1971 Honda CB750

[7t1HondaCB]

Okay guys as the title says I have a 1971 Honda CB750...the odd thing is that I have a sandcast engine in it that my mechanic was excited to let me know about. The sad thing is that it's leaking oil from under the engine case. My mechanic said that it looks like someone has already tried fixing it some how and welded under the case or the oil pan as the mechanic advised that the metal is a bit wavy.

My question/dilema is could the wavyness on the case or oil pan be repaired? My mechanic advises that it would be better to just get another engine that is meant to be on this bike and sell the sandcast motor.  He also says I would need a tranny, clutch cover & oil pan gasket that is meant for the sandcast engine and that they are hard to find and work properly.

Any suggestions? I would like to get this bike on the road and ridden soon as it's just sitting in my garage.

[Re-run]

That would be crazy if you had a sandcast engine in it. There should be numbers on the top right(if you are sitting on the bike).

I would post pics of the spot so we are able to see it. Just keep them under 5 MB in size.

[TOOLS1]

It very well could be a sandcast K-0 titled in 1971. Back then there were not relay model years, and the year was assigned when the bike was titled. I have seen several bikes that were titled 2-3 years after the manufacturing date. I even have a CB 350 manufactured in 71, but titled as a 74.
As for the "wavy" oil pan, pictures would help. However all the parts you mention are readily available. Honda did not change the engine for quite some time, so the parts were used for several years.
TOOLS

[cardinal430]

Is a sandcast engine desirable and if so why? How would I know if I have one?

[TOOLS1]

Very desirable!!!!!!! Honda only made 7,000 of them when the CB 750 first came out in 1969. You can tell if you have one by the rough surface texture from the sand mold, and from the serial number.
TOOLS

[Re-run]

http://www.ebay.com/itm/Honda-CB-2-rare-1969-cb-750-honda-cb-sandcast-750-parts-bikes-title-reg-racer-wrinkle-/121456975254?forcerrptr=true&hash=item1c47665d96&item=121456975254&pt=US_motorcycles  2 basket case sandcasts

Complete, perfect sandcast, $42000

Pretty worth it dontcha think!

[cardinal430]

WOW !  my bike looks like it's in way better shape than those things, even with a few mismatched and missing OEM parts,  but sadly I don't think it is a sand cast .  I was at the salvage yesterday and they guy there tried to show me what one looked like,  he had a cylinder head  and a case that was charging a lot of money for.  but I can't really see on mine that well until I clean it up and degrease down there but it looks smooth.  My serial number is 1016096 frame and 1016322 engine.  Sounds like it should be in the first 7000 but maybe there wasn't a direct line of numbers?  That ebay parts bike showed Jan / 69 ,   mine is Dec 69.

[TOOLS1]

No, yours is not a sand cast. The sand cast engine numbers ended at "CB750E-1007414". However it is still a K-O and worth some $, but since the case has a hole in it, it would drop the value. However it would take a lot of the pressure off of keeping it original, and would make finding an engine, or cases easier to find. I have a very nice early die cast K-O engine, and it would take $2,000 to get me to part with it. However I could set you up with a rebuildable K-2 bottom end.
TOOLS

[cardinal430]

?? My engine case hasn't got any holes. Are you referring to someone else's? I see where I was confused with the serial number. 

On Oct 22, 2014, at 11:54 AM, "TOOLS1 [via Honda CB750'S]" <[hidden email]> wrote:

No, yours is not a sand cast. The sand cast engine numbers ended at "CB750E-1007414". However it is still a K-O and worth some $, but since the case has a hole in it, it would drop the value. However it would take a lot of the pressure off of keeping it original, and would make finding an engine, or cases easier to find. I have a very nice early die cast K-O engine, and it would take $2,000 to get me to part with it. However I could set you up with a rebuildable K-2 bottom end.
TOOLS

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[TOOLS1]

I'm sorry. I was thinking this was another post where a guy has a sand cast with a hole in the case.
TOOLS

[cardinal430]

its all good.   I need to post a new topic maybe but how in the heck do you get those fork ears off to replace them????   would you go at it from the bottom somehow or take the handlebars off.   they have that goofy little notch in them that makes it look like quite a puzzle.  don't now how to remove those dust boot retainers to get a look at the thing.   Is that the "triple tree" or is that the one at the top , or both of them " triple trees" ?

thanks.

[TOOLS1]

You should start your own thread. It gets really confusing when you are talking about more then one subject in a thread. That is why "highjacking" threads is so frowned upon in forums.
TOOLS

[cardinal430]

I'm sorry I've never heard of "hijacking". I'm not sure I know how to start my own thread. I don't want to be a hijacker. I guess I will copy and paste my question as a new topic. Is that what you want me to do?  It will seem redundant but it's exactly what I want to know.

[TOOLS1]

Hijacking is taking over another persons thread. It would be nice of you to start your own thread, and you will get more replies. Also they will be directed just towards your specific question.
TOOLS

[7t1HondaCB]

Sorry for the late response guys, haven't had computer access for a while but I'm back on now.

Anyway, I'm going to try and get pictures tonight when I get home including serial numbers.

I sure hope once pic's are viewed someone can tell me if my engine can be repaired. I hate having to walk by my bike everyday in the garage and seeing a huge puddle of oil!!

[7t1HondaCB]

Here are some pics, looks like it's not the oil pan but the engine case. My mechanic says that someone has applied heat to it and since my engine is leaking pretty bad he says that either the gaskets for this engine are unobtainable and wouldn't know how to tackle this job. He charged me $250 to tune up my bike (adjust valves, sync carbs, change oil), but it's still leaking oil like a mutha fkr. Anyway, is this true? He says he doesn't even want to tackle it as it will always leak oil? I hate oil leaks and if I knew more about motorcycles I would try but I don't know squat!!!  

 

[TOOLS1]

I cannot really tell much from the pictures, but it does not appear to be cracked. As for your mechanic, you need a new one, or maybe an old one. Every gasket, and seal for that engine is available. Honda can get them, or you can look at our list of suppliers on the top of the home page. I would suggest vintagecb750.com or ebay. If the oil pan is damaged, there are several of them on ebay, hell I might even have one. As for replacing the oil pan, and gasket, that is easy. You just drain the oil, remove the bolts, and drop it down. Reverse for installing.
TOOLS

[7t1HondaCB]

TOOLS how about the clutch cover? my mechanic also said that the clutch cover or complete side cover looks to have been worked on also? I know someone used some kinda red gasket goop of some sort to try and stop the leak...i have a feeling my mechanic is being a lazy ass and not wanting to remove the covers/gaskets and what not and just says it can't be done. I wish I had a good mechanic in my area...sad thing is this guy comes highly recommended for working on the older Honda bikes!!

[TOOLS1]

I would have to see more to evaluate what needs to be done, but you do not exactly need a sand cast clutch cover, one from any cb 750 engine will bolt on. Where are you located? Also a sandcast CB 750 engine just came on the Kansas City craigslist for $300.00. Damn I hate being poor.
TOOLS

[7t1HondaCB]

TOOLS1, here are some pictures of what I'm working with. I really don't know what to do??

What do you think is going on here? see puddle under the bike? I'm really getting frustrated about the oil leak and having to constantly fill this bike up. Other than this oil leak bike runs okay as in the a.m. she runs super cold and have to warm her up for at least 5 minutes.

Any ideas or any other areas needed to be seen let me know.