Topic: Cb650, Carbs Blowing out Air, Exhaust sucking in air

[wdmcdonald]

Ok, so I recently took apart and rebuilt this motor to replace the starter clutch (couldn't get at it from the bottom). I can't figure out what I did wrong but something is way off... The tailpipe sucks in air, a pretty strong suction. And the carbs are blowing out air. I thought I had a fuel issue but when sprayed starter fluid in and cranked the motor it all blew back out.

I know I set the cam right, I checked it three times... the engine is set at TDC (1.4T) and the index on the cam is facing forward on the right side. Center of the index mark lined up with the face of the head.

Adjusted valves twice and those are all good. What else could this be? Is it possible the the cam is still set wrong?

I'm really at a loss as the bike was running perfectly fine before I took it apart... strong spark in all 4 cylinders as well.

Please help so I can get this thing running and ride!!!

Thanks

[pangloss]

Engine turning over backwards.?  Put it in gear and see..   Battery reversal..??

[trueblue]

The battery in backwards is the only thing I can think of, if this is what you have done expect to be buying a new reg/rec unit in the near future and possibly even the ignitor units   

[pangloss]

Advance retard plate with T out by 180. ??

[pangloss]

Is it a standard ignition system..??

[tool14]

cam is set wrong 180 degrees out.

[iron_worker]

Pretty sure setting the cam 180 degrees out won't do anything.

If you're at TDC on #1 then #4 will also be at TDC. One of which will be on the compression stroke and one will be on the exhaust stroke ... this is determined by your cam. Changing your cam by 180 degrees is like turning your crank 360 degrees ... one full rotation. You'll be back in the same spot with 1 and 4 at TDC but this will now reverse which piston is on the compression stroke and which is on the exhaust stroke.

I don't think it will have any affect whatsoever.

IW

[pangloss]

I said advance retard plate (T.1.4) on the crank out by..180... will certainly cause a reversal of intake/ exhaust sequence. The advance retard plate locator pin on the 650 is 180degrees different to the
550 hence my question regarding ignition system.

[phil71]

just move the carbs to the front and the headers to the back, problem solved.

[wdmcdonald]

I will check double check the battery but I didn't touch any of the electrical so I don't think that's it. It could definitely be that timing plate though...

If I accidentally put it back on 180 degrees out would it cause the exhaust/intake timing to be reversed?

[wdmcdonald]

Also its a pulse ignition not points.

[scunny]

nothing to do with ignition.
it's early in the morning here so brain not working yet. got to be cam.

[wdmcdonald]

nothing to do with ignition.
it's early in the morning here so brain not working yet. got to be cam.

I know I meant if I put that plate on wrong, then I when I lined up the 1.4T with the index mark then it wouldn't have really been at TDC when I set the cam. Or is this not possible?

[Vinhead1957]

There are two instances when1and 4 are lined up to set the cam. The valves on cylinder 1 should relaxed. No action, at the point where you would normally adjust the tappets. The cam only travels at half the speed of the crank so you have two opportunity for camsetting. To get it set bring it to TDC 1&4 check the cam to see which valves are active on cylinder 1 and cylinder 4. Now this is the important you leave the crankshaft alone. You need to note which cylinder both valves are relaxed! Either 1 or 4. You need to make it the opposite if what  it is
You cannot just turn the cam or you will risk hitting a piston with another valve. You have to unbolt the cam gear and unbolt the cam so no valves are  being pushed open. Turn the cam 180 the bolt it back in. The cylinder that did relaxed valves 1or 4 should be opposite from the begining. Good luck be patient.

[trueblue]

THERE IS NO WAY FOR THE CAM TO BE 180 OUT.  If it appears to be so then roll the engine over once and it will line up again.  The cam turns half a turn for every full turn of the crank, there is no witchcraft occuring in there.  Though in saying this it is possible for the cam timing to be out and cause the suck and blow to be reversed, but usually when this happens valves end up bent.  The ignition timing has nothing to do with this problem, I would bet my balls on it.  The ignition timing and cam timing are two completely seperate systems.  Remove the cover over the ignitors and press the starter button, if the engine turns clockwise then you have a badly timed cam, if it is turning anti-clockwise, then you have the battery cables reversed.  The one thing that doesn't correlate with the battery cables being reversed is the starter clutch should just freespin and not turn the engine over.

[dave500]

re check your cam timing,if its blowing air the wrong way you may have already bent a valve?

[wdmcdonald]

I really don't think its a bent valve. Bike was running fine before I took it apart. I guess ill just take the cam out again and start over. I'll post some pictures for input.

[curemode2002]

I had the exact same problem you are writing about the issue is the cam and crank being 180 Degrees out. There are two 1.4T marks on the crank. Wha I did was put my timing mark on the cam the wrond direction and messed it all up. I want to say we reassembling the timing mark on the left side of the motor goes to the rear but I don't have my manual to double check. What I would recommend is if you can remove the cam gear bolts so the crank can turn but not the cam and run the crank to the other 1.4T mark you should be good to go.

[pangloss]

TWO. 1.4 T    So rthere is no 2.3 T..   oh Boy...!  A real trap that one...

[curemode2002]

There is a mark for cylinders 2 & 3 but it doesn't say 2.3T it is really kind of confusing. If you spin the crank with the head off the 650 puts 1&4 at TDC together and 2&3 at TDC together if I remember correctly. The Cam spins two revolutions for every one of the crank so the cam can be 180 out on the 650's (Wrong Sorry 180 degrees for every 360 degrees of the Crank).

[dave500]

this post has been modified to reflect curemodes above modified post that stills needs a slight modifcation,the cam still cant be 180 out!

[curemode2002]

dave500 is right wdmcdonald I got that messed up the cam spins 180 for every 360 of the crankshaft. Sorry didn't mean to confuse you. I can however tell you if you do not have the cam and crank lined up right you will see the behavior you are seeing. And guys if he smacked a valve I would hope he could hear that turning the engine over on the starter it would make quite a racket. Besides if he has suction the valves are sealing. I will see if I can get you pics of what you need from my manuals when I get home wdmcdonald.  And as I will state again when I put my head back on and lined up with the timing marks on my crank and cam I had the same behavior no smacked valves just out of alignment, so granted maybe not 180 but the same behavior. The Clymer manual has good black and white pics of what you need to line it up at.

By the way dave500 thanks for being a class act.

[dave500]

no problem cure,im a class act alright,youve come clean,the amount of posts on this subject where repeatedly the 180 out thing gets bandied around is insane,no wonder guys do bend valves,try instead of assembling the cam notch forward,install it backwards,now rotate the crank 360 back to the 1/4 tdc marks,where is the cam notch now?its magicly where it should be.

[crazypj]

Sounds like you put starter clutch in backwards so it turns engine wrong direction.
Did you try kickstarting?
 If battery is in th4e right way round it can't be anything else
I'm with Dave on the cam 180 out BS

[curemode2002]

crazypj you can't kickstart the 650's no kick on these which really sucks. Good point on the clutch but I would think they would only go one direction.