'03 Suzuki Z440.... (if shadetree mechanics drive you insane, don't click!)

[RIDE-RED 250r]

So, last may I picked up and '03 Z400 with a Wiseco 440 big bore.

This quad has been ridden pretty hard but overall still rides and functions well. I ended up buying it with some reservation due to a low RPM knock it has, but went with it because it came wit quite a nice pile of extras for the price.

This low RPM knock is present under a load, or no load and goes away pretty quickly just off idle.

My first instinct was the lower rod bearing starting to get sloppy, so I went ahead and got a good used crank and figured I would get the engine gaskets and replace the crank this winter.

Well, now that my R project is mostly done and now just waiting for a few last odds and ends I figured I would wheel the Zuki in and get started.

Guy I bought it from stated the cam chain was new, along with the big bore being very fresh, bla bla bla...

With these dual cam engines, the camchain is kind of a weak area and wear pretty fast compared to most of their single cam counterparts. Plus, when the chain gets too worn, due to there not being as much chain wrapping around each cam gear on a dual cam as opposed to single cam, they are much more prone to jump timing and bring you bundles of joy in head problems...

So, I get the topend off in-chassis and the forst thing I notice is the ACCT only has 2 clicks left, meaning the cam chain is about at the end of it's rope... So, they probably used a cheap ebay chain, no big deal, I'll remedy that. But it still doesn't explain the knocking..

I then pull the cyinder thinking I am sure to find a worn lower rod bearing. First thing that jumps out at me after I pull the cylinder is a nice 1/4" wide streak running the full length of the stroke in the otherwise like new looking cylinder. Upon checking the corresponding area of the piston I find that the lower flat oil ring is has about 1.5" of it broken off and MISSING! The remaining end got peened over the edge of the ring land and cuased the previously mentioned streak in the cylinder. Oddly enough, this thing never blew smoke at any time I rode it last summer.. But what BURNS me is that you just KNOW that whatever numb-nut put tis thing together was having trouble sliding the cylinder down over the piston and instead of re-grouping and starting over probably just pounded it down on with a rubber mallet or something. How the heck else would an oil ring just break like that??!! It's not like ring gap was tight and it caught a port or something, no ports in a thumper cylinder! So, that made me kind of mad. Unfortunatley, because I just don't have the budget to buy another brand new sleeve and have it installed, for this year I'm just going to have to hone the cylinder as best I can without going too crazy on it (steel sleeve, not Nikisil), get new rings and run her for this year.

So, now the bottom end is setting on the bench and I begin to start looking things over.. And without even removing any of the clutch side components, like crank gears, counterbalancer, clutch, etc, I can slightly jiggle the clutch side crankshaft end enought to see movement in the piston, and to hear a soft knock. BINGO! Found my smoking gun.

The funny thing is, I would be willing to bet they did the whole big bore, camchain and crankshaft in an attempt to address the knock it has only to put it back together and have the knocking still occuring! LOL! So they turned around and sold it... No big deal, she'll run like a watch when I get through with it..

So, I just recieved my flywheel puller and crank bearings today and depending on whats going on this weekend, I will be getting the bottom end done. The wife did't give me the kitchen pass to get the rnew rings and camchain all at once with the puller and crank bearings as we are a bit tight this week due to a bad previous couple weeks of work...

I'll probably be ordering the last 2 parts needed next week and finish this thing up. Very much looking forward to having a nice sounding, non-knocking hot-rod thumper.


If this is of interest to any of you guys, let me know and I'll post some pics of the job...

[atc007]

Great bike for sure! And like you said. She'll whisper like a Swiss watch when you're done ! Check your frame around the upper A arms for cracking.. My bet is it's at least rusty if not through. If not. It's a late ser # or hasn't been tested hard enough lol..

[RIDE-RED 250r]

Well, at some point someone stripped it down and repainted the frame and a-arms. The frame is dark blue and the a-arms black. It has been welded in the "weak spot" the early Z's are known for. But I don't worry about it too much as this quad is just for playing around out back and cruising gravel roads on Tug Hill. I don't jump.. at all!

It's definitely snappier than the stock 03 z400 my wife had. We just sold it to a friend. I have decided I want to switch to 400ex's for the kind of riding we do. After learning more about the hassles sometimes associated with dual cam engines, I want to switch to Honda and their single cam with adjustable rockers. Those valve shims are a royal pain!

I'll likely be working on this engine in the garage this weekend. I'll post up some pics. Tell ya what, that thumper has one heck of a BIG piston! LOL! 94mm, and riding a shorter stroke than a stock 250r... Thump thump thump!