Author Topic: brandEn's leak free top end thread = Tips, Tricks and Suggestion encouraged  (Read 64586 times)

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Offline Nuffsa Fugginnuff

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This site is an excellent source of 'stuff'. Especially when one is on the process of a project bike. Gone so far as to buy the My CB750 Book by Mark Paris.
Alcohol & explosives, the key to a lasting relationship.

Offline DWS

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78CB750F3
PD 42A with original breadbox
4 into 1
valves adjusted to .003 (intake and exhaust) ( as was suggested for cooling )
slow jets#35 Main #110
 turned out to 1.5 some paper work says 1.75
4800 feet altitude

78 Honda CB 750 F3 Restoring now(Almost done)
BSA MX 50 Next
BSA b50T Parts

Offline edwardmorris

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Adding this here as it's relevant and sorta critical info about the dpwel pins for the top end and wrong parts diagrams

Beware, for a 750 engine the 12 x 22 pin is incorrect.  The parts manuals say 12 x 22 but they would be too long not allowing the head to be flat on the cylinder.  What was actually used is part number 94301-12180, 12 x 18.  Every engine I have had apart (at least five) had the 12 x 18 pins.

Offline PeWe

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My engine had the 22mm dowels between case and cylinder.
I see that Yamiya750 must have mixed up case-cylinder with cylinder-head.  The other way will work in my engine (K6) I think it had 12x18mm cylinder-head earlier. I have 15mm now.

12x15mm
http://www.yamiya750.com/index.php?main_page=product_info&cPath=246_21_249_54&products_id=1715

12x22mm
http://www.yamiya750.com/index.php?main_page=product_info&cPath=246_21_249_54&products_id=1716
CB750 K6-76  970cc (Earlier 1005cc JMR Billet block on the shelf waiting for a comeback)
CB750 K2-75 Parts assembled to a stock K2

Updates of the CB750 K6 -1976
http://forums.sohc4.net/index.php/topic,180468.msg2092136.html#msg2092136
The billet block build thread
http://forums.sohc4.net/index.php/topic,49438.msg1863571.html#msg1863571
CB750 K2 -1975  build thread
http://forums.sohc4.net/index.php/topic,168243.msg1948381.html#msg1948381
K2 engine build thread. For a complete CB750 -75
http://forums.sohc4.net/index.php/topic,180088.msg2088008.html#msg2088008
Carb jetting, a long story Mikuni TMR32
http://forums.sohc4.net/index.php/topic,179479.msg2104967.html#msg2104967

Offline 01Thomas

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Bump so I can find this thread again
1971 Honda CB750 Four K1 [Engine: CB750E-1113521 / Frame: CB750-1113838]
1977 Seeley Honda CB750F (F1) [Engine: CB750E-2551214 / Frame No: SH7-655F]

'96 Yamaha YZF750SP & '81 Moto Guzzi SP1000 & '80 Moto Guzzi 850 LeMans II & '82 Bimota KB-3 [Frame No 49] & '66 Ducati 50 SL/1 & '53 Miele K-50 & '38 Miele 98

Offline MCRider

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Bump so I can find this thread again
You can save the thread as a favorite place. That's what I do, using a folder aptly named.

PS this is a good one to save.   :D
Ride Safe:
Ron
1988 NT650 HawkGT;  1978 CB400 Hawk;  1975 CB750F -Free Bird; 1968 CB77 Super Hawk -Ticker;  Phaedrus 1972 CB750K2- Build Thread
"Sometimes the light's all shining on me, other times I can barely see, lately it appears to me, what a long, strange trip its been."

Offline 01Thomas

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Thanks good idea but that'll only work until ones' PC bombs out and one gets a new one and then the favourites are all gone with it.

Bump so I can find this thread again
You can save the thread as a favorite place. That's what I do, using a folder aptly named.

PS this is a good one to save.   :D
1971 Honda CB750 Four K1 [Engine: CB750E-1113521 / Frame: CB750-1113838]
1977 Seeley Honda CB750F (F1) [Engine: CB750E-2551214 / Frame No: SH7-655F]

'96 Yamaha YZF750SP & '81 Moto Guzzi SP1000 & '80 Moto Guzzi 850 LeMans II & '82 Bimota KB-3 [Frame No 49] & '66 Ducati 50 SL/1 & '53 Miele K-50 & '38 Miele 98

Offline oldhatt45

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01Thomas,

Your Favorites are only gone if you Don't back up things like your email, favorites, and personal documents.

Back up can be done by copying your favorites, etc. to a Flash Drive, the Cloud, etc.
There should never be a case where you lose everything.

That's just my 2 cents so please don't take offense.

Charlie

Offline flybox1

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Bummer...this is a thread has been totally derailed  >:(

'78 750K (F3 engine) PD42b's, Modified airbox w/K&N  filter, 40/110 jets, 1 needle shim, IMS@ 1 turn out. Kerker + Cone 18" QuietCore

Past Bikes
1974 550K0 (stock), 1973 CB350F (stock), 1983 Yamaha XS400K (POS)
77/78 cool 2 member #3
"Knowledge without mileage equals bullsh!t" - Henry Rollins

"This is my CB. There are many like it, but this one is mine…"

Offline oldhatt45

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I apologize.

Maybe we can get one of the moderators to remove the last few off topic posts.

Charlie

Offline lucky

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A few comments.

Good write up and good photos Branden.

Those part#3's are locating dowels not "knock pins".
And they will all need to be measured now on every engine, since 40 years have gone by.
The cylinder heads have been through a lot of rebuilds possibly. Height has to be checked or the cylinder head may not tighten down.
You need those locating pins.
You cannot get rid of all of them. They align the cylinder head with the cylinders.

If the locating dowels are too long you WILL have problems.

Never "grind" Honda Valves!! Period.
Just install new valves. It is not like old cars used to be.

You can re cut the seats though (if there is enough material left), after all of these years.

Offline AintNoEasyWay

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I made some shims out of tongue depressors. BRILLIANT! Made installing the cylinders easy.


BrandEn, thanks again for such documentation. I've been using it all to get my top end rebuild finished. I'd like to use your method for installing the cylinders onto the piiston, & I'm wondering what you did for the clamps you used as compressors for the rings.

What size clamps do you recommend? What method did you use to keep the rings compressed as you put the cylinders on & then remove the clamps? Does the fastener on the clamp make it difficult?

Offline MCRider

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Some of my observations using hose clamps. USe the size that is closest to the size of your piston. This keeps the clamp as round as possible, so compresses the rings evenly.

Don't put the buckle of the clamp over a ring end gap. the gap wont close and may hangup when you drop the cyls.

Tighten the clamp slowly making sure it pushes the rings into the grooves. Then back it off just enough that you can rotate it with the rings. Just a tad. You'll want the cyls to push the clamp down the skirt of the piston, rings going into the cyl. When the cyls are first resting on the clamps, squirt some oil onto the cyl walls where the rings are, to help the cyls drop down.
Ride Safe:
Ron
1988 NT650 HawkGT;  1978 CB400 Hawk;  1975 CB750F -Free Bird; 1968 CB77 Super Hawk -Ticker;  Phaedrus 1972 CB750K2- Build Thread
"Sometimes the light's all shining on me, other times I can barely see, lately it appears to me, what a long, strange trip its been."

Offline flybox1

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...to add to what MC was advising, also position your clamp screws in an accessible manner. 
I had to stop and rotate a few once my cyls were on....
I used a 15-20mm wide strip of .5mm sheet plastic kitchen cutting board around the rings underneath the clamps. 
this made sliding the clamps downward quite easy, and ring ends did not catch anywhere on the clamp cutout holes.
'78 750K (F3 engine) PD42b's, Modified airbox w/K&N  filter, 40/110 jets, 1 needle shim, IMS@ 1 turn out. Kerker + Cone 18" QuietCore

Past Bikes
1974 550K0 (stock), 1973 CB350F (stock), 1983 Yamaha XS400K (POS)
77/78 cool 2 member #3
"Knowledge without mileage equals bullsh!t" - Henry Rollins

"This is my CB. There are many like it, but this one is mine…"

Offline edwardmorris

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Just FYI, the OE ring compressor tools are still available for around $50 shipped from partzilla. Well worth the investment even if its just rebuilding one motor. They'll sell themselves when you're done.

Offline brandEn

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Those last 3 posts are all GREAT advice

Offline AintNoEasyWay

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Agreed. Thanks guys & thanks again brandEn!

Offline AintNoEasyWay

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...to add to what MC was advising, also position your clamp screws in an accessible manner. 
I had to stop and rotate a few once my cyls were on....
I used a 15-20mm wide strip of .5mm sheet plastic kitchen cutting board around the rings underneath the clamps. 
this made sliding the clamps downward quite easy, and ring ends did not catch anywhere on the clamp cutout holes.

Is there some sort of plastic that fits over cutting boards that you're referring to, flybox1? Not sure if I've seen it around before.

Offline evanphi

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ALSO smooth out the inside of the hose clamp bands with some sand paper to make sure no gouges are put in the rings.
--Evan

1975 CB750K "Rhonda"
Delkevic Stainless 4-1 Header, Cone Engineering 18" Quiet Core Reverse Cone, K&N Filter in Drilled Airbox
K5 Crankcase/Frame, K4 Head and Cylinders, K1 Carbs (42;120;1 Turn)

She's a mix-matched (former) basket case, but she's mine.

CB750 Shop Manual (all years), searchable text PDF
Calculating the correct input circumference for digital speedometers connected to the original speedometer drive

Offline flybox1

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...to add to what MC was advising, also position your clamp screws in an accessible manner. 
I had to stop and rotate a few once my cyls were on....
I used a 15-20mm wide strip of .5mm sheet plastic kitchen cutting board around the rings underneath the clamps. 
this made sliding the clamps downward quite easy, and ring ends did not catch anywhere on the clamp cutout holes.

Is there some sort of plastic that fits over cutting boards that you're referring to, flybox1? Not sure if I've seen it around before.
I just grabbed what I had in the house.  Any thin flexible plastic will do. 
Cut a ring out of the lid of a rattle can, tennis ball can, the flat of a 2litre soda bottle....etc   ;)

If you go the clamp route, set your upper edge of the clamp right on top of the upper ring. no big overlap here.
When you set your cylinders down on the pistons, it will take very little downward movement to get the first ring in the bore, and you're off.....  Do #2&3 first....then 1&4
« Last Edit: May 28, 2015, 10:20:07 AM by flybox1 »
'78 750K (F3 engine) PD42b's, Modified airbox w/K&N  filter, 40/110 jets, 1 needle shim, IMS@ 1 turn out. Kerker + Cone 18" QuietCore

Past Bikes
1974 550K0 (stock), 1973 CB350F (stock), 1983 Yamaha XS400K (POS)
77/78 cool 2 member #3
"Knowledge without mileage equals bullsh!t" - Henry Rollins

"This is my CB. There are many like it, but this one is mine…"

Offline MCRider

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The Flybox idea of plastic sleeve is great! I never liked the feel of the steel clamp against the steel rings.

But, it does work as well, without the plastic.
Ride Safe:
Ron
1988 NT650 HawkGT;  1978 CB400 Hawk;  1975 CB750F -Free Bird; 1968 CB77 Super Hawk -Ticker;  Phaedrus 1972 CB750K2- Build Thread
"Sometimes the light's all shining on me, other times I can barely see, lately it appears to me, what a long, strange trip its been."

Offline koendd

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so, I'm close to finishing my engine build (F2).
But I have a question about the o-rings on the cylinder base.

you mention four smaller o-rings and two bigger.
I get the bigger ones go on the recessed area on the crankcase where the oil feeds up but what about the 4 smaller ones?

I don't see them in the parts fiche?



any idea what size they should be?
Cause I have some small ones that fit but the base gasket doesn't clear them...
1972 cb750K2 brat
1976 cb360
1984 GPZ900R

Offline bytio

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No 6, there are 4 of these but if you have the HD studs these are a bit fat, so I used slightly thinner ones,

Offline bytio

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These go on the studs that have the dome/acorn nuts on the F2, you will see on the bottom of the F2  cylinder the 3rd stud hole in from outside has a slight cut out for this o ring. No oil should come down this hole, it keeps dirt etc out the crankcase

Offline koendd

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aha, so I use four on the studs with dome nuts and 2 on the middle ones where oil feeds up, right?
1972 cb750K2 brat
1976 cb360
1984 GPZ900R