Engine Rebuild

cpotts454 · Posted: April 18, 2008, 12:30 pm Post subject: Engine Rebuild

Hello everyone! Its starting to get nice around these parts and I am about to get the old 77' out of hibernation. I meant to rebuild the motor over the winter, but I never got to it. I am going to attempt to rebuild it next week. Before winter time I had some loud knocking noises coming from the top end so I want to find and replace things that might be wrong.

First let me tell you, this will be my first time rebuilding any engine. I do have a manual for the rebuild.

y question is this, what is the bare minimum parts needed in order to rebuild my motor (providing nothing is wrong), and what kinds of things do you recommend replacing while I am in there?

Thanks for the help.

Cooltouch · Posted: April 18, 2008, 6:14 pm Post subject: Re: Engine Rebuild

You'll need a decent set of micrometer calipers -- aka dial calipers -- and a set of these:

www.harborfreight.com/...umber=5649

You'll use both to mic your pistons and your bore diameters to find out if they are still within tolerance limits. If they aren't, you'll have to have your cylinders bored to the appropriate oversize, buy matching oversize pistons, and rings.

Since you will be pulling the head off, you should, at a minimum, lap the valves. Having a 3-angle valve job done would be better. If your bottom end sounds okay, then you probably won't need to open it up. If you have any doubt, or if you're having trouble with your transmission, then you should probably open it up. Inspect everything while in there and replace parts as needed.

Do Replace:

- Timing chain
- Timing chain guide bar
- Rings
- Cam bearings if they have any excess play, rough spots, or notchiness
- All seals and o-rings

That's about all I can think of at the moment.

Best,

ichael

TheDude · Posted: April 18, 2008, 7:12 pm Post subject: Re: Engine Rebuild

cpotts454, great question, I’m looking forward to reading what people have to say about this. I will be rebuilding my first four stroke engine in the not too distant future.
Cooltouch, As an industrial technology teacher, I feel a need to clarify some measurement terminology as shown in the images below.

Cheers,
Jerry

TheDude · Posted: April 18, 2008, 7:35 pm Post subject: Re: Engine Rebuild

ps, you are going to want all three of these items. Use the telescoping gages in conjunction with the micrometer calipers.
micrometers are very accurate (up to .0001" resolution), but the range of measurement is only one inch, so you will need a set.
dial calipers are the workhorse and can measure inside, outside, and depth to .001".
also, I would avoid harbor freight if possible for precision measurement tools (I buy almost everything else there).

cpotts454 · Posted: April 18, 2008, 8:16 pm Post subject: Re: Engine Rebuild

Great info CoolTouch. I am going to order the basic parts from Mikesxs.com. Obviously if I open it up and find something that is out of tolerance I will have to buy more, but here is my buy list at best case scenario:

1. Premium 72-84 650 Gasket Set $48.00 USD /Set
2. Cam Chain $39.00 USD
3. Guide Stopper $26.00 USD EA.
4. Valve Lapping Sticks $4.50 USD /Set/2
5. Piston rings - $29.00 USD /Set * 2

Total rebuild cost - $ 175.50... Does this sound right?

Lets just say that I have the stock bore on this block, does mikesxs sell stock piston rings? I couldnt find them.

cpotts454 · Posted: April 18, 2008, 8:18 pm Post subject: Re: Engine Rebuild

The Dude,

Let me first tell you the Big Labowski is probably my favorite movie.... also, thanks for the advice on the measurements.

grizld1 · Posted: April 18, 2008, 11:03 pm Post subject: Re: Engine Rebuild

cpotts, don't forget a tube of Three Bond 1104 for the head cover. For a cheap upgrade that'll keep head fitting torque in spec longer, replace the 4 rubber-sealed washers on the top end studs with copper; Suzuki part no. 09168-10017 is what to use (thanks to Bob Bertaut of 650Motorcycles.com for that tip). As to new standard rings, I think 650 Central offers them. If Michael doesn't have them, you might try www.yamatopdog.com .

If there's a good automotive machine shop in your area, they'll often mike out pistons and cylinders for a price somewhere between cheap and free. If you can reuse your pistons with new rings, be sure to have the bores honed.

5twins · Full Member Joined: Aug 05, 2006 Posts: 1616

Yikes! all those measuring gauges. I never (well, almost never) do that stuff. I just look. If there's no visible wear and scrape marks on the bore, you should be good. I do check ring end gaps and test the valves for leaks but all this bore measuring .... well, it was runnin' pretty good when I took it apart. Or was it ..... if you're rebuilding because of a major failure then you better check all that stuff.

nj1639 · Posted: April 19, 2008, 7:14 am Post subject: Re: Engine Rebuild

cpotts,
I did a top end rebuild this last winter. Had a scored right cylinder, 30 lbs compression.
I found a retired machinist to do a rebore, 2 over for 40 bucks. Pistons and rings were purchased after the bore for proper fit.
Had valves and seals done, 40 bucks. Same machinist.
Set of xsjohns needles(+/- 40 bucks).Gaskets and sealer, front cam guide and cam chain.
I tore it all down and put it all back together and it runs great.
This machinist ain't too far from you.

xsjohn · Posted: April 19, 2008, 8:03 am Post subject: Re: Engine Rebuild

Scored right cylinder.....now that doesn't suprise me....bet that won't happen again now with those right and left needles........xsjohn

jimmythetrucker · Full Member Joined: Mar 12, 2008 Posts: 1283

Plastigage is useful when fitting insert bearings. I'm not sure there's an application for it in this context. The XS650 is all roller bearings, isn't it? No need for Plastigage there that I know of.

xsjohn · Posted: April 19, 2008, 3:12 pm Post subject: Re: Engine Rebuild

Plastigage is what you put in between your teeth on these to relieve the pain of vibrations if you gear them too low and try to go anywhere farther than the local beer store.........xsjohn

Retiredgentleman · Posted: April 20, 2008, 1:00 am Post subject: Re: Engine Rebuild

Yea John, I've been thinking about my bikes low gearing ( 17/36)...........no looose fillings yet but don't want to give my dentist any more money...........he already drives cadillac SUV.

XSAndy · Posted: April 20, 2008, 2:43 am Post subject: Re: Engine Rebuild valve grind

No need for lapping sticks when doing a valve grind. I did my first rebuild this year and a guru up the road suggested that better than lapping sticks is a portable drill. battery powered that is. Put your paste in the valve area to grind and slide the valve into place.
Then just connect the valve end to the drill the same way you do a drill bit.
Use some forward and reverse with your drill while pulling gently back on the valve. Heaps faster and probably a better smoother action than trying to do it by hand. Only just enough of the vavlve pokes out the back of the guide so be a little careful attaching the drill. otherwise it's easy!. if I can do it anyone can.
Of course this is only good for the final coarse/ fine grind and can't be used to do the first few angles in the seats. For those if they need it I'd get a pro to do it anyway.

XSAndy · Posted: April 20, 2008, 2:43 am Post subject: Re: Engine Rebuild valve grind

No need for lapping sticks when doing a valve grind. I did my first rebuild this year and a guru up the road suggested that better than lapping sticks is a portable drill. battery powered that is. Put your paste in the valve area to grind and slide the valve into place.
Then just connect the valve end to the drill the same way you do a drill bit.
Use some forward and reverse with your drill while pulling gently back on the valve. Heaps faster and probably a better smoother action than trying to do it by hand. Only just enough of the vavlve pokes out the back of the guide so be a little careful attaching the drill. otherwise it's easy!. if I can do it anyone can.
Of course this is only good for the final coarse/ fine grind and can't be used to do the first few angles in the seats. For those if they need it I'd get a pro to do it anyway.

royfisk · Posted: April 20, 2008, 9:10 am Post subject: Re: Engine Rebuild

xsandy
that is not a valve grind, that is a manuver called seating the valves. A valve grind is a procedure where one would remove the valve and regrind the angle on the edge of the valve. A seat cut is then done to match the valve grind, then one would proceed to seat the valves. I would not use your method due to fact that seating valves should only require a light scuffing of the 2 surfaces if the valve and seat are both good. And if there not then they need grinding and seats cut. The drill method described can take off way more material in a fast way then neccesary.

royfisk · Posted: April 20, 2008, 9:12 am Post subject: Re: Engine Rebuild

lapping sticks you do not need to grind valves is true , you need a valve grinder

jimmythetrucker · Full Member Joined: Mar 12, 2008 Posts: 1283

If the valve grind was done properly, there's no need to do much lapping. A few passes with fine-grit compound and a wooden lapping tool ought to do the trick -- unless the guy who ground the seats did the job with a cinder block and didn't use a finishing stone.

Lapping smooths the seating surface and helps to form a more perfect seal between the valve and the seat, as I'm sure you already know. But just as important as a perfect seal, lapping shows us WHERE the seat seals against the valve. A properly ground seat, after minimal lapping, will show a circular track at about the center of the sealing surface on the valve.

Th "track" on the valve sealing surface should be the exact width of the sealing surface on the seat but should be more narrow than the sealing surface of the valve. The mechanic should see two more narrow, "unlapped" tracks on the sealing surface of the valve, one above and one below the track created by lapping.

If the "track" formed by lapping is too "high" (toward the valve stem) or too "low" (toward the lip of the valve), the seal formed by the surface of the seat and the surface of the valve may be imperfect. The valve and/or the seat may not cool efficiently. This can result in compression loss, in fouling, in burning, and/or in damage to the valve, to the seat -- even to the head itself.

In short -- putting grit on a valve seat and spinning the valve against it to create a smooth surface isn't the sole purpose of a lap job. When lapping valves, be sure you understand precisely WHY you're doing WHAT you're doing. Correctly done and understood, your lap job tells you if the monkey who ground your valves did a proper job. Never take his competence for granted because even the best grind shops screw up at least once a year. The engine you save will be your own.

royfisk · Posted: April 20, 2008, 9:32 am Post subject: Re: Engine Rebuild

you are right

jimmythetrucker · Full Member Joined: Mar 12, 2008 Posts: 1283

One more thing about valve jobs -- Smart money ALWAYS replaces the exhaust valves in an air-cooled engine because, in an air-cooled engine, exhaust valves have to endure an extraordinary amount of heat. Intake valves run much cooler and can be safely re-used if they're not damaged in any way. But ALWAYS, ALWAYS use new exhaust valves when you rebuild your head.

royfisk · Posted: April 20, 2008, 10:21 am Post subject: Re: Engine Rebuild

I dont agree with that jimmy. your right to the point that the exhaust valves need replaceing more often then intakes. But they dont always need replaceing. I have a grinder and can regind my valves and stay within spec. I can also recut my seats. And that is not restricted to air cooled engines either water coolers burn up there exhaust valves first too.

cpotts454 · Posted: April 20, 2008, 10:54 am Post subject: Re: Engine Rebuild

Well I am ready to do this rebuild. I trailered the bike to my parents garage (my dad works on old cars so he has lots of tools), and starting tomorrow I am going to pull the engine out of the bike and probably tear everything else off as well. (I want to spray everything with flat black primer, I am going for the black on black look until I can afford a real paint job)

So, thanks everyone for all the advice. I will probably require more of it while I am doing the job as well.

nj1639, once I tear to engine apart to see what I am going to need, I might need to get a number for your machinist to do a bore job. What city do you live in Indiana? My actual home is located in Jeffersonville.

jimmythetrucker · Full Member Joined: Mar 12, 2008 Posts: 1283

That's alright, royfisk -- I have no problem with people who disagree -- as long as they remember I warned them. Cool

And yes, you're right: water-coolers burn the occasional exhaust valve, too -- but not nearly as OFTEN as air-coolers.

Actually, my experience in rebuilding air-cooled engines all comes from the two years I spent in a VW shop (1973-74), so the things I remember could be dated or it could be they don't apply to Japanese motorcycles, and you could be absolutely right. I've never rebuilt an air-cooled Japanese engine because I never yet had one go South on me, and I never worked in a bike shop, repairing catastrophes wrought by God and by idiot others.

aybe the Japanese build better valves than the Germans. Maybe the Jap valves cool better. I believe the Japanese use better steel -- at least in their more expensive cars. Even so, I'm not persuaded to take the risk. Exhaust valves are cheap and, when I've already got the engine torn down in front of me, they are easily replaced. On the other hand, tearing an engine down to replace an exhaust valve (and maybe a piston, too) is both expensive AND a giant pain in the ass.

That's my logic. It could be illogical, and it doesn't mean your logic is wrong in any event. It just means I'm gettin' old.

I wish I knew half of what you know about motorcycles, and I'm trying to learn as much as I can. In ancient times, you know, students didn't sit in class and take notes. They learned by arguing with teachers. My experience as a teacher in modern schools convinces me that the ancients had the right idea. Don't be offended if I disagree with you today because something that happens tomorrow may cause me to change my mind. Learning things the hard way may not be wise -- but it's goddamned effective.

Peace, Brother.

nj1639 · Posted: April 20, 2008, 1:08 pm Post subject: Re: Engine Rebuild

cpotts454 wrote:

Well I am ready to do this rebuild. I trailered the bike to my parents garage (my dad works on old cars so he has lots of tools), and starting tomorrow I am going to pull the engine out of the bike and probably tear everything else off as well. (I want to spray everything with flat black primer, I am going for the black on black look until I can afford a real paint job)

So, thanks everyone for all the advice. I will probably require more of it while I am doing the job as well.

nj1639, once I tear to engine apart to see what I am going to need, I might need to get a number for your machinist to do a bore job. What city do you live in Indiana? My actual home is located in Jeffersonville.

Well, you're closer yet. I'm up in the Vevay area but the machinist is in the Lexington In. area. Let me know if you need the contact.
Rick

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