Re-Ring a Kbike?

[wmax351]

Crap. Looks like my bike is oil smoking when I rev it. That paired with the bad manifold vacuum suggests it needs rings.  :cowpoop: :cowpoop: :cowpoop:

I've been debating whether it is easier to swap the engine or change the rings in situ. Cost is about equal. I think it may take less time to do the rings, as the engine does not have to come out. And I don't have an unknown: The rings are going to be new.


Any thoughts?

[Rick G]

If the bores are OK then new rings is the way to go.

[racinrich]

we rering car motors all the time,if there are no gouges in block it will work,we also replace valve stem seals,even one gouge in one cylinder will continue to burn oil,our motors carbon up the ring lands and rings stick in the piston,low tension rings have contributed to condition,we are not sure if it is from cheap oil or cheap gas are aggrevating the condition,close inspection and don't forget to check timing chain

[wmax351]

we rering car motors all the time,if there are no gouges in block it will work,we also replace valve stem seals,even one gouge in one cylinder will continue to burn oil,our motors carbon up the ring lands and rings stick in the piston,low tension rings have contributed to condition,we are not sure if it is from cheap oil or cheap gas are aggrevating the condition,close inspection and don't forget to check timing chain

Do you have to de-glaze the bores before putting rings in with a nikasil bore? If not, I can do the whole thing with the engine in the bike. Pull the head, pull the crank cover, pop out the pistons, clean them up, new rings, and back on. Total cost is about $250 for 3 sets of rings, some gudgeon pin clips, and a head gasket.

[racinrich]

yes but the hone stone grit should be matched to ring type,motorcycle machine shop should be able to steer you to right grit,correct  hone pattern is as important.

[wmax351]

yes but the hone stone grit should be matched to ring type,motorcycle machine shop should be able to steer you to right grit,correct  hone pattern is as important.

I've done some reading on the honing of Nikasil. It seems that there is actually no abrasion of the nikasil itself, but rather removing any cylinder glaze and aluminum fouling (from the piston) from the walls of the cylinder. Sounds like green or red scotchbrite is enough usually.

[argent brick]

Would you please post step by step pictures if you put new rings in?

[wmax351]

Would you please post step by step pictures if you put new rings in?

If I end up doing this, I will. Not sure. It still has a lot of life left, just will burn oil and more gas. I may just "Ride it till it won't move".

[argent brick]

And how many miles do you have on your K bike?

[wmax351]

And how many miles do you have on your K bike?

97k

[argent brick]

That is great that someone has megamiles on their brick, have you had to do any major work before now?

[wmax351]

That is great that someone has megamiles on their brick, have you had to do any major work before now?

MegaMiles? PSshhhh. One guy has over 800k on a K75. Rebuilt at 500k, and had a salvage head added in between.

Anton Largiader had ~ 370k on one when he crashed it.

[wmax351]

My other question is: What should the idle vacuum be. Mine is about 22 cm of mercury (75kpa absolute). K bikes have throttle bodies, which can affect the idle vacuum. If someone can check theirs or knows what a normal value should be, that would be great.

Edit: In the FSM, this picture gives some clues. It does not appear to be anywhere near the 45 CM/hg (40kpa absolute) that is normal for  most engines, which have a single throttle body and a plenum. Maybe I am just having moto-hypochondria.

[racinrich]

the grit of the stone is the same as sand paper lower number is coarser old chrome rings used 200 ,chrome moly rings used 600.pattern does 2 things 1 holds oil on cylinder 2helps rings seat onto wall. ring rocks in groove and polishes wall,old chrome rings were hard and took a long time to seat hence 200 deeper hone marks on walls,chrome moly rings have a coating impregnated on face (softer than hard chrome) 600 grit smoother less break in time.scotchbrite pads would not work due to the inconsistent pressure exerted outward plus it would be difficult to get a consistent pattern thru out the bore.
here is a link which may be helpful.www.flexhoneblog.com/2009/03/deglazing-nikasil-cylinder.html
within this link is another helpful link on deglazing.dis assembly is easy,getting the honed surface right is hard and not for beginners.it is an art.like the link says if not right it will still have problems.

[Filmcamera]

My bike is now burning SO much oil I think I have no choice but to change the rings.  I am 99% sure it is the rings because it burns almost no oil when I am riding with my wife, ie never passing 4500 rpm but tons when I am riding with my buddies, ie 8000 rpm.  I might end up doing the valve stems as well.  I am more than a little nervous about doing all this but do not think I have much choice.  The other day we did a 100 mile trip and I used 5 ounces of oil.  I am currently researching info on how to do the job so if anyone has a good link I wold be very grateful.

[Laitch]

My bike is now burning SO much oil I think I have no choice but to change the rings.  I am 99% sure it is the rings because it burns almost no oil when I am riding with my wife, ie never passing 4500 rpm but tons when I am riding with my buddies, ie 8000 rpm.

First, do both a compression and a leak-down test.

[Martin]

As per Laitch, but before you renew the rings I would try running a high detergent oil. Carbon build up behind the rings will effect oil consumption. Gryph is having oil consumption issues and I believe he is trying an oil called Marvel Mystery Oil. And as far as high mileage there is a Brick in Sydney with 1.2 million k's on the OEM engine reported in a article in Old bike Australasia No 41. I managed to score the magazine in a two for one swap off a dental hospital. Unfortunately due to copy write laws I can't copy and post. The magazine does turn up on line and is available on digital issues and maybe backorder.
Regards Martin.

[Filmcamera]

I will do the compression test this weekend.  I do not have the tools to do a leak down test but will see if I can take it to a shop to do one for me next week some time.


I will also look into a detergent oil, probably hard (or impossible) to find in Costa Rica but it cannot hurt to ask.


I am going to go ahead and do the rear main seal anyway this weekend/next week.

[The Mighty Gryphon]

I'm going to guess that the compression test will show even compression in all the cylinders of about 135-140 on a cold engine.  That's what my engine showed and why I didn't go into the rings when I did the valve stem seals.
The reality is that somehow the oil control rings aren't working on my engine while the cylinders look good, still showing the hone marks.  At over $60 per cylinder for rings(can't just buy the oil control rings) plus over $80 for a head gasket I can't see any rational reason to do the rings on a bike that runs great except for "excessive" oil consumption(BMW specs oil usage as high as 1qt per 600 miles?!).  I can buy a lot of full synthetic oil for the ridiculous price of a ring job on a K100RS16V engine.
I'm selling the bike with that engine and being up front about oil consumption with all potential buyers.  I started running Marvel Mystery Oil in the fuel and in the crankcase last Fall, but haven't run enough miles(less than 400 miles) to tell if there is going to be any improvement.  Right now, consumption is around 1qt per 800-900 miles.  Engine smokes a bit more than my K75's on startup, and doesn't smoke when warm. 

Depending on the compression test, I might think hard on doing a complete ring job, rather look at the oil control ring and see if it is stuck in the ring groove.  It may be possible to get by with just cleaning things up.

[Filmcamera]

Last time I did a cold engine compression test about a year ago I had 120 on 1, 2 and 4 and 130 on 3.


Believe me I have no desire to do a complete ring job, the cost of the rings and gasket is not far off the price of a used engine!  It does worry me though that if I ride the bike hard (as everyone says I should) my oil consumption goes through the roof. 


Anyway I will report back after doing the compression test and aldo when I have the tranny off again to do the rear main seal, I am pretty sure the clutch is fairly well doused in oil.

[caveman]

I would make sure the crank case vent is not restricted or blocked first. Then I would treat oil with rislone (not sure of spelling) the stuff will free stuck or clogged oil control rings. If after treatment the engine uses more oil then it points to leaking intake valve seals. Just my 2 cents.


FWIW, I've been running 15-40 rotella t and not having to add any if changed by 3,000 miles (adding a pint will get me out to 5,000 miles on trips)

[Filmcamera]

I did a compression test today.  Cold I got 125, 125, 130 and 125. I then warmed the engine up and did another test.  Oddly(?) I then got exactly the same results, I thought a warm engine normally showed higher compression?


I am going to try an find somewhere to do a leak down test next week.



Anyway that really is not too bad so I am going to recheck the valve clearance and maybe opt for doing the valve seats rather that the rings at this point.

[Laitch]

I would make sure the crank case vent is not restricted or blocked first. . . .

+1 Restriction in that system could increase oil consumption. To inspect it, you'll need to get into the air box. Photos in this thread.

[Filmcamera]

I will check it but it is pretty new, I changed it less than 3000 miles ago