RM-Z250 Oil starved cam journal? How bad?

[2strokesteve89]

I've measured the journal using plastigage, and it seems to be 0.076 mm play. But I'm unsure if I did it correct, I put two pieces of plastigage, one on top and one on the bottom, and both showed about 0.076 mm on the worst part. Am I supposed to add up those measurements, or go by one of them?

The manual specifies 0.020-0.062 as the normal values, and 0.15 as the service limit. Would that mean it's still useable, or is it a bad idea?

And final question.. Looking at exploded views, I was under the impression the oil pump would be on the left side of the engine, but looking at it there's no cover besides the flywheel. Do I have to split the engine to get to the pump, or is it actually on the right side?

EDIT: turns out I'm too stupid to look at exploded views. It's on the right side.

You're ok with the journal clearance, if one of those readings was different it would indicate an out of round condition. It should be the same wherever you check it. So it is just outside of normal but well within its service limit. So to answer your question, it can be run that way.

 

[ossagp]

you add them together if you used the two pieces of plastigage at the same time, thus to me at least, placing it well beyond a sensible limit.

 

[JoniX]

Hmm I might have to redo the clearance test.. I put the cams in the loose head and when I put the exhaust cap on the cam, the cam got pretty much stuck and can't be rotated, and that's without even tightening the screws. There's probably an edge left from when I sanded down the overhead that prevented me from removing the buckets, I'll have to look further into that.

Or can the head be warped from when I removed the cylinder bolts?

 

[2strokesteve89]

Take one piece of plasti gauge and redo your test.

 

[JoniX]

Yeah I will try that, but I'll see if I can find out why it's stuck first of all. Seems weird, I think it's the cam cap that it gets stuck in.

 

[JoniX]

Also.. removing the oil pump calls for removing the clutch housing and primary gear as well. And according to the manual I'll be needing a special tool to hold the clutch housing, and then a special gear holder. Any idea if it's possible to DIY any of those tools, or any other ways?
I remember on my old Husqvarna I just put it in gear and hold the rear tire while attaching the clutch bolt.. probably not the best solution, but that bike was a POS anyway and I did not care if something broke.

 

[SRAD97750]

Any idea if it's possible to DIY any of those tools, or any other ways?
I remember on my old Husqvarna I just put it in gear and hold the rear tire while attaching the clutch bolt.. probably not the best solution, but that bike was a POS anyway and I did not care if something broke.

Impact gun is your friend here. If all else fails I put the bike in top gear and stomp the rear brake and it'll break loose that way. -BIG DAN

 

[JoniX]

So the chain and drivetrain won't take damage from all the torque?
How about attaching it again afterwards then? Just impact it till it feels tight enough or use my torque wrench for proper torquing (98 Nm)?

 

[ossagp]

Also.. removing the oil pump calls for removing the clutch housing and primary gear as well. And according to the manual I'll be needing a special tool to hold the clutch housing, and then a special gear holder. Any idea if it's possible to DIY any of those tools, or any other ways?
I remember on my old Husqvarna I just put it in gear and hold the rear tire while attaching the clutch bolt.. probably not the best solution, but that bike was a POS anyway and I did not care if something broke.

You will need to see if something is really far out of round. When you do the test again you will need to make sure that the cam can actually "bottom against one side before the cap is put back on, and isn't being supported with clearance space left on the side that doesn't have the plastigage.

 

[SRAD97750]

So the chain and drivetrain won't take damage from all the torque?
How about attaching it again afterwards then? Just impact it till it feels tight enough or use my torque wrench for proper torquing (98 Nm)?

Remove with impact, install with torque wrench. It won't cause any damage to the drivetrain if it's in gear.-BIG DAN

 

[JoniX]

I redid the plastigage test with only one plastigate on top of the cam, and this time it showed 0,076 mm on the worst spot and 0,051 mm on the best. However there definitely are an out-of-round-problem, as the cam cap won't fit properly over the camshaft (or well, it did after I torqued everything, but it would not move at all). It's actually the left and right side that's tight and not the top, so perhaps the plastgate test would be even tighter without the out-of-round.

Any ideas of what to do? Sand the cam cap sides down a bit, or would a machine shop have to do it?
Would it be foolish of me to replace just the cam cap and put the rest back?

Remove with impact, install with torque wrench. It won't cause any damage to the drivetrain if it's in gear.-BIG DAN

Thank for the info!

 

[2strokesteve89]

I redid the plastigage test with only one plastigate on top of the cam, and this time it showed 0,076 mm on the worst spot and 0,051 mm on the best. However there definitely are an out-of-round-problem, as the cam cap won't fit properly over the camshaft (or well, it did after I torqued everything, but it would not move at all). It's actually the left and right side that's tight and not the top, so perhaps the plastgate test would be even tighter without the out-of-round.

Any ideas of what to do? Sand the cam cap sides down a bit, or would a machine shop have to do it?
Would it be foolish of me to replace just the cam cap and put the rest back?


Thank for the info!

If you have a dial or digital micrometer, measure the journal diameter of the camshaft in several different spots, if they are all the same you may have a problem with the head, if you have different readings it is the cam but it doesn't rule out a problem with the head.....when that head was cast it was made in one piece after this the cam bearing journals were line bored to specification, then the journal castings are cut in half, thus making each cap a match to that particular journal, if any modifications are made to the mating surfaces of the head or cap the possibility of camshaft damage/seizure is probable as a result. For this reason I would not recomend sanding or changing out a cap with another. When checking for the integrity of the camshaft and journal centerline and clearance issues, I like to install the cam shaft with the caps properly torqued and the camshaft able to spin freely by either removing the valves or the shim buckets. If the camshaft then rotates freely and smoothly without any signs of binding then I feel better about the centerline of the bore and cam shaft true, I would then measure for runout at the end of the cam as well as any up/down movement in the cam, using a dial indicator. Hopefully this will help you out enough to know what your next step is.