Honda CB750 with low compression.. Will it run?

[@28bikes53]

I appreciate that you don't edit out your little mistakes (brake cleaner) etc because it helps the rest of us noobs feel normal for doing the same things! Also, you explain things very well and offer lots of excellent suggestions on what to do next. Thank you! Keep up the great work!

[@SanjanaRanasingha]

True

[@mjmorganuk]

Non-flammable! - Leaving that type of detail in your vids, keeps me watching. Much respect.

[@ClassicOctane]

I try to keep it real. I'm just a guy in his garage that plays with old motorcycles.

[@edman1015]

Just to know - do a cylinder leakage test on low cylinder - get the low cylinder to TDC with valves closed - inject air into the cylinder and see where the air is leaking - through the valves or around rings - leaking valves you can hear through intake or exhaust - leaking rings you can hear air at the dipstick.

[@ClassicOctane]

Good idea. I have been meaning to invest in a leak down tester for a while now.

[@rocketrobMontana]

@@ClassicOctane yeah, I'd like to see you try this test next time "will it run" encounters low compression.

[@vashdesigns1556]

I love that you never have a meltdown (at least on camera). I am pretty sure I would not have your patience and do something I regret. Love your videos Taylor.

[@blurboards1]

Your problem solving videos are the best. Thanks for sharing.

[@ClassicOctane]

Glad you like them!

[@The9meister]

You have now done a dry cold test, now squirt oil down into the barrels, and now do a wet test, if compression readings stay the same, valves worn, if the compression increases, rings and cylinders are worn...

[@ClassicOctane]

Compression went up. Top end rebuild parts are on the way.

[@rodolfomienert8292]

no sweeter sound then when a dormant-for-a-while engine starts and runs!!

[@ClassicOctane]

Couldn't agree more.

[@AndTodaysProjectIs]

2 things...I would have never in a million years thought about using brake cleaner as starting fluid. Secondly, I would have NEVER noticed that it said non-flamable LOL. Well done and thanks for even showing the flub

[@RickRose]

Picking up a 77 CB750K parked 12 years ago for "electrical issues." I will doubtless be consulting your archives. Thanks for great content.

[@oilinmyblood3906]

Thank you so much Taylor! I have been wanting to see more CB750's on your channel for a minute and now there coming! Hell yeah dude I can't wait!!! I will be one of the first to be watching them I give you my word on that brother, thank you for the CB750 videos again Taylor, keep up the great work brother and be safe out there.

[@ClassicOctane]

Thanks for watching!

[@MegaAK28]

i have a 1977 cb750 that i have been working on for over a year when i have time and have been waiting for you to build one for a while so i'm excited to see this build take off

[@ClassicOctane]

Awesome! Good luck with the project.

[@Ted007-r5r]

Re: Oil Spill I think you'll find the sump check valve leaks, so the tank oil drained into the sump over time. When you topped it up, there was actually too much oil in the system. then the pump in the sump returned all the sump oil to the tank. Happens a lot on older Harley's. Keep up the great videos.

[@drakeb6168]

Love these videos. You have assisted in giving me the knowledge to tackle a rescue for an 82 cb650sc that was just wasting away on a dudes porch.

[@danaowen9014]

A few drops of oil in the cylinder If the compression comes up then it's the rings being bad, if the numbers do not change it's the valves.

[@spdermnky]

I'm buying a 80s 750f today. Glad I found this channel.

[@ClassicOctane]

Welcome!

[@kevinhunter7581]

I recently got a 71 cb500 as my first bike. I just wanted to say your wiring video on the cb500 helped me figure out the winker relay was the cause for my indicator issue. Keep up the good content.

[@ClassicOctane]

Great to hear!

[@bigospig]

As someone else said, checking valve clearance might be a good idea before pulling and replacing the engine.

[@imcyberpunk]

You would have to pull the valve cover off, which you can’t do while the engine is in-frame. Super inconvenient design lol I’ve got an ‘86 Shadow that’s the same way

[@preez77]

imcyberpunk you don’t have to do that. Checking valve clearance is part of routine maintenance and there are 8 covers that come off in order to do so.

[@Ed-cg7dl]

Chris Prezbyl KZbin mechanics get me good. Love the guys who don’t own or haven’t owned a SOHC Honda who’ve watched 30,000 cafe build videos and think they have it all down front to back side to side. The caps use a 17... they come right off. .002 intake and .003 exhaust on this engine.

[@preez77]

evan donnelly I’m a certified KZbin mechanic myself and I wear that badge proudly! Remember not to overtighten those tappets or that will be a very round 17mm

[@Ed-cg7dl]

Chris Prezbyl Tappets take 3400 foot pounds of torque.

[@seanmckinnon6649]

Honestly don’t know why you don’t have more subscribers World needs more Honda nuts like us!

[@ClassicOctane]

The will come Sean. Thanks for watching!

[@jameskenyon7221]

Just wanted to say thanks for all your videos. My build is a 1976 cb550. There was several times I would need a reminder on how something went together. The carb build was very helpful. The wiring video was very helpful as well.

[@Ted007-r5r]

Check for a tight valve on #4. Also check compression with a little oil in top of #4. If comp comes up it's rings.

[@TheSudsy]

sounds like a beast

[@preez77]

Wouldn’t you want to check valve tappet clearance? It can definitely reduce compression. You also had spark plugs in other cylinders while doing compression test second time around.

[@blipco5]

Chris Prezbyl - That's so basic I assumed he already did and maybe forgot to mention it.

[@preez77]

blipco5 could be

[@blipco5]

Yeah, could have a tight valve in number four.

[@ClassicOctane]

I did that first thing. I forgot to mention that in the video.

[@ClassicOctane]

^ that

[@martinmoss317]

If you are pulling the engine anyway it would be nice to know what has actually caused the low compression - at least you'll know in case you need it in the future.

[@ClassicOctane]

i just put it on the engine stand today. I will be doing a top end rebuild and filming it for you guys.

[@reggiechin230]

As someone already said below - it would be interesting to know what's causing the low compression on # 4 cylinder. I'm looking forward to seeing the rest of this build.

[@ClassicOctane]

Engine teardown and top end rebuild video coming soon.

[@trevorklein9410]

Love your videos man! It inspired me to buy a 1972 Honda Cb 500! Your video on how to search for bikes is what helped me find a great deal

[@zzzarybaxz]

Inject some oil into the cylinder when the pressure rises, the rings are not tight and if nothing changes, the valves on the head :)

[@jimviens-realtor]

Also...once oil has been pumped through the system it can seal some of the gaps and cause compression to go up.

[@brendonbentley6617]

If it were mine, I'd take this bike for a non-stop 200 mile ride and then test the compression again. ...Just sayin'

[@09woody]

Great video. Just gone through the same process with my cb750f 1979 twin cam. Keep up the good work Taylor 👍

[@thoforn]

Love to see a Honda Shadow fix sometimes if you find a old one ..750 cc :)

[@LuisGGomezPhoto]

Valve clearance! I owned a 750 K1, and I've known it from the hearth. Thanks for your videos, I enjoyed them heartily. Bye.

[@ClassicOctane]

Checked before the second test. They were right in spec and unfortunately didn't help our numbers.

[@flexjay87]

My first time watching this channel. '69 Camaro in the driveway, is a nice touch.

[@ClassicOctane]

Thanks for watching.

[@Beachmangarage]

There’s an eBay listing in Ontario Canada for a 77-78 gas cap (new). I ordered one from the same seller. Probably a little overpriced as they are hard to find but it does fit well.

[@mccraeroberts9978]

Any luck on finding a full tank? My current project came with the stock tank but its practically rusted through

[@n8guy]

@@mccraeroberts9978 They definitely come up on eBay. I've been close to winning a couple.

[@alfonsoleonardo6178]

Always great explanation man 👍🏼.wish you were here Illinois 😜 workin on my 2nd cafe racer…good job man!!!

[@paulfellows2094]

good detail work love the bike do keep at it mate waiting for next one

[@simonallan9941]

That's not such a problem if you like persevere and add some Moreys to the fuel and maybe use some "Rostoff" to soak the cylinders rings, because if you stick with the original cylinder rings, they are the best with awesome tempering/hardness and will outlast anything you can buy, I bet that compression will increase dramatically after 10,000 miles 😉.

[@lilTryhard]

I'm dealing with something eerily similar on a 79 Suzuki GS850. Even down to the grit that blew out of the exhaust! A little bit of ATF helped with the compression, but its still only at maybe 90psi across all cylinders.

[@wildsmooth9201]

I would take it out and rebuild. Clean it up, hone the cylinders, replace all the gaskets, check intake valves for leaks , new valve stem seals, New piston rings. If your blowing oil out the exhaust, you probably have issues with the rings. If its just smoking it could be a number of things.

[@ClassicOctane]

Parts are on the way

[@scramblinman7156]

Great job man! I have a 78 CB750K engine and carbs if you need some extra parts. Think this year model engine fits the older “F” bikes but not certain of that.(I am about 100 miles north of you)

[@MsIvicao]

Put some oil in #4, if compression get better you will know it's a ring/cylinder issue if not check valve clearances as couple of guys already suggested... I enjoy your videos very much so tnx one more time....

[@ClassicOctane]

Did that and the numbers bumped up. I will be doing a top end rebuild on it and showing it here on the channel soon.

[@webbhughes6291]

You could always drop a small bit of oil down to the chamber to see if the compression goes up and then you know the cause are worn rings.

[@ClassicOctane]

Confirmed it's the rings. I'm going to be doing a top end rebuild. I will film it and post it here ones it's done.

[@webbhughes6291]

@@ClassicOctane Looking forward to it! I just got my first 750 and will look forward to your tips and tricks that you learn and pass on. Would love to see a series on this bc you do so many 500/550's

[@jimviens-realtor]

I was able to pick up an '81 CB650 project bike. I'm looking forward to stripping it down and doing a brat/cafe style build. I'll definitely be using your videos to guide me through the process!

[@preez77]

Jim Viens those bikes are fairly hard to turn cafe/brat. I did it with 80 cb650 and it needed a lot of work. Earlier 550 and 750 are easier because of frame and tank shape and wheels that are same size. Your bike has cv carbs that are harder to tune if you’re deleting factory airbox. I don’t mean to discourage you, if that’s your first project you will learn a ton but be prepared for long haul with it. Looking back I’d probably wait for a different bike to come along.

[@donzimmer63]

Taylor - love the content, I hope u keep it up. Question - I'm a new shade tree mechanic just getting into vintage japanese bikes. KZ400, CX500 and now a 1978 CB750K8. Doing the top end on mine and the rocker cover seems to me to have a spot at the top of the cam chain to have actually worn threw the aluminum from contact with the chain. Or do I just not know that there is a designed opening there? Appears to be worn through, but I had nothing in the oil. It would seem with that much material floating around I'd find it. Possibly a common issue with a loose/misadjusted cam chain? Any advice is appreciated. Can send a pic of the hole if that helps.

[@MarkJames61]

Great lesson Taylor, so simple and logical.

[@ClassicOctane]

Thanks Mark!

[@roberymcgoff1904]

Just dropping you a line. From your friends at Black Heart Cycle in Connecticut.

[@GillK95]

How come we haven't seen a CB650 yet? Do you not like those?

[@danolopez662]

I enjoy "will it run" vids a lot! 👌🤙

[@ClassicOctane]

Thanks!

[@whitecompany18]

A Royal Enfield classic tank looks the same if not better and are easily available cheap on ebay if you can't sort a cap .

[@spencerprewitt3534]

I might have another gas tank cap for you! Let me know man. Is it the long rectangle style cap?

[@ClassicOctane]

It's the small round one underneath. I believe my customer found one but if not I will let you know. Thanks!

[@buckneighkidd419]

Awaiting will it run part 2!

[@Nighthawk75]

Would be cool to see a trike build something different than your normal stuff.

[@ClassicOctane]

I would like to build a bike with a side car at some point.

[@geoffreyjones2000]

@@ClassicOctane I have 3 side cars in Maryland, sir

[@Thewatson77]

Great video as always Taylor 👍🏼

[@ClassicOctane]

Thank you!!

[@philipflynn7781]

KEEP A FAN BLOWING ON ENGINE WHEN RUNNING FOR A LONG TIME. AS THE OTHER GENTLEMAN SAID RUN IT FOR A WHILE. ALSO WHEN REMOVING ENGINE LAY IT ON RIGHT SIDE ON FOAM. IT TAKES TWO PEOPLE. TAKE WHEELS OFF ETC. YOIU WILL SCRATCH THE FRAME ALL TO PIECES IF YOU TRY JIGGLINNG IT AROUND TRYING TO GET IT OUT . YOU CAN ALSO CUT THE THE TOP FRAME BAR OFF AND HAVE IT FLUTED TO PUT BACK TOGETHER.

[@jonathanbrown1120]

You call that low compression, my 79 kz 650 read 65-50-75-60 psi. Engine only had 6,000 miles. Piston rings looked fine after teardown but valves were horribly pitted. After a complete rebuild, **Lap job** everything ran like new. 180-195 each cylinder

[@persistencewins]

Hey Taylor, great job as always. Would you please let me know where you get parts for the cb750 whenever you have a chance? Thank you for sharing your knowledge.

[@ClassicOctane]

I get a lot of classic Honda parts from 4into1.com

[@persistencewins]

@@ClassicOctane thank you so much for the info n please keep up with ur video entertainment/teaching classes…it’s so cool n ez to learn from a person that have a passion for whatever they do…

[@rvega314]

A leak down test would tell you a lot more. Like your videos. 👍🏻

[@ClassicOctane]

Going to order a leak down tester today.

[@John_Ridley]

I was just yesterday at the store to buy brake cleaner and the main shelf of it had been restocked with non flammable. I noticed and grabbed the good old flammable stuff. How else are you going to check for vacuum leaks?

[@jackmasterification]

Such helpful content thanks boss

[@ILikeCatsMoreThanILikeYou]

So what was it like living in Dawson's Creek?

[@Jacklee-qh1cv]

If you remove the exhausts you'll be able to see if a valve isn't closing properly.

[@jerryking1434]

I've heard of a goofy repair/fix for a low compression engine .. No..I haven't done this .. Get engine running ...somehow pour or blow ..into carb some comet clenzer..supposed to have enough grit to polish or remove rusty build up on valves..then supposedly blow back out the exhaust ...???

[@oilinmyblood3906]

Hey Taylor I would do a cb350twin, a cb450DOHC, CB550 and a CB750 for your collection, I say why the hell not if you can and if you got the room for them, and obviously you do, and if you do post videos for all of those builds you better believe I will be watching all of them!!! Oh and just as a suggestion have you ever thought about doing a 1975 to 1977 Honda Goldwing build? I am really really wanting a Goldwing of one of those years and I know I will have one eventually but I do need to sell at least one of my three CB750's before I get the Gold Wing, I think that it could be a very very cool build!!!

[@ClassicOctane]

I think a Goldwing could be cool. I haven't really messed with one yet.

[@oilinmyblood3906]

@@ClassicOctane yeah me either but I can't help but want one because they are dead on reliable with extremely long service intervals as long as the bike has been properly service throughout the years, I have only seen about three Honda Goldwing build that I think are pretty badass actually one of the builds is a valkyrie motor with a Goldwing frame, it's on Racer TV channel and he also has an other one that was built by krackenhead customs, and that build utilizes a CB750 Super Sport Tank so the original tank under the seat is completely gone so it is truly a very light and naked Goldwing, it is by far my most favorite Honda Goldwing build the date, if you have not checked it out you seriously have to brother, it really is a work of art and you can tell that it was not an easy build and very very time-consuming but once you look at it you could care less about how long it took to build, you need to check it out Taylor if you are interested in a Goldwing build in the future

[@jamiestanley8774]

Ive just comp test my k5 . PSI Cycl # 1and 4 @ 100 # 2 and 3@ 75 that was a hot test The few times ive actually rode it i thort it went ok 90mph quick squirt down the road . What should i do if numbers are to uneven .new pistons n rings or try a leak down test . ?????

[@tracksidesolution]

Ah crap. That’s bad news for my 750. I have the same exact running condition on cyl 3. I better check compression and find out.

[@banditnev]

Good luck hope it works out 👍

[@jimmac521]

my 750 would never start on a low charge.

[@jamesal0]

check valve clearances and take it for a good hard ride

[@davidhoward5586]

Did you do a valve job on the head when you had it apart?

[@markwilliams9793]

Really good video.

[@ClassicOctane]

Glad you enjoyed it

[@AverageCarGuy]

Good series. What kind of bike lift is that? I’m trying to find one for my garage and can’t seem to find something that makes sense.

[@ClassicOctane]

This one if a Handy lift.

[@nathanbutler8240]

Do you still have to run the cdi box with points? Or is that only for electronic ignition

[@nicholasjheinz7461]

Great content!

[@ClassicOctane]

Thanks!

[@willjourneaux8110]

hi taylor have you ever done or thought about working on one of the old honda cx500 would love a build on this

[@ClassicOctane]

I have a rough example of one. Unfortunately I don't have a title for it so it's probably not worth investing time and money in.

[@Bugglers]

Hi, does anyone have any experience with the ignition points on a cb750. On every video ive seen the ignition points are located on the right side but on my bike thats where the alternator is situated. Does anyone know why, is it something special with the -82 Cb750?

[@daveco1270]

I don't think those are stock coils for a 75 CB750. I'd swap those point out for a Dyna S ignition.

[@ClassicOctane]

That's the plan. Just needed to get it running first.

[@daveco1270]

​@@ClassicOctane I have a 1975 CB750K so it's nice to see you work on one. Looking forward to the next "will it run" to see if that engine is worth swapping out. It's a shame the Honda engineers didn't make it easier to pull that top off while it's in the frame.

[@MyMGBJourney]

Can classic Hondas hang a valve open if they're not adjusted properly? I know that hung valves can cause low compression and keep the cylinder from firing.

[@ClassicOctane]

Yes, but I checked these before the test.

[@marknumbers7117]

I'll be ordering parts for a CL 350 and CB 750. Common-motor has some parts for smaller Hondas but not for larger 750s. Where can I go for parts for larger Hondas? Also, where do you get your cool tires with the more aggressive tread for the scrambler style bikes? Any insight is helpful. Cheers.

[@ClassicOctane]

4into1.com has tons of 750 parts.

[@marknumbers7117]

@@ClassicOctane Thank you! Your videos are legit! I just started really getting into olders Hondas and Yamahas last year. I have a ton to learn but I have been so happy wrenching on these bikes. I now have 2 CL 350s and 2 CB 750s. I also have an older Goldwing. I dont know what the heck Im doing with that. But it has cool looking motor. Thanks for the information.

[@BasicPoke]

I would like to see you fix an engine rather than swap it out. But thanks for the videos, will keep watching.

[@ClassicOctane]

Top end parts are on the way. Video on it will be out soon.

[@DanielHansenTrades]

I got a 1983 Kawasaki csr650. I have a compression of 110 on number 1 and 100 on the rest. Do you think it’s possible to still run and drive or will I need to do a rebuild?

[@DanielHansenTrades]

It hasn’t ran in 2 plus yeats

[@petergreenshields7381]

Hey Taylor; how much on average are you paying for cb550 donor bikes in the USA; just wondering, I was shocked at the prices over here in England, £4,000 - £5,000 up

[@ClassicOctane]

Roughly $1000 USD

[@sandmanhell913]

i got a 1971 cb500 up for seil

[@Braxton-kd6gf]

What do you do for side covers if you don’t have any and they’re crazy expensive? Looking for alternatives.

[@ClassicOctane]

I have seen some clean builds that ran without them.

[@jomomma8291]

Did you try pulling the clutch lever when you hit the start button?

[@ClassicOctane]

I didn't but thats a good idea. I forgot some of these Hondas have that safety feature but most don't.

[@preez77]

They don’t have clutch safety on 75-76

[@joelwhite3337]

Is it necessary to have the throttle wide open when doing a compression test? I never knew why but was told that by my father (RIP). Thanks!

[@preez77]

Joel White your dad was right. Throttle needs to be open. It makes a big difference in what the gauge reads. Closed throttle will greatly restrict air flow. I got about 50psi less once when I forgot to open it. You should also do it on hot engine if possible.

[@ClassicOctane]

Definitely, my first test there were no carbs on the bike so the intake side is wide open. On the second test I have the throttle stuck wide open.

[@chrisglover480]

Watching from the UK... what happened with the Land Rover discovery?

[@ClassicOctane]

Ended up sending it to a Land Rover shop to get a bunch more work done (cam, trans, diff, transfer case all needed to be rebuilt or replaced)

[@chrisglover480]

@@ClassicOctane Ah got it! Loving the channel, keep it up!

[@ronanteague293]

Do a top end rebuild.

[@ClassicOctane]

Parts on the way.

[@MrGMawson2438]

Nice one

[@ClassicOctane]

Thanks for watching

[@davidhoward5586]

A leak down tester would tell you exactly where to look to fix this problem.

[@evanmalinowski6302]

Are you still building bikes for customers?

[@ClassicOctane]

Yes, all of the bikes currently in the shop are for customers.

[@evanmalinowski6302]

Classic Octane does email or dm work better?

[@micksterboone4517]

Don't get the non-flammable kind. lmao

[@ClassicOctane]

Glad I noticed when I did. Otherwise I would have been chasing my tail for who knows how long.

[@01thomasss]

Please don't chop that good-condition front mudguard. Rather find a knackered one and cut that - if you really must. Even better, ask the owner to get caught in the rain on a bike with minimal mudguards. I'm that'll change his mind.

[@johnmurray3324]

He did not check rocker's

[@dungnguyen-vh6wx]

Hi Taylor, my name is Andy.try to get schedule with you to have my bike built by you. I have sent you a email&message on the website also. I’m live in Austin. Your problem solve is awesome

[@ClassicOctane]

Hey Andy, i'm currently booked out until Q1 one next year. Let's stay in touch and get you on the schedule lather this year.

[@dungnguyen-vh6wx]

Sure Taylor, Thank you so much

[@chezgalatea2032]

Should have at least checked the valves- too tight = poor compression

[@Dynaudio99]

Watch out for carbon monoxide

[@grantferguson251]

Why didn't you turn the throttle all the way open on this one?

[@ClassicOctane]

First test had no carbs second test I had the throttle stuck wide open.

[@jerryking1434]

Have you bought motorcycles with ..no title...lost tytle..salvage title...can you ever get them registered and Streetable...insurable..???

[@ClassicOctane]

I have quite a few bikes that I bought with salvage titles and rebuilt them. Here in Texas it's not a big deal to fix the bikes then have the title office issue a "Rebuilt" title. That rebuilt title can be transferred to a new owner just like the original. Missing titles are harder because you need to go through what's called a bonded title process that's a bit of a pain from what I hear. In Texas you cannot register a bike without a title. So no title = no street riding.

[@blipco5]

Love your channel but you really need to get a good exhaust fan system with fresh air coming in as well. Your lungs will thank you fifty years from now. That shit is cumulative.

[@ClassicOctane]

Agreeded

[@fishaussie9112]

Do more wrenching and less. Talking From down under

[@AJ-ut3ul]

"making old things run is my biggest passion"... but won't just take the top end off and fix the issue 🤔🤔

[@jackbeanstock7710]

another CB... just rename your channel to CB bikes.......