Worn Cam?

Thanks Taffy. I'm waiting to hear from my machinist (was hoping it would take less than a week to meausre a piston and rod) and I'll go from there.

Given the future parts availability and how quickly I'm losing interest in working on the bike I'm really contemplating replacing the rings and slapping it back together. It might burn a bit of oil but damn, at least I'll be riding!

spanner said:

I think in theory replacing the big end rollers and cage early could extend
the life of a big end pin and rod.
Unfortunately it is hard to judge the bearing condition without disassembly, and by the time we see indicators of trouble as shown in your first photo it may be to late.
Once the silver plating on the cage wears through the cage rubs on the rod wearing radial grooves into the ID complete failure will follow.

Is the complete crankshaft still available?

I have a 628 bore with one similar score and it ran just fine. With No excessive oil consumption.

What you save on piston and liner you could spend on the crank, if it is found to be in need of replacement.

If you end up getting a new crank I know someone who is looking for a used 550 one for a special project, so that could help out with the cost of a new one.

Click to expand...

I guess the million dollar question here is the condition of the rod bearing. That will determine where I go next. I was kinda hoping that the swarf on the magnet was from the ring getting eaten up, but I don't know the answer to that yet.

It might be prudent to service the rod bearing now, assuming the rod and pin are OK. Can the radial clearance (0.05mm) be checked reliably to determine the condition of the bearing or do you think the crank needs to be split for a visual inspection?

Taffy, is the 32mm bearing on your site the one I need for the FE550?

In what situation would I need to replace the crank? At about $1000 for a new crank (almost what I paid for the bike!), wouldn't it be more cost effective to replace the con rod, bearing and pin? Is it just because the OEM rod isn't available anymore?

Thanks for the help. The advice on this forum is only reason I've had the balls to tear into the bike like this!

-Kent

Well, back to work on the world’s slowest engine rebuild. I’ve finally got all the parts in front of me on the work bench and will be trying to get it buttoned up this weekend, time permitting. There were lots and lots of things that have slowed me down up till this point (4 months so far, wtf!), but losing the wrist pin circlip while trying to mount the piston last week was probably the most frustrating! it’ll probably turn up in the dryer’s lint trap or something...

Anyways, I ordered a pile of OEM parts from a local dealer. International Motorsports in Langley, BC knocked 20% off their list prices which brought them in line with the discounted prices from the US (better in some cases). The majority of the parts arrived in 2-4 business days and I didn’t have to pay shipping so that worked out much better than ordering from Munn. The only part that took some time was the new liner, but it only took just over 2 weeks to arrive from Europe. I opted for a new liner for $330 compared to $370 to repair.

The remainder of the parts that I couldn’t source locally I was able to get from Taffy, including the IWIS cam chain and good used cam. Taffy shipped right away but both orders got stuck in customs for a month...

The crank bearing/pin was in good shape so I just replaced the con rod bearing for good measure. I also had the machinist mount the new KTM RFS main bearing races. Oddly enough he wouldn’t setup the crank end play for me as he doesn’t do any engine assembly, just machining. I measured the crank axial play at .53mm (.021”) so I didn’t bother having him add any shims afterwards.

I’m reusing the piston with the new rings and liner. The rest of the $1100 worth of parts was made up of things like cam bearings, cam followers, gaskets, o-rings, fasteners and a few case bearings.

So I’ve got some Three Bond and Im ready to slap it back together. Questions:

- What do you guys do for piston ring orientation? My understanding is the compression ring will spin around and find it’s own home naturally. How about the oil control ring?

- What oil to use to allow the rings to seat? Is the typical JASO MA2 (Motorex or otherwise) good? Or should I use something with higher friction?

I won’t ask for advice on the best way to break in the engine as that’s a whole topic on it’s own.

Thanks!

Kent

Now that I've actually installed the piston, I don't think there's much you can do to control the orientation. Even if you line the rings up nicely, they will probably move as you rotate the cylinder liner around to get it properly aligned in the case.