Topic: to bore or part out?

[cb(r)]

hey guys I need some suggestions.

I bought a really cheap 78 cb750.  the seal (gasket) at the base of the jugs are leaking bad and not very much compression.  so if I am to pull the engine I might as well bore it.  (my thinking anyway).  I do not want to get radical.  I would ride on the street and maybe a slight cafe look to mess with the crotch rocket kids a bit.
so to the questions
should I bore?
what should I bore it to?  I want rock solid not much tweaking but a little more ummmph!
while the engine is apart what else would be good to change or upgrade?
how much are bore kits going for? 

carbs were completely rebuilt at beginning of summer.  I need to put new rubber on and fix, replace or rebuild front brakes. 

now to the other questions.  parting out?

should I just part out the bike? 
what kind of money would I look to get  from what parts?
I paid $100 american
I do have a stock cb350t and one in the slooooow build stage as well.

lot of Q and A.  this is my first cb750  so I am not sure of the little probs and quirks of these bikes.

thanks for any insight. 

[Tim.]

I'd stick with stock size pistons (as in within the 1mm or so bore limits recommended by Honda) unless you find a nice piston/ring kit in a larger size for a good price.

For improved performance, a mild bore alone won't do anything for you.  You need to get into a cam, carbs, ignition etc.

Which model 750 is it?  F (SuperSport) or K?  I know people have talked a lot about the heads in the later model F engines not being as good as earlier years, but am not sure if that translates to the K models also.

You will be much better off $$$ wise to find a better engine altogether.  Rebuilding an engine with a fresh bore, new pistons and rings, new gaskets etc. is not cheap.  Spend your money on making the 750 handle better with improved suspension, new head bearings etc.  Remove some weight from the bike too - cutting excess metal off is free horsepower.

[754]

Pull it apart and see what you are up against, maybe it just need rings and valvejob. If it is too far gone, then part it.

Either way you spend money to fix, or more money on a newer/or better bike. You may want to do it on the cheap but, you feel better knowing what you are riding on.

In my opinion, I would go the bore kit and headers.. soon after riding it you will wish you had. Good bore kit is probably 600 bucks with boring.. but that does not buy much anymore..I saw a partial exhaust for a Ducati the other day..1500.00 for part of the exhaust!!

[cb(r)]

this is a k model that I have not tore into.  I guess that would be the first step after I get a manual.  I am going to get rid of some of the pieces like the king queen seat with funky sissy bar.  I am probably selling the tank, rear fender, center stand... weight stuff and ugly stuff. 
as far as  boring the engine first overbore.  I can get that done very reasonable.  like 10 bucks a plug.  ( I know a guy) Ihave to clean though.  But hell I spend twice that much on one roll at the craps table.
I have  a 2 week holiday coming up so if I get inspired I think I am pulling the motor.  thanks guys. 

If there are any more suggestions I am all ears.

thanks

[JLeather]

You can pick-up a decent overbore kit, even an 836, for $250-$400.  CycleX has cast 850 kits for $249.  They work fine with stock sleeves.  You can pickup a hotter cam for around $250.  Gasket kits are around $60.  That work, with a nice exhaust and proper jetting will yield a very fun rider.  Considering how little you've got into it right now, for under a grand you can ahve a really nice bike there, and I don't know of any bike you can buy that cheap that's this much fun.

[eldar]

The K8 engines are probably the strongest out of the bunch. If you can swing the cost, juice it up. I know others here are partial to the earlier bikes but as for the engines, the K8 has all the refinements for the whole series for reliability, and all the power stock as he F1 did.

Bolt-wise, it will go into the earlier frames if that is your game.

[Bodain]

  Considering how little you've got into it right now, for under a grand you can ahve a really nice bike there, and I don't know of any bike you can buy that cheap that's this much fun.

I do. Yamaha RD 350 /400

[KB02]

I was given a K8 for free as a parts bike due to engine being seized up. The plug were out for I don't know how long. The rings were all (3 out of 4) rusted in place. I'm currently in the rebuild process. (It can be done!! ) If you've got the time, patience and cash flow, I say build it up. I'm planning on using the Cycle-X 850 kit which, at $250, appears to be the cheapest of the lot. 836 kits are far more well known and more abundant, but not always cheaper. Plan to be into your engine for at least a grand if you do it half way near right.

[Jerry Rxman Griffin aka MuthaF'er]

If you're talking boring here why go anything less than 836?? Can't vouch for the CycleX 850 kit but at $249 that ain't bad. You gotta buy a kit anyway and bore the cylinders. Skip one roll on the table to buy a cam and valve springs while you're at it. I wouldn't do anything less if I had to enlarge the cylinders. Oh yeah, get a set of heavy duty cylinder studs. Next step up if you hit a roll is to send your head out for porting. That will double what all the above costs are.

[cb(r)]

hey guys,

sorry for the late response.  I have been extremely busy, but most people are at this time of the year.  I was going to pull the 750 engine this weekend but we got pounded with 8" of snow and mid teens (F) temperatures.  so it was a little cold and the bike is in the back shed so I could not move it to the garage.
with that being said I think if I need to just hone of replace rings or fix sticky valves... I am going to just get it on the road.  If it needs a bore I am going 836 +. also valves and bolts.  If I do the 836 or 850 then there will be a lot of left over 550 parts being sold at a cheap price to make $$$ and room for a 750 project.

thanks for all your responses.  this site is simply the best!  If there is any more info that you guys would like to send; I am all ears.

I hope you all enjoy your holidays/vacations and winter projects!

kevin