Waking up my nicely rested engine. What would you do?

Lately I've been able to spend some time working on the engine. And....I have some questions.

I pulled off the head and the cylinders. The cam looks like new with no wear marks on the lobes and the rockers are the same, nice and shiny. The front cam chain guide looks like new. I'm tempted to reuse it instead of using the one that I bought from MikesXS last year.

It sounds like a lot of people reuse the one that is on the tensioner side but end up replacing the front guide because it is frequently pretty beat up. Should I reuse my front guide? If the OEM ones were made better than Mikes what would I be gaining by switching it out? Beside 'new glue' that was made in China.

The wear strip that is on the tensioner side has two shallow grooves in the plastic. See the first photo... Is this one fine for reuse?

The pistons had a nice snug fit in the cylinders before I disassembled it. The cylinder walls look very clean to me and everything feels smooth. Up at the very rim of the cylinder there is a uniform build up of varnish. Where I was able to wipe it away the metal is consistent with the cylinder wall. I think that once I get the varnish off I will not find a ridge where the rings stop their stroke. What is the best solvent to dissolve the varnish? Carb cleaner did not help.

Here are some photos of the cylinders. Would you hone these or leave them alone? I will be using new ring sets when I reassemble.

IMG_1774.jpg

IMG_1776.jpg

IMG_1777.jpg

IMG_1778.jpg

IMG_1779.jpg

IMG_1780.jpg

IMG_1781.jpg

IMG_1782.jpg
 
Everything looks to be in very good condition. Tough call on tensioners and camchain. Main concerns on tensioners are about age, material separation, and mount thread quality. Main concern on camchain is about amount of stretch, revealed in the 'droop' test. Something I've always wanted to try, already been done by members here, is to polish the plate edges of the camchain to reduce tensioner wear.

Camchain info: http://www.xs650.com/forum/showthread.php?t=32241

Tensioner info: http://www.xs650.com/media/albums/1640/

My take on the cylinders (being an old-school cylinder borer), is to at least rehone them, because of the light vertical score lines, and the old-school rule of ALWAYS honing when replacing rings. Member Paulrxs650 has a thread here somewhere discussing his experience with smoking rings/cylinders. Paul?
 
Yes, a hone for new rings is the norm. Your rear tensioner should be fine. They all get those grooves to a certain extent. The problem with the front is usually the glue failing, not wearing through. Make sure the rubber strip is not coming loose anywhere. That "varnish" is actually a light carbon build-up. Some paint stripper should remove it.
 
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Thanks for the info. I will buy a hone, would something like a KD three blade hone engine cylinder hone do the job and how aggressive should the stones be...medium or fine?

I already decided to install a new camchain. I'll do the droop test on the old one just to see the condition.

I'll take a close look at the original front guide to see that there is no separation of the wear strip. If it's still tight I'll reuse it.....I found an old thread from 5twins photo comparing front guides..one photo showed one from Mikes that was delaminating so I guess that new or old they can come apart.

And ...reusing the tensioner side guide means I would be trusting the same 37 year old glue on that part.

Makes sense to me....!
 
The three blade glaze breakers are a little too aggressive by today's standards. Do the google search for 'ball+hone', and regular search for 'ball-hone' and 'flex-hone'. Plenty of info there...
 
Now that you have the pistons and cylinders opened up, you need to measure the pistons and cylinders for wear, to determine if they are still in spec. Good idea to measure for valve guide wear also, using a dial indicator.

You can find the details in the Yamaha Service Manual specs. at www.biker.net
 
Yes, use a ball hone, not the stone type. With the stone type you can actually enlarge the bore if you're not careful.
 
Hi, yes, I did have an issue with my rebuild, whereby I very lightly honed the bore to remove some light marks. I foolishly re-used the old rings due to the cost of buying them as they were, along with the pistons and bore well within tolerance.

However, after a few miles the left pot started to smoke lightly on start up. So, engine back out head off, new rings gaskets etc and more money than it would have cost in the first place. Also quite annoyed with myself into the bargain, as i am quite a perfectionist!

If you are going to hone, use new rings. If the barrels are decent, don't hone and use the original rings, as long as all is in spec and tolerance of course.

Please listen to 5twins comments about the type of hone to use. The stone type can and will remove more material quite quickly, rendering the rings and pistons you so carefully measured up, useless.

The ball hone is much gentler and resembles a mad looking bog brush with abrasive ball on the end of each bristle. The stone type, is as it says, usually three stones (similar to what you sharpen a knife on) which are spring loaded and spin in the bore. These are normally more common than the ball, so if you only have that type to use, make sure that you use plenty of lubricant, I normally use thin engine oil. Place the bore in the cylinder attached to the drill and start it on a medium speed. Make a couple or three passes up and down the bore, then DONT stop it in the bore, pull it right out. You will get flicked by oil so be prepared :)
 
Okay Guys,

I ordered the Flex-Hone and arranged to get the pistons and cylinders measured tomorrow.

Thanks for the guidance. ...gotta go clean up the pistons.
 
Progress...

I took my cleaned pistons and cylinders to the most local Yamaha-etc.-etc.-etc. dealership to have the parts measured for wear. The cleaned pistons show no signs of blow by and skirt wear was not deep but it does extend from the skirt bottom to about 1/2 inch below the oil ring.

It turned out that the engine builder/mechanic that came up front to see what I wanted had rebuilt an xs650 and added a fifth gear overdrive a couple of years ago. So... we talked xs650 for a while.

Results...( the bill was an affordable $21...Thanks Nielsen's)

The cylinders have minimal wear and the taper and out of round measurements are well within spec.

The ring gaps were just barely out of the original specification window and well under the wear limit.

The pistons appear to have been the wear part. One piston to cylinder wall gap is exactly at the wear limit and the other is slightly over the limit.

So it looks like new pistons are in order. I did not find any standard size pistons other than the ones available from Mikes. Are these good or should I try and find new OEM pistons?

I came across earlier piston/ring thread comments from 5twins suggesting using 1st oversize rings on standard pistons when putting standard pistons in a used bore. Do others agree? I understand the logic and will probably go that route. And yes,...I will gap them.
 
I did a search for new old stock OEM standard pistons.

I don't think that they exist...(and you probably already knew that)!
 
You are right 5twins that is a substantial savings. Good prices on other parts also. I sent them an inquiry about standard size pistons. I am curious, he describes the second oversize set as being for '74-'76, wouldn't those be the same part as a 1977 Xs650D?

Have you purchased aftermarket pistons from this seller and do you think that these are the same aftermarket pistons that Mikes sells?

For that amount of savings I might have to consider going oversize. What is a fair price to have the cylinders bored?

Thanks.
 
I don't know why he lists them as being for '74-'76. They are 447 type pistons so will fit '74 up until the end of the model run ('82 or '83). No, I haven't tried them yet but plan to (unless some catastrophic failure reports pop up around here). Cylinder boring prices seem to vary widely. My cycle shop charges what I consider to be too much but they send them out and tack a fee on top of what the machine shop charges. I would call around to machine shops and go direct, eliminating the middle man (the cycle dealer). You might get prices then as low as $15 or $20 per hole.
 
Update...

I ordered the second oversize pistons from Cruzinimage-co in Japan, (his name is Mitsuo).

I read enough past threads discussing the pistons he sells to make me think that the quality is fine and that these are likely the same aftermarket pistons available at MikesXS and 650central.

I also sent the seller a note about the 74-76 product description letting him know that being 447 series they should fit all model years after that as well. I suggested that he look into it and maybe change the ad, might sell a bunch more.

Piston Set w Rings $ + Japan Shipping $ + Local Cylinder Bore $ = Less $ than just buying pistons and rings anywhere else.

Hmmmm....fresher engine and change in my pocket.....I had to go this route.
 
Please do report on shipping time and quality! I have long considered buying 4? sets of these and taking them and 4 sets of cylinders to a local shop to be match bored. Perhaps set up an exchange service; your used cylinders for a ready to install set up.
 
Yep...I will put up a post when they arrive and tell you what I can about the quality. My cylinders will be match bored to the pistons to hit that original gap spec from Yamaha too.

I'll get the new piston dimensions from the machinist and then take a photo with a new and OEM piston on one pin to see how the ring grooves match up.

I hope these pistons fit...if he changes the ad on my suggestion and they don't fit I will be like Typhoid Mary of the XS world.

I think your piston/cylinder sets would be a popular item...you might end up being on a first name basis with your UPS guy. Come to think of it you could already be 'best buds'...does he eat lunch with you?


XStretchified
 
XStretchified650 said:
.you might end up being on a first name basis with your UPS guy. Come to think of it you could already be 'best buds'...does he eat lunch with you?


XStretchified
Click to expand...

No but I share a morning break with my USPS rural carrier, we swap leads, he's an antique snowmobile guy.
 
Buying 447 pistons for your 533 engine isn't the seller's fault .....
 

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