www.zxrworld.co.uk

Right guys.

I've been doing a bit of searching on the forum, but I can't find much concise information on these.

What I need to know, boils down essentially to - is there anything radically different involved in doing the HG on the DOHC ZXR engine, than doing a head gasket on a DOHC car engine?

Beyond that, I need to know;
- Materials for the ZXR's components - block and head, cast steel and ally respectively?
- Skimming tolerances for the ZXR's head/block (if I need to skim at all)?
- Head bolt torque figures and tightening order - and are the head bolts reusable, or are they stretch in and replace type?
- Cam carrier bolt torque figures, et tightening order if applicable. Actually, thinking about it, do these engines use line-bored carriers for the cams, or are the carriers merely a moulded part of the head itself?
- Will I need any specialist equipment for the job (besides a valve spring compressor, which I've borrowed as I'm going to be regrinding and lapping the valves and doing stem seals) - particularly could anyone point me at a cam locking tool for timing, or a nice cheap carb balancing tool?
- Valve clearances! - can anyone point me at a guide to doing this for the ZXR's, or someone who has done it before a few times themselves, maybe give me a good step-by-step walk through of the process?

If there isn't a guide for valve clearances already anywhere, but I can get help or instructions from another member, I'll look into dong a guide myself for future use.

Also worth contemplating at this point I suppose is compression - presuming I have the HIGH Comp pistons (which I believe I may well do, and zimm shared this notion after riding it), I assume my options on skimming a larger amount to raise compression is simply limited by the valve clearances cut into the piston crowns? And by the same logic if I have LOW Comp pistons, my options are somewhat more open, along with clearances less desperately important?

Maybe I'm barking up the wrong tree there, I have to admit valve clearances is not something I've looked deeply into before, nor compression, it simply occurs to me that I see a lot of stuff about having no base gasket (... oh, that's another thing), and raising compression.

What's that all about, no base gasket? I presume that's something to do with the HG, and raising compression by removing a layer from the (presumably multi-layer) gasket?

Any and all advice gratefully welcomed, folks!


Chris.

from how i understand it, you might want to remove the gasket between the block and crankcases (base gasket) to raise compression and close up the squish to a tighter (but acceptable tolerance), improving combustion

personally i wouldn't bother on a road bike, if the headgaskets gone (i have had a few on various things) i would just take the head to SEP at kegworth, or somewhere similar, they know what they are doing and they know the spec's, and they ain't a lot of money! then build her up with genuine parts, following the manual on here to the letter.

as for valve clearances, buy some good feeler guages and torque wrench and follow the manual again, to the letter! its daunting, but not a hard job, just remember to gently and equally release the cam caps, do the correct shim changes, and do everything up in the correct sequence up to the correct touque, as per the manual!

i'm sure cargo and others could go into more detail, and probably will will elaborate on any hints or tips, or if i got something wrong!

hope that helps

cliff

To go into detail would take an age to type out........................

Vard I'll PM my phone number and we can chat................ much easier cos you have a fair idea of whats involved anyway.
It's not that big a job..................funny enough i've an engine on the bench now.................for the exact same job.

Check you pms and ring me.

Oh, wait, now, Cargo?

It's all in the manual mate.. chapter 4 of the H model.

http://www.zxrworld.co.uk/Manuals/H%20M ... er%204.pdf

if you get stuck (and you wont) just bring it over here or give me a ring.

no fancy tools needed ... unless valves/seats need replacing.. which they shouldn't

likewise skimming .. if it aint warped just clean it all up.

Cliff, much obliged.

I don't think I'll be worrying about the base gasket then, as you say, just not worth dicking about with on a road bike.

I would LOVE to take the head somewhere and just go 'oh, sort it out for me...' but I'm skint. No, in fact, I'm skinter than skint, so this is a budget job, buying parts m'sen and doing the work m'sen.

RE: The manual 'on here' - am I missing this? All I can find is a link to a dealership which sells them, and some microfiches in Japanese.

Don't suppose you could hit me with a link to this could you?

*Edit* Oop, zimm's beaten you to the punch on that one!

How did I miss this before?

Ta,


Chris.

here we go, matey!

http://www.zxrworld.co.uk/zxr400/manual.html


oops, i'm too slow!


zimm,

incidentally, how you gonna check it aint warped? i've only seen it done on a milling machine with dial guage attached.

we talking about a "known straight edge" and feelers here?

no picking, just curious, always handy to learn something!

cliff

AH!

The underlined text is a hyperlink!

That's how I missed it before.

I hovered over the images above the links, and didn't see an option to click, so moved on.

Might point that out to Baz, be good to have the images hyperlinked also.

Cliff, that's my plan. A good metal ruler is my 'straight edge'.

i found this thread useful for doing valve clearances

viewtopic.php?f=55&t=8002&p=83205&hilit ... wap#p83205

this is with engine in place but if your doing HG its easier with the engine out.

Wait, what?

HG is engine out?

it can be done in the frame, but re-assembly is tricky.

Fucking not cool.

Engine out is easy....................we'll talk tomorrow.....thursday about 12

Ok, warming to the idea of engine out a bit now, have had a bit of a natter with zimm on MSN.

Can anyone tell me roughly how much bore travel there is between piston BDC and the bottom of the bore?
Also, when at half travel?

*EDIT*

Thinking about it, I can't see any reason why the pistons would need to be TDC/BDC position for lifting the block off the crankcase, so if they were all at half travel, that'd give me plenty of room to play with. Anyone have any good reason why not to do this?

What I'm thinking is that if I'm going to be rebuilding without the base gasket (mostly for less cost and less work - the thinking for which I'm about to explain), then I could simply lever the block off the upper crankcase by just enough to snip the original base gasket, (this presuming there is one fitted), remove it and tidy up the faces. Then mate with high temp silicon sealant, rather than lifting the block until the pistons do in fact come free of the bores, thereby saving myself having to go to the trouble of relocating the pistons in the bores, without snagging rings.

I'm thinking that if I've got anything like a couple of inches to play with before the BDC pistons start popping out of the bottom, it'll be simply far easier in this fashion, and as a slight by-product-bonus, the benefits of compression and squish - (that really is a funny term, is that really the technical name for it?)

Please feel free to point out anything that I've missed that nullifies this whole notion, guys.

simples ...

its a bitch to get the mating surfaces clean enough while holding the block 2 inches off the crankcase with one hand

try it.. but i bet it turns into an oily mess.