Topic: CB500 / 550 Valve stem seals the same?

[Tim.]

Looks like I need new stem seals, and I have an old Honda upper gasket kit from my 500 that has the stem seals in it.  I presume I can use these on the 550?  Just wanted to make sure.

Turns out the guy I had do my valves last year didn't bother putting in the new seals I gave him for the 550... my luck.

Now, what symptom would crap valve seals cause?

[bryanj]

Yup Tintin all the seals are the same after the first 6 months of build in 71

[Tim.]

Yup Tintin all the seals are the same after the first 6 months of build in 71

That's some serious knowledge.

Any thoughts on what behaviour I would expect to see in a bike with absolutely shot stem seals?  I presume this, combined with perhaps slightly sloppy guides could cause serious oil burning.

My engine is completely torn down now, after my rebuild 2000 miles ago (last spring).  It's burning oil something fierce.  I was about to order new pistons/rings and do another bore on another set of cylinders, but I'm thinking I might just get the head cleaned up, button it back together and see what happens.

Pistons/rings/bore will run me another $400, which I'd rather save if I could right now.

While I'm asking - any thoughts on the o-rings around the cylinders in the base gasket?  I didn't seem to have any when I tore the bike down.  Honda doesn't seem to stock them any longer, so I'm not sure I'll be able to replace them, but obviously would go the extra mile if it was terribly important.

[bryanj]

Tintin a 750 F2 i took to the IOM TT years ago was doing 350 Miles per pint on worn guides which went to 150 Miles per pint when the seals broke. As far as i know the "O" rings arround the liners are to stop oil going upwards and leaking throough "porous" alloy castings ( you can cure that by stove enameling the cylinders--usually black) Dave Silver, in a two year old catalogue, listed 0.5mm 550 rings at £10 per set so that $75 looks good, as long as its a 3 piece oil ring

[Tim.]

Yeah, what I think has happened was that the guy who rebuilt my head last year didn't put in the new seals I gave him.  He also lined two of the exhaust guides with a bronze liner - the other two were fine.

So, 2000 miles and a year later, I'm burning oil like there's no tomorrow.  Seals failed and the other two guides aren't as good as they should be either.  Burning enough oil apparantly can glaze up your cylinders, which then causes lower compression.

So now I have a bike with low compression and dead seals.  I've ordered all new exhaust guides.  The machine shop www.conceptsonwheels.com - check them out - does some serious work and they have my head now.  They're suggesting we do a fresh bore on a spare set of stock cylinders, vs. re-honing the old ones.  I'm torn between buying a new piston kit which will include pistons/rings/pins/gasket for $120 or Riken 0.5mm rings for $75.  I'm not 100% sure the Riken rings will fit the pistons I have, which are 3mm over pistons for a CB500 (58.95mm at the top).

The Riken rings are a 3-peice oil ring, while the rings in the kit are a single peice.  Funny that now on eBay there are quite a few 0.5mm over pistons and rings from Honda, but they're very very expensive - $100 per piston which is nuts.

I'm likely just going to order another complete kit and do a fresh bore/hone on the spare cylinders.  Seems a shame to ditch 2000 mile old pistons/rings/cylinders, but I'll keep them around as a spare set.  I'm sure I could just deglaze / hone the cylinders and put it back together with the new head and it would likely be fine, but I don't want to take any chances again.

The bore and piston kit will cost me $375 or so, while just a hone and new rings would run me $200.  Just the hone would likely be $120.  So, for the extra $250 to go all the way from minimum work to the full rebuild, I hope to have peace of mind and no further problems related to this for the next 30,000 miles or so.

[bryanj]

Tintin, The bore glaze is usully down to running in TOO gently--was a common problem on the first Kawa 1000. Personnally i would deglaze, which you can do with whwt i know as a "Flap" wheel and fit new 3 piece rings along with the new guides, which will have to be reamed after fitting--make sure the shop has the correct sized reamer or its all a waste of time!

[Tim.]

They've got everything needed to do the job - they were actually talking about making me new guides at one point.  I got new ones from Honda though.  If I were racing it, I might consider having fancy bronze ones made up or whatever they make them out of for better heat dissipation, but for $13 each new, I'll stick with Honda's.  I'm also of course replacing the little o-rings under them at the same time.

I'm going to get the rings from Sirius Consolidated - $70 for 4 sets of Riken 0.5mm overbore rings, which have the 3 piece oil ring.  I've been offered the piston kit for $80 + $20 shipping US, which is seriously tempting too.  I'm going to haul my old pistons back up to the machine shop just to make sure they're still good to use with new rings.

I'm going to let them bore a new set of cylinders for me.  I'll keep the originals around too, but will give the machine shop the opportunity to do the complete top end.  They're very reputable and do major projects.  They also powdercoat etc. in-house.  A full hot-rod shop.  Have a look at their website, there's some neat stuff on there including some bike work (old Indian's).