KZ650B TOP END REFRESH

At 48,000 KMS the bike is still running well, but has developed a head gasket weep, 1/4 teaspoon a ride, and a cold start produces a grayish smoke that burns off after it warms up. No smoke one fully heated pointing to valve stem seals.

I have sourced the valve stem seals, base, head gaskets...New standard piston rings, all associated cam chain dampers and Orings. 

The valves and cam chain were changed at 33,000 kms.....so definitely behind on a valve adjustment. 

Up in Calgary so 4 weeks of good riding remain. Since May I have done: new oil and plugs,  a brake job front and rear. I did a double disk conversion up front, new brake line, 2 sets of pads and a fresh set of shoes with brake flush and it was a huge improvement. Full polish on cases, wheel bearings, did the steering bearings to taper rollers, chain and sprockets front 16 / 40 rear with 530 chain,  Bridgestone spitfire raised white letter tires ready for next spring. 

Bike was riding great after some carb work out of storage and new cam end plugs to stop a pesky leak - not the first time.  Put on about 3500kms so far this season. No oil issues until recently. Pulled hard, but recently fouled #1 plug with carbon and slight bog on the throttle in low gear at highway speed 70 mph. Oil is weeping under #1 cylinder. 

I'm going to Crack her open and the plan is to do a valve lapp, new stem seals, shims, and the valve cover, head and base gasket, cam chain gasket. Media blast the jugs while off. 

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Question

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I have new rings for the pistons, but I have to purchase a dingleball hone to remove the glazing for the new rings. What size hone should I buy? 3"? What grit: 240, 320? I did a lot of poking around, but no answer to the questions could be found.

Thanks for the info in advance. Any advice appreciated. 

I calculated the DIY service I have completed to date and has saved me about $3000 CAD in labour costs per time and local avg shop hourly rates. 

I have the tools on hand: inch pound torque wrench, valve spring compressor....etc. 






 

Ensure you have a kawasaki workshop manual to read before starting the tear down. 
Unless you know about them or read the manual to educate yourself about them there are few little quirks that can catch the unwary out. Eg, there are two 6mm thread bolts down the cam chain tunnel that often get missed as they are not obvious. Without removing them no amount of banging and bashing will get the head off. 

Regarding the hone abrasive size either of those will suffice. 

Breaking the seal of the base gasket can be a little awkward the manual explains the safest procedure to avoid breaking fins from using a pry bar in the wrong places. 

I would do a compression check before disassembly.  If good then you may want to avoid changing rings and base gasket.

Check your valve springs against the spec in the manual.

If you hate the shim under bucket design you can consider switching to shim over bucket....to make future shim changes easier.

If you pull the cylinders you should check them for wear.  Will need a borehole gauge.

Good new is I have the shop manual, Clymer and Haynes manuals. There is a gent that did a top end rebuild on a 78c in a 14 part series on YouTube. Very well done series. Goes through all of the work right down to torque specs and order of the procedure. 

what size hone.....3" dingleball? 

Thanks. 

Compression test kit arriving today. 
Most guys say the jugs will likely shift when removing the head so may as well do the base and the cam guide damper blocks as well. Hate to have to do it twice. 

I am going to wait until the riding season starts to break up for deep fall before opening up the top end. Might as well at this point. 

Love the bike so I would really like to get it running like new again. 

 

2.5" hone is the closest.  I'd use 240 grit, but 320 is fine also.

I'd also use OEM gaskets.  Get the PN off Partzilla or similar, then go hunting on eBay for the best price.  Try not to buy something that's clearly super old, though.  Look for a clean package, indicating the gaskets are decently fresh.

Fresh oil drips piling up on the garage floor. Aside from the puff of smoke at start up it runs like a champ. Starts first kick on 1/2 choke or first touch of the button and idles at 1100rpm and is unwavering. 

A bit of trepidation, but I do not have any choice but to get at her. 

 

Well I replaced the chain and sprockets. 530 xring and 16 x 40.
The bike had a 38 on the rear beforehand and I found it a bit boggy. With the 40 tooth on the rear the bike sits right at the begining of the sweet spot in all of the gears. After a month of the new setup I am very pleased. 

I can only imaging how snappy a 42 rear would be....but at 100 kmph I am at 4k rpms in top gear with plenty of get up if I need it. No need to gear down like before. 

Probably 2 weeks left n the season so I will get after the top end 1st weekend in October. Shame I have to do it because aside from the oil it is running great. The puff of smoke on startup is definable valve seal leak. 


 

Did you end up doing the rings? What was the compression reading??

No need to use a hone on the bores you will prob still see the x hatch of the original factory machineing. Also why make the cylinders  have MORE cylinder to piston clearance? Honing is really just to get that final size and finish after a cylinder bore. Do a compression check with and without a little oil in the bore. (throttles wide open) and go from there. +1 for OEM gaskets, i use genuine for base and head on my Z500 for peace of mind also OEM valve stem seals for the same reason, paid divedends over the years. If you find any scoring you may get them out by honing but do not use the ball type hone, use adj hone with v fine grit stones and plenty of oil, take care not to over do the job as you will take materail away. I cannot over emphasis  the need to be maticulas  in the cleaning of the bores when reassebly is done.

Well, if I was doing this job, I'd use OEM gaskets, new rings, new valve stem seals, and a dingoball hone to break the cylinder glaze.  With only 48 kms, the cylinders won't be worn enough to worry about, unless you find a bunch of scuffing.  Also, check the cam chain rollers, and consider upgrading them if they are original, since they are a week point in those engines.