Topic: Should I Buy This 75 CB750F?

[Jessamine]

Hi y'all! I'm Jessamine. I'm new here and currently rocking a KLR and a Helix, but would love to join the club!

Found what might be a great deal (or might be a terrible mistake) on the local Craigslist this week, and went to check out the bike in person the same day; it's a 1975 CB750F with a clean title.  Asking price was $900, and I talked him down to $600+Delivery to my workshop (which is swell 'cause I only ride two wheels).

Current and PO made a few questionable choices (like trading the stock airbox for pods  ), but overall the bike looks in decent shape. Current owner is a "bolt-on" kind of guy (little to no skill with diagnosing or repairing internals, but can swap the farkles well enough); new tires, rebuilt shocks, new gauges, new bars, good brakes, etc.  Looks like everything on the bike is in great shape-- except one big problem:

He says he took the bike into a local shop for a new head gasket and a valve adjustment, rode it home, then spent a few months swapping parts before his next ride.  On that ride, he says he was cruising along and the engine suddenly died with a single clunk sound and hasn't started since.  His best guess is a snapped cam chain, but he doesn't know and doesn't want to spend the money to find out. My limited examination of the engine would seem in line with his guess: I feel no noticeable compression at the spark plug holes, can't see any valve movement in cylinder when moving the starter gear with the kickstarter, electrical seems well done-- though carb#1 is leaking some gas from the overflow port when the starter is engaged so there may be a simple fuel delivery issue at fault.

I've done a full rebuild on a CB350-Four and fixed many other things on 70s-90s Hondas, and I'm a pretty capable mechanic all around, so I feel confident I could do whatever it needs, up to splitting the cases if I absolutely have to. Question is how risky of a buy is this? Any alternative theories? I'm not sure how much interference the valves on these bikes have with the pistons-- would a snapped cam chain definitely result in damaged valves? If I'm crafty enough and the chain did snap, could I sneak a new one with a master link over both sprockets without splitting the cases and working it over the crankshaft?  I've got this vision in my head of using an extending magnet and long reach tools to thread a new chain end thru the tensioner, around the crankshaft, and back up from the abyss-- but maybe that's pure fantasy.     It'd be swell if it had just hopped the sprocket and was hanging loose on the camshaft because the shop forgot to reinstall the tensioner properly 

What do y'all think? Worth taking a chance on it for a project bike, or am I setting myself up for sorrow/an engine swap?

[rocket johnny]

seems a bit high for a non runner .  and it is a f  to boot  .  just my opinion

[Jessamine]

and it is a f  to boot

Out of curiosity, what's not to like about the F?

[flybox1]

Got a little excited about the $600 title d and delivered and then read about the cam chain.
Engine work can be done but you could be in it for a few grand....or, source a gently used head/valves online for a few hundred.
Might be more depending on what you find once its opened up.
Basically think of it as youre getting a roller, and price that accordingly.

[Bankerdanny]

Some perspective from a '76 F owner: If the tank is in good shape it is worth $300 on it's own. I know I have been looking for a rust free or even just a little rusted for the past several months and I am not alone. A functional rear caliper assembly and master cylinder are also worth money, and a titled frame is usually worth a couple hundred on its own. So $600 with title for a parts bike is probably fair.

[Jessamine]

Thanks for all your opinions so far!

More pics of bike:

[scottly]

can't see any valve movement in cylinder when moving the starter gear with the kickstarter,

Were you looking into the spark plug holes, or looking through the tappet cover openings?

[Bankerdanny]

Heck, that's $200+ worth of almost new Avon tires on it.

The biggest downside of the 750 vs your 350/4 is that the engine has to come out to get the valve cover off or you have to install a frame kit (members Scottly and Frank754 make one that many of us have bought) that will allow you to get the valve cover, head, and cylinders off without removing the engine. But it is $160, so more cost.

[jamesw]

I wouldn't be running to get it...at least not at that price.

I'd keep looking, or put it on your short list.

Like flybox1 said, I'd be pricing it as a roller parts bike, just in case the engine work ended up being too much.

If the tank was original paint and the badge holes not smoothed over, it'd be worth $300. I've bought 8 F tanks in the last year, and if it's clean inside, I say it's worth $200-$250 on its own.

[Jessamine]

can't see any valve movement in cylinder when moving the starter gear with the kickstarter,

Were you looking into the spark plug holes, or looking through the tappet cover openings?

Just thru the spark plug holes.  I didn't remove any tappet covers.  It was 102F and humid, so I didn't dig in to examine it as closely as I could have.  But I could do that when he drives over with the bike, before making the purchase official.

[Jessamine]

Heck, that's $200+ worth of almost new Avon tires on it.

The biggest downside of the 750 vs your 350/4 is that the engine has to come out to get the valve cover off or you have to install a frame kit (members Scottly and Frank754 make one that many of us have bought) that will allow you to get the valve cover, head, and cylinders off without removing the engine. But it is $160, so more cost.

I've seen that kit, I think.  I've got TIG welding experience and access to a welder, so I could do that in the future.  If I buy the beast or another like it.

[Jessamine]

I wouldn't be running to get it...at least not at that price.

I'd keep looking, or put it on your short list.

Like flybox1 said, I'd be pricing it as a roller parts bike, just in case the engine work ended up being too much.

If the tank was original paint and the badge holes not smoothed over, it'd be worth $300. I've bought 8 F tanks in the last year, and if it's clean inside, I say it's worth $200-$250 on its own.

I agree it's a shame they got rid of the badges.  Nothing more iconic on these bikes.

I'll be perfectly honest: I'm looking for a project bike, and I know/love old Hondas, but I'm not committed to building up a CB750.  Seems like the market in the Philadelphia area kinda sucks though!

[jamesw]

I wouldn't be running to get it...at least not at that price.

I'd keep looking, or put it on your short list.

Like flybox1 said, I'd be pricing it as a roller parts bike, just in case the engine work ended up being too much.

If the tank was original paint and the badge holes not smoothed over, it'd be worth $300. I've bought 8 F tanks in the last year, and if it's clean inside, I say it's worth $200-$250 on its own.

I agree it's a shame they got rid of the badges.  Nothing more iconic on these bikes.

I'll be perfectly honest: I'm looking for a project bike, and I know/love old Hondas, but I'm not committed to building up a CB750.  Seems like the market in the Philadelphia area kinda sucks though!

You could check out this too....2 bikes in this sale for $600.
https://philadelphia.craigslist.org/mcy/d/1974-honda-cb750-plus-parts/6624646614.html

[jamesw]

You could also post a WTB: project bike.

And because you're not set on a 750, I bet there's someone on this board that has something or who might know someone who does.

[scottly]

One thing that can happen when someone works on the top end of the motor and doesn't really know what they're doing is using too much or incorrect sealant, which plugs up the oil passages feeding the camshaft. This can cause the cam to seize. Look through the cover holes on both ends of the motor and see if everything looks wet with oil, or bone dry. If bone dry, suspect oil starvation to the cam. On the 750, unlike the smaller fours, the cam rides in cam "towers" fastened to the head, instead of being an integral part of the head/cam cover.
The frame kit that Frank designed doesn't require welding.

[754]

Jess , keep in mind if its stock, no component that is in the engine cost more than 200 bux, most are half  that.
 Plus it's very easy to work on, so get it, dig into it, see what you got.

The frame kits Scott and I made  are weldless, way less work to install.
And they weigh a third of what the weld kits weigh.
 And going back to stock is dead easy.

[seanbarney41]

I'd buy that for $600...part it out or swap in another engine.  The guys that don't like f's are collectors who don't ride.

[Bankerdanny]

Heck, that's $200+ worth of almost new Avon tires on it.

The biggest downside of the 750 vs your 350/4 is that the engine has to come out to get the valve cover off or you have to install a frame kit (members Scottly and Frank754 make one that many of us have bought) that will allow you to get the valve cover, head, and cylinders off without removing the engine. But it is $160, so more cost.

I've seen that kit, I think.  I've got TIG welding experience and access to a welder, so I could do that in the future.  If I buy the beast or another like it.

Fortunately Scottly and Frank's kit doesn't require welding.

[Bankerdanny]

I wouldn't be running to get it...at least not at that price.

I'd keep looking, or put it on your short list.

Like flybox1 said, I'd be pricing it as a roller parts bike, just in case the engine work ended up being too much.

If the tank was original paint and the badge holes not smoothed over, it'd be worth $300. I've bought 8 F tanks in the last year, and if it's clean inside, I say it's worth $200-$250 on its own.

It depends on what they did to smooth it. In the end you can trip off the prongs that would be used in the stock setup and use trim cement to attach them. I wouldn't let that particular mod stop me from buying the tank if it is otherwise solid.

Which reminds me to advise you to look at the tank VERY carefully. The biggest downside of the 75-76 F bikes is tank rust. This is what the underside of my tank looked like when I removed the body filler that had been used to fill in the channel that runs along the outside of the tank bottom.

If the tank has sealer in it this is something of a red flag. Without a solid tank I would not buy this bike for more than a couple hundred dollars.

[flybox1]

I'd buy that for $600...part it out or swap in another engine.  The guys that don't like f's are collectors who don't ride.

LOL

FYI, I bought my F3 engine for $100.  They are out there.

One of those $10 usb cameras that plug into your phone or tablet to look down spark plug holes or up your nose are nice for seeing inside the cyls.  Under the valve cover might be more difficult....

[754]

If you are in a darkened room , with a strong flashlight, you can see the 2 outer cylinders quite well..

[Jessamine]

Frank & Scott: Oh, that's rad! Nice engineering!   Do y'all have an official post for the kit?

Scott: Oil starvation damage was my guess, too-- I had no idea the oil ports in the head were so easy to plug up, though.  I was just figuring it sat long enough that the cam was dry from gravity when he fired it up.  Will popping open some tappet covers be enough to get a proper look inside?

Banksy: Holy #$%* are those holes all the way thru the base??  I at least know this one isn't leaking, but I'll be sure to get in for a close examination.  I had to prep and seal a rusty CB400 tank once and it was such a pita.  I was looking at the lines of this bike and thinking it would be nicer with a shorter tank, though, whose back curve would match up with the front of the V (see attached). Then I could move the seat forward and maybe get rid of the duck tail 

Sean/Flybox: brb need popcorn

[754]

Open the tappet caps, at least outer ones. They should all be oily inside. If it's not I suspect seizure which generally is one side. If it's dry, flashlight in darkened room will usually reveals some ground metal or damage.
 At this time, you contact Scott for the kit.
 The line you drew is more like a K tank, which are cheaper, then you need longer seat or move yours up.

[Jessamine]

Open the trappers caps, at least outer ones. They should all be oily inside. If it's not I suspect seizure which generally is one side. If it's dry, flashlight in darkened room will usually reveals some ground metal or damage.
 At this time, you contact Scott for the kit.
 The line you drew is more like a K tank, which are cheaper, then you need longer seat or move yours up.

Gosh that's a fine looking bike. Yeah, that's definitely the shape. Silly that they didn't change the frame any when they lengthened the tank for the F!  Likelihood of someone wanting to trade?

[MauiK3]

Restoring a 750 is very rewarding. I’m partial to K0 to K4 or so. Most parts are pretty available, this forum is a wealth of knowledge to tap. Keep looking for a runner or get one (or two) cheap enough to make a runner.