Digging Deeper

February 16, 2017

Next, i’m dissasembling engine cylinder head and inspecting it for wear. Engine ran but unfortunately i did not have enought time to ride the bike as it was pretty cold outside. No smoke, pretty good idle.

Grease and gunk everywhere.

Camshaft. Words like SOHC or DOHC didn’t mean anything to me before i started working on the bike. SOHC - single overhead cam, a roller with lobes. With DOHC (doube) you get two. On bigger displacement engines its usually 2.

Camshaft removed. Gotta get a micrometer and measure everything.

This is the first engine i’m working on so it’s going to be a learning experience. Pistons dont look too bad. However, there seems to be fresh marks left by valves. I’m not sure if i will be able to keep the stock pistons. Also, unlike other engines i’ve seen (CB350/550), both pistons on KZ400 move to the firing position at the same time instead of one by one. I’ll be easier to fit new piston rings.

Both pistons have marks on the exhaust side.

I dont know what happened so will have to get the valves out, clean and check if they’re bent. This is definitely unexpected.

Valves. It’s hard to see on the photo but there’s a slight mark on the left valve. Looks like it was hitting the piston.

Right cylinder bore appears to have some scratches. Bore surface should be smooth but this one is definitely not. Not sure what my options are right now, either go with oversize piston or just hone it a bit.

Feb 17, 2017

While trying to figure out what to do about the engine bores and pistons (and who knows what else) i decided to do something else. Plus didn’t really have much time.

Starter rotor and other smaller parts turned out to be pretty clean after metal rescue. One thing about metal rescue - parts will turn black if you leave it for too long. Brushed some of that black cover stuff off. Looking good.

Got to prime the chain cover while the weather is warm. It was really nice out, i wish i had a bike to ride around.

Decided to paint the headlight bucket. I had a few cans of spraypaint with different colors (black, gunmetal). For now i’ll keep it black.

I had an extra side cover with a few broken pieces and cracks on it as a test bed for painting. My original plan was to paint all plastics and tank using Duplicolor Gunmetal rattlecan. I think it’s too light, i was looking for something darker.

February 18, 2017

Orbital sander produced a very trippy color palette.

February 23, 2017

Didn’t appomplish anything today. I spen almost 2 hours trying to get the cylinder off the engine. It’s just stuck. Gave up and decided to remove valves from the head. Again, no luck there as i need a special valve spring compressor tool. Sigh.

March 4, 2017

Engine teardown finally moved forward. I bought the valve spring compressor tool and was able to get 3 valves out. Last one had a stuck valve retainer that i couldn’t get out.

With valves and springs out i still have to get a tool to get proper measurements. Both exhaust valves hit the pistons at some point so i will be replacing them for sure. Intake valves looked fine, just lots of carbon buildup. Next step is to wash all of the gunk from the head and check if valve seats have to be re-cut.

My previous attempts to remove the cylinder block were unfruitful so i decided to soak it with PB Blaster. Surely, after about an hour of waiting and light prying it came right off.

Gunky, but smiling.

Here’s the real problem. One of the cylinder bores has a bunch of marks on the surface, and they’re not small either. Bummer. Second bore looks pretty good and does not have any marks at all. I’ll try to find a local machine shop to take a few measurements and decide what to do next.

Looking way better now.

In addition to my issues with the cylinder block, i now have another troublemaker: cam chain tensioner rubber piece has slit off the metal frame. I was hoping to get it replaced without tearing into the bottom end. No dice.

Removed and cleaned pistons. These will have to be replaced.

Most of the bike looks like this now :)

March 5, 2017

Tried to remove the last valve off the head.

As you can see from the picture, the tool is now bent. It’s also a reason why i couldn’t remove the last valve. I use a heavy duty adjustable clamp (from the pic above) to get the job done.

Cleaned up camshaft surface and discovered a few scars. Man, this engine just keeps giving.

My next step is to split the engine case and replace the cam chain tensioned. I dont know what i will find in there, hopefully everything is clean and in good shape.

There are so many bolts and screws in the engine case i decided to mark every single one of them. I feel like it’ll be a fun puzzle putting everything back together.

March 11, 2017

Big day today - splitting my first engine case!

First, i continued to remove all top case bolts and marking them so they are all correct when i start putting the engine back together. I found that marking the case and then using it as a photo reference will definitely help.

Next, i removed the clutch basket and primary chain. It was a bit tricky due to lack of proper circlip puller, but i got it done. Clutch plates are going to be inspected and if they’re out of spec - replaced.

Clutch shifter mechanism.

Hooray, cases are finally split! Everything looks pretty clean to me, that does not mean that everything is in spec though.

Transmission, this is what makes your motorcycle move.

To replace the broken cam chain guide i need to remove this block.

Lower case. Havent found any broken bits which is a good news. Will cleanup all the gunk.

Bottom of the engine is always messsy, lets fix that! Most of the buildup should be fairly easy to remove, just takes time.

March 12, 2017

Turned out that the chain guide replacement part i had it not the one i actually needed. What a bummer. There wasn’t any engine work for today, so i decided to clean up the lower case.

Turned out to be nice. Next i decided to take a stab at side cover polishing.

Not bad either.

April 1, 2017

I’ve been out for work and other stuff so haven’t had any time (or parts) to work on the bike. However, just wanted to recap a few things for the future me if i ever get to work on another build.

I think winter is over and just got my TU250X back from storage, feels good riding again. My first thought was “fuck it, maybe i should just sell the kz bike”. On the other hand, i haven’t really done much (except for learning). Why not keep going? Good call. I’ll just do that. Done, $200 worth of parts is purchased.

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