The 'build thread' of a Kawasaki Z250 C, a total beginner's point of view...

sham

New Member
Hey Tommy,

Thanks and thanks for the tips over on 1800.
I'll look into it - not sure you're from but I'm in Syd, Australia and the only deflection torque wrenches I can see are about $250...
Still annoyed with my failure to ground the electricity...took the spark plug wire thing a bit too literally...
Wondering why the fuse didn't blow - think it has to do with the fact that the electricity going to the ignition was under the 25A or so, but is then transfered into volts by the ignition? Just talking to myself now.

Anyways, yeh thanks.

Btw, appreciate that story of you and your dad. Ha, I never had such opportunities, but it sounded cool.
 

sham

New Member
Are they any good? Last time I bought a budget ratchet from Bunnings, the thing broke first go.
 

TommyRocker

New Member
We always called them deflection torque wrenches, I guess they are technically called "bending beam" or "needle point" torque wrenches? I like Deflection better... Anywho, I don't know your stores or prices, but ebay Australia seems to have lots for around 20 of your dollars. I just picked mine up at the local hardware chain store.

And yeah, I don't have a lot of those stories with my dad, he was a sailor and when he was home he tended to be a pretty distant guy, but I certainly do remember the ones I did have. I wouldn't say go out and buy every specialty tool you might need, but certain things are pretty universal. A torque wrench is one of them.
 

teazer

Well-Known Member
DTT BOTM WINNER
Cheap tools unfortunately do not last, but even a cheap torque wrench is probably better than no torque wrench. My preference is to buy GOOD quality tools at GREAT prices. I don't like junk ( i tried that few times and it never worked out for me). I don't need 110% pro level lab quality tools either.

And I try to borrow tools to see what's good and what isn't before I buy and I do the same with friends. I'll take round a bunch of tools to assist on an engine strip and inspection, or I have them bring their parts to our shop. That way I get to play with different engines and keep learning and having fun and passing on the secrets ...
 

TommyRocker

New Member
teazer said:
My preference is to buy GOOD quality tools at GREAT prices. I don't like junk ( i tried that few times and it never worked out for me). I don't need 110% pro level lab quality tools either.
I agree, but I've found that there are certain cheap tools that tend to work fine. Especilly the simpler things. With ratchets, cheap ones are a nightmare. With a breaker bar, cheap is fine, or better yet, a long pipe. Snap ring pliers? Spend the extra change on good ones... Wrenches? I've never had problems with cheap ones. As long as they are the right size, they seem to work just fine for me.
 

sham

New Member
I had a look at super cheap auto, but it still wasn't that cheap, so I'll most likely get one sent over from Hong Kong. At least I can get someone to look over it, so hopefully it will be a decent one for a similar price.

Anyways, I undid the alternator and valve covers tonight. Found out my valve clearances are way off - almost double the recommended distances for both valves. So just one question in regards to that - to get the timing mark to the "T" mark, is the inlet valve suppose to be at its peak (ie highest position)? cos I found that while it is traveling along its upward movement before it hits the "T", it continues to go up after this.

I was with a friend and we were both under the impression this should not be, however, after further reading, I'm starting to believe that this is ok, as the TDC position (which I believe is what this "T" mark is) is suppose to be where both valves are open, hence allowing for the measurements to be taken. This means both valves are not at their lowest or highest positions. Can someone confirm or clarify this please?

At the end of the day, all this seems to go back to my need for a torque wrench, as the locking nuts have to be adjusted to a specific torque. So I guess I'll have to wait a bit now.

The O rings also looked a bit squished, so I'll probably get that gasket and o ring set, if its still being sold on eBay.
 

teazer

Well-Known Member
DTT BOTM WINNER
A 4 stroke engine does two complete revolutions per cycle. One time at TDC the engine is firing and both valves are closed. The other time it's at TDC both valves are slightly open. The exhaust is almost closed and the intake has just opened.

Obviously you can't check clearance when the valves are open because there isn't any. You check valve clearances on most bike at TDC when the valves are closed.

Turn the engine over a few times watching the valves and all will become clear. Watch all 4 "strokes" Intake, compression, power and exhaust. They overlap slightly in a real engine but you can see what is happening if the valve caps are removed and plug is out.
 

sham

New Member
Oops, just realised that I was turning the crankshaft the wrong way around (clockwise) instead of the specified anti-clockwise. Can someone tell me what the effects of this is as I did this a lot (read probably 20 rotations plus)

I'm reading that I may have affected the tension of the chain, or that I may have loosened the crank and rod bearings? Or that it doesn't do anything at all...

Any advice would be great, on what to do if something has gone drastically wrong, or a heads up if nothing has.

Thanks.
 

sham

New Member
Ok so - disregarding the first question last night asking whether TDC should be at the very top of the valve movement or not, which came about from me and my friend reaching TDC via the wrong direction, hence it wasn't at the time (half a rotation) specified by the manual.

On top of the question regarding possible damage, I have noticed that the crankshaft turns a lot easier as the inlet valve is moving up, as I am nearing TDC. It literally almost "slips". Is this normal, or should it be a controlled motion?

My feeler gauges aren't very accurate I realised, but I am getting readings of between 0.5 and 0.75mm, which is no where near the 0.13mm maximum of the inlet valve, and 0.22 of the oulet.
 

TommyRocker

New Member
Unless you loosened the crank bolt you were cranking on, you're probably fine(just don't keep doing it). Do you have the plug(s) removed? The sudden ease of rotation could be compression being released(maybe it was capable of some compression all along...). Or, as the piston reaches TDC there is less sideways force being exerted on the piston(you're putting more energy into the piston moving up and down and less into forcing it into the cylinder wall).
 

sham

New Member
How will I be able to determine whether I loosened the crank bolt? It seems peculiar to me that I can turn it both clockwise and anticlockwise and yet it doesn't "unscrew"? Ha. Anyways, yeh I did the have the spark plug removed - the first couple rotations I made in the right direction produced quiet a bit of noise, like it was getting back into sync? But I may be paranoid. The sideways force sounds interesting.

I found an article on camshaft timing which I glanced at very briefly. I'd like to take a read tomorrow as it seems to explain some basics, though it isn't dedicated to motorcycle engines.

http://www.circletrack.com/enginetech/ctrp_0805_camshaft_timing/viewall.html
 

teazer

Well-Known Member
DTT BOTM WINNER
STOP.
First up, can we please have one thread rather than two with the same issues. It's confusing and counter productive.

You may have loosened a bolt and if so it will tighten when you change direction.

Yes it's possible that the cam chain tension is out of whack but that would be unusual. If there was too much slack it might be possible for a cam chain to jump its sprocket. Unlikely but possible.

The reason that your motor is easy at some points in the rotation and hard in others is the cam. As you are opening a valve, the cam pushes on the rocker and that pushes down on the valve compressing the spring. When the valve is closing, spring pressure helps you.

In addition, there are points like TDC and BDC where the piston doesn't move much compared to 90 degrees ATDC where the piston is moving at highest velocity.

It is not a side thrust issue.

Do you have any articles on 4 stroke basics?
 

TommyRocker

New Member
That does make more sense. Coming from multicylinder, multibank engines, there generally isn't much perceptible difference in valvespring tension throughout the rotation(nor is there with side thrust)because there are always valves opening and closing. With a single, the valvesprings are definitely the likely "problem" that he noticed.

and good call on one thread...
 

sham

New Member
Hey teazer - thanks. I'll try to keep conversations to the one place from now. I hadn't actually thought to read up on 4 stroke basics before you mentioned it, but I'm not going through various articles on-line and its been really helpful.

From what I have read on 4 strokes, this is how I understand the issue which I am facing.

I can now connect the earlier issue I discovered (which I'm still facing), of fuel not being sucked through the carb, with issues with my engine - that fuel is not being pulled through because the intake cycle is not happening properly. This can be traced to the lack of compression (30PSI), as the engine will require 3 things to start.

1. Fuel
2. Compression of fuel by the piston
3. Ignition of fuel (spark plug)

My valve clearance being much larger than the specified maximums means that I am leaking air from the valves, which affects compression.

So for now, I think I will hold off on the gasket and o ring set, get my hands on a more accurate set of feeler gauges and hopefully borrow a torque wrench until mine gets delivered. I'll get some new oil and a new oil filter and change them and hopefully it will start up. Otherwise I will have to look for other reasons why I'm getting such low compression.

Thanks for feedback.
 

scrapper

New Member
I'm actually having the reverse issue with the fuel being blowing through the carb
on an 1981 G1 Z250
http://www.youtube.com/watch?v=6gGfpW_R-lg
After trying to sort the timing and valve clearances for a week I pulled off the head
this came down to the valve stem being bent , (the bent valve spring snapped when I pulled this out)
I could see the stem didn't sit correctly either so it would have been losing lots of compression as
well as causing it to pass the wrong way.
I managed to find a complete running engine on ebay for £60 , So will drop this in while I wait for
the stems and springs to come up on ebay at a reasonable price to rebuilt this engine.
 

sham

New Member
Hey scrapper - sorry to hear that, though a complete running engine for 60 pounds sounds like quiet a good deal.

I guess for me, the good thing is that mine isn't sounding like your video at the moment, so hopefully it is just a valve clearance issue which can be fixed, and hopefully there won't be damage to the engine. I'm sitting around waiting for a torque wrench to arrive, so twiddling my thumbs for now.

Hope your rebuild goes well - be great if you documented your process on here - I'm sure we'll be coming across similar issues. Good luck.
 

sham

New Member
So torque wrench finally came along with the dad - for some reason it didn't want to work yesterday, maybe I was too tired or something, but worked a treat today.

Got the valve clearance fixed, installed the new oil filter and gave it a oil change - the stuff that was coming out was black...

Battery is now charging again - its on 12.2 which is around 50% according to the charts - then it will be compression time again.

Fingers crossed.
 

sham

New Member
Nothing happening lately. Did get the bike to 103 PSI (dry test) before battery died. Haven't had time to do anything since then.

Just note to self : need new fuel cap gasket, most likely 51059-008 (fits Z200s). Can't find parts manual for Z250 C, and the D models have a different tank and fuel cap.
 

sham

New Member
So its not a battery issue now - looking like a rectifier and maybe CDI issue? Time for 1800 cafe again...
 

DTT Bike Of The Month Gallery

DTT Light or Dark

www.cognitomoto.com
https://www.townmoto.com
www.speedmotoco.com
www.jadusmotorcycleparts.com
www.lostapostle.ca/
www.sparckmoto.com
Top Bottom