Topic: CB750K4 Piston Rings and other engine stuff

[batdan]

I noticed that there are rings at Z1 enterprises for around half the price per set from Servicehonda. Is there any reason to get the ones from Service Honda rather than the ones from Z1 Enterprises? I don't one want to waste money. Also who makes good gasket sets and seals for the bike? I have heard people suggest getting all NOS Honda stuff but is that REALLY necessary? It seems to be quite a bit more money for something that has probably been sitting in a warehouse for 20 years.

Also is there anything else that oughto be done to the motor and checked when doing a rebuild?
So far it is stripped down to the engine cases which I'm gonna clean and repaint with some black VHT paint.
I plan to replace all the crank and connecting rod bearings, all gaskets, seals, the transmission bearing that was pressed into the case (I forgot to remove it when cleaning the case out and got some dirt in it), and the head has been sent in to MRieck. I'm sure i need to get the cylinders honed too. Also I plan to put a new cam in there (Webcam grind#41)and a new sprocket and maybe a new chain (from dynoman). I had my father (a machinist) measure the cylinder bore and the crank journals for wear and they all seemed to be withing spec according to the service manual. Anything else that oughto to be done or replaced? Like cylinder studs (will this help prevent oil leaks) or new valve springs or some other part that I just as well may replace since it's already torn down? I've never taken apart an engine before so I'm trying to be ABSOLUTELY sure I don't screw it up.

Also I seem to have two different although nearly identical castings of pistons. Two are marked "300       8"  and the others are  "300       11" Does this matter at all? Also the pistons are kinda scraped up like someone scraped off the carbon before or something and they're also slightly pitted. Would it be an advantage to polish them up a little?

Well that was more than I meant to ask, but hopefully someone will be willing to answer some of these questions so I'll feel a little more confident about this rebuild. It's fun to work on the engine but I certainly still want it to work when I'm done!

[kettlesd]

Those rings on Z1 are made by K&L. They ae the ones with the regular three-piece oil rings. Anyone have thoughts on them? I did a search on K&L and nothing came up.



 http://www.z1enterprises.com/detail.aspx?ID=1947

[bryanj]

Replace the primary chains and all the cam chain tensioners with a new cam chain. Valve stem oil seals are also a good idea whilst the head is off and a tacho drive oil seal whilst the cam cover is off

[Lumbee]

...wow Bat...I think u got it covered...sounds like u'r going all the way, or close to it.  I normally only rebuilt the topend.  the bottoms are so buttet proof, theres usually not a probablem down there.  As far as gaskets go, Athena and Verish are u'r options, I've used athena on 3 rebuilds, and have been pleased, hoever I did have on head gasket leak 2 months after the rebuild...not sure if thats the gaskets fault or not though.  Verish is a little more expensive (few dollars) and I've heard the quality is better, gonna try a Verish gasket set next...

[batdan]

Thanks bryanj, I will consider those things although they seem pretty expensive.. Also Lumbee, you mean Vesrah gaskets, right?
Anyway here's everything I have on my list to buy and where to get it from. I'm not certain if I'm gonna buy a new camchain tensioner primary chains or valve springs yet. I'll probably get the valve springs but not the others. There's things on my bike that need help other than the engine and I need to try to save some money for those too. For instance, when I had a new rear tire put on before it involved sandblasting...

Service honda:
all new main and connrod bearings (all green)        $150
?new primary chain                                  2x$77(sorta pricey)


Dynoman.net:
new camshaft webcam grind 41           $180
adjustable cam sprocket                 $40 
tubaki cam chain                        $37
Vesrah k4 gasket set                     $80
--->maybe new valve springs?          -->$70
Oil seal kit                            $35
??cam chain tensioner set               $90(kinda a lot...)

Z1 enterprises:
new standard size rings                 4*$14

plus that new trans bearing
(I'll probably order that with new wheel bearings
since it doesn't have a groove in it or anything)

plus valve stem seals from somewhere

So I think that's everything as far as parts to buy for the engine goes. Hopefully nothing missing as I'm probably gonna order these in the next couple weeks. The engine is going to be painted black eventually and the covers are going to be polished. We'll see how that looks. This damn thing had better not leak oil! I thought the old head and cylinders were painted black but it just turned out to be filthy from grease and dirt!

[Lumbee]

This damn thing had better not leak oil! I

....don't be to discouraged if it does...not saying it will, just preparing you for the possibility.  As I said, I've done 3 engines...I followed the same process on all of them (with Athena gaskets), and one started leaking 2 months after the rebuild.  Are you planning on using some type of sealer?  I know lots of folks do.  I do not.  However, thats just my preference.  I would rather have a leaky gasket, then crud in my engine.  Plus, I get a kick out of having a nicely sealed engine know I did not use any sealer.

...oh, and yes, I mean Vesrah...

[andy750]

Having had my K4 engine rrebuilt a couple of times now (and currently under rebuild again) I have used several Vesrah gaskets with mixed success. First rebuild - lasted 10,000 miles (2 years) before leaking - oil had eaten away at the gasket. No sealant was used on gasket. 2nd rebuild - leaked after rebuild very badly. Now on the recommendation of Mike Rieck (master SOHC engine builder) Im going with Cometic gaskets - if you get Cometic gaskets and compare them directly to vesrah gaskets you will see the difference in quality.

Good luck with whatever you chose.
cheers
Andy

[MRieck]

 Daniel
 I PM'd you. Get the valve springs. I can get the stem seals.
  Mike

[Lumbee]

...hey Andy, do you have a source for the cometic gasket set?

[andy750]

Best to ask Mike Rieck as he got it for me but I believe he got it from Dynoman (also on this forum).

good luck,
Andy

[batdan]

Looking at dynoman.net it looks like they only list Cometic head and base gaskets of varying thickness. It looks like you'd need to get a kit for all the other ones. But I suppose those are the ones that you would want not to leak the most.

[bryanj]

Think about all that 30 year old hard heat treated rubber on the tensioner wheels that is just dying to break up and jam in all the tiny orify (if thats the plural of orifice)!