Author Topic: 1973 CB350F "Modest Original" build (Read 102116 times)

iiAtlas · « **Reply #125 on:** February 10, 2016, 01:52:18 PM »

All -

Found this on the engine and thought it was worth noting. There is a very strange "gap" here between the two and three cylinder intakes.

It looks almost like a cutout. I shined a light in and could not see it come out anywhere in the cylinders, so I don't think its a crack. Is this a casting mark?

Just thought I'd share, was surprised when I saw it.

grcamna2 · « **Reply #126 on:** February 10, 2016, 03:42:53 PM »

I believe those are casting 'cutouts'(if that's the correct word..

)which serve as kind of drains for when water gets on top of your cylinder head.. I think

sbeckman7 · « **Reply #127 on:** February 10, 2016, 05:34:40 PM »

Yep mine has them too, nothing to worry about

iiAtlas · « **Reply #128 on:** February 11, 2016, 10:09:00 AM »

Quote from: sbeckman7 on February 10, 2016, 05:34:40 PM

Yep mine has them too, nothing to worry about

Quote from: grcamna2 on February 10, 2016, 03:42:53 PM

I believe those are casting 'cutouts'(if that's the correct word.. )which serve as kind of drains for when water gets on top of your cylinder head.. I think

Phew!

Piston work tonight. First, pictures of the sides as you all requested. This is pre-cleaning attempt.

1(a)

1(b)

2(a)

2(b)

3(a)

3(b)

4(a)

4(b)

As you can see, the most notable signs of blow by are on pistons 2 (side b) and 3 (side b). To my eye, the walls looks relatively good. Next up I decided to start trying to remove some of that gunk off the piston heads. I did a 20 minute soak in the chem-dip and then went at it with a disk similar to the one below.

1

2

3

4

They certainly are shinier than they were...someone with more knowledge will need to tell me if I a) ruined these, or b) did an okay job. Either are totally possible. I decided removing the gunk HAD to be better than leaving it on there. Did I go too far? Did I ruin these four pistons? I wasn't able to get at the right angle to remove the gunk in the valve clearance cut outs on the piston. With a Dremel I should be able too but didn't want to go much further than I already have.

One thing I did ruin, the rings on #2

I attempted to measure them but I think I may have done a horrible job. I took my feeler guages and went around the top of each ring seeing which would fit in. Factory said .006". For the most part this was true. Sometimes only a .004" would fit. On one or two occasions I was able to fit .008". Is the factory spec of .006 a max or does it hold true both ways? Is being able to fit only a .004 in some locations a bad thing? I also may have been wielding the tool incorrectly. I will have to redo all of these measurements, but thought I'd share to gather some more info.

sbeckman7 · « **Reply #129 on:** February 11, 2016, 10:19:00 AM »

Hmm I hope you didn't remove too much material from the tops! At least they look clean

iiAtlas · « **Reply #130 on:** February 11, 2016, 10:25:09 AM »

Quote from: sbeckman7 on February 11, 2016, 10:19:00 AM

Hmm I hope you didn't remove too much material from the tops! At least they look clean

I do too..."At least they look clean

" was my attitude at the time. I'm ready to be schooled by the much more educated members here on the forums...bracing for impact...

grcamna2 · « **Reply #131 on:** February 11, 2016, 10:57:06 AM »

I use a small,sharp flat blade screwdriver on the tops of the pistons and spend a good amount of time carefully scraping away at the carbon but try not to remove any metal as that will lower your compression ratio or alter the efficiency of your squish area which can affect how the engine builds power.The 'long,slow' process of cleaning them works Best.

I recommend carefully scraping off the heavy stuff next time and then soaking them in some strong carb. cleaner to soften the stuff up so you can easily scrape away the last bit of it w/ a very dull safety razor(my preferred way..)and just keep away from doing any scraping on the lower/bottom piston skirts.I've also used #0000 steel wool very lightly on those lower skirts to gently smooth them w/o removing metal. That's the 'challenge'

when cleaning pistons.

iiAtlas · « **Reply #132 on:** February 11, 2016, 01:03:40 PM »

Quote from: grcamna2 on February 11, 2016, 10:57:06 AM

I use a small,sharp flat blade screwdriver on the tops of the pistons and spend a good amount of time carefully scraping away at the carbon but try not to remove any metal as that will lower your compression ratio or alter the efficiency of your squish area which can affect how the engine builds power.The 'long,slow' process of cleaning them works Best.
I recommend carefully scraping off the heavy stuff next time and then soaking them in some strong carb. cleaner to soften the stuff up so you can easily scrape away the last bit of it w/ a very dull safety razor(my preferred way..)and just keep away from doing any scraping on the lower/bottom piston skirts.I've also used #0000 steel wool very lightly on those lower skirts to gently smooth them w/o removing metal. That's the 'challenge' when cleaning pistons.

D'oh. This was my most heavy handed approach thus far. I think it was because I didn't really know what was under there or what to expect! Live and learn. I'll be more careful with the valves. I don't think I took away much metal but of course who knows. What should be my next steps for cleaning these Pistons? Should I attempt to polish put the scratches? Thanks for the input grcamna.

grcamna2 · « **Reply #133 on:** February 11, 2016, 02:27:12 PM »

iiAtlas,
I'd just carefully finish scraping/cleaning the rest off the domes on them until you can see the same aluminum on all 4 of them and then compare how the shapes of the domes look between them.. hopefully you can sort of shape/clean/polish the domes on all 4 pistons(make sure you remember which # cylinders they orig. came from along w/ the ringsets) until they all match the one that has the most metal removed from that dome.I don't think you've done that much harm.When you run it for a while the carbon will fill those areas back up anyway.

iiAtlas · « **Reply #134 on:** February 11, 2016, 02:29:06 PM »

Quote from: grcamna2 on February 11, 2016, 02:27:12 PM

iiAtlas,
I'd just carefully finish scraping/cleaning the rest off the domes on them until you can see the same aluminum on all 4 of them and then compare how the shapes of the domes look between them.. hopefully you can sort of shape/clean/polish the domes on all 4 pistons(make sure you remember which # cylinders they orig. came from along w/ the ringsets) until they all match the one that has the most metal removed from that dome.I don't think you've done that much harm.When you run it for a while the carbon will fill those areas back up anyway.

Thanks, slow and steady this time. I've got a long night ahead of me...appreciate the help.

grcamna2 · « **Reply #135 on:** February 11, 2016, 02:38:53 PM »

The other areas to be very careful with are the ring 'lands'/grooves in the pistons.I would soak the pistons and rings in strong carb. cleaner for a good wile to soften up all the carbon in the ring grooves and on the rings.I use an old piston ring to clean out those ring grooves very slowly and carefully.I take an old piston ring and break it in half then use a bench grinder and slowly grind the broken end until it is fully squared and still sharp on the tip(but not on the flat sides,you don't want to remove Any metal from inside those piston ring grooves)and use that old piston ring to slowly remove carbon until you see an even band of aluminum.Soaking the piston in strong aluminum cleaner/carb.cleaner/solvent really makes short work out of this task.

Did you have your cylinders and pistons checked for proper clearance yet(sorry haven't been following all the way through your thread)so you're sure everything is 'tight' to spec. on the fit ?

iiAtlas · « **Reply #136 on:** February 11, 2016, 03:09:07 PM »

Quote from: grcamna2 on February 11, 2016, 02:38:53 PM

The other areas to be very careful with are the ring 'lands'/grooves in the pistons.I would soak the pistons and rings in strong carb. cleaner for a good wile to soften up all the carbon in the ring grooves and on the rings.I use an old piston ring to clean out those ring grooves very slowly and carefully.I take an old piston ring and break it in half then use a bench grinder and slowly grind the broken end until it is fully squared and still sharp on the tip(but not on the flat sides,you don't want to remove Any metal from inside those piston ring grooves)and use that old piston ring to slowly remove carbon until you see an even band of aluminum.Soaking the piston in strong aluminum cleaner/carb.cleaner/solvent really makes short work out of this task.
Did you have your cylinders and pistons checked for proper clearance yet(sorry haven't been following all the way through your thread)so you're sure everything is 'tight' to spec. on the fit ?

I knew the walls and piston ring areas were sensitive so I made sure to keep clear of them, thankfully. I've just broken the ring on #2 so that can be the one I sharpen

I'll do another batch of soaking in the Chem-dip that seemed to help loosen.

I have yet to measure the clearance while in the cylinder. I suppose I should do that before going much further.

grcamna2 · « **Reply #137 on:** February 11, 2016, 03:35:20 PM »

Do you have an inside(I have calipers but that isn't enough to go down inside) micrometer? it might be best to take the cylinders to a machine shop that cares to measure the pistons/cylinders after you've cleaned them.

iiAtlas · « **Reply #138 on:** February 11, 2016, 04:18:12 PM »

Quote from: grcamna2 on February 11, 2016, 03:35:20 PM

Do you have an inside(I have calipers but that isn't enough to go down inside) micrometer? it might be best to take the cylinders to a machine shop that cares to measure the pistons/cylinders after you've cleaned them.

Have a set of exterior mics but no interior. Will order some off eBay. Tough to find an able and willing machine shop here in NYC :/ all the more reason I try to do this work myself.

I've scrapped the piston heads to the point I'd consider them "done" now. Wouldn't want to remove any more material. I'd like to give the ring groove cleaning a try but I'm worried about removing material.

grcamna2 · « **Reply #139 on:** February 11, 2016, 05:01:16 PM »

Soak those 4 pistons in a strong solution for the recommended time and those carbon deposits will come right off w/ that piece of broken piston ring and a light scraping motion,it won't hurt them.

sbeckman7 · « **Reply #140 on:** February 11, 2016, 09:27:07 PM »

For what it's worth, I had tremendous success de-gunking my V12 pistons with a standard utility razor (the kind that are sold in packs)

Before the razor, rag, and brake cleaner:

And after

grcamna2 · « **Reply #141 on:** February 11, 2016, 09:57:49 PM »

Nice

That's quite a dished piston;what type of high performance engine is that,a Jag ?

sbeckman7 · « **Reply #142 on:** February 12, 2016, 12:09:59 AM »

Quote from: grcamna2 on February 11, 2016, 09:57:49 PM

Nice That's quite a dished piston;what type of high performance engine is that,a Jag ?

It looks much higher performance than it actually is

8.8:1 It's BMW M70B50, 5 liter V12. Had about 300hp/tq in 1988, hopefully a bit more soon

But I digress... Sorry iiAtlas!

iiAtlas · « **Reply #143 on:** February 12, 2016, 06:32:03 AM »

Quote from: sbeckman7 on February 11, 2016, 09:27:07 PM

For what it's worth, I had tremendous success de-gunking my V12 pistons with a standard utility razor (the kind that are sold in packs)

Before the razor, rag, and brake cleaner:

And after

Wow, now THAT is an awesome job! I feel slightly embarrassed about my approach

this is my first batch of pistons so I really didn't know what to expect or if they were even salvageable. Now I realize it was just carbon build up and an approach similar to that of my carbs would've been beneficial. Live and learn I suppose! And I thought four was bad...try 12!

sbeckman7 · « **Reply #144 on:** February 12, 2016, 10:08:30 AM »

I'll admit 12 was a lesson in patience I am not eager to repeat! It was about 30 minutes per piston.. Live and learn indeed!

iiAtlas · « **Reply #145 on:** February 15, 2016, 06:43:35 PM »

Valve time! Before I dive in I thought I'd get some opinions on strategy. My current plan is to plug the spark plug wholes (probably with the old spark plugs themselves) and pour chem-dip in the entire seats (circled below).

I'll let it sit for about an hour then go at it with a razor blade, and only a razor blade. This sounds pretty good to me. Now some questions...

Valve springs in or out? Is there anything back there I wouldn't want to get chem-dip on? Would it be better to soak the valves individually out of the body?
Any tools I can use other than chem-dip and a razor blade?

That should do it! Still hunting for a source on OEM CB350F piston rings, no luck so far. Going to order a smaller ring compressor tool so that I can put the pistons back in the block and do some measurements. Looking forward to inching this along!

seanbarney41 · « **Reply #146 on:** February 15, 2016, 07:03:52 PM »

Razor blade is not gonna work because there are no flat surfaces involved. Red scotchbrite soaked in acetone makes for reasonably quick work of this...brass brush is good to have here too...but it has got to be BRASS, no steel bristles...

iiAtlas · « **Reply #147 on:** February 15, 2016, 07:05:55 PM »

Quote from: seanbarney41 on February 15, 2016, 07:03:52 PM

Razor blade is not gonna work because there are no flat surfaces involved. Red scotchbrite soaked in acetone makes for reasonably quick work of this...brass brush is good to have here too...but it has got to be BRASS, no steel bristles...

Saving me time already! Earlier in this project I naively thought GREEN scotchbrite was the lightest...WRONG!

Will pick up some of the red variety. Thanks for the tips.

grcamna2 · « **Reply #148 on:** February 15, 2016, 07:34:44 PM »

Quote from: seanbarney41 on February 15, 2016, 07:03:52 PM

Razor blade is not gonna work because there are no flat surfaces involved. Red scotchbrite soaked in acetone makes for reasonably quick work of this...brass brush is good to have here too...but it has got to be BRASS, no steel bristles...

+1 I also like to use 'Berkebile 2+2 instant gum cutter' which is good and strong too;wear skin and eye protection !

seanbarney41 · « **Reply #149 on:** February 15, 2016, 07:37:52 PM »

Quote from: iiAtlas on February 15, 2016, 07:05:55 PM

Quote from: seanbarney41 on February 15, 2016, 07:03:52 PM
Razor blade is not gonna work because there are no flat surfaces involved. Red scotchbrite soaked in acetone makes for reasonably quick work of this...brass brush is good to have here too...but it has got to be BRASS, no steel bristles...

Saving me time already! Earlier in this project I naively thought GREEN scotchbrite was the lightest...WRONG! Will pick up some of the red variety. Thanks for the tips.

There probably is even finer than red, the acetone keeps the scratching down and dissolves the carbon and varnish...red seems to be ok for just about everything so I keep lots around

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Author Topic: 1973 CB350F "Modest Original" build (Read 102116 times)