Topic: Tried search... where to buy replacement engine? help me diagnose!?

[jordanp]

Hi all,

New to the forum here.... got a 78 cb750k with supposedly just throttle cabling issues, and in need of front brakes. It hasnt been ridden in about 6 y ears. I drained gas, oil, and all that good stuff... removed a little debris from the tank, replaced the oil filter... So today, while my kids were napping I went out to tweek on the bike. Checked 1 and 4 spark plugs... 1 had some carbon deposit, not too bad... 4 was pretty oily... cleaned those two up a bit( didnt have time to check 2 and 3) put the gas tank back on and connected to the carbs. I have the throttle working now with a ghetto spacer between the sheath and the cable end. I start the bike, and it runs pretty rough. Not sure if it's running on all cylinders or not... pretty smokey. I have NOT checked compression, I have NOT checked the points. I cannot tell if the smoke is black or white... but I am getting the feeling that a piston or two or rings are bad... is this possibly an ignition problem? I doubt it but hey a guy can hope he didnt just buy a huge money pit of a project that he wont be riding anytime soon! Anyway... If the engine does need a rebuild... I would rather just replace it... so where would I go to get a good condition motor for this beast? I am in the Bay Area CA, USA... all help is appreciated!

[Gordon]

You're jumping ahead several steps.  You don't yet know what's wrong, but already looking for a replacement engine.  If you don't already have one, buy or download a shop manual and go through the whole tune-up procedure, and check the compression.  If/when you still have problems then we'll be in a much better position to help you, because we'll know more about what the problem is.

[donny]

 more than likely you don't need a new engine/rebuild...but these things can/will be a money pit.
just keep on fixin' ....
points, etc....

[kghost]

After sitting 6 yrs...how well do you expect the rings to be seating?

My advice is tune it up properly....

Then run it and give the rings a chance to seat before tearing it apart or replacing it.

[mlinder]

Start at the beginning.
Clean the carbs. Properly and completely. You said you emptied gas, and it's been sitting for 6 years. You can bet the carbs are gunked.
Bench synch them after complete cleaning.
Next check your points. If they need replacing, then replace them.
Set your cam chain tensioner next.
Then adjust your valves properly.
Replace your sparkplugs. NGK d7ea's.

Check your plug wires and boots. In good shape?

Now start it. See if it runs on all four. Do a carb synch and go wring it's neck for an hour. See if the smoke has burnt off. If it continues smoking, time for a compression check.

[OldSchool_IsCool]

You can tell which cylinder is firing by flash touching the exhaust pipes.  Wet fingers and quick touch, they get HOT when they are firing!

But even that is getting ahead of things.
- get manual
- fresh oil
- clean/replace air filter(s)
- fresh gas
- adjust tappets
- set points gap
- set timing
- new sparks
- drain carbs

[Spanner 1]

My K1 750 sat a full 10 years un-touched....I did all the tune-up stuff and first time out it smoked-up the Interstate like a West Coast fog !....but after a few miles running, and since, it's clean as a whistle......take your time and do a full go-over, I bet it will work fine....

[andy750]

I think if you want a bike that runs, is low maintenance from day 1 and need it now then perhaps this bike is not for you.....a replacement engine will not solve your problems....if you want to spend some time solving your current issues and yes spending a little time and money along the way, and enjoy doing so, then you will have a cheap reliable bike at the end of it....its a process and it wont happen overnight. Talking about a 31 year old vehicle here....

good luck
Andy

[Alan F.]

I don't know Donny too well (no disrespect intended Don), but the others: Andy750, Spanner 1, OldSchool_IsCool, Mlinder, Kghost and Gordon are all top guys in their own rights.  I'd follow their advice and stick with it if this bike is worth it to you.
The membership here can get you through anything your bike might throw at you.
Good luck and welcome.
-A

[Jerry Rxman Griffin aka MuthaF'er]

As Gordon suggests, get the shop manual. Thats your start. You have a large learning curve that we'll get you through. DO NOT get in a hurry and make sure you use a VERY methodical step by step approach. You may have to invest a few more $$$ but then again you may not.

[BeSeeingYou]

I don't know that I would do a complete carb tear down and cleaning at this point.  That is a lot of work to do to find out that the engine has other major problems.  Not saying that it does but maybe a compression check is the first order of business.  After that do a quick cleaning of the carbs in place by removing the float bowls.  Then you can pull the floats, needle valves, and main and pilot jets for cleaning.  If you pull the airbox it gives your plenty of access to do this. It's easy to check the points too so do that.  Put in some new plugs or at least pull all of the old ones to clean and gap.   All this can be done in an hour or three and it may get the bike running good enough to solve some of your problems and tell you if you have any others.  Then depending on what you find you can do a more thorough cleaning, tuning, and repair.  Mine sat for 25 years so 6 years is no big deal as long as it was not sitting outside the whole time. 

[mlinder]

Sorry, srust, I have to disagree with you a bit here. If the carbs aren't clean, and a complete tune isn't done, you'll have no way of telling if there are other problems inside the engine, other than low compression. That being said, you can do a compression check anytime after valves are adjusted properly. But, since a carb synch is done after all that other stuff, you can easily do a compression check before cleaning the carbs. Just don't expect it to run right until the carbs are cleaned and synched.It takes me a couple hours tops to tear down, clean, rebuild, and bench synch a rack of carbs. Yeah, I've done a few, so it may go a bit faster for me than some people, but it's a valuable skill to have, and if you want to ride old bikes, you need to know how to do it, and do it correctly.

[jordanp]

You guys are funny. I specifically said I had not done all of those things yet. The thread is about finding a place that sells engines "just in case" even if I don't need one now, I may in the future, and I'd like to know what and how much I'm dealing with. As it stands now, I have half a$$ed cleaned the carbs ( they were functioning well to begin with, not gunked up) replaced all the spark plugs, and in the process realized I really need new wires. By the way, where is the best online place to get wires? I then proceeded to break the metal brake line that enters the caliper, while trying to get the caliper off to unstick the bastid. Now I need to replace that piece... where besides ebay can I find this stuff? Oh, I also checked, and adjusted the points. I was going to start the thing again today but I did not have time to get the exhaust back on before going inside to do my wife's chore list . Tomorrow I go back up to motionpro and I am trading my pull cable for a 79 pull. The sheath is 4" longer and the cable is 1 1/2" shorter... should do the trick. Now if only I can stop breaking stuff.

[andy750]

For all the parts you`ll ever need check out the FAQ - where to buy SOHC stuff online - lots of listings there. A few good ones...bikebandit.com and servicehonda.com.

However for small hard to get parts or larger items Ebay is the best place.

cheers
Andy

[jordanp]

Thanks Andy, usually I am pretty good about going through the FAQ's on forums... It has been a whirlwind week for me. I just want to get this thing operational and ride it till winter. Then do a frame up resto on it. I am really hoping that these cables straighten out at least one issue! The brakes on the other hand will be a bit more difficult to get my hands on without paying oem new prices from bikebandit and the likes.

[Bodi]

There are motorcycle wreckers that have used engines, and ebay has them pretty regularly. Ebay is a total crapshoot, you get what you get and it may not be pretty. Wreckers will usually back up their sales a bit - if you buy an engine they say was in running order when pulled and you find a tangle of broken bits inside, they should make amends. Little things like worn out rings and bores or a transmission with 5 neutrals... it's buyer beware.
If you have a ton of cash lying around that you don't need for anything else there are shops that sell performance built engines.

[mlinder]

We didn't tell you where to get a replacement engine, because more than likely, any used 30 to 40 year old engine will need the same work your current engine does. Barring catastrophic bottom end failure, or top end manglement (I just made that word up, it kicks ass) all of these engines are going to need the same thing, so may as well work on the one you HAVE and save money. Now, if you want a 'running' engine to put in the frame while you work on the original engine, I see where you are coming from. Though, in my opinion, I'd just buy another bike to ride while I fix the other.