Author Topic: Question for the beginners who've rebuilt a SOHC4 (Read 1746 times)

nomad · « **on:** January 18, 2011, 03:45:44 PM »

Anyone here that's never torn down and rebuilt an engine, do it for the very first time with their SOHC4? I want to know if after all was said and done if you would do it again or pay a professional mechanic and be done with it. I'm thinking kind of crazy right now and am considering doing it having never rebuilt any kind of engine before in my life. I am mechanically inclined, but have never done anything so involved. Do I need to have some sense talked into me?

dragracer · « **Reply #1 on:** January 18, 2011, 03:54:55 PM »

Although im having a little issue right now with a cam chain, i would say go for it!!! Get a book first, read it from cover to cover. Then follow all instructions. It will be well worth the effort. Goes back to the teach a man to fish philosophy.

cookindaddy · « **Reply #2 on:** January 18, 2011, 03:56:27 PM »

I don't think you need sense talked into you, except by yourself.
I did it myself last year and had never rebuilt an engine before completely.
Ask yourself if you have the space (the engine takes a lot more space when it is pieces) and the tools (not much special as it turns out and some of them you can make yourself) and the patience (lots and lots of patience).
And there is lots of help here should you ask...
I could not have done it without the info and the fine folk on here.

sangyo soichiro · « **Reply #3 on:** January 18, 2011, 03:56:48 PM »

I guess I fit into that category. That said, my engine is currently still apart. But I plan on having it done by the time the good weather returns. Since taking my SOHC apart I've rebuilt one other engine. The SOHC is taking so long because I'm doing a lot to it. Now I just have to get a couple more parts and start the reassembly.

I'm glad I did mine myself. I like learning, and it was just plain fun.

kck3 · « **Reply #4 on:** January 18, 2011, 03:57:44 PM »

I guess it depends on how you look at it. You have to start somewhere and there are many on here that would be more than glad to assist you if you had any questions about it. These bikes are rather easy to work on, but intimidating at the same time. If you pay someone to work on it, be prepaired to spend $$$ and also be prepaired to run into people that don't know how to work on them.

Could always buy a beaten up engine and practice on that-same goes for carbs. Can buy some old ones one ebay and get your skill set up to par.

73hutch · « **Reply #5 on:** January 18, 2011, 04:07:05 PM »

i was in the same boat as you a few years ago. i went for it (messed a few things up), and learned so much. it feels really good when you DIY. plus your going to pay someone a bunch of money to rebuild it.

MidnightLamp · « **Reply #6 on:** January 18, 2011, 04:21:15 PM »

Just remember the most important bit. The minute those cases are split, it'll cost you a decent amount of money and patience to get them back to the same state as before you split them

All joking aside, remember that you'll need to buy a new gasket and seal set (usually) at the least. Budget about $300 to do a good job from start to finish if everything is in decent condition (this includes gaskets, rings, honing, blasting, etc...). Unfortunately it'll solidly turn into this:

"well, if the gears are just sitting there...I might as well just get them undercut"
"well, I did pay for the undercut so I might as well put in a big bore"
"well, it's bored out now, might as well port it"
"well, it's race ported now, maybe I'll bore it out to 1000cc's"
"well, ape has a new stroker crank now...."
"well, I'm single and broke now, might as well get a few more parts bikes..."

MCRider · « **Reply #7 on:** January 18, 2011, 04:25:59 PM »

Its actually an easy engine to rebuild all things considered. Take a tired, beat 20,000 mile engine and with rings, hone, lap inthe valves, decarb, gaskets, you'll have a hummer once again. $300 for the basic rebuild. I tend to go way overboard cuz I can, but there was a time in my life when I did everything on the cheap and still got good results.

joehardy · « **Reply #8 on:** January 18, 2011, 04:28:32 PM »

If you are patient, thorough and anal about cleanliness you should be fine. The SOHC 750 was the second engine I built- it's actually amazingly simple once you get into it. Note, parts and tools; micrometers, dial guages, torque wrenches if you don't have them, are expensive. And accelerating through the gears with a motor you built is a pretty amazing experience to top it off.

fmctm1sw · « **Reply #9 on:** January 18, 2011, 04:34:30 PM »

One of the things that really worried me was the transmission. All those gears and stuff... It's really not that complicated though. I started with a small four so even the weight of the stuff really wasn't a big deal..

MCRider · « **Reply #10 on:** January 18, 2011, 04:38:44 PM »

There aren't that many people around right now that know the CB750 any better than you do (or will). Except us. A lot of shops won't even take it, too old.

If its just a top end job, and it hasn't been grenaded, you can do it all with a basic craftsman metric set, impact driver $12 and a torque wrench $25-$50. Borrow the torque wrench from an auto parts store maybe.

Keep it simple.

Roach · « **Reply #11 on:** January 18, 2011, 04:48:32 PM »

well put it this way at least you can take it apart and find out how everything went together. when i got my bike last june the whole motor was in boxes every last bit. but i dove into it balls first. everything worked and it started first kick. they are simple motors. get a torque wrench, socket set fealer gauges and you are good to go.

you will probably need to order a few things

gasket kit
oil seals

oh and dont over torque anything the cases are realy easy to chip

greenjeans · « **Reply #12 on:** January 18, 2011, 05:02:47 PM »

The first engine I ever rebuilt was a CB750. You can do it. Be methodical, use the manual, go slow, and everything
will fall into place.

You can do it.

fmctm1sw · « **Reply #13 on:** January 18, 2011, 05:07:11 PM »

oh, and take pictures. Or find someone who took one apart and look at the pictures if you get uncertain about anything...

MidnightLamp · « **Reply #14 on:** January 18, 2011, 05:19:45 PM »

Also, one other pointer...DO NOT REMOVE THE HEADSTUDS WITHOUT SEARCHING AND READING ABOUT BREAKAGE. It's a seriously uncool thing when studs break.

CrankyOldGuy · « **Reply #15 on:** January 18, 2011, 05:37:55 PM »

I see you have a CB750 K4. A good reference is a must. "Hondaman's "My CB750 book" is a such reference in my opinion. It is listed in the Bikes & Parts For Sale classifieds. It has sections on engine teardown, reassembly and inspection ... and much more. There is a good section on carbs .. how they work, cleaning adjustments, etc.

As others mentioned take your time, label everything you disassemble, take plenty of pics, and don't force anything.

Above all this forum and its members is your best resource.

Harry O.

nomad · « **Reply #16 on:** January 18, 2011, 05:59:51 PM »

Quote from: CrankyOldGuy on January 18, 2011, 05:37:55 PM

I see you have a CB750 K4. A good reference is a must. "Hondaman's "My CB750 book" is a such reference in my opinion. It is listed in the Bikes & Parts For Sale classifieds. It has sections on engine teardown, reassembly and inspection ... and much more. There is a good section on carbs .. how they work, cleaning adjustments, etc.

As others mentioned take your time, label everything you disassemble, take plenty of pics, and don't force anything.

Above all this forum and its members is your best resource.

Harry O.

Thanks for the advice everyone. Hondaman's book is now on it's way to my doorstep (thanks for the discount code Hondaman). I've got most all of the tools that have been mentioned, so aside from a couple of specialty items, I should be good to go.

q2418130103p · « **Reply #17 on:** January 18, 2011, 06:41:17 PM »

I like to have a roll of masking tape to tape pieces together the same way they came apart, assuming they are small pieces of course.

DH · « **Reply #18 on:** January 18, 2011, 07:51:24 PM »

I did my first top end rebuild of my former k4 when I was 17, in 1975.
A local shop told me it needed a valve job. #1 cyl kept fouling the plug. I took the engine out, removed the head and cylinders, installed new gaskets and had the valves ground. Reassembled it all and put the engine back in, all in about 2 weeks time...Fired it up, took it down the street and it promptly fouled number 1 again...
Somehow, someway, it eludes me to this day, the choke flap for number 1 carb had become detatched from the rest of the choke linkage, leaving it always in the closed position. Ran very well after
I fixed that. I learned, the hard way, more than one thing during that whole excercise, and at least had the benefit of understanding
what made the 750 tick. Took me a few years to develope trust
toward Honda shops after that. Don't be intimidated by it. Keep things organized in the order of disassembly. Work in a clean area where parts won't get scattered. Take your time and enjoy the learning experience. It's really cool to here the thing fire and run
when your finished.

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Author Topic: Question for the beginners who've rebuilt a SOHC4 (Read 1746 times)

nomad

nomad

DH