1980 CB750F for $180, modern suspension and upgrades for a cafe racer build

Papinbrew said:
Lol its pretty early still, are you being facetious?
Click to expand...
I've been giving my two cents' worth on the forums for over 15 years now and it's clear that many people don't believe there's any harm in just pouring in some gas and oil and "giving it a go", rather than AT LEAST opening up all the engine covers and TRYING to determine what the untoward sounds are actually being caused by.

Since the advice is free, there is neither a mandate for you to apply it, nor a warranty if it's dismissed (or applied).

Do I dare say "do as I SAY, not as I DO"?

ONCE IN A WHILE, I'll do a "rapid revitalization" on one of MY bikes, but NEVER on a client bike. If I'm expected to deliver a bike that's not going to have issues, I can't risk not knowing what the source of an incorrect noise was, before starting the bike up.
 
grandpaul said:
I've been giving my two cents' worth on the forums for over 15 years now and it's clear that many people don't believe there's any harm in just pouring in some gas and oil and "giving it a go", rather than AT LEAST opening up all the engine covers and TRYING to determine what the untoward sounds are actually being caused by.

Since the advice is free, there is neither a mandate for you to apply it, nor a warranty if it's dismissed (or applied).

Do I dare say "do as I SAY, not as I DO"?

ONCE IN A WHILE, I'll do a "rapid revitalization" on one of MY bikes, but NEVER on a client bike. If I'm expected to deliver a bike that's not going to have issues, I can't risk not knowing what the source of an incorrect noise was, before starting the bike up.
Click to expand...

Roger that! I'll be opening the top end this afternoon then.
 
Pulled the cam cover, found the noise. Bouncy chain. I'm headed to the auto parts store now to pick up oil, and a 12mm wrench. (I got, 99 wrenches and a 12 ain't one) for the cam chain adjuster. Fingers crossed that's all it is. Top end looks moist still, no rust.

https://youtu.be/3DMKsoV6_Is
 
My original reply (in part):

"Also a possibility that the camchain adjuster is messed up."

Might be more than just the adjustment, but I hope not. If it has skipped a tooth at either end, you're screwed.
 
pop the top cover off and check valve chain tension and valve (cam) timing. IIRC the chain tension adjuster is automatic - two sliding wedges or some such. It's been a while since I had one apart. Could be the PO had teh top off and put the tensioner fully "out" to get the chains back on and maybe didn't adjust it.

Either way, that noise is not good. Sounds like negative valve to piston clearance.
 
https://imgur.com/4J5VepW

Ok, I've adjusted the cam tensioner as per the manual, and also checked valve clearances. The noise is completely gone, and the cam chain doesn't flop anymore.

. I don't have the shim tool yet so I can't swap any out right now. I also can't get the screws off the timing cover, I got two but one of them is buggered, and I've been hitting it with my JIS#2 impact driver with PB blaster to no avail. I'll have to let it sit and try again.
 
What are your valve clearances? If I remember correctly, intake and exhaust is .005 +/- .002 per the manual.

I had to tap my timing cover screws with an impact driver to get them loose. Gently, but had to be tapped nonetheless.
 
J-Rod10 said:
What are your valve clearances? If I remember correctly, intake and exhaust is .005 +/- .002 per the manual.

I had to tap my timing cover screws with an impact driver to get them loose. Gently, but had to be tapped nonetheless.
Click to expand...


Ok, had a productive afternoon. Happy national beer day!

http://imgur.com/28j9TkY

That imgur link is my work note of the valve clearances including shim size underneath. I was able to pick up a valve shim tool today, some marvel mystery oil, Shell Rotella T 15w-40, and get the oil changed. I also got my battery in the mail, the very last thing I did today after all the oil was in there was check the starter. She cranks over quickly and happily, again no funny noises. Pulled a plug and grounded it while checking the starter and I've got a blue spark. We're getting closer! Oh, I also wasn't able to extract my timing cover screw. I just left it, and I'll spray it again tomorrow with PB blaster, then attempt to impact drive it again.
 
I'm VERY glad to hear it was only the camchain adjuster. You've done well.

At this rate, this is going to be one of the better low-budget rescues of the year.
 
J-Rod10 said:
What are your valve clearances? If I remember correctly, intake and exhaust is .005 +/- .002 per the manual.

I had to tap my timing cover screws with an impact driver to get them loose. Gently, but had to be tapped nonetheless.
Click to expand...

Ok, I only have a Clymers manual (please don't shoot me yet), and the manual states .08mm gap +/-.02 (.003 in). As per the Clymer specs I'll be able to swap around my shims currently installed and get the whole valvetrain back in spec. If anyone has the FSM handy I'd love a quick link to the proper specs.
 
Turns out I need six shims. I need two 280, and four 290. That will get me to .003-.004 across the set, and the CB1100f.net site says they should be closer to .006. I'll see if my local guy can help. I got roped into doing a full rear brake overhaul on my roommates 4runner this weekend, so I wasn't able to get any further work done. I also need an extractor set, my 3rd bolt on the timing cover is completely marred, Thanks to yours truly. My JIS impact driver didn't do the trick even with two days of pb blaster. I'm making a list of things here and there that I'll be picking up, this list is ever growing. Kind of overwhelming, I need a bigger paycheck....
 
There is a guy on CB1100f.net selling individual shims for $1 a pop. Save you from buying a whole kit, and using a hand full of them.
 
Sorry for the long lapse. A busy spring it had been.

As of yesterday I've gotten my carbs fully broken down and rebuilt. All new rubber O rings, all new gaskets, full solvent soak, and ultrasonic cleaner on all the parts. Also new air cutoff diaphragms and accelerator pump. Bench sync, and it's good to go. I got new valve shims in and all my valves have a .006" clearance with + or - .001" deviance. The compression on the cold engine is here:

1: 145 psi
2: 147 psi
3: 125 psi, 155 psi wet
4: 125 psi, 155 psi wet

I put the carbs on, fueled up and noticed my carb one was flooding out the overflow. Cranked over and cylinder one fired consistently, but was the only one firing. Tested spark and my right coil was not getting spark. Gonna order some CBR600 coils. Also need new spark plugs. I feel like I'm stuck right now, with the direction I should take. Pull the engine and just overhaul it? Rings, cylinder hone, lap valves, polish combustion chamber, all new gaskets, bead blast paint off engine? Or leave it until I can get it running and maybe the compression will normalize after a break in period? Any advice for a direction would be appreciated.
 
With those compression numbers I'd ride it for awhile see if it smokes and retest the compression down the road after a few hundred miles. If it gets worse pull the engine for a top end rebuild. If they improve or even stay the same I'd ride it the summer.

Psy

Sent from my SM-G903W using Tapatalk
 
I just want to say, IF IT WAS ME (and it's NOT), I'd go back together with original configuration suspension, but high-end upgraded internals in the front, and high quality rear shocks.

The 750F suffers from horrendously low gearing, I'd go with significantly taller final drive ratio sprockets.

Alternators are KNOWN cr@p, most likely will need attention.

Powdercoat all black parts, decent paint with original bodywork (probably have to replace the bottom of the tank).

MAYBE headers and re-jetted carbs, KEEP THE AIRBOX!

ALL NEW brake hoses, kits in the calipers & masters, and all new Ferrodo brake pads.

Maybe do a period factory race bike replica paint job...

Resist the urge to go with USD forks and grotesque 18-piece swingarm. The comstars of that era are actually a good classic look.

THAT'S JUST ME.
 
grandpaul said:
MAYBE headers and re-jetted carbs, KEEP THE AIRBOX!
Click to expand...
But why? :p
Nothing goes more hand in hand with the cafe racer spirit as swearing on your goddamn bike while getting the carbs just right.
And than screaming of joy when riding the bitch with those sexy ass air pods 8)
 
Well, here's a drawing I sketched up real quick to get an idea of what I want. It's not really cafe, not really brat.... just custom, and I like it. I want to keep the factory forks, factory foot controls and passenger pegs because I two up often, upgrade rear shocks, install Renthal superbike bars, and the nice K&N pods. I am talking with my buddy at his motorcycle custom shop and he's going to help me with the frame fabrication, I want all the welds cleaned up cause they're ugly as fuck, and a rear hoop welded with hidden incorporated LED lights within. The pipes on the bike are completely fucked. At least the headers are OK, but it looks like a cartoon where Wiley Coyote put some TNT in the tail pipe. So I've been thinking of having my boy fab me some scrambler style pipes that ride the sides, either a 4-2 on one side, or a 4-1 underneath with Yoshimura muffler. I've been looking and looking for airbox solutions as all the boots are bad on mine, and it's missing it's airfilter side cover. Probably more stuff missing too that I don't even know about. BUT since the engine has to come out for the frame work, maybe that's all the excuse I need to break it down and rebuild it.
 

Attachments

  • IMG_20160613_194218.jpg
    IMG_20160613_194218.jpg
    2.4 MB · Views: 352
Oh, as far as color scheme goes, I wish I could keep the factory tail piece. But it's been wrecked so it's all busted up. I don't feel bad about keeping this one custom. I've really been falling in love with having my frame powdercoat ed white, stripping the tank and leaving it a brushed steel with clearcoat rust protection OR a wine metallic red. The forks I'd probably strip and repaint black, or polish. Depends on how it works out stripping my engines old paint off and what I end up doing for that one. But I really like the idea of a white frame that has really clean welds. It would seriously be eye catching.

So far I've ordered new plugs, and scored a pair of CBR600 F2 coils on ebay for 31 bucks.
 
You must log in or register to reply here.

DTT Light or Dark

  • DTT Light
    • www.jadusmotorcycleparts.com
    www.lostapostle.ca/
    www.sparckmoto.com

    Spread the Love

    Back
    Top Bottom