Topic: Need help cb650

[Nymotorcyclerepair]

Couple questions here...I have a 1980 cb650 I got from someone and they said the cam might be 180degree off. Bike would not start. I check into it and looks like the were right. I put the motor with 1-4piston tdc my intake valve one number 1cyl is almost at the top of the cam lobe which would mean it's About to open. As it should. I believe. That being said now the cam is correct to tdc the intake valve is about to open. Now. Person I got it from says they adjusted the valves with it 180deg off. As I thought with pistons 1-4 at tdc you should adjust intake:2-3 and exhaust:1-3 and the opposite for pistons 2-3. Is this correct? Or is it the other way around.
-The bike was turned over with the cam 180 off but I don't think any valves are benT.
-I turned cam 180 so now intake is opening with piston 1-4at tdc it kinda spits an spudders.
-The accelerator diaphragm is cracked. I'm getting no gas to any cylinder. Is this because of a cracked diaphram?
I poured gas down cylinder one an two but just got some poping doesn't sound like it wants to fire. I will have to adjust valves now since they can't be correct. Any help would be great! I have new diaphragm in route. If it would be eaiser to explain I wouldn't mind a phone call or two with Any ideas. 607-643-5524.name is Joseph leave message if I don't answer. This has got me little crazy.
What is the correct valve adjusting sequence and tolerances. I think ex is .005 and intake is .003?
 

[dave500]

the cam cant be 180 out,if it looks to be just rotate the engine 360.

[tkonetzke]

Sure it can be, well sort of. Firing on exhaust stroke. Which would be ignition timing. Do you have spark? Compression? Fuel? I would verify those before searching for other culprits.

[cgswss]

To set the cam timing, you must remove the head cover and line up a mark on the cam timing mark with the front of the head surface.  Your cam chain will have slack in it so it is important to turn your engine clockwise.  to check this you will have your right side cover off and (by turning clockwise) align the crank to the 1.4T mark and the mark on the end of the cam will be aligned with the front of the head surface.

Here is something to try.  pick up some started fluid for a diesel,  Turn the gas off  crank the bike and spray the starter fluid into the air box.  This should allow the bike to start and run clean as it bypasses carb problems.  If you get back fires, check your plug wires  left coil should feed 1 and 4  right coil feeds 2 and 3.

You most likely know all this, but I thought I'd give you a little reminder.

[dave500]

Sure it can be, well sort of. Firing on exhaust stroke. Which would be ignition timing. Do you have spark? Compression? Fuel? I would verify those before searching for other culprits.

these fire on exhaust stroke anyway,its a wasted spark,set up your cam as per the honda book,then rotate the engine 360,,where is your mark now??whoa!!!its #$%*ing 180 #$%*ing out!!

now rotate the engine another 360,hey,,im a #$%*ing genius,i fixed it.

[thrutheframe]

Couple questions here...I have a 1980 cb650 I got from someone and they said the cam might be 180degree off. Bike would not start. I check into it and looks like the were right. I put the motor with 1-4piston tdc my intake valve one number 1cyl is almost at the top of the cam lobe which would mean it's About to open. As it should. I believe. That being said now the cam is correct to tdc the intake valve is about to open. Now. Person I got it from says they adjusted the valves with it 180deg off. As I thought with pistons 1-4 at tdc you should adjust intake:2-3 and exhaust:1-3 and the opposite for pistons 2-3. Is this correct? Or is it the other way around.
-The bike was turned over with the cam 180 off but I don't think any valves are benT.
-I turned cam 180 so now intake is opening with piston 1-4at tdc it kinda spits an spudders.
-The accelerator diaphragm is cracked. I'm getting no gas to any cylinder. Is this because of a cracked diaphram?
I poured gas down cylinder one an two but just got some poping doesn't sound like it wants to fire. I will have to adjust valves now since they can't be correct. Any help would be great! I have new diaphragm in route. If it would be eaiser to explain I wouldn't mind a phone call or two with Any ideas. 607-643-5524.name is Joseph leave message if I don't answer. This has got me little crazy.
What is the correct valve adjusting sequence and tolerances. I think ex is .005 and intake is .003?
 

Step one is to buy a manual if you don't already have one, I would buy the Clymer Manual and the Honda Shop Manual.  Everything you need to know is contained in these two manuals.

[thrutheframe]

these fire on exhaust stroke anyway,its a wasted spark,set up your cam as per the honda book,then rotate the engine 360,,where is your mark now??whoa!!!its #$%*ing 180 #$%*ing out!!

now rotate the engine another 360,hey,,im a #$%*ing genius,i fixed it.

   I have to disagree Dave.  On the intake stroke if the cam is 180 out then the lobe would not be aligned to open the intake valve as the piston falls and no fuel/air mixture would enter the chamber.   Then on compression the lobe would align to open the exhaust valve during the upstroke resulting in no compression.  On combustion the lobe would align to open the intake valve (plus or minus the difference between TDC / ignition timing and valve timing).  On exhaust the lobe would not align to open the exhaust valve.
  If I have it wrong someone will certainly let me know.  I admit that I don't have the scenario for combustion fully sorted out but I don't have a manual in front of me.

[trueblue]

these fire on exhaust stroke anyway,its a wasted spark,set up your cam as per the honda book,then rotate the engine 360,,where is your mark now??whoa!!!its #$%*ing 180 #$%*ing out!!

now rotate the engine another 360,hey,,im a #$%*ing genius,i fixed it.

   I have to disagree Dave.  On the intake stroke if the cam is 180 out then the lobe would not be aligned to open the intake valve as the piston falls and no fuel/air mixture would enter the chamber.   Then on compression the lobe would align to open the exhaust valve during the upstroke resulting in no compression.  On combustion the lobe would align to open the intake valve (plus or minus the difference between TDC / ignition timing and valve timing).  On exhaust the lobe would not align to open the exhaust valve.
  If I have it wrong someone will certainly let me know.  I admit that I don't have the scenario for combustion fully sorted out but I don't have a manual in front of me.

WTF are you on about, the cam determines which stroke the piston is on, all the piston does is go up and down, I have seen this too many times lately and it is frankly giving me the sh!ts, not so much that people don't know whether or not it is possible to be 180 out, but the fact that there are people out there that argue the point that it can be, the crank turns twice for every revolution of the cam, so therefore, one revolution of the crank the cam turn through 180 degrees, everytime the piston gets to the top the spark fires, on both the compression and exhaust stroke, so that isn't a problem either, a little basic logic says that there is no way the cam can be out 180.  Just to be clear
 THERE IS NO WAY FOR YOUR CAM TO BE 180 OUT ON ONE OF THESE BIKES

[thrutheframe]

  Put waste spark aside and think about the positions of the valves on a given stroke for a moment then re-read what I wrote.  Doesn't it make sense?  Also the cam does not determine which stroke the piston is on, like you just said, the piston only has two strokes, up and down.  The cam determines the position of the valves which is what determines if a given up or down stroke of the piston is an Intake, Compression, Combustion, or Exhaust Stroke.  Your response doesn't address the position of the valves in the equation, a closed intake valve on the Intake Stroke would certainly prevent fuel/air mix from entering the combustion chamber.
  On top of that think about why we're all here.  Isn't the purpose of the forum to educate and share information?  If I have it wrong(and I admit I very well could) tell me why in a calm and intelligent fashion.  Yelling at me about waste spark and 360 degrees of crank rotation versus 180 degrees of cam rotation doesn't qualify as an intelligent response.  I genuinely want to know why I'm wrong, I come here to learn and share the knowledge I have aquired here and first hand.
  My apologies to Nymotorcyclerepair for creating a sh!t storm in your thread.

[cgswss]

OK guys- when you have the head in one hand abd the motor in front of you there is no such thing as a "compresion stroke"

When you align the marks on the crankshaft so it is pointing at "1.4T" both cul #1 and cyl #4 are at top dead center.  But there is no "compression stroke" yet because we don't have any valves.

Now we set the index mark on the end of the cam so it is "top dead center on the compression stroke of cylinder 1"  If you were to set that index mark so it aligned to the back of the head, you would be setting the valves to TDC on the compression stroke for cylinder #4.  And If you turned the crank one turn the mark would be aligned with the front of the head (TDC Compression #1)

The important thing is to make sure you are lining up these marks with the front of the cam chain under tension.  This is why you always turn the engine over clockwise (looking from the points side (right).   If you go by the mark and turn the crank back (counter clock wise) the crank will turn a few degrees further to take up the slack in the cam chain.  If you have to back up, turn the crank a 1/4 turn so you can take out the backlash and move the cam and crank together.

The problem most have is that they think about a 4 cylinder engine like in a car.  There you normally have a disturber that fires the plug only once for each 2 turns of the crank.  On the Honda MC the they fire two plugs for each  turn of the crank.  This means that every time the 1 &4 pistons come to the top both plugs fire, but only one is on the compression stroke.

SOOOO you can't realty have a cam "180* out of time"  but you can get the timing screwed up by not turning the crank in the correct direction when timing the cam.

[fmctm1sw]

I genuinely want to know why I'm wrong, I come here to learn and share the knowledge I have aquired here and first hand.
  My apologies to Nymotorcyclerepair for creating a sh!t storm in your thread.

I started a poll on this too a few days ago...  I fully expected to be chastised but there's not much out of that thread yet.   

[MJL]

Sure it can be, well sort of. Firing on exhaust stroke. Which would be ignition timing. Do you have spark? Compression? Fuel? I would verify those before searching for other culprits.

that's normal for a wasted spark ignition. There are two spark events per 4stroke cycle,  one on compression and one on exhaust.

[iron_worker]

Installing the cam "180 out" only changes the firing cylinder from #1 to #4 and #2 to #3 (or vice versa). 1 more rotation of the crank (or 1/2 rotation of the cam) and you'll be back to the other cylinder.

With wasted spark the cam cannot be 180degrees out.

IW

[Nymotorcyclerepair]

Ok. Slot of other nonsense was added to this. But now I have my cam the two dots on the cam sprocket flush with the top of the head piston 1and 4 up the first valve on cylinder one just about to open the intake. So this would mean I'm at the compression stroke and at top dead center. Al I'm getting is sputtering. No spark plugs are getting gas. The accelerator diaphragm is dry rotted new one on order but dont think that's the problem. Not sure why no gas to any cylinder. Could I have bent valves because the cam was opening on exhaust stroke?

What is the correct sequence to adjust the valves?

[cgswss]

Viewed from the left you have two dots, on the end of the shaft-viewed from the RIGHT you should have a single dot.  The single dot on the right is the mark you use along with the 1.4T (0n the right side) and you should be turning the crank clockwise to get there.  As someone mentioned earlier your cam lobes will be pointed down at this point.  If you work from the right side there is no confusion.  Single dot pointing forward, crank at 1.4T, turn clockwise.

On the compression stroke, the intake valve would have just closed and you a bit less then a half of turn from the exhaust opening.

Did you turn the head over and put gas in the combustion chambers wile it was off?  if they hold gas, you don't have a valve problem (well you could still have an oil seal problem but that would not stop it from running.

Did you ever pick up some starter fluid?  If runs on started fluid, its a good bet that your should be looking at the carbs and forget the valve timing, spark timing, and valve adjustments (for now) and just work on the fuel side which is almost for sure a carb problem. 

when I'm trying to find that hard to find problem I keep narrowing it down from both sides.  Take off a float bowl and turn on the gas-- You should have gas pouring out of the carb.  push the float up and the gas should stop.  If it doesn't flow we look upstream from the carb.  If we have normal flow and normal "stop" plus it runs on starter fluid, then we know the problem is inside the carb.  there are only a couple of things that stop the gas from being used once we know we have gas in the float bowel.  If you didn't want to remove the float bowl, a little trick I used to do was to go to a hobby store and get some clear fuel line  pull the black drain line off the bottom of the carb and put the clear in its place.  now loop the clear line up beside the floatbowl and open the little carb drain screw on the bottom of the carb.  If the gas is on, you should see the clear line fill with gas up to just below the seam at the top of the bowl.


if you are not getting gas, you may have fuel line diaphragm (Sits on top pf the carbs between #3 and #4 and acts as a "automatic" fuel shutoff)  I don't know which models had these.  If yours does, I'd just bypass the sucker until you have some of the other problems worked out.

[thrutheframe]

I get it now.

  I already knew that when the crank turns 360 the cam only turns 180 but when I was drawing out my little pictures to sort out in my head if the cam could be 180 out I wasnt thinking about that.
 
I'm going to go eat my crow now.

Iron Worker and cgswss, your posts made the little light come on.  Intelligent posts were the key to sorting out my confusion.

[chewbacca5000]

I had a couple of CB650s and I think I know what you are talking about, but without pics I can't do anything.  Need to see the cam and that you are at TDC 1,4.