Topic: 76 CB750K engine rebuild thread - With Video!

[michrobi]

wow, Webcam's Degreeing instructions are written by someone that just put out a doobie.

"Rotate the engine until you are back to Top Dead Center (TDC). Zero your dial indicator. Next you will start turning the engine until you are .050 off the seated position of the valve (It is very important to turn the engine it’s normal way of rotation)."

Yeah, that valve isn't at the seated position at TDC, so if the reader zeros out their dial at TDC and starts turning the crank to 0.050, it's all over. Lot of "oops what I meant to say is something else" s  in that Webcam instruction writeup. May as well not even be there really.

I think I'll set the mark on the cam straight at 12 o clock while the crank is on TDC and call it a day man.

[Flying J]

see if this helps. I think it made a lot more sense after i read this.
http://www.muzzys.com/articles/lobe_centers.html

[michrobi]

Okay I'm pretty sure I have the Lobe Center of my #1 intake correct at 107°. I apparently don't understand the difference between TDC and BDC because the readings I got were;

Intake Open 0.050 at 42° BBDC (Before Bottom Dead Center)
Intake Close 0.050 at 18° ATDC (After Top Dead Center)

I define Top Dead Center for #1 as; When the crank has the #1 piston at the top of the cylinder block. Indicated by the cam niche being at 12 o'clock and the points marker being at the "T" line for the 1-4 end. (Assuming your case's mark is accurate.) At this position both the intake and exhaust valves for #1 are slightly open and the valves for #4 are closed. This is my degree wheel's 0°/360°.

Now, I'm pretty sure I have that understood correctly, unless TDC is when the valves are closed and I've just described TDC for #4. If so, please tell me.

So what is Bottom Dead Center? Is it the 180° mark on the wheel that is also the T mark for 2-3 on the crank points? Or is it the 0°/360° mark on the wheel that happens at the cam niche's 6 o'clock?

I hope someone understands that and can help a guy out. I'm struggling.  

[mec]

when #1 and #4 is in TDC then #2 and#3 is automatically in BDC.
btw: you should better replace your cam sprocket. the hole for the M7 screws is way to long, big.
otherwise you risk:
http://forums.sohc4.net/index.php?action=dlattach;topic=44736.0;attach=80210;image

mec

[michrobi]

It's a new cam sprocket.

[michrobi]

How come you guys didn't tell me I was turning the engine the wrong way?   

[Jerry Rxman Griffin aka MuthaF'er]

(It is very important to turn the engine it’s normal way of rotation)."

I'm assuming a favorable outcome now? And just who was burning one? 

Report back in tonight or you're fired 

[michrobi]

Here is the degree procedure for a SOHC...

Once you have true TDC, turn the engine clockwise (The opposite direction of the kick starter) until you start up the lobe. When you reach your 0.050 on your dial, make a note of the degrees Before Top Dead Center. Then continue your clockwise rotation until the dial has traveled all the way up the lobe, and back down the other side stopping on the same 0.050 reading. Make a note of the degrees After Bottom Dead Center. Then the same procedure on the exhaust valve, making notes of the opening 0.050 and closing 0.050 degrees.

Here are my results with the engine rotating in the correct direction.

Intake
Open = 12° BTDC
Close = 42° ABDC
Lobe Center = 105°

Exhaust
Open = 47° BBDC
Close = 14° ATDC
Lobe Center = 106.5°

A little math will give you the degree that your lope peak is set at. The formula is (open + close) + 180 / 2 - "The smaller of the two readings" = lobe center.

So, for my intake it's 12 + 42 = 54
54 + 180 = 234
234 / 2 = 117
117 - 12 = 105° lobe center

And my exhaust is 47 + 14 = 61
61 + 180 = 241
241 / 2 =120.5
120.5 - 14 = 106.5° lobe center

I was turning the engine the same way the kick start turns. I can't find anywhere where it says the engine rotates clockwise (opposite the kick starter direction). It's my first engine that has an opposing crank. Took a day to learn that the hardest of possible ways. So now I know where my centers are, how do I know what I want to adjust them to? Or is the method to simply adjust the cam so the centers are the same for both intake and exhaust?

[mrosso]

If you're looking at the motor from the left side of the bike (rear fender to your left, front fender to your right), the engine crank and clutch basket turn clockwise, right? 

[michrobi]

Standing on the rider's right hand side looking at the clutch cover, yes clockwise.

[mrosso]

Doh! I meant right side of the bike (driver perspective)...

It's the drugs talkin' again...

[michrobi]

There needs to be a smiley option for a doobie smoker.

Hey Mike, if I hit my 2 week mark I get a JMR sticker, right? Wasn't that the deal? Isn't that what you guys heard too? 

[michrobi]

[michrobi]

Shifter and tappet covers on



Going to put a new clutch pack in after it's in the bike tomorrow. We'll see how that goes and try for the initial startup tomorrow night. If not then Saturday. I'll get it on video.

[michrobi]

Motor in the frame


My Dad and Nephew stopped by to help me get it in there


We'll see if I can get it put together early enough to start it tonight, but it's a hot bastard out there so no promises.

[Flying J]

You are going to pull it back out to paint it?

[michrobi]

I decided not to paint it. I don't ride in the rain if I can help it, and if I happen to once in awhile I'll wipe it down and treat it. It's only till the big bore is built.

[michrobi]

[youtube=425,350]KkwJM27txos[/youtube]

Time to get this mutha tuned up sweeeet!   

Oh man I love the smell of new rebuild burn in the morning!

I've been up for 23 hours and my back is killing me, I'm goin to bed now   

[MRieck]

There needs to be a smiley option for a doobie smoker.

Hey Mike, if I hit my 2 week mark I get a JMR sticker, right? Wasn't that the deal? Isn't that what you guys heard too? 

We have a winner!

[Colonel]

Congratulations!

[Gamma]

Well Done.

[michrobi]

I can't get it to time properly. The ignition only has 3/4" of adjustment and it wants to go further than the slot allows. I figured that meant my cam was too far out, so I lifted the valve cover while the engine is in the frame to turn the cam a little bit closer to 12 o clock. Now I have no improvement in the timing, it still wants to turn the same direction more than it can, and oil is pumping out of the front under the head. I took 2 weeks vacation to do the rebuild and god decided that needed to be the hottest most miserable two weeks in the history of time. Add to that the fact that every other nut, bolt and screw absolutely has to strip out just to keep some spice in the relationship. At this point I think the engine will need to come back out, so I can attach the valve cover properly and see why it's leaking. That's going to have to wait until it's not 105 degrees from 10am to 10pm.

I shoulda just bought a new bike   

[michrobi]

Alright alright, pay no attention to cry baby Carl up there, he was a little hot. So I pulled the valve cover off and it looks like one of the lumps got caught on the inside of the cover, that should be good once it's on all the way.

[michrobi]

Got the oil leak all sealed up, and it's running a little better after the cam readjustment. Still lacks power and backfires a lot.

[michrobi]

Looks like the stator stopped stating during the rebuild. The oil light stopped working too. I went back through from the wire block to the stator 4 times and all the wires seem okay. Not sure what I did or didn't do. I'll try swapping it for this one out of a 75F I have here and hope that fixes it.

The timing issue persists. The thing I find odd is the bike idles good or bad depending on the time of day it is. The only thing I can think that might cause that is the Martek ignition has had it's day in the sun and must be ready for the shelf. I have a Dyna 2000 on the way.