Topic: 1974 cb750 fun "Spruce Goose" (STEP 2: frame/suspension)

[mashfu]

That's some gravy you got on that valve.

Looks like you had enough meat on the bone for your cylinders, though.

Can't wait to get the others off, gonna have a feast- GRAVY FOR ALL! Might need to take some more meat off cylinder 3... still has a small edge that im hesitant about.

[calj737]

if you're honing the cylinders that much to remove the rust, then you probably need a re-bore, pistons and rings. Best to get a micrometer and measure everything up.

[mashfu]

Ya, ive been measuring all the cylinders and trying to keep the clearance between skirt and wall as small as i can. What ive been doing is measuring the skirt and setting a telescoping gauge to no more than .04mm from the skirt diameter. After ive set the gauge i place it through the cylinder at many different points rocking it back and forth. If the gauge is able to freely rotate between a positive and negative angle i know ive gone too far. Since i still have not been able to swing past 0 i assume im good.
I know this probably iant the best way of going about this, but im trying to stay away from reboring if i can. Its honestly looking like i will have to since the out of round is very questionable...

Newest development is i think i may need new exhaust valve guides. Being that i do not have a dial gauge to check clearance, just eye balling the wiggle they're no good.

[calj737]

Based upon the look of the valves, I'm not the least bit surprised your guides are shot. I'd do a very careful examination of both sides.

[edwardmorris]

You have your engine torn down fully, this is the time to get it right the first time. I'd recommend going with the first oversize anyway as the stock size will most likely have left the bores out of round (better explanation in Mark's book). Getting them bored out in parallel will yield you a much smoother engine. Same goes for the head, new guides and valves will give you better results. Now if you're planning to just flip it on ebay/craig's list, that's another story

[mashfu]

Yep Calj, definitely going to carefully check them all around. I was just surprised that the intake valve which had the worst of the gunk has no play whatsoever... Will take the rest of them off on the weekend.

Edward i fully agree on getting it right the first time, i knew in the back of my head the cylinders were developing into a problem; guess i just wanted to delay thinking about them. First 750, therefore this will be mine and MINE ALONE, probably will have more projects to come so until then, no flipping. My plan so far is to get a std spare and rebore this one.

[calj737]

I wonder if the lack of "play" is due to accumulated gunk? Are you absolutely certain they're fully cleaned? The stocks weren't renowned for their longevity or durability to corrosive conditions.

[mashfu]

Sprayed the guides with compressed air/denatured alcohol then some wd40 and let the valves soak in chemdip before i went at them. Checked them both after this. Both valve stems are fine in the intake guide as opposed to when they are in the exhaust guide.

[mashfu]

So after some tapping and accidental fumbles, i managed to get the exhaust valve guide out. The driver slipped a few times and i scratched the housing, shouldnt be too bad?

[mashfu]

Been super busy with work recently, so ordering parts and reading Hondaman's book was all i could do... Found an awesome deal on a cylinder+piston but the seller is taking their sweet time on shipping them. Was really hoping to get everything assembled this weekend but i guess it will have to wait.

Did manage to get some stuff done today, cleaned the countershaft up and the oil pump. Spent way too long getting those evil clips off of the countershaft but after deciding i dont need to reuse them, i just bent the hell out of them and carried on. Pretty happy with how they turned out!

Happy Turkey day everybody!

[70CB750]

Yeah, the clips can be a pain.  I had a pair of old ring pliers and ground them to match the profile of the clip - it is kind of squarish.   It worked much better than anything else I tried.

[mashfu]

Haha i know i need to get myself a pair of either clip pliers or ring pliers when i put them back on! For now a needle-nose actually does a dang good job, as long as the clip is exposed, which when each gear is taken off in order works out just fine. When checking out how to take off the bearings on the mainshaft, i saw a post on using M5 to help get leverage for a puller. The bearing came right off! For the next bearing on the mainshaft, i followed Hondaman's instructions and just used a hammer to tap it off. Next up is ordering all of the bearings, gotta think of a way to re-purpose these old ones into something cool!

Pretty excited, the cylinders and pistons came in today and they look awesome! definitely going to go over them a lot more in detail tomorrow, as well as give them a nice hone. Oh ya also got the clutch from a different seller (i dont know what the f*%k this guy sent me but it isnt what i ordered) hahaha fun stuff. I am all ears if anyone knows what this clutch goes on. Hopefully he just mixed up the orders and another person will be looking at my clutch...

[mashfu]

And here is the clutch, off of a "1975/1976 cb750f" i believe it is an xs1's clutch hopefully he just mixed up orders.

[BPellerine]

did you drive the guide out cold?marks on the gude bore can cause oil to leak down if gouged.bill

[mashfu]

Thanks bill, I did drive the guide out cold, just to clarify would an oil leak be caused from the bore of the actual valve guide or the bore for the valve guide to slip in?

[mashfu]

Honing done! Such a big difference with a good set of cylinders... Parts cleaner soup resting in the tub

[Zaipai]

Actually looks pretty good at least its a start.

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[Davez134]

Make sure your honing marks form a nice cross. Hard to tell from the angle of your pictures. It is important that the honing has a crosshatch like this



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[mashfu]

I tried getting an angle where the crosshatches showed but was unable to with the lighting. Your crosshatch pattern definitely looks like it has a wider angle than mine. Will go over them again with a faster in and out rate or slow down the rotation; all things considered, this was only about 15 seconds each cylinder!

Here's a closer picture, thanks Dave for the great comparison picture!

[BPellerine]

Thanks bill, I did drive the guide out cold, just to clarify would an oil leak be caused from the bore of the actual valve guide or the bore for the valve guide to slip in?

it would be from marks in the guide hole in the head.billp

[Davez134]

I tried getting an angle where the crosshatches showed but was unable to with the lighting. Your crosshatch pattern definitely looks like it has a wider angle than mine. Will go over them again with a faster in and out rate or slow down the rotation; all things considered, this was only about 15 seconds each cylinder!

Here's a closer picture, thanks Dave for the great comparison picture!

Yeah, faster with the hone. Just make sure not to remove to much material. I use a flex home and takes about 5 ish passes up and down to get a good patten. Any scrap ones you can practice on?

[mashfu]

@Bill would getting oversize valveguides be a solution to this or would std size be alright if the marks are mainly clustered closer to the port rather than the top of the head? 

@Dave yep i actually have a set that has massive pitting that i've been using to practice on. Planning to bore it out eventually, but for now it is the guinea pig.

[BPellerine]

hard for me to say without seeing,but an oversize guide would work but have to make sure the clearance is right.might be ok as is too,best to heat head to drive the guides out,and clean carbon from port side before so no scratches when they come out.bill

[mashfu]

just took some measurements along the bore, we'll say y is the axis along the marks and x is the axis along the untouched surface. Y-axis varied between 12mm and 12.05mm the later being where the scoring occurred. Along the x-axis i came up with 12.00mm as the largest diameter. Not sure if this will give any insight into the issue.

[mashfu]

Couldnt for the life of me get the clutch outer basket to come off the sprocket last night, so today i got some wood poles and tapped the suckers apart. With the basket nestled on my lap and the sprocket resting on the calves, after the sprocket fell through i was able to catch it with my calves. I used a 2" diameter followed by 1 3/8" because i saw in edmorris's thread what the two peices look like separated. Glad all these projects exist! Dont mind the white sweats, i like seeing how dirty they can get!