Could it be related to my valve adjustment? Could it be carb related? Electrical or timing? The plugs look a little wet/dark while #'s 2 & 4 look normal. Couldn't say for sure yet but I think I did a fantastic job rebuilding these carbs for the 1st time ever if I can say so myself. But idk. Whatever it is I hope it's just an adjustment.

and I do have spark

[Yamahawk]

They are too cool to fire... ...just kidding.
1 and 3 cylinders are not firing, and that's why your plugs are wet looking. If you can lay your hand on the pipes without sizzling your skin, there isn't any combustion in those cylinders. A safer and saner way to check is to get a remote temperature sensor gun from Harbor Freight (cheap at $30) and point it at each pipe while running the engine. Any difference in temperature is immediately apparent, and tells you what isn't happening.
Charlie

[Deltarider]

They are too cool to fire... ...just kidding.
1 and 3 cylinders are not firing, and that's why your plugs are wet looking. If you can lay your hand on the pipes without sizzling your skin, there isn't any combustion in those cylinders. A safer and saner way to check is to get a remote temperature sensor gun from Harbor Freight (cheap at $30) and point it at each pipe while running the engine. Any difference in temperature is immediately apparent, and tells you what isn't happening.
Charlie

Although I have an infrared temp sensor, I find flash touching a lot easier and quicker for a diagnose.

Could it be related to my valve adjustment?

Not if you know how to do it.

Could it be carb related?

If I may ask, what did you make taking the carbs apart? Did you happen to mess with the float height? Are slow jets in place and open? If your main jets have O-rings, are they still OK and seal well? Do chokeflaps open unhindered?

[Duke McDukiedook]

If you have a decent spark at those plugs when they should spark you're left with the fuel part of the equation.
Crabs it is.

[juntjoo]

thanks. so they're not firing but why just those two?

[Yamahawk]

^^^ What he said... if you have spark, it is fuel related.
Charlie

[Deltarider]

and I do have spark

so they're not firing but why just those two?

Which is it? No spark on 1 and 3, I'd check if the connection plugcap - wire is still firm and I'd check if resistance of those plugcaps is not too high.

[juntjoo]

They are too cool to fire... ...just kidding.
1 and 3 cylinders are not firing, and that's why your plugs are wet looking. If you can lay your hand on the pipes without sizzling your skin, there isn't any combustion in those cylinders. A safer and saner way to check is to get a remote temperature sensor gun from Harbor Freight (cheap at $30) and point it at each pipe while running the engine. Any difference in temperature is immediately apparent, and tells you what isn't happening.
Charlie

Although I have an infrared temp sensor, I find flash touching a lot easier and quicker to diagnose.

Could it be related to my valve adjustment?

Not if you know how to do it.

Could it be carb related?

If I may ask, what did you make taking the carbs apart?

I just cleaned them and replaced a lot of rubber. So it could have been the valve adjustment. I'm no expert but I did set the gaps while at "TDC" but the manuals don't explain how to know WHICH tdc. So after examining the operation of the valves it looked to me that with two choices of TDC, I just needed to pick the one that would allow me to get under the tappet to measure, as I discovered you cannot even insert the gauge at the wrong TDC,... but idk why I was able to do #1 intake at first but not able to do #3 till I rotated the shaft 360 since 1 & 3 intake are to be done together. So after rotating, I did #3, then rotated AGAIN to prepare for #4 and #2 after which it seemed to work out, but I'm not sure about the initial rotation I did. You're only supposed to rotate one, ultimately I did twice. Sorry, confusing, but could 1 and 3 be off such that not enough fuel is making it in producing weak combustion hence warm pipes?

[juntjoo]

They are too cool to fire... ...just kidding.
1 and 3 cylinders are not firing, and that's why your plugs are wet looking. If you can lay your hand on the pipes without sizzling your skin, there isn't any combustion in those cylinders. A safer and saner way to check is to get a remote temperature sensor gun from Harbor Freight (cheap at $30) and point it at each pipe while running the engine. Any difference in temperature is immediately apparent, and tells you what isn't happening.
Charlie

Although I have an infrared temp sensor, I find flash touching a lot easier and quicker for a diagnose.

Could it be related to my valve adjustment?

Not if you know how to do it.

Could it be carb related?

If I may ask, what did you make taking the carbs apart? Did you happen to mess with the float height? Are slow jets in place and open? If your main jets have O-rings, are they still OK and seal well? Do chokeflaps open unhindered?

nom adjustable floats. all measured good and equal and passed a simple float test. Cant see all choke plates w/ carb installed but I'll check after removing again(forgot to loctite choke plates) but t before putting them back up I spent a lot of time on them amd they all appeared free and in sync. No main jet seals. Slow jets as with all holes I tested to be clear with a wire and carb cleaner(the little group of jets just under throttle plates right?).. thanks

[juntjoo]

If you have a decent spark at those plugs when they should spark your left with the fuel part of the equation.
Crabs it is.

thanks. I wouldn't know about the timing. I will in a couple days tho. So with timing are 1 & 3 related?

[juntjoo]

and I do have spark

so they're not firing but why just those two?

Which is it? No spark on 1 and 3, I'd check if the connection plugcap - wire is still firm and I'd check if resistance of those plugcaps is not too high.

I was just repeating yamahawk. I was thinking "firing" meant combusting. They're firing, but obviously not combusting, but plugs are wet so fuel is getting there. So... timing?

[Duke McDukiedook]

If you have a decent spark at those plugs when they should spark your left with the fuel part of the equation.
Crabs it is.

thanks. I wouldn't know about the timing. I will in a couple days tho. So with timing are 1 & 3 related?

If you have a timing light with an inductor coil you would if you hooked it up to each wire to check to see if that wire is firing on the specific fire mark.
That's what I assumed you were talking about since you said spark was not a problem- or you laid a spark plug against the head for the different spark caps to check for a decent blue spark.

Crab#1 and #3 could be clogged in some of the air or fuel passages. You need to clean ALL of them with pressurized air and crab cleaner and wires. All orifices must flow.

[Yamahawk]

I have heard of boiling the crab bodies in Simple Green, or you could use the conventional crab boil and throw in some legs and claws...
Charlie

[Nathan B]

I have heard of boiling the crab bodies in Simple Green, or you could use the conventional crab boil and throw in some legs and claws...
Charlie

Haha I see what you did there.


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[TwoTired]

Double check your ignition coil wires.
One coil's output lead should go to cylinders 1&4.  The Other coils output leads should go to cylinders 2&3.

Your reported symptoms would be consistent with attaching one coil to 1&2 and the other to 3&4.  Which would make two cylinders dead.

There are certainly many other possible issues to check after the above verification.

Cheers,

[Gene]

^^^^^ Check the simple stuff first.

[Scott S]

 After reading your valve cover and valve adjustment threads, I would NOT run the engine anymore until I checked, double checked and triple checked the valve adjustment.
 I don't mean to sound like a butt, but prove me wrong. Check your valve adjustment again, please.

[juntjoo]

After reading your valve cover and valve adjustment threads, I would NOT run the engine anymore until I checked, double checked and triple checked the valve adjustment.
 I don't mean to sound like a butt, but prove me wrong. Check your valve adjustment again, please.

I will, thanks

[juntjoo]

After reading your valve cover and valve adjustment threads, I would NOT run the engine anymore until I checked, double checked and triple checked the valve adjustment.
 I don't mean to sound like a butt, but prove me wrong. Check your valve adjustment again, please.

watch /listen to this:

to hear what it sounds like. this is before I recently took off the valve cover again to deal with oil leaks. I originally thought it sounded good but on second listen and discovering the cool pipes it sounds to me like I messed up the valves didn't I? I've already resigned to the probability I've toasted the head. What's it a few bolts and a few hundred dollars and another week? It's a good education I say.

Really? I did the adjustments at TDC... I'll have to take a closer look after I wake up.

edit: can't sleep so here are some pics if they provide any useful info. Seems like #1 screw doesn't come through as much as the rest.

#1 and #2 intake adjusting screws https://imgur.com/a/rgmyz

#3 and #4 intake adjusting screws https://imgur.com/a/CBKEK

thanks a lot

[Scott S]

 Did you have the cam chain tensioner out? How far apart was the engine?

 The valves are easy to adjust on the 650, compared to the 500/550. I would double/triple check the valve adjustment. The valves sound a little noisy in the vid, and I think I hear some cam chain noise. It's easy to NOT seat the tensioner properly (ask me how I know).

 It also sounds like you could use a carb sync, but don't bother with that until the valves and ignition stuff is sorted.

[DaveBarbier]

+1 On Scott, how far apart was the motor? What was the purpose of taking it apart? Oil leaks? Metal in the oil?

Here's Dino explaining how to do a valve adjustment on his 750. This may help but it's been a while since I've watched this one but I think he explains things really well.

[juntjoo]

Did you have the cam chain tensioner out? How far apart was the engine?

 The valves are easy to adjust on the 650, compared to the 500/550. I would double/triple check the valve adjustment. The valves sound a little noisy in the vid, and I think I hear some cam chain noise. It's easy to NOT seat the tensioner properly (ask me how I know).

 It also sounds like you could use a carb sync, but don't bother with that until the valves and ignition stuff is sorted.

no I didn't do anything with the cam tensioner, whatever that is, nor did I do anything with the engine but remove the head cover

[juntjoo]

Double check your ignition coil wires.
One coil's output lead should go to cylinders 1&4.  The Other coils output leads should go to cylinders 2&3.

Your reported symptoms would be consistent with attaching one coil to 1&2 and the other to 3&4.  Which would make two cylinders dead.

There are certainly many other possible issues to check after the above verification.

Cheers,

thanks. they are all correctly connected.

[juntjoo]

+1 On Scott, how far apart was the motor? What was the purpose of taking it apart? Oil leaks? Metal in the oil?

Here's Dino explaining how to do a valve adjustment on his 750. This may help but it's been a while since I've watched this one but I think he explains things really well.

thanks. I had put a spark plug socket a tad too fat in #1 and it got stuck. Geez Honda, you could have left .5mm extra so we could get a standard socket at the store

[DaveBarbier]

I hear you. I picked up the Honda plug wrench because I saw it on eBay for fairly cheap. A pain in the ass if you don't have a thin walled socket.