Overheated crankshaft and dirty pistons

Hello everyone!
So I decided to tear down my engine, to the bone (to the engine case to be exact). Put on new gaskets, hoan the cylinder walls if need be, lap the valves and check the clearances on the shims but when I took the cylinders casing of - a crap ton of dirt fell from the bolt holes (mostly sand) and fell into the engine casing sooooo yeah, I'll have to tear it down to the last piece, clean it and hopefully get everything back together in a working order....
But before I do that I'd like to check in with you guys about a small issue I encountered with my crankshaft and my pistons....
The crankshaft has overheated a bit....
hat dark spot is mostly it and there is one more on the other side of the same counterweight. So anyone knows what could be the reason for this? (my guess is bad oil orrrr a blocked oil port of some sort) And is it safe to ride with it as is or must I replace the shaft? (Have in mind that a new crank is not something I can get cheaply since I live in such a small country so I have to import everything...), so if I have to change the crank + pistons and I guess the cylinder casing and the cylinder head - It would cost me the same as getting a new engine (500$ is my estimate, for a motor of an unknown origin).....

And the pistons. All 4 were like this - I couldn't get the damn pins out, used some heat and a bit of wd40... Only at the last pin i figured out that i can clean the holes and the pin gets out with a little bit of effort.... Should i keep them and clean them or is it time for a new set?


Should I proceed with the tear down and clean the casing, clean the pistons and roll with the same shaft, or are the pistons ready for the scrap yard along with my crankshaft...

As always any and every advice and idea are welcomed with open arms, because currently I'm lost on what to do....

 

You were going to tear it down to the bone? If you think those heat zone marks are not there from new (I've never seen a 650 crank) I would carry on an tear it down. If the crank has got that hot the chances are its toast, as well as the cases?

 

Crankshaft throws and sprocket blue color can be from the factory heat treatment:

http://www.xjbikes.com/forums/threads/starter-clutch-replacement.85364/page-4#post-509738

 

Hey, that looks familiar....

I did have that same discoloration on mine. I have put over 5k miles on it since getting everything back together and have not had any issues with it.

 

I read the entire thread - thank you! I got a bunch of useful info. My crank looks very similar to the one on yhe picture. So guess I'll tear down the entire engine, clean it, inspect (and replace/fix) and rebuild it.

The top and bottom halves of the engine case were bound together using Yamabond?

And any taughts on the pistons? I think they are salvegable but I got an advice from a guy who tunes race car engines that the best option is to change the entire engine for a newer one - but where is the fun in that?

 

I used loctite 515 to put mine back together. 518 is good too.

Sorry, I can't offer any advice on the pistons,I haven't had the pleasure of dealing with that myself. I do know that rings are expensive and hard to come by.

 

Yes clean them up and use them but with new rings. Any idea how many miles/kms on the motor? My brother also builds race engines and the standards/tolerances he works to are way different from mine. I want the motor to run and
hopefully not burn too much oil. he is 'blue-printing'and looking to extract every last HP without the thing rattling to pieces (Austin Mini engines developing 120 HP per litre). Which small country?

Cheers

J

 

Umm, Sweden?
"The Koenigsegg V8 is the most downsized homologated production ICE in the world, with 220hp per liter (using regular pump gas)"
From Koenigsegg web page.

Jeezus. I was impressed when Honda beat 100 per liter with the S2000!

 

Sorry for the slow reply guys, college has been bombarding me with school work so I had to put a few things on halt....

The bike has 100k km, but the engine has been changed by the PO. So I have got no clue to be honest on how much miles it has done. I have taken everything apart, and the cylinder NO.2 has a straight line marking from a stuck piston ring... Now the thing is - for me to rebore and change pistons + rings on all 4 cylinder is stupid expensive and besides, the other 3 cylinders are fine... Finding an engine donor in Slovenia (my country) is a no go and I have scouted e-bay for a cylinder block with pistons but some have score marks, and other don't even have pictures showing the inside walls - don't need one more cylinder block with a required rebore...
What I have found is a 0.50 OS original piston with rings with an acceptable price, but the question is - will the 0,50 OS piston cause the crank to vibrate the engine apart or is it an acceptable practice to rebore only one cylinder? I could try and shave some weight off the piston but don't want to compromise the structural integrity of it, so yeah - any idea on what to do?

 

No!!

 

Darn, I had my hopes up that it would be one of those unexpected hidden tricks that none knows about Can atleast the cylinder sleeve be changed in the xj engine, have you done it or heard of anyone attempting such a feat? And since I'm here, is the 50ml of LOCTITE 518 enough for the entire engine casing or do I need more of the magic goo?

 

Yes, sleeves (liners) are available, what engine/model of bike are you servicing?

 

50 ml is enough to seal several sets of cases.

 

Yes again - I was planning on doing this on a bore that had some water corrosion - my local engine shop would have heated teh whole block up and pressed out the damaged liner, so perhaps if you can find a block with at least one good liner you could be in luck - or wait and see what Chacal can offer - might be less hassle. BTW I used my damaged bore in the end and it hasn't been too bad a bit down on compression but not smoking that much and fine to do a few hundred miles I year I reckon.

 

It's a xj 650 1982 4k0 YICS.

Well, I'll take mine on Monday to a machine shop near by to get all the cylinders and pistons measured (the guy is super nice, he said he'll measure 'em free of charge), but I doubt no.2 it's under 0,1mm +even if it is he still needs to grind the walls... Did you grind the walls or you just ran with it as is?

 

Well the full story now I remember is that I took the bores to the machine shop to see if a professional hone (light sanding) would work to get rid of teh corrosion but he said not and suggested the sleeves swap. In the end I sanded them myself by hand trying to create a cross-hatch on the cylinders with 300 grade wet & dry paper and light oil. Clearly this is not ideal but since I only paid 125 quid for the bike in bits it makes it hard to justify three of four times that for rebore and new pistons. Maybe I should have tried the sleeve swap. I might soon recheck compression now that teh motor has a few hundred miles on it.

 

Well, for 125 quid I wouldn't complain either but I'm well past the point of no return so I'll try to do my best with the bike. How's the bike running tho?

New question for the pros out there. Just a theoretical question that could soon turn into a practical test - I know that the xj650 and xj650 turbo don't have the same item part no. for the pistons but they have the same part number for the piston rings and pins. Is there a reason for this? Could one go for the STD xj 650 turbo pistons in an xj 650 engine?

 

The motor in it is from a Radian and runs very well - not too much smoke but doe use some oil maybe 500 ml in 600/700 miles.

 

This is a pic of how the bore looked - you can see where water has pooled a roughened the bore through corrosion. This happened in a couple of second hand motors I bought so in teh end I just use the
best set I could find. IIRC the 'bad bore was down about 15 psi on compression compared to the good ones.