500K2 engine rebuild. Newbie questions

[ebmbiker]

Good afternoon chaps,

Newbie member JB here,

I've bought a 500K2 project bike that's already been dismantled by the previous owner 10 years ago. Including the engine.

I know I need new main crank shells as I've only got 4 of the originals, the rest are missing. Besides seals and gaskets, what else am I going to need whilst I'm doing it? It's been decades since I've done any engine building, and those were 2 stroke singles. So what's the list of 'whilst you're in there' things to do?

Cheers, JB

[philward]

Apart from the piston/rings checking (cruzinimage on ebay are quality/cheap) change primary chain/rubber dampers (kawasaki chain is same and cheaper) (http://www.sohc.co.uk/index.php/topic,25977.msg238189.html#msg238189). Camchain (DID) and use genuine camchain train rollers/tensioners. Check gearbox bearings but generally serviceable. Check clutch pushrod as they are known to break (NurseJulie usually stocks them)
Check cams/rockers/bearings for wear.
Ex Honda technicians will be along shortly with detailed advice

[Oddjob]

Phil pretty much nailed it.

Buy a set of JIS screwdrivers, most important thing. Also see if you can find them in socket version.

Camchain, genuine no longer available unless your lucky, I'm looking into whether you can use a DID 219FTH chain instead as it's stronger than the standard DID chain and cost is very low considering.  Check tensioner blade, guide is usually ok, check tensioner adjuster screw slot, see if it's mangled.
Primary chain, buy the Kwack chain it's 92057-1011, half the price of Hondas and the same chain. Check the oil gallery running under the chain to see if the chain has been hitting it, replace the damper rubbers inside the primary drive hub, you'll need an impact driver to open that.
Check all roller bearings for notchiness and general motion. There are only 4.
Replace all o-rings and seals if possible, you'll need a rotor tool to remove the rotor to replace the one behind it or borrow one.
Check camshaft for wear on lobes and wear on journals, check the head for the wear as well. Check cam followers for wear, if in doubt post a pic on here for advice.
DON'T use an impact driver to remove the tacho drive housing, especially the one holding the cable in, you'll break the housing most likely, check to see if it comes out intact, a lot don't.
Check sump bolt thread in oil pan.
If in doubt, take a picture before dismantling, remove in sequence then reassemble after removal to make sure you know how it goes, use elastic bands if possible to keep things together. Watch when removing the gearbox from the cases, the ends will fall off if your not careful meaning you can't be sure how they went on.

Sounds like a handful but TBH these engines are easy to work on.

[murdock]

estamos ansiosos esperando.
 lo primero que necesitas es el manual de servicio
y revisar todo completamente

we are anxiously waiting.
 the first thing you need is the service manual
and check everything out completely

[ebmbiker]

Phil pretty much nailed it.

Buy a set of JIS screwdrivers, most important thing. Also see if you can find them in socket version.

Camchain, genuine no longer available unless your lucky, I'm looking into whether you can use a DID 219FTH chain instead as it's stronger than the standard DID chain and cost is very low considering.  Check tensioner blade, guide is usually ok, check tensioner adjuster screw slot, see if it's mangled.
Primary chain, buy the Kwack chain it's 92057-1011, half the price of Hondas and the same chain. Check the oil gallery running under the chain to see if the chain has been hitting it, replace the damper rubbers inside the primary drive hub, you'll need an impact driver to open that.
Check all roller bearings for notchiness and general motion. There are only 4.
Replace all o-rings and seals if possible, you'll need a rotor tool to remove the rotor to replace the one behind it or borrow one.
Check camshaft for wear on lobes and wear on journals, check the head for the wear as well. Check cam followers for wear, if in doubt post a pic on here for advice.
DON'T use an impact driver to remove the tacho drive housing, especially the one holding the cable in, you'll break the housing most likely, check to see if it comes out intact, a lot don't.
Check sump bolt thread in oil pan.
If in doubt, take a picture before dismantling, remove in sequence then reassemble after removal to make sure you know how it goes, use elastic bands if possible to keep things together. Watch when removing the gearbox from the cases, the ends will fall off if your not careful meaning you can't be sure how they went on.

Sounds like a handful but TBH these engines are easy to work on.

Cheers Oddjob, exactly what I wanted to know. Unfortunately, the engine was already in pieces when I bought the bike so I didn't have the opportunity to photograph and label things. The cam lobes, followers and journals are all smooth with no visible damage. I can see that the primary chain has marked the case, but not much. I'll post a photo of it once I'm back in the workshop.

Cheers, JB

[ebmbiker]

Here's a photo of the marks in the lower case from the primary drive chain. Thoughts?

Cheers, JB [ Guests cannot view attachments ]

[Bryanj]

Thats about as bad as it can be, its the groove at the topp right in the angled bit that is the problem.
Will be OK with new chain and damper rubbers.
Rubbers are still available to order from any Honda dealer

[Oddjob]

Yep, that's a bad un. Almost through the oil gallery, there are some things you can do.

First replace the chain and damper rubbers, that will stop it rubbing for a good while.

Replace the chain every 30K at least, sooner is better. You can't take a chance anymore as any more damage will mean a new set of crankcases.

Fit a CB650 primary chain tensioner, these can be hard to find but it's a mod worth doing, especially with that damage, you need a special bracket making to fit the tensioner. This is a mod I'm doing on my engine when it's next in pieces, which will be this year sometime. I had 2 of the brackets made as the engineer didn't want to make only one so I had to tempt him with 2. Cost me £50 each but one is spare if you ever go this way.

I'd replace the roller bearings on the primary drive as well, all that alloy flying around is bound to have gone into the bearings and the chain must have really been whipping around to do that much damage and that would have been hard on the bearings, for the cost, replace them.

[Bryanj]

Ive always wondered if youcould machine a steel tube to line  that gallery and slide it in

[Oddjob]

Not sure Bryan, I was cleaning one the other day and I think it goes round a corner so maybe not.

[Nurse Julie]

Blimey, that was a close shave 😱😱😱😱 I think we have had at least one, maybe 2 that have been worse than that but that's up there with them.

[ebmbiker]

Well I’m glad I showed you guys the damage. Is it worth getting the bad scar over the oil gallery built up with weld?

Oddjob, do you have a drawing of the 650 primary tensioner bracket mod you’d be willing to share? Machining is my background so I’m pretty sure I could make one.

Cheers, JB

[Oddjob]

Yeah got it somewhere.

Will post when I find it.

Here you go.



Would a picture of the finished article help?

[Oddjob]

Well I’m glad I showed you guys the damage. Is it worth getting the bad scar over the oil gallery built up with weld?

As long as you don't melt into the tunnel, yep if you can do it.

[philward]

Yeah got it somewhere.

Will post when I find it.

Here you go.



Would a picture of the finished article help?
[/quote]

Interested in a photo please Ken