Topic: cylinder walls hosed? opinions please

[gtyler5]

I know now why the 750 F2 engine would not turn over  what a nasty mess, but with some "love" and a lot of pb blaster I got it apart. My questions is are these cylinders too far gone or will a hone job clean them up? I don't have much experience in this aspect so I am looking for opinions. I can not afford the F2 bore kits, so maybe it will become an F bottom with a K top?

[TwoTired]

I think you have to clean the bore, find and measure the deepest pit in the cylinder wall.  Then assume you have to hone or bore to the deepest pit.  Add that up to determine the bore dimension.  Then compare that to the cylinder bore wear limit.
That will tell you if you if you must go to the next overbore size with new pistons and rings.

[Whaleman]

You know my first thought was it would need an overbore but I believe TwoTired is correct. I would remove the cylinder and hone with a ball type hone to see what you have. What I find is that the rust is not even everywhere but can pit deeper right at the top of the top ring. 99.9% of the bore might hone fine except for deeper pits at the top of where each piston rested for the last 10 years. The ball hones can be borrowed for free from auto parts shops so you are not out any money to try. Dan

[1080]

I would split the block and inspect the rest of the motor.

[Old Scrambler]

New Sleeves?  Might be a lot cheaper.  I've been told that F2 barrels do not attach to K bottom cases.  I have a very similar looking block in my shed. Yes, inspect the bottom-end. At least pull the oil pan for a close look. Any sign of water marks is BAD.

[HedNut]

This is what mine looked like....(first pic)...not quite as rusty as yours...but same idea?
I cleaned it out as best possible, and ran a "3 stone" hone through it....carefully.  And all the little pits came out...and it was suprizingly still in spec!?  Crazy I know... I thought I would need a oversize for sure.... but giver' a try...you might be pleasently pleased.

[754]

Ummm, I think you need an oversize...

 Its not all about the high spots, if its pitted..

[MRieck]

Ummm, I think you need an oversize...

 Its not all about the high spots, if its pitted..

I agree. I have seen more than 10 cases of wormholes that go very deep into cast iron. Even an 836 will not clean it up. Ask McGrew....he will confirm this. This stuff does not possess supernatural powers.

[dave500]

id get it rebored for peace of mind.

[supersports400]

Hi,

The cast iron (that where these are made off) has an open structure, the quality of the casting depends on the process Honda used at that time. My experiences (on earlier liners used in the early twins) with cast cylinder liners are good, even if there are deep holes in it. These liners with deeper holes in it are tending to use a little oil.

Far more important then this is the geometry of the bore, and it's overall surface quality. It has to have hone lines in it for holding the oil, it has to be a perfect cylinder (mathematically), the bore shouldn't have any horizontal edges (made by the rings)  and most of all the piston / cylinder clearance has to be within specifications. Renewal of the rings only could be an option,

If you're planning doing 100.000 miles on it, you could consider having the bores chemically layered (ferrosil, like nicasil, but then for cast iron ), it's expensive, but save you the trouble of boring cylinders after 30K or so, only change the pistons.

Jensen

[HedNut]

Geeeeeze... you guys are scaring me...Wormholes!  I'd like to see what those cylinders looked like before they were touched... although what MRieck sais is GOLD in my books.   
I won't be boring mine for this run though...We're broke at my house...so every penny counts.  If she runs next summer, and I fall in love ...then I plan on doing things proper! I really wish I could now... but it seems since I've been married the word of the day is "budget"
My only other experience with a rusty bore was the ol' 72' Honda MT125 Elsinore... my fathers, sat behind the camp untouched under a vinyl tarp for over 10 years...cylinder looked way worse than the one in my CB...and a lil' cleaning, hone, new rings and I beat the CRAP outa that ol' two stroke all through highschool, making her scream to run with buddies who had new bikes.  She held out...and ran until the points blew apart 4 summers later...  HONDAS ARE TOUGH COOKIES...

Bore them if you can afford...
Re-sleeve if you can afford it....
Get another block if you can afford to...
If your a broke ass like me...cross your fingers, clean, hone, measure and clinically inspect them before moving forward.
   
I'm pretty confident in my thrifty work...

[gtyler5]

thanks to everyone for their support! after cleaning the cylinders a little it is my opinion they are hosed at least for my budget. where the tops of the pistons sat there is some major pitting, thanks to the previous owner! Since I have been off work for several weeks due to a hip fracture I have put the head, pistons, and total seal piston ring set up on ebay. maybe later I can use the funds to get a K head and have it worked up. I am a little sad to let it all go, but I am not building racers so maybe someone else will put it all to good use. I am keeping the cam. the bottom end looks good so far, once it warms up here I plan to look further into that.