Topic: Top end rebuild , no clue what I"m doing , Pics , Piston rings snapped in two

[coolcat2002]

Haven't ridden it since I bought it 2 months ago. 1974 cb750 k4  40K  It runs rich.  I just wanted to clean it. 

There's a question for every picture, please advise.

I don't know anything so please school me.

I used a screw driver and hammered it in to get the cylinder out (I believe that's the term).  I hope I didn't mess up the surface.

Questions:

1. Can I put it back in with pistons 1 & 4 up , 2 & 3 down?   I used the kick lever and accidently reposition it.


2. Should I replace this? Cam Chain Tensioner rubber.


3. I used a dead blow hammer on the grill to get the body out.  I wonder if the split piston ring is the result.  Is this normal?


4.Is this surface clean enough?  I notice the gasket stuck to the top but surprisingly not the bottom.  I used a razor blade to scrape as much as I could.




5.  Should I remove these white spacers?  How do you get in between the narrow grills to clean it?  I tried your advice with Acetone & Brass Brush but it's hard to get to there.


6. Do I go ahead and clean these?  Picture of exhaust valves.


7. The other two exhaust valves.  I'm afraid to check the valve guides because I don't have the special tool like the manual says.  Should I attempt it?


8. I Saran Wrap these to prevent dirt/ moisture but they popped when I kicked the kick start lever. Are they removeable?  I see a hex behind the intake.


9. My gaskets I got from http://www.cmsnl.com/.  I hope they don't suck cuz they were $29 to ship it here from Netherlands.


10 Lastly,  Do I used engine lube assembly oil while I do all this?


Please advise anything on the pics or whatever.
I've read that I should do plenty since I don't know what the PO did or didn't do.  I think I'm too poor for regrind of cams, bore cylinders, or any thing fancy  but I will buy new chains if yall think it's wise.  I don't know what yall mean by engine "seals" vs. my gasket kit.  I hope they are included.

God bless.

[seaweb11]

Real quick:
Don't try and remove the spacers in between the fins. They are there for a reason.

One of those valves looks well past its life due date and I bet the bike blew blue smoke before it was stored. Personally based on some of the questions and your newness to all this, I would advise you find a machine shop that has a clue and take it in and have the valves done.  Try and find the time to sneak in when they are working on it and see what they do. Learn what you can from that, make a good relationship with that shop and use them in the future when you need their services for any of your projects be them bike related or not.

 cam chain rubber?   I have no idea

The bases definitely need more cleaning before reassembly. The machine shop can do it for $40.00 or so, or you can do it yourself easily  with a fine scrub pad or perhaps some 1000 grit steel wool and Varsol.

 Saran Wrap: you pushed air through the motor when you put pressure on the lick start. It was "sort of running for 4 rotations.
You plugged the exhaust!

My 2 cents. Hope it helps. 

P.S. Once it is a part that far, get er done and have fun with the new learning curve

[TwoTired]

I used a screw driver and hammered it in to get the cylinder out (I believe that's the term).  I hope I didn't mess up the surface.

Me too.

Questions:
1. Can I put it back in with pistons 1 & 4 up , 2 & 3 down?   I used the kick lever and accidently reposition it.

sure, I suppose.  The movement is no issue.  Be carefull getting the rings back into the cylinders.  You can break rings and/or piston ring lands, if not.

2. Should I replace this? Cam Chain Tensioner rubber.

Not sure. But, if it is shedding black bits, certainly.  Does look kind of nasty compared to the Honda Shop manual picture.

3. I used a dead blow hammer on the grill to get the body out.  I wonder if the split piston ring is the result.  Is this normal?

Broken rings are not normal.

4.Is this surface clean enough?  I notice the gasket stuck to the top but surprisingly not the bottom.  I used a razor blade to scrape as much as I could.

Gasket needs a clean metal surface to seal against.  NOT traces of old gasket.  Not good to use steel tools on aluminum.  Gouges are bad.

5.  Should I remove these white spacers?  How do you get in between the narrow grills to clean it?  I tried your advice with Acetone & Brass Brush but it's hard to get to there.

The white spacers are there to keep the fins from ringing, and keep the engine quieter.

6. Do I go ahead and clean these?  Picture of exhaust valves.

Yes, it is part of decarbonization.

7. The other two exhaust valves.  I'm afraid to check the valve guides because I don't have the special tool like the manual says.  Should I attempt it?

Without a valve spring compressor?  Probably not.

8. I Saran Wrap these to prevent dirt/ moisture but they popped when I kicked the kick start lever. Are they removeable?  I see a hex behind the intake.

I don't know.

10 Lastly,  Do I used engine lube assembly oil while I do all this?

I wouldn't.  Moly based lubes make your wet clutch slip.  Just assemble with liberal amounts of engine oil.

Please advise anything on the pics or whatever.
I've read that I should do plenty since I don't know what the PO did or didn't do.  I think I'm too poor for regrind of cams, bore cylinders, or any thing fancy  but I will buy new chains if yall think it's wise. 

If the cam lobe rubbing surfaces and cam followers look smooth, no pitting, galling, etc., they are probably okay. All the wear limits are listed in the Honda Cb750 Shop Manual, which you really should have to do work such as this.
The cylinders should be measured for diameter wear, roundness, and taper limits.  This determines if boring is required.  You will have to hone for the new ring (s), at least.  This will remove some metal and move you closer to the wear limits.
If you have to bore, new pistons are a must.  If not, the pistons need to be measured for wear, piston skirt diameter ring land wear, etc.
New piston rings need the end gap checked/ adjusted.

I wouldn't disturb the lower end unless you suspect an issue there.  Leave the rods in place.  These lower parts last a long time.
If you do split the lower cases, then replace your chains if you think you'll be putting another 50K on the engine.  
How long do you need the engine to last?

Cheers,

[coolcat2002]

You are geniuses people.    
The bike was blowing out black smoke out the back.  I don't remember if it was blue but most likely.  The carbs were taken apart and they were clean, nothing wrong that I can see.

Now to check  on the Valve, guides and spring.

This is more of a What Tools to Buy vs. What's Nice to have at What Price Thread.  I wish they have those so I'll start it here.
(Things like $100 for a http://www.carbtune.com/ tool is just something I lose sleep over.)

4. What tools should I buy or recommend?  Most of these I have no idea what they do but I'll figure it out.
Just need to know what to buy first.

- Valve Lapping Tool  ( $40)
- Piston Pin Removal Tool or a Piston Pin Puller ($12- $50)
- Valve Guide Reamer 7mm ($75)
- Tappet Tool Set - 8mm 9mm 10mm  ($30)
- Valve Shim Changing Tool ($15)
- Valve & Rocker Clearance Adjustment Tool ($20)
- Instead of a Valve spring compressor ($150?!!)  can I use a big C clamp instead? 

I ask because it says Honda special tool to remove the camshaft, I used a big punch from my chisel set.  But I don't want to mess it up too much for using the wrong tool because I was cheap.

2. Ok, if the white spacers are so important, how come no one talks about them here.  Do you recommend buying new ones?  I have a few missing.

3. This sucks because only the top piston rings of two pistons are broken in half.  Now I have to buy 2 complete piston ring sets. Why don't they just sell each ring for like $2.50.


Women have it easy when shopping.  "What purse should I buy?"
This one.  See, simple.  Men have to pick the right tools for the right job, very hard.

[bryanj]

I have seen broken rings in an engine that was "abused" from cold, you really need to replace rings on all four pistons, i have seen sets advertised somewhere, crc i think. Check if the ring grooves have widened as this is bad news

Not being rude but it is obvious from your questions that you have never worked on a bike engine before and i would respectfully suggest you find someone on this forum local to you who has and see if you can work on the engine together, yes i would help but the air fare is a bit high!

Cam chain rubber definately needs new--what about the other one? and the cushion blade.

You list a whole load of tools that arent needed then ask if you can use a "C" clamp instead of the only tool you do really need!---again you need to find a good mentor also i know of no "special" tool for removing the camshaft.

[c_kyle]

Not to be a smartass, but why would you even try this if you have no idea what to do?  I would not open up my engine by myself; it would only cost me more money in the long run.  Hopefully, these guys can help you out.

[Bodi]

Looks like you're learning a lot!

You should have a valve spring compressor - one for small engines is all you need, a car one might work but the usually expect much larger valves. A big C clamp can work, but you need some sort of fixture at the spring end to let you work on the keepers. I have a black iron pipe union - 1/2" NPT I think - that I sawed a big notch in. I can get the keepers on and off through the notch.
The valve seating kit - all you really need is a bit of lapping compound, this used to come in a small tin with a lid on both ends so you have "coarse" and "fine". Haven't bought it in years, that can only has a few teaspoons of compound but it's lasted me about 20 years. Most of the "spinner" tools have a suction cup larger than the valve, again you want a small engine spinner not a car one.
Don't bother with valve guide reamers. You only use them after installing new guides and that is not a home do-it-yourself job; find a good engine shop to do it for you - they will have the reamer.
There are no shims, so no use for a shim changing tool.
I've never had any trouble with the piston pins, maybe some automotive ones press in but these should come out easily.
I have a tappet tool set but I can't imagine it costing $30.00, it's just a cheapo screwdriver (well, a square tip nutdriver I suppose) and a crappy set of 3 offset box wrenches.
Valve and rocker clearance adjustment tool? That's what the tappet tool set does.
I don't know what you used a big punch for on the camshaft, or what Honda tool you might need. Undo the sprocket and weasel it out.
Don't mess with the bottom end unless you want to do bearings. The pistons are plenty easy to slip in the bottom of the cylinders with just finger work on the rings.
Don't use steel wool. Scotchbrite scouring pads are abrasive enough and won't leave iron bits in the aluminum - a bad thing.

[Sam Green Racing]

I would do like Bryan sugested, get some help,  not trying to be rude but you might give up on what can be very pleasing, knowing that you have put the motor back together your self. Also, if you aint got any money, you shouldn't be playing with these old bikes.

Get some help...it would help if you let members know your location.

Good luck and welcome to the forum.

Sam.

[coolcat2002]

I just got my grades back. I actually got an A-.  Yes!   That one class cost $2500 and $167 for the book but I probably learned more from this forum.  Sad huh.  The threadcrapper just don't know that I waste my money on stupider things.

Ok I followed this Dan guy.  His website is pretty good so far. http://www.dansmc.com/valve.htm

I used a Dead blow hammer and a spark plug socket instead of a valve compressor.  IT actually works. Hallalujah. That's also a pic of the cam sprocket.



Here is the bottom part, you can see the valve guide. 


I cleaned the bottom with Carb Cleaner.  I have a venier caliper and will start measuring the springs tomorrow and a feeler gauge for the Piston..  Unfortunately I have summer school and a job so this will be slow.  Plus I'm going to order piston rings (replace all for the 2 piston with split rings) and will try to find a shop that does Vale guides and seats  in my Washington DC area.  Unless one of yall have a machine and I can mail my head to you and I can Paypal you? 

Damn I hate cleaning gaskets but I got 5 different roughness of scouring pads.  I'm going to buy some Varsol.  I saw a whole gallon of Naphtha at Home Depot, maybe I can try that for removing gaskets.