Topic: Strange piston measurements - correct? Possible cause of my grief?

[bwaller]

You're right it does sound odd but I do have a stud available & I'll get him off to you this week! Let me know your address.

This is from a 550 top case but is not threaded full length, sounds like you have something not quite original there. Maybe that's why it stripped, I can send a couple if you want to change em both.

[Tim.]

Here are the pics - seems odd that both front corner studs would be changed.  Now that I look at it again, I don't think there's a nut that goes on the stud at that point, is there?  I think there's a nut right at the top, but not mid-way down obviously (feeling more stupid with every passing second).

Maybe this was a result of trying to remove it in the past?  Don't think it will cause any problems - opinions?

[Tim.]

This is piston #2 with the different oil ring - you can see it's much much smaller than the top two rings.

[Tim.]

You can see here that the one-piece oil ring on another piston is pretty much the same size as the other rings.

Given the oil ring doesn't provide the seal for combustion, perhaps a smaller ring on #2 isn't so much a problem?  There were no particular problems with #2 - had the same leakage % as the others.

[Tim.]

A pic of the head and cylinders after removing and a quick wipe down - no indication of leaking from one cylinder to another.

[bwaller]

Looks like some sort of threaded rod in place of the original stud. Are they both 8mm or something non-metric. I'd suggesting replacing them both, I'll send you two originals, they won't stretch as much, as long as long as the threads are original.

That is normal for three piece oil rings and they are an improvement over the one piece. If there is only 2000 miles on the pistons I still think a deglaze and a new set of 2nd oversize 550 rings will be the way to go if that's what fits. 

[Big Jay]

I do not think those are ART pistons. I believe they are Henry Abe. Did your pistons say ART on them?
.002 clearance is perfect if they are ART.

Jay

[Tim.]

They do say ART on them - cast into the underside of the piston in the same way 'HONDA' is cast into the outside of the original ones.  I'll specify the .002 to the machine shop, and will get them to confirm what the current cylinders were bored to in comparison.

Both front corner studs are the same threaded rod.  I haven't had a 500/550 apart like this for a while, and will confirm with the parts manual and service manual what they show as stock.

[Tim.]

Yep - sure enough, the parts manual shows standard studs across the front of the engine.  Very very odd.  Perhaps in the last 30+ years some PO's had overtightened the front corners in an attempt to quell a head leak.

They seem to be the same size/thread as the others, just threaded all the way.  Any harm in this?  The only value I can see in the smooth narrow shaft on the others would be to protect the pistons during manufacture/servicing.

I found out the hard way by scratching the top edge (above the rings) of the #4 piston on the threaded rod.  The piston would have cleared a smooth narrowed rod like on the other studs.  Given I don't plan on doing this often, it would seem I could live with these studs and avoid the potential disaster of messing up the threads in the engine casing in removing/replacing the two studs with new ones.

[Tim.]

BTW - not sure a new set of rings is possible, unless like I say I buy a whole new kit.  Are new rings absolutely necessary with a fresh bore/hone?  Maybe for the $120 I'll just replace the works again.  Make it an annual tradition

[bryanj]

Those studs are just mild steel stud bar and need to be changed for the correct ones or the head torque will not stay even! 500 and 550 are the same and all the back are the same with all the front same but front and back are different. BE carefull if you order new as the 500 book has the part numbers the wrong way round. (havent checked the 550 book will do so later!)

[Terry in Australia]

Here are the pics - seems odd that both front corner studs would be changed.  Now that I look at it again, I don't think there's a nut that goes on the stud at that point, is there?  I think there's a nut right at the top, but not mid-way down obviously (feeling more stupid with every passing second).
Maybe this was a result of trying to remove it in the past?  Don't think it will cause any problems - opinions?

That's no "factory" stud mate, some PO or dodgy mechanic had obviously busted the OEM item and replaced it with a short length of POS quality "all thread" from his local hardware store. Cheers, Terry.

[Tim.]

Alright, alright - I need new front studs.  Bwaller - my mailing address for the studs is:

Tim Aysan
200 Consilium Place Suite 1600
Scarborough, Ontario  M1H 3J3
Canada

I'm going to call Honda to check availability of the parts locally, but of course don't expect them to be available.

Now, I just need hints on removal / reassembly 

[bwaller]

Tim,

As long as you're sure the threaded rod is indeed 8mm, tighten two nuts together somewhere down the rod and use a wrench on the lower nut and at the same time use a good pair of visegrips on the stud at the base of the rod as close to the upper case as possible without scatching the gasket surface. Work both wrenches together gingerly to see if it will loosen. If it doesn't crack loose easily, take the thing to your machine shop to have them apply some heat.

I'll get these studs off to you today. They are stock from a 550 with broken cases.

If anyone has a set of 2nd oversize Honda 550 rings new or used you could get a hold of you could check to make sure these will fit. I expect they will, then you could look for a complete set of Honda rings and would be to best solution to your rebuild as long as the pistons are good and the P/Cyl clearance is right.

Who would know but the problem with those kits may be the rings and switching to Honda parts may work out. Worth a shot.

[bryanj]

I do know that Honda changed to the 3 piece ring early in the 500's life, allong with different valve stem seals in order to "cure" an oil use problem. Trouble is i cant find out how much the engines were using that upset mr Honda BUT from experience i suspect it was not a lot as at that time they prided themselves on the fact that you didnt ought to have to top up the oil between changes and most times you didnt! If you have the part numbers check out www.westernhillshonda.com

Ive just checked my parts book(s) and the front stud in all of them is 90033-323-000 EXCEPT in the 550 K3 book where it is 90034-323-000 and I think that this is the correct number with the other parts books having a missprint (NOT unheard of)

[Tim.]

Thanks for the input guys - if the studs don't come out easily, I'll pull the engine out and take the entire lot to the machine shop.

Then I'll have the excuse I was looking for to tear the entire bike down, get the frame powdercoated etc. and put it back together.  I was looking forward to riding in the next couple of weeks, but if now's the time, I guess it's time.

[dusterdude]

tintin,contact hastings rings or some other ring manufacturer and see if they will make a set of rings for you.

[bwaller]

The studs are on the way.

[Tim.]

The studs are on the way.

Truly appreciated.  Discontinued at Honda of course.

I spoke with the machine shop.  I'm taking my three sets of pistons/cylinders and 2 heads up there tomorrow morning and their task will be to get me one good set out of it

Now I need to find a top-end gasket kit for the 550.  As it turns out I'm missing the o-rings around the cylinder sleeves at the base.  Not sure how desperately important they are, but if they help seal the bottom end and protect the base gasket, I'm all for putting them in.  Of course they're discontinued by Honda as well, which is surprising considering it's just an o-ring.

I'll try extracting the rods tonight - crossing my fingers.

[bwaller]

Just in case you give a damn I checked and 0.5mm oversize rings are available at a couple different online sites for around $25 US per set.

[clarkjh]

tintin

When you took everything apart, was the grove on the scrapper ring up or down?  I have found reference of ring with groove up, and different ring with groove down.

James

[Tim.]

Just in case you give a damn I checked and 0.5mm oversize rings are available at a couple different online sites for around $25 US per set.

Yeah,  I found Riken sets at Sirius which is actually up here for US$75 for all 4 sets.  While it's entirely likely they would fit the ART pistons I have, can I be sure?

For US$120 I can get new pistons, rings, pins, clips and a new head gasket.  For the extra $45, it seems to be a safer bet than mixing the ART pistons and Riken rings.

I've ordered 4 new exhaust guides from Honda for the head - needs new ones, and a complete Honda OEM gasket kit (A and B) from Western Hills Honda.  I need a bunch of o-rings and the little rubber UFO's for the top end, and want a proper 550 base gasket.  For US$78, I got the complete set.  Will likely need lots of it going forward.

With any luck, this will be the last time.

[bryanj]

Tintin, Riken were one of the original suppliers to Honda so they ought to fit and if they are the three piece rings (oil) they would be better than the single in the kit. Check the ring gap widths between the standard you have out and the overbore ones you have, if the same, which i suspect, you are ok