Low compression CB750 engine teardown. Found the problem.
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- เผยแพร่เมื่อ 23 ต.ค. 2020
- Hope you guys enjoyed this one. Let me know what you think in the comments.
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"Im not going to do a 'How to...' video, this is more of an overview"
...Proceeds to do an overview video 10 times better than 99% of 'How to's!' Lol. Watched every bit of it and I dont even have a 750, great vid as ever! Excellent job mate.
Thanks Alan
Just a few quibbles with the terminology used in your commentary:
The "top" ring is properly called the compression ring
The "second" ring is properly called the scraper ring
Yes, the "third" "ring" is called the oil control ring and consists of an expander in the middle with rails above and below it.
As well, after honing the cylinders you MUST use clean white rags, preferably something soft like cotton (old clean white tee shirt material that's 100% cotton without silk screened stuff on it works great) to clean the cylinder bores of all the grit from the hone stones AND the cast iron powder from the liner surface itself. Wipe the bore with a cotton rag dampened with mineral spirits (NO WD40 or similar lubricants) and then toss the dirty rag. Repeat this process until your last rag will not show any black stuff at all. You'll be surprised at how much rag material you can use just to ckean ONE cylinder bore. Your whole engine will thank you for taking this extra step of getting rid of all that abrasive crap.
As to installing the block and coaxing the pistons/rings into the bores: you really should thoroughly bathe the rings with engine oil before trying to get them into the bores. You'll find that things go much easier.
It would also be a great idea to lube ALL the cam bearing surfaces AND the lobes with engine oil or "startup lube" before installation.
Just finished the top end rebuild on my 78’ 750 following this video. Thank you Taylor for the information and wisdom. This is the single best video on TH-cam covering this imo
I wish I had this video to watch 30 years ago! Nicely done.
Great call choosing to do the top end rather than just engine swapping. This is much more interesting and helpful.
Glad you liked it
1
I'm
@@ClassicOctane taught me a bit about engine timing! Thanks!
I had the pleasure of attending and graduating (youngest to grad age 16) from American Honda Midwest Service school back in 1970 right after the Daytona win. The class was held in Bob Hanson’s Race shop in Racine Wisconsin. My instructor was Bob Jamison who prepped the winning 750. He was a real stickler for detail and this is what I learned from his philosophy. You did a great straight forward job however what you missed was...the troubled cyl probably had rusted (at least) the intake valve. If you’re not intending on inspecting the valves, do a leak down by pouring solvent in the intake and ex to see if it’s getting past the valves. The cam tension rollers get brittle and under all circumstances be changed. The rubber compound on the knockoffs are not near the original Honda part.
The valve seals also get hard, and while you’re in there, it’s an evening job to pull the valves, lap them in and put new seals in. Make sure u check and lube the stems.
Sure you did
Jamison grad 69
I really have to complement your skill at methodically explaining each procedure as you moved along during the whole top end rebuilding process. You have a real gift for teaching and making things crystal clear from start to finish! This video is definitely valuable content. Subscribed! Keep them coming’
Wow, thank you!
@@ClassicOctane I agree, really well done, and even though mine is a Kawasaki all the same principles apply. Just one thing, would you recommend engine-in or engine-out? I was originally thinking engine-in but after watching this I might be investing in an engine stand. Cheers.
Thanks, very nice to watch.
Having already disassembled the cylinder head, you could have taken the opportunity to grind the valves too...
You do a great job with these videos, very comprehensive without being boring and educational as well.
I'm in the midst of a top end rebuild on my bike. This vid gives me hope. lol.
When removing Piston Rings you should place small rags around the 4 Con Rods so any mishap and you dont end up with foreign objects drop into the bottom of the motor..
Not only that but connecting rods can be damaged if they come in contact with crankcase resulting in stress riser crack and rod to fail in service
You stole my comment. When he snapped ring a piece could have dropped into engine.
Mate. I've been watching you for a while now, and I must commend you on your entire approach to your content. I've considered trying it myself, but the whole 'talking to camera, explaining stuff, then editing and publishing these videos, along with actually fixing a real life motorbike, is a bit of a handful!' So you, my friend, are something else. Just thought I'd say something positive (and truthful), cuz we all need that shit now don't we.
Lazy Bones well said!!!👍
Agreed!
Thanks! I really appreciate the kind words.
Someone already said it, but it bears repeating,....you are an excellent teacher. Very complete presentation in understandable terms. Well done!
My ADHD has now got me binge watching all your videos. And now you have a huge fan up here in Everett, WA. And this all started with your video of the most awesome explanation of rebuilding the carbs on the CB550. Absolutely great videos. Very good editing. There's no unnecessary waste of words or time. Thank you sir.
Definitely made me get the confidence to rebuild my top end! Awesome content!
always a good idea to remove the valves and lap them in by hand.Particles of rust can sit on the surface of the seats and hold the valves open slightly.Its just peace of mind,and saves having to strip the engine down again.cheers Graeme from New Zealand,enjoy your programmes
I'm actually looking at doing my own cb750 project, also in Austin! I had to watch this video just to mentally prepare myself. Great explanations and video!
what beautiful work. outstanding job.
Yeah, I still have my piston ring pliers from 20 years ago for the one time I needed them and do not regret buying. And the ring compressors.
Thank you, always enjoy your videos.
Absolutely love your content on the Honda cb’s. Trying to find a 70’s one right now to build one, absolutely love the sound and how much you can customize the look of this bike 🙌🏼😌
Very methodical, low key presentation. Well done.
love those large , air-cooled fours
I appreciate your videos. Enjoyable and informative. This one, like so many of your others, gives me confidence to take on new challenges. Thank you.
I see you start all four pistons in the cylinders at once... I start the middle two first then the outer ones and that seems to work well for me. good job on the video and it looks like you do good work. great to watch ...you are a natural teacher.
Awesome video! Helps a lot to visualize what I need to do when it's my first rebuild. Keep up the videos on the cb750. Can't wait to see the next ones!
Thanks, will do!
I had planned on doing this work on my K2 during the downtime this winter. This will be an invaluable help along with the various sacred texts I've collected.
Good luck!
The best man! Go Classic Octane!
such a great vid, thanks for taking the time to share!
My pleasure!
A - Im a strong believer in cleaning up the engine prior to removal and conducting a leakdown test on it at that time as well . In addition if it wasnt a runner I'd be tearing down the bottom end and checking bearing condition and clearances . Also the bore & pistons should have all been measured . Minimum piston - wall 0.001 - 0.002 clearance . Ring end gap top 2 = 0.007 - 0.016 . Oil ring = 0.012 - 0.035. little tip ... you can increase the taper prior to boring / honing ... makes installing the pistons a snap. Cam timing . I always check again AFTER cam chain tension has been set . Use assy lube cam bearing surfaces .Your videos are well done.
Pistons with jammed rings can make the bore go oval so measuring is a must before deciding what's needed.
Your correct in ascertaining the trepidation most folks place on a refresher with engine teardowns, associating it with marked levels of terror that things will be thrown out of kilter from small missteps taken along the way. A hundred diversions probably accounts for most unsuccessful repair procedures more than misdirections that take place. Great synopsis of one's route to travel when putting these plants back together. Best of luck with your frame and suspension refit and upgrades. Warmest regards.
I just might be buying an old CB 750, your info is wonderful. Keep up the good work!
I know it takes energy to explain wuch is highly appreciated because of my inexperience thnks
Piston Rings are probably set to have the gaps away from the front & back of the cylinder because that would be where the most pressure is applied by the rod/crank as the piston moves through the cylinder.
This is also my understanding.
I was taught as an apprentice that the ring gaps go on the opposite side to the thrust side of the piston.
I knew there had to be a reason for it.
Just a perfect explanation which we owners of cb's thank you a lot. Thankyou master
Got rid of a 750 4 years ago. Wish I still had that thing.
Congrats Taylor once again for another well done job & explanation. I got 2 toys both cbs to restore, a cb750c & a cb1100f sports. I will get there. Thanks for sharing ur clear videos helping everyone. Keep it up!
Will do. Thanks!
thanks for the walkthrough man!!
Cool...you made it look easy..thanks for posting
Very good instruction video ! Thank you !!! Greets from Belgium (Europe) 👍
Awesome video! Very informative and explained well! Great job👍
I'm glad you bought the pliers, spiraling on rings is not a preferred method.
Love your vids. This is like ASMR for motorcycle nerds.
Glad you like them!
Great technical lesson.
thaks a lot for all the info. i think the ring gap not being at the forward or rear of the pistion is because there's some force fore and aft as the pistion mooves up and down which makes the bore oval/oblong over time.
Thanks Tyler!!!
GREAT VIDEO, LEARNED A LOT, THANKS FOR SHARING
Awesome video 😊
I had this excact scenario with a 750 Honda, i managed to free up the rings by carefully heatcycling the piston,and managed to loosen all of the stuck piston rings
Great info out there! Keep going strong!
Appreciate it!
Very good in explaining everything step by step ! That is very clever of fasting the engine to the engine stand
Can you show how the engine is mount to the stand and fabricate the frame to the engine . That would be helpful for us . I have a engine stand and trying to figure on how to attach a cb550 engine to the stand .thanks and keep up the good work !
Had a 1978 Honda 750 Four F2 got rid of it when the tappet noise went bad that was back in 1983 and have regretted it ever since wish I had your knowledge back in the day.
Great workshop.
Thank you so much for this video. It makes me feel like I can take on a similar project. Keep up the great work you are doing. Big fan!
That's always my goal. I hope to give everyone the confidence to tackle a project they otherwise wouldn't have attempted.
‘71 cb350 twin setting up & have watched & rewatched most of your content. I was going in anyway, but with quite a bit of weight off the shoulders that the bite doesn’t seem as big. Gives us, who are beginning to finally scratch an itch a another facilitating resource to the tasks being undertaken. Thank you sincerely for your efforts in documenting to share your love/work. Hats off to you sir.
Absolute awesome video from me,.. so glad you decided to keep the original engine to the frame,. Surely the rebuild will be more worthy in original state as engine plus chassis,..once again excellent video from me, take care,..
Thanks!
Nice one Ty, you make me think that I could rebuild a Honda CB750 engine, you make it look soooo easy. Great video man. 😎👍👍👍🇬🇧
You can do it!
Love your channel and all your hard work and effort you put into this videos and I discovered you from Ronald fingers fingerprint workshop
Very good video/info on top end rebuild. Thx, new subscriber.
I've used Easy-Off Oven cleaner (it is carbon after all) on piston faces and valve bowls, then a parts washer.
Great video, One thing I'm sure you do anyway is I spend at least half an hour on each cylinder scrubbing after the honing process as that fine stone and metal paste sits in the honed cross-hatch and takes alot of work to get out, I use paper towel and lacquer thinner until after a wet scrub the towel comes out white with no signs of grey, without doing this engine life is severely shortened, I have race motors going around that I built in the 90s smoke free with great compression.
This is very helpful since I'm planning to eventually do a top end rebuild on my 78 CB750K!👌🏽
Go for it!
Well done Taylor, you've saved another engine and it was good to see what was wrong with it, the video made good content .....👍🏴🇬🇧
Thanks
Was wondering why no assembly lube on install?
Well done.
Really like your videos. Very informative. thanks and very much appreciate it.
Thanks for watching!
Nice video once again. I have always tought that you hone the cylinders to have something in the cylinder walls where the oil would stick better
Great job man, but, I would add i always clean out the ring grooves on the pistons with a piece of old piston ring in case there is slight carbon build up under the rings. Here in the UK we call the top ring with the chamfer a ridge dodger , It's there in case you have a slight lip on a bore to stop the ring hitting it (Which you probably know already )
Great job and the video surely will assist with my head removal
great episode Taylor
Thanks
Awesome vid man! Wish we could have seen the vid of it getting pulled and what you did for that. Good job on stressing the head bolt removal and installation process. Could have used a little lube for the cams and pistons, but when I saw you adding oil at the end, definitely shows you know what's up. Keep up the good work!
Yes. I picked that up too.
very interesting video. It seems so easy watching you do it. Can't wait for the next one. Hi.
Thanks for watching
I have 3 CB750's and a CB550, all of which I would consider yard bikes with extensive exposure and neglect, but, I am hopeful I can get one or two of them running. You have the most comprehensive classic bike repair channel I have ever seen on TH-cam, thank you for publishing these videos. BTW, where is the vid of this engine running?
fantastic vid. I put a big bore/big cam kit on my Grom clone a few months ago and it was nice seeing it's pretty much the same process for this give or take 3 cylinders 😂
Excellent, loads of respect and support Rodge David Kidderminster UK
Wow...beautifully done..
Hi friend, thanks for the video, I need to do this job to a cb550f, now I'm not in a panic,
550s are even easier because you can do it in the frame.
Excellent video.
Nice work as always
Appreciate that
Created one of these engine rebuild video series myself... it took me a while to setup cams, etc ... so I really appreciate the fresh content Taylor. Hope all is well.
The sonic cleaner (that I purchased after seeing yours) did wonders for my pistons... 50% simple green, 50% water. I noticed you didn't add Hondabond on the pucks?
Great work!
Thanks!
Thanks very much Taylor. Very good informative video. I learned a lot. It won't be as intimidating as it would have been. As you say, slow and methodical is the key. Cheers, 👍🇨🇦
Glad it was helpful!
You can score the bore if you have gaps front and rear, not over the gudgeon pin either or you could theoretically snap the end off.
dry ice blasting is the go, tho in a moulding shop we used powdered cork blasting
Excellent. Great video. Enjoyed it.
Many thanks!
Excellent video. I may have to do all this to my K6 one day. Also, I noticed I've got the same boxer t-shirt that you're wearing. So I'll remember to wear that when I do the work....for good luck 😌👍
cheers for the vid
Top vid matey!
Excellent job..learned a lot..tks
I have to do the same to an 85 650 Nighthawk, first I have to get two other bikes finished, might not get to the Nighthawk until spring now. Winter is here.
Good job. Outstanding. Installing the pistons is the part I hate. I set no. 2 and 3 in the up position and install those in the cylinder first then rotate to even (also allowing the cylinder to drop with the center pistons} and then install the outside pistons no. 1 and 4. I don't have your finesse.
Great videos keep the good work 👍
Thanks, will do!
Great video as always but, damn, I get huge workshop envy :-)
Nice work Tyler 👍
Thanks 👍
I'd use two rectangular magnets that cover both the cam and the cylinder head on either side of the camshaft to keep the cam from spinning while you're trying to rotate the cam sprocket.
Super video muy educativo me encanto!!!!!
Good video. Thanks for making it. CanI suggest next time add a comment on how to test now well the valves are sealing. Such as using a flash light to see a gap. Or gasoline/kerosine in the valve to look for drips. Not that hard to lap the valves since you are in there.
CB750 problem SOLVED! ....Convert it to electric. haha
Love the video, brother. You know your stuff and always a pleasure seeing good dudes wrenching.
This brought back very old memories. The only thing I'd have done differently is pack old socks/underwear/t-shirts into the barrel holes under the pistons before trying to take rings off; I'd put them there anyway just to stop things getting into the motor. As noted, rings are brittle; the last thing you want is to have to tear down the motor because a piece of piston ring disappeared into the belly of the beast. Many, many years ago, a pal with a 69 CB750 bought a new Yoshi cam complete with new cam supports and a full gasket kit. Missing from the kit were O rings for the oil lines to the head so he went to a local parts store and bought O rings. They were too big and squished when the head was torqued down, significantly reducing the oil ways. About a mile down the road on the rebuilt motor, the new camshaft seized. Very sad.
Great job on the video and the rebuild .. I have experience with that myself.. The only part I didn't understand is why you separated the cam sprocket from the shaft. But I watched the whole video and it is very good....not easy to do that. You are helping a lot of people to do it right.
the answer is obvious to rotate it and set chain timing correctly.
Top job mate
Thanks