Author Topic: My first complete build 72 CB750 - completed for now... (Read 55897 times)

algophobe · « **Reply #325 on:** December 31, 2020, 02:06:29 PM »

Quote from: PeWe on December 30, 2020, 07:08:58 AM

Perfect book for living room. Read with clean fingers from page 1 and forward!
When done you'll get the feel for it.

I hate good technical books to be used in the garage with oily fingers covering important data.

I have also a reprint of CB750 shop manual.
https://www.ebay.co.uk/itm/Honda-Factory-Workshop-Shop-Manual-Book-CB750-750-4-SOHC-Reproduction-HWM003-/251652308622

the shop manual (digital form on my ipad) is what's i've been working off and the hard copy of the clymer manual (which leaves a lot of details out). what fun is it when i pay someone to do the work robbing me the opportunity of learning or falling flat on my face

but i'll leave the precision machining to the experts. so far i think i'll try my hand at de-shrouding the combustion chamber and cleaning up the intake and exhaust ports before i send it off to have new guides and valves placed by cycleX.

algophobe · « **Reply #326 on:** January 15, 2021, 06:46:07 PM »

got some work on the head. took work to clean off all the carbon from the exhaust ports. my main goal with the exhaust ports is to smooth it out as best i can, especially remove the casting lines and not necessarily widen the ports. what i do notice is that 1/4 ports are noticeably wider than 2/3. but it does look as if 2/3 are a little shorter. i sanded it with a die grinder using sanding mandrel with 80, then 100, 120 grits. then using the dremel with the abrasive buffing wheel to 180, 220, 320. For #$%*s and giggles i polished them with the course rouge. its no where near perfect but a learning opportunity and hopefully makes the exhaust flow a little easier.

i won't bore you with pics of every port, but here are some samples.

the valves took some beating, but they'll be sent out to be replaced at the end along with a new valve seats cut.

for the intake ports, i'll be grinding down the transition zones and deshrouding the combustion chamber but not go crazy like this.. going by the theory that the turbulence from the surface will help mix air and fuel better since its a carburated system. more to come.

algophobe · « **Reply #327 on:** January 26, 2021, 03:48:27 PM »

the combustion chambers were de-shrouded and sanded to 180 grit and on the in-take side, i opened up the passages a little from the carb boots to the port just above the intake valve. then the head and cylinders just got shipped to Cycle X for some work.

Terry in Australia · « **Reply #328 on:** January 26, 2021, 04:33:42 PM »

Looks good mate, and just smoothing the casting marks will improve the engine's performance, so worth your while.

algophobe · « **Reply #329 on:** March 19, 2021, 10:11:03 PM »

Finally the head and cylinders came back from CycleX! So peeerty. Blasted, cylinders bored and honed to 2+, new valves and guides and seats re-cut. New matching 2+ pistons from CycleX as well.. The shine from my home port job is gone from the sand blast.. but I'm ok with leaving it this way.

It's been a while since I've been back in the workshop. Excited for this weekend.

PeWe · « **Reply #330 on:** March 20, 2021, 02:51:16 AM »

It's so nice with refurbished clean parts that ensure functionality.
Fresh guides with valves cost some, but is the base for a well working engine.

Inlet ports work better with a harsher surface than a polished.
Something about how fuel and air mixes.
My last head, recently refurbished.

algophobe · « **Reply #331 on:** March 20, 2021, 09:40:33 AM »

Yes. I cut back the intake ports to make the transition wider but left all the castings and roughness alone. I see you had your's knife edged

PeWe · « **Reply #332 on:** March 20, 2021, 10:54:01 AM »

Yes, support the guides and maybe better for air flow compared to a naked round guide.

algophobe · « **Reply #333 on:** March 20, 2021, 11:32:57 AM »

So before putting her back together.. i want to replace the cam chain (part of the while you're in there to do's). I bought the endless EK chain and a few extra links to do this without having to spit the case. Anyone have any advice? Is it an easy thing to do? Would you trust it?

PeWe · « **Reply #334 on:** March 20, 2021, 02:11:11 PM »

I should open the cases and replace all chains. The stronger cam chain with rectangular side plates.
Primary chains, BMW Diesel engine late 1990's timing chain with 68 links. 2 of them.

Why rivet chain when you have engine out without cylinder?
When at it, new cush rubbers in the primary chain drive hub too.

algophobe · « **Reply #335 on:** March 20, 2021, 02:58:11 PM »

Quote from: PeWe on March 20, 2021, 02:11:11 PM

I should open the cases and replace all chains. The stronger cam chain with rectangular side plates.
Primary chains, BMW Diesel engine late 1990's timing chain with 68 links. 2 of them.

Why rivet chain when you have engine out without cylinder?
When at it, new cush rubbers in the primary chain drive hub too.

it's a bit of me being lazy i guess, I've had the case split apart at the beginning of this build about 5-6 years back. only put 600 miles until i had issues with compression, therefore went thru the trouble of taking the top end apart again. it was an oversight on my part in not changing all the chains at that time. but now, i'm in a situation where i have the bottom cases still intact with the cylinders off and only hoping to replace the cam chain by breaking it and slipping it through then reassembling the top end again. i've never broken apart these cam chains before and have the Motion Pro chain tool. but not sure how to best flare out the solid pins.

scunny · « **Reply #336 on:** March 20, 2021, 03:44:49 PM »

You may have the taper type joining link. you just press on the side plate with vice grips or similar.
That is what is in my 650 for the last 10 years. I was worried about the clip, so took it to the local morse chain experts, and they assured me that is the way to fit it, no peening over.

algophobe · « **Reply #337 on:** March 20, 2021, 06:14:26 PM »

Well that's good to know... I measured the thickness of the pin mid body and at the end and there appears to be no difference. I ended up using the chain riveter to flare it out a little bit even though it didn't have the hollow tip. not major peening over but it makes me feels a little more secure. The chains is still nice and laxed. It took me three tried without binding up the link.. thankfully I bought three extra Master links. Phew!

algophobe · « **Reply #338 on:** March 27, 2021, 04:56:00 PM »

Made some progress. With my limited experience, so far I've realized that my least favorit part of a build is putting the cylinders back on over the pistons. Especially those outside pistons and rings.. no great way to keep them stable after the center two are on. Got the head on as well and torqued down. have to order up some new dowel pins to place back on the cam towers. but I had a chance to modify the cam towers and added extra oil holes and widened the rocker arm oil holes as well according the Hondaman book.

algophobe · « **Reply #339 on:** April 18, 2021, 09:20:22 PM »

Managed to get a little time to finish putting in the cam and rockers. My little man visited me in the workshop and thought it was time to introduce him to the build.. you know "start em young"? He has pretty good motor skills for a 2 1/2 year old. But I turned by head for a second and he's already drop two ratty dowel pins that i've replace into the opening access to the spark plugs. fortunately he didn't put them into the channel for the cam chain... PHEW! lesson learned!

i decided to leave out the 8 small bolts that holds the rods for the rockers as suggested by Mark Paris's book, along with the additional holes for oil on the cam towers.

algophobe · « **Reply #340 on:** May 01, 2021, 08:08:13 PM »

With the engine nearly back together, I worked on the frame. Ended switching from the weldless frame kit to the Gordon frame kit as I noticed that the shop started making them again and had some available. it would solve my issues with remounting the key switch since I cut it too far forward. Mocked it up and started TIG welding it into place after tacking them together. I’ve just started TIG welding this year so its been a rough start. Kinda tricky with the solid inserts welding to the roughly 1.6 mm thickness stock tubings. I bought a basic Lincoln setup and welded using 95 amps with 0.3 pulse on 220 volts using 3/32 created tungsten and 3/32 rods.... a work in progress learning this stuff.

algophobe · « **Reply #341 on:** May 02, 2021, 07:14:24 PM »

So this happened...

I was testing fitting the center piece after welding the inserts in and before final welding of the inserts to the main frame portion. bolt it down and hit resistance and now can't be backed out. not even with a little impact hammer. the heat may have shrunken the center piece a little bit also distorting the threads. the top half of the insert is straight (threadless holes) and the bottom half is threaded (which was welded circumferentially yesterday). if that wasn't bad enough a second bolt that was put in smoothly now won't back out either. i should have lubed it or re-tapped it before screwing it down or something. trying to figure ways to salvage this. at little heat torch? lube? just cut it off and drill it out?

algophobe · « **Reply #342 on:** May 16, 2021, 08:04:52 PM »

I managed to get the bolts off by cutting the head which allowed me to remove the center piece of frame insert off the frame.. then welded the nub of screw to a long 1 inch square bar and twist it off.. the welding heated the threads enough to make it easier to come off. With the other stuck screw which was flat to the surface, I drilled the center out of it and tapped it to recreate the threads. Then grinded down the welds and then painted. Alot more work than I had bargained for but I'm happy with the result.

Terry in Australia · « **Reply #343 on:** May 17, 2021, 02:56:15 AM »

Looks good mate, interesting re: the welded frame kit, I installed one years ago using a MIG and had no issues at all threading the bolts in or out? But there you go, you learn something new every day.

BenelliSEI · « **Reply #344 on:** May 17, 2021, 06:50:34 AM »

Lot of effort, but I agree; nicest installation. Very clean look..... Never used one, but that would be my first choice.

algophobe · « **Reply #345 on:** May 17, 2021, 07:44:15 AM »

Thank you. The problem with the threads may have been my welding technique.. as I am learning how to TIG, I may be applying too much heat distorting the threads. I lingered in one spot too long trying to fix my beads. The larger slug at the head of the frame didn't have same problem, I'm only guessing because it has more mass to distribute heat.

calj737 · « **Reply #346 on:** May 17, 2021, 02:19:12 PM »

Quote from: algophobe on May 02, 2021, 07:14:24 PM

So this happened... I was testing fitting the center piece after welding the inserts in and before final welding of the inserts to the main frame portion. bolt it down and hit resistance and now can't be backed out. not even with a little impact hammer. the heat may have shrunken the center piece a little bit also distorting the threads. the top half of the insert is straight (threadless holes) and the bottom half is threaded (which was welded circumferentially yesterday). if that wasn't bad enough a second bolt that was put in smoothly now won't back out either. i should have lubed it or re-tapped it before screwing it down or something. trying to figure ways to salvage this. at little heat torch? lube? just cut it off and drill it out?

Next time, place a piece of shim stock between the frame and welding lugs before welding. The heat of TIG welding will definitely pull the removable section. And if you do thread bolts in, coat them in anti-seize before welding. This will help prevent them from galling and allow them to screw out once everything cools off.

And next time, drop down to 1/16” or smaller filler. You’ll need less heat, leave less work afterwards, and have ample strength anyway.

algophobe · « **Reply #347 on:** May 24, 2021, 11:31:01 AM »

Quote from: calj737 on May 17, 2021, 02:19:12 PM

Quote from: algophobe on May 02, 2021, 07:14:24 PM
So this happened... I was testing fitting the center piece after welding the inserts in and before final welding of the inserts to the main frame portion. bolt it down and hit resistance and now can't be backed out. not even with a little impact hammer. the heat may have shrunken the center piece a little bit also distorting the threads. the top half of the insert is straight (threadless holes) and the bottom half is threaded (which was welded circumferentially yesterday). if that wasn't bad enough a second bolt that was put in smoothly now won't back out either. i should have lubed it or re-tapped it before screwing it down or something. trying to figure ways to salvage this. at little heat torch? lube? just cut it off and drill it out?
Next time, place a piece of shim stock between the frame and welding lugs before welding. The heat of TIG welding will definitely pull the removable section. And if you do thread bolts in, coat them in anti-seize before welding. This will help prevent them from galling and allow them to screw out once everything cools off.

And next time, drop down to 1/16” or smaller filler. You’ll need less heat, leave less work afterwards, and have ample strength anyway.

when you refer to a shim, are you talking about placing a thin ring to fill the gap like this? pardon the bad disproportionate drawing.

algophobe · « **Reply #348 on:** May 29, 2021, 04:41:33 PM »

Dropping the engine back in was a sinch with the frame kit installed. I decided to relocate the rectifier/regulator to another location with better air flow for cooling and simplifying the wiring coming from the stator. Decided to upgrade from the cheap white connectors to Apex versions bought from Revival.

algophobe · « **Reply #349 on:** May 31, 2021, 10:22:08 PM »

So this bike is gonna fight me every step of the way it seems. I’ve finished putting back the wiring. The oil system installed and I’ve kept the valve cover off to allow me to inspect the oil flow to the valve train. I fill the oil reservoir with 3 quarts and connect the starter directly to a 12V AGM extra battery and turn over the batter for 30 second bursts or so. No oil noted the the top. I disconnected the oil filter since it would be directly down stream from the oil pump and nothing comes out.

I’m curious if turning it over with a motorcycle battery alone would produce enough oil pressure to open the OIL LEAK STOPPER VALVE on the OIL PUMP. As long as the engine turns then there should be enough pressure right? When I first put the engine back together in the first round, I use a truck battery and it worked... not sure if that would make a whole world of difference.

I guess at this point I’ll have to empty the oil tank again and check the hoses and oil galleys. If that doesn’t work then I’ll have to check the oil pump.

Hopefully no critter has crawled in during the year that the engine was sitting still with the two oil hoses off and oil filter off.

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Author Topic: My first complete build 72 CB750 - completed for now... (Read 55897 times)