Topic: Need advice for engine work

[Justin]

Hey all!

I've been working on restoring/building my 1971 CB750 (K1?) and I would like input on engine pieces.
I want to build the engine up a little, but mainly I would like to ensure that it is bulletproofed for longevity. I plan to ride this bike for a long time , probably some touring but mostly ripping around the town and between the East SF Bay Area and where I live in the Sierra Nevadas. It'll live in the garage at my house and I'll ride it to work sometimes and on weekend rides in the mountains along the twisty and beautiful scenic roads. It probably won't ever see snow, as I only live at about 2000' elevation. I give a description of the riding that I'll do so that the proper engine advice can be given. I'm not building a race machine, just a fun toy.

I've heard that 836cc kits are the cat's meow, but I wasn't so sure about going over square with the engine. Let me know what you think!  I was wanting to keep smaller bore.

I was thinking about putting a new cam in it but didn't want to be too aggressive. I think it'll depend on whether I bore to 61.5mm/maybe 62mm (762cc) or bore larger to 65mm for the 836cc kit.

What's the 5mm valve stem kit all about?? I don't know a thing about it, I don't know if they're supposed to be larger or smaller than the factory valve stems?

new clutch and stronger springs or factory stuff? Either way I'll do the modify the basket with the drilling.

Should I consider the lightening/balancing of the crankshaft? Cycle X does some pretty expensive stuff to the crank that seems neat...

are the factory connecting rods good enough or should I be looking at new ones?

to send the rocker arms away for hardening/lightening or not to?

undercut the gears in the trans or don't bother?

lightened alternator?

heavy duty cylinder studs?

I know just about enough to understand but I don't know much about building engines and the science of it all. If anyone has advice, even just about one question, I would love your input.     Maybe I should break the questions into individual topics and post in the high performance section? I was hesitant to post there because the forum is for high performance and racing, and I'm really only striving for mediocrity and longevity with this build. I've got a newer bike that'll go fast without me having to rip the engine apart, I really just want to keep this one until I'm too old to throw a leg over it

Please let me know what you think!

[goldarrow]

Before any of those you mention happening, what's the condition of the bike as it is now?

[Justin]

The bike is currently in piles all over my garage, and my brother's garage. It was running last year up until about May/June. I took a few things apart to replace/repair (the tires and rear brake) and everything I removed looked worse and worse so I decided to restore/rebuild it. I just bought media for blasting the frame that's been stripped as well as some other bits, which I'm planning to do the media blasting this weekend.
I've got the top end and cylinders removed from the engine. The valves don't look so good, they're all black and 3 & 4 had some yellowish looking crud caked on the inside (visible through the ports). Pistons had tons of carbon build up sitting on them.
All factory internals I think.
The bike had been sitting for a very long time before I got it 2 years ago. I've maybe put 300 miles on it since I've had it.

[Stev-o]

How many miles on the engine?  I have an 836 K4 and love it.  Highly doubt the stock engine that Honda built could be any more reliable. 

[Justin]

I appreciate the advice Cal!!
I am getting a hardweld cam from megacycle (125-00, pretty mild I'd say) and I'm probably going to have the rocker arms hard welded.
I have the HondaMan book and I'm reading up on the oiling mods to the top end as I write this.
Thanks for the advice! keep it coming!!

[seanbarney41]

Spend the most money on the cylinder head ports...this is where the 750 is really lacking

[Justin]

Spend the most money on the cylinder head ports...this is where the 750 is really lacking

I just got the Eastwood porting polishing kit and I'm going to spend several weekends in the garage getting the cylinder head properly ported. Either that or I'll send it to Mike Rieck if I hear back.

[Trad]

Spend the most money on the cylinder head ports...this is where the 750 is really lacking

I just got the Eastwood porting polishing kit and I'm going to spend several weekends in the garage getting the cylinder head properly ported. Either that or I'll send it to Mike Rieck if I hear back.

I'd send it to Mike. Why F**k around. If you've never done it before could end up costing you more in the long run. Plus Mike will give you the best result possible.

[seanbarney41]

Spend the most money on the cylinder head ports...this is where the 750 is really lacking

I just got the Eastwood porting polishing kit and I'm going to spend several weekends in the garage getting the cylinder head properly ported. Either that or I'll send it to Mike Rieck if I hear back.

I'd send it to Mike. Why F**k around. If you've never done it before could end up costing you more in the long run. Plus Mike will give you the best result possible.

Mike does amazing work that few others have the skill and knowledge to duplicate...but, if you have ever had a peep into a K2 or later 750 intake port, and have half an idea of how fluid dynamics works(yeah, you better do some research, Hondaman's book is a very good start), you will see there is very little you can do that is any worse than what is already there.

[Justin]

Spend the most money on the cylinder head ports...this is where the 750 is really lacking

I just got the Eastwood porting polishing kit and I'm going to spend several weekends in the garage getting the cylinder head properly ported. Either that or I'll send it to Mike Rieck if I hear back.

I'd send it to Mike. Why F**k around. If you've never done it before could end up costing you more in the long run. Plus Mike will give you the best result possible.

Mike does amazing work that few others have the skill and knowledge to duplicate...but, if you have ever had a peep into a K2 or later 750 intake port, and have half an idea of how fluid dynamics works(yeah, you better do some research, Hondaman's book is a very good start), you will see there is very little you can do that is any worse than what is already there.

Maybe it's because I wrote a novel for the poor chap, but Mike isn't messaging me back. I think I overwhelmed him with my barrage of questions    Part of me feels bad because if he did respond to answer all my questions, I'd be getting his expertise for free and I really ought to pay him for all that hard earned knowledge.
Hats off to HondaMan in the same respect, I should be paying him for his priceless wealth of advice.. If people accepted beers for payment I owe that man the whole beer factory! 

I work at a machine shop (that makes medical equipment) so I have an idea about porting and polishing, but I have been doing some homework. I may give it a try on my own on the extra head I have before looking twice at my k1 head. And while I'd rather keep the dough for other engine stuff (It's a long, awesome story but my income is small, doing the Lord's work), I think Mike's expertise is well worth it to send my cylinder head over for some of his Midas Touch. If only I could trust UPS when I label something FRAGILE!!!  I'll likely have Mike do the work, I'll keep the updates on my build post! 

I appreciate all the response!! All the advice is GREATLY appreciated!!

[slikwilli420]

I talked to Mike last night about my Stage IV head and he is all jammed up with a variety of things including his day job and snow removal. I have not heard one thing other than he is a man of his word and that he will bend over backwards to get you what you need. Patience is the ultimate virtue but it will be worth it.

[SOHC4 Cafe Racer Fan]

People have to remember that JMR is a one-man operation, and one that Mike does in addition to his day job.  You do not go to Mike for a quick porting job.  You go to Mike for the best porting available.  In addition, Mike is pretty good about answering emails, but if he's stacked up, it may take a while.  As it is, this is someone asking for advice on how to do porting and not actual work.

[Justin]

I had brief correspondence with Mike last night and his statement was "I'm stacked!"  Sounds as though between all the snow they've had in Boston, work, and machine work, he's running behind. (I had to use a secret handshake to get him to the keyboard myself).

He does do amazing work and his experience is really key. But, if you're not building an oversized motor with oversized valve train, and only want some general improvement, then you could probably use another option and get very good results.

If you do seek a State III job with new guides, Serdi cut, and extensive porting, he is the ONLY bloke I know of that is that good.

Cal,
Your advice is wonderful. Thanks for the good words!
I think Mark has talked me into an 836cc kit...
I'm waiting on Mike Rieck before doing any of the head work, except I may be removing the valves because they're pretty much paperweights now if you've seen the pictures on my build thread.

I talked to Mike last night about my Stage IV head and he is all jammed up with a variety of things including his day job and snow removal. I have not heard one thing other than he is a man of his word and that he will bend over backwards to get you what you need. Patience is the ultimate virtue but it will be worth it.

slikwilli420, (Willi I presume?) Thanks for the heads up, pun intended. I don't want to rush Mike at all. I've got all the time he needs (it gives me more time to sock away $..) and I am truly looking to have the best work done. I relish doing all the work myself but there are things that are better left to the best 

People have to remember that JMR is a one-man operation, and one that Mike does in addition to his day job.  You do not go to Mike for a quick porting job.  You go to Mike for the best porting available.  In addition, Mike is pretty good about answering emails, but if he's stacked up, it may take a while.  As it is, this is someone asking for advice on how to do porting and not actual work.

CB750 C.R.F., In one of my lengthy emails to Mike I asked Mike for a quote for the head work, I didn't ask him for advice on how to do porting.  I did ask for advice on what to do with my engine (undersquare vs oversquare 836), about cam recommendations, reliability and several other questions. I guess I didn't realise that Mike has a day job and moonlights the CB750 stuff. I somehow imagined that he runs a CB750 shop back east, but I'm now understanding much more clearly and I intend to be patient as it takes. 




I have another question for everyone..

With the 836cc kit, can the factory carbs feed the engine sufficiently?

[Justin]

Mikes practice is: send the head, he examines, then contacts and confers with you if the scope is unknown. In my case, I had decided on bore, stage, and cam. He decided the rest and gave me a ballpark figure. I paid a deposit on the hard goods and he went to work.

The result: purest of bike porn! Motor is currently being assembled and maybe someday it get fired up.

Your stock carbs can feed the motor if they're well rebuilt and your cam is not too radical.

Cal,
I didn't really want to send the head without giving him a heads up. Is that what you're suggesting I do, though? Sorry if this is a dumb question....

[MRieck]

Thanks for the words of support guys. I just PM'd Justin and will be going over his questions etc this weekend.
 It has been very busy for me with my regular job, my second 6 hour per week part time position and the engine work. I developed tennis elbow about a month ago which limits how long I can stand there and port. Getting old sucks too.
 Just to let you fella's know I had my son write up a new price list with up to date prices etc.
 Thanks again for the kind words.
Mike

[SOHC4 Cafe Racer Fan]

And there you go!