Topic: 650 cam swap question???

[mgmt1234]

I dropped in the 650 cam but when I went to put the valve cover back on the rockers are hitting the top of the valve cover. Did I do something wrong because I thought this was an easy swap. Could my timing be off? could that be a reason why the motor wont turn over or is this a machining problem? The motor will turn fine without the valve cover on. Engine work is a little over my head not my specialty at all, so forgive me if I sound little amateur.

Also when I timed my cam I have three dots on the cam sprocket no lines so I went of the middle dots. I'm thinking its the timing but I'm so lost and the service manual is mind screwing me. Ill take any advice or let me know if there's a video of this being done? Thanks.


Heres where im at with my bike

[cb650]

Timing issues wouldnt cause it to hit the cover.    The 650 cam is timed off the slot on the right end. on a 650.

[mgmt1234]

Then why are the rockers hitting the top of my valve cover?

[thrutheframe]

Did you loosen the lock nuts and run all of the tappet adjusters in all the way?

[dave500]

sometimes the cam lobe might foul the underside of the rockers with this swap,youll have to lay the cam in the cover and check for this,and grind the rocker slightly for the lobe to clear.

[geminimotors]

Some folks have mentioned needing to grind some reliefs in the cylinder head and/or cover to accommodate the 650 cam. Myself and others haven't had any clearance issues. Can anybody shed some light on this in conjunction with Mgmt's  thread?

[Scott S]

  The 650 cam is timed off the slot on the right end. on a 650.

 I've been wondering about this myself. Use the slot on the RIGHT HAND side...OK. Does it matter which way it faces, front or rear? I've seen pics showing it both ways. To the front of the motor and to the rear.

[trueblue]

  The 650 cam is timed off the slot on the right end. on a 650.

 I've been wondering about this myself. Use the slot on the RIGHT HAND side...OK. Does it matter which way it faces, front or rear? I've seen pics showing it both ways. To the front of the motor and to the rear.

Doesn't matter which way, it will work either way

[Scott S]

 That's kinda what I was thinking. Because the cam fires twice for every crank revolution, right?

[Scott S]

 Excuse me, TURNS twice.....not fires twice.

[Bailgang]

It takes 2 complete revolutions of the crank to make the cam turn 1 full revolution.

[trueblue]

That's kinda what I was thinking. Because the cam fires twice for every crank revolution, right?

Thats right

[mgmt1234]

If I adjust the tappets will that change the way the motor performers? Also is it safe to grind on the rockers?

Im thinking about just forgetting it this is turning out to be a pain in the ass.

[Scott S]

 I had to clearance the head for the 650 cam, but not the valve cover. Some people say it just dropped right in, others had to trim both.

 Did you swap the CB550 cam gear on to the 650 cam?

 I noticed the three dots, but use the 1/4 timing mark on the advance unit and the notch on the cam to set the cam timing.

 Did you turn the cam over in the head to see if it clears? Remove the gear/chain from the cam and just spin the cam in the head by hand. It may be hitting the head.
 Did you do the rubber band trick when installing the rocker cover? One of the adjusters may be binding on top of the valve.

[mgmt1234]

I do have the 550 gear on, I'm going to have to go back and re time it because I used the dots on the cam gear not the cam notch. I did not know that. But before I do anything im going to pull it off and check if its hitting, Ya the rubber ban trick works pretty damn well. Thanks for your help ill let you know in the next day or two what happens.

[hymodyne]

I made this swap a few weeks ago and I've been very impressed, both with the simplicity of the job and the improvement in performance.  I had to dremel a few of the lobes spaces for clearance, but 2nd through 4th are much stronger (running 110 needles and screened velocity stacks). my big issue is the 650 tach. I picked up a 750 speedo and will use a new 550 tach cable I have, but finding a 650 tach drive is virtually impossible. Right now I have a blanking plug installed  made from the pieces of my  550 drive gear housing (don't ask).

valve adjustment was just like always, and after I retorqued the head twice (second time engine hot) and I have more power (110+) and all the leaks at the head and juggs that prompted the swap are gone.

Hym

[mgmt1234]

Someone told me that any tach with a 1:4 ratio would work on the swap. Ever hear anything like that?

How did your timing go on it. did you get it the first time?

[Bailgang]

Someone told me that any tach with a 1:4 ratio would work on the swap. Ever hear anything like that?

How did your timing go on it. did you get it the first time?

I'm using a 750 tach that's a 1:4 ration on my 550 and it works fine with my 650 cam swap.

[Bailgang]

That's kinda what I was thinking. Because the cam fires twice for every crank revolution, right?

Thats right

Are you joking or are you seriously referring to the camshaft? If you are referring to the cam and the engine in question is a 4 stroke engine then there is NO WAY that cam is making 2 full rotations for every 1 crank rotation. It doesn't matter if it's simply an overhead valve car engine, flat head briggs and stratton lawn mower engine, single overhead cam, double overhead cam car OR motorcycle engine, if it's a 4 stroke engine then that cam or cams are spinning at half the speed of the crank NOT twice the speed of the crank. 

[Scott S]

 Yeah, I was backwards on that. It's OK...chill out. My mistake. Shoulda said it the other way around.

 I'm still trying to wrap my mind around the mark facing either way, though. I set it up per the Honda manual. Cam notch facing the front when on the 1/4 timing mark.

[Bailgang]

Yeah, I was backwards on that. It's OK...chill out. My mistake. Shoulda said it the other way around.

 I'm still trying to wrap my mind around the mark facing either way, though. I set it up per the Honda manual. Cam notch facing the front when on the 1/4 timing mark.

No probs here at all, I was just stunned that someone actually agreed with you. They probably just had it backwards too.

[KC3]

So is the consensus that any 4:1 tach will work?? Any place on the forum that I can find a list of tachs used in different bikes?

I did the swap last fall and had just enough time to break it in before winter hibernation. I had to file the engine case a bit in two "holes" where the cam lobes were hitting, but not much at all! Just a mm or two. The head clearance was perfect. I would think grinding the rockers would be a bad idea.
I had no timing issues. Set tappets like normal twice --> once during the swap and once a week ago after a proper break in period. Also changed the oil after the break in --

Hope this helps.

[trueblue]

Yeah, I was backwards on that. It's OK...chill out. My mistake. Shoulda said it the other way around.

 I'm still trying to wrap my mind around the mark facing either way, though. I set it up per the Honda manual. Cam notch facing the front when on the 1/4 timing mark.

No probs here at all, I was just stunned that someone actually agreed with you. They probably just had it backwards too.

I didn't have it backwards, I could just tell that he had the general gist of what was happening and didn't have the energy at the time to make the necessary corrections.

[Bailgang]

Yeah, I was backwards on that. It's OK...chill out. My mistake. Shoulda said it the other way around.

 I'm still trying to wrap my mind around the mark facing either way, though. I set it up per the Honda manual. Cam notch facing the front when on the 1/4 timing mark.

No probs here at all, I was just stunned that someone actually agreed with you. They probably just had it backwards too.

I didn't have it backwards, I could just tell that he had the general gist of what was happening and didn't have the energy at the time to make the necessary corrections.

That's cool TB, you definitely had me worried for a bit. You wouldn't believe how many people genuinely get it wrong. After re-reading my post it does come across as being harsh and I apologize for that.

[Bailgang]

So is the consensus that any 4:1 tach will work?? Any place on the forum that I can find a list of tachs used in different bikes?

Can't say on that 1 but the only reason I chose the tach I'm using is because once I realized the 750 tach had the ratio I needed, I knew where I could easily get one and match it up to make sure it mounted the same as my 550 tach and also would still look like it was a matched pair to the speedo. There was a bunch of 650 tachs on ebay but it was difficult to determine due to lack of pics the sellers were posting to know for sure. Finding a tach with the ratio I needed was the easy part, making sure it would make a matched pair to the 550 speedo was another issue.