Author Topic: Should I Buy This 75 CB750F? (Read 3365 times)

754 · « **Reply #25 on:** July 06, 2018, 04:04:37 PM »

If your tank is ok, you get one of those tanks, AND Cash..before you trade.

seanbarney41 · « **Reply #26 on:** July 06, 2018, 04:16:50 PM »

Quote from: Jessamine on July 06, 2018, 02:54:59 PM

Quote from: 754 on July 06, 2018, 02:25:55 PM
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?

oh? you want to do that? than nevermind...don't buy it! The world certainly doesn't need anymore mindless internet robots that can't figure out how to customize an old motorcycle without ruining the frame

Jessamine · « **Reply #27 on:** July 06, 2018, 05:08:20 PM »

ERROR: DISS NOT RECOGNIZED

scottly · « **Reply #28 on:** July 06, 2018, 05:25:48 PM »

You're going to fit right in here, Jess.

IMHO, the 750F and 400F tanks are the best looking of all the SOHC fours. Frank has a 400 tank on a 750.

I just shipped the last kit I had this morning, but should have more in a week or two.

seanbarney41 · « **Reply #29 on:** July 06, 2018, 06:12:19 PM »

Quote from: Jessamine on July 06, 2018, 05:08:20 PM

ERROR: DISS NOT RECOGNIZED

lol, thanks for having a sense of humor

Jessamine · « **Reply #30 on:** July 06, 2018, 06:23:26 PM »

Don't worry, mate... I hate "Cafe" bikes too. The heinous, unsafe, ugly things folks do to some bikes to achieve the moto equivalent of a thigh gap is shameful.

754 · « **Reply #31 on:** July 06, 2018, 07:12:15 PM »

I took the 400 tank off, in a gold phase now like the first 750 I had in 75.

cjespersen · « **Reply #32 on:** July 07, 2018, 12:12:37 AM »

Sounds like the timing chain is broken or it jumped timing. I had this problem with my 350F. I don't know about the CB750F but the 350F is an interference engine. I'm in the process of replacing all 4 of my intake valves because they got bent when the chain jumped the sprocket. See if the kickstarter works, often it will be frozen if timing is off. Also see if the bike wants to push air out the back of the carbs.

Jessamine · « **Reply #33 on:** July 07, 2018, 06:15:47 AM »

Quote from: cjespersen on July 07, 2018, 12:12:37 AM

Sounds like the timing chain is broken or it jumped timing. I had this problem with my 350F. I don't know about the CB750F but the 350F is an interference engine. I'm in the process of replacing all 4 of my intake valves because they got bent when the chain jumped the sprocket. See if the kickstarter works, often it will be frozen if timing is off. Also see if the bike wants to push air out the back of the carbs.

That really sucks, mate!! Did it hop the cam sprocket, or snap? And this was while you were riding, I guess?

I don't know about how much valve interference there is, either; searching thoroughly only turned up the fact that the DOHC CB750 (79 anyway) was non-interference. But I am concerned about that. How much of a pain is it? A full valve job is one of the few things I've never had/gotten to do on a bike, so there'd be a learning curve if I had to do that. Sounds expensive, too. $:-\$

The kickstarter generally spins the engine freely. One time (out of maybe 25) while using it to rotate the crank at the CO's garage, it didn't want to return and felt stuck at the end of travel. Blipping the electric start button freed it up.

Jessamine · « **Reply #34 on:** July 07, 2018, 06:40:14 AM »

Mentions of CB750 valve interference:
77 CB750K with interference:
http://forums.sohc4.net/index.php/topic,160979.msg1850267.html#msg1850267

76 CB750K with interference:
http://forums.sohc4.net/index.php/topic,162041.msg1863124.html

76 CB750K with interference:
http://forums.sohc4.net/index.php/topic,162041.msg1863124.html

So it's probably safe to say it's an interference type engine, despite being an F. So unless the CO (and by association, me) got reeeaaally lucky, there are probably some bent valves.

Stev-o · « **Reply #35 on:** July 07, 2018, 11:03:18 AM »

Quote from: Jessamine on July 06, 2018, 06:23:26 PM

Don't worry, mate... I hate "Cafe" bikes too.

First off welcome. Not sure if you are being sarcastic, but if not, this is not the bike for you.

If that motor needs a rebuild, it would be real easy to get upside down. Sounds like the PO didnt know what he was doing, may be other surprises as well.

And those clubman bars look silly mounted like that!

754 · « **Reply #36 on:** July 07, 2018, 01:17:07 PM »

Not a huge deal to fix one..
Hardest part getting out the motor. If organised and read up on procedure , a few hours..or so.
Unless you want to cut.
Like I said, no pieces over 200 bux, most way less.

cjespersen · « **Reply #37 on:** July 07, 2018, 03:10:48 PM »

I got the 350F from a guy that replaced the gaskets on the top end and couldn't get the bike running again. Long story short he didn't tighten the cam chain tensioner causing the chain to jumped the sprocket several teeth. The result was the intake valves slamming into the pistons.

The pistons are in great shape along with the exhaust valves but the intake valves are all bent just enough to make them worthless. In total it was about $200 in parts and tools to fix the valves. I needed a Valve Spring Compressor C-Clamp ($15.93 on ebay) and a valve lapping tool ($8.00) the NOS intake valves I got for around $33-$40 each on ebay.

That's my experience when it comes to purchasing a non-running bike because of mechanical failure. I wanted a project and that's what I got. I do enjoy time in the shop on this bike and if that is what you're after then go for it. If you want to flip the bike then I would pass.

Jessamine · « **Reply #38 on:** July 09, 2018, 07:36:57 PM »

Oops, I bought it

PO clarified the circumstances of the bike dying; said it was at the bottom of his driveway, and he was JUST ABOUT to ride away when it died and wouldn't start back up. The mystery deepens! I'll let y'all know what I find in a few days.

Jessamine · « **Reply #39 on:** July 09, 2018, 07:55:07 PM »

Initial observations, because I want an excuse to write about this bike more:

Brakes seem to work great and the reservoirs are squeaky-clean inside. I also noticed a PO replaced the lines with stainless steel braided stuff. One issue though: there's apparently a very slow leak from the top of the front master cylinder (slight wetness near the bolt holding the lever on, but the reservoir is basically full); guess I need a rebuild kit!
The seat is so uncomfortable! Why do #CafeRacers have no seat squish? It's gonna get reupholstered or replaced for sure.
Gas tank is quite clean inside and apparently sound structurally-- just the tiniest bit of surface rust above the gas line, which should dissolve easily enough. I found the badge holes, too; doesn't seem like they did much fill work before they painted it. I'm curious whether they even stripped off the old paint job before blacking it out... anyone know what would strip spraypaint but won't touch the original paint if it's still there underneath?
The tappet covers are very tight on the bike, and my 17mm wrench and socket don't seem to be the best fit for them. Hmm.
Engine number is E2506234, within the expected range for a 75 F0
Air pods are no-name Taiwanese jawns. Tuning this bike will be F U N Anyone have an extra stock airbox?
PO clarified also that when he got the new headgasket the shop also did a full valve job, so if they're not bent to hell (fingers crossed) I should have awesome compression out the door.
PO confirmed he did not even check the cam chain tensioner. That'll be item #1 the first work day I get on it.
PO said taking the engine out should be much easier than normal, because "the guy who had it before me cut the tabs to make it easier to remove." I don't know WHAT that means. It seems to have all the stock mounts intact to my neophyte eyes, so maybe it was just something extraneous?? Anyway, he was adamant I could drop the engine in half an hour.
apparently, aside from the new LED brakelight, the rear piece is stock. Nice.

754 · « **Reply #40 on:** July 09, 2018, 08:03:57 PM »

Make sure you use a 6 point on the tappet covers.
Seats are uncomfortable because some go for looks and don't ride too far. Sometimes though , not very thick can work good still.
Oh and Congratulations..

scottly · « **Reply #41 on:** July 09, 2018, 08:08:54 PM »

Item #1 should be to pull the tappet covers and see if the rockers are going up and down, IMHO.

Jerry Rxman Griffin aka MuthaF'er · « **Reply #42 on:** July 09, 2018, 08:14:45 PM »

And get new o-rings for the tappet covers

scottly · « **Reply #43 on:** July 09, 2018, 08:33:33 PM »

In Lisa's case that was a misdiagnosis.

seanbarney41 · « **Reply #44 on:** July 09, 2018, 08:38:23 PM »

Jessamine, I have a stock pan and foam (original cover is ripped) I would trade for that seat, plus I will throw in an airbox too...pm me

Jessamine · « **Reply #45 on:** July 09, 2018, 09:07:08 PM »

Quote from: seanbarney41 on July 09, 2018, 08:38:23 PM

Jessamine, I have a stock pan and foam (original cover is ripped) I would trade for that seat, plus I will throw in an airbox too...pm me

I'll hit you up once I get into the engine and have a look.

78whiteorbs · « **Reply #46 on:** July 10, 2018, 06:50:14 AM »

Quote from: seanbarney41 on July 06, 2018, 01:18:57 PM

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.

^words of wisdom there! I concur.

Jessamine · « **Reply #47 on:** July 11, 2018, 09:03:11 PM »

Project topic is live! Moving discussion of this bike over there.

http://forums.sohc4.net/index.php/topic,173115.0.html

News:

Author Topic: Should I Buy This 75 CB750F? (Read 3365 times)