Mella yella (zxr400) rebuild.

[FROSTY:Me]

After my last outing at Pukie it seemed Mella yella had got a tadd sick.
Before stripping him down for a rebuild I thought I'd better do a baseline run to see just how bad he is.
After 2 runs on a local dyno I thought the hp test was for someone elses bike. 41 then 42 hp seems a tadd low.
Alex did a compression test for me.
In theory he shouldn't be running it seems. Worst compression is in number 2 at a big 50psi compression.
The others are better but right at the bottom end of the range for a bike to run on.
It seems one of my oil rings has sucked the kumera as well as 3-yes 3 valves bent
Origonally I planned on boring him out to 420cc but I figure now that just a rebore to max oversize a valve grind and replacing the bent valves will be enough to freshen him up.
I still need to sort out the rear shock but It might be a case of borrow the olins out of my zxr750

[vifferman]

It seems one of my oil rings has sucked the kumera as well as 3-yes 3 valves bent

How do valves get bent? Over-revving?
BTW - It's a bit of a worry you calling your bike "him"

[White trash]

ZXR400s, although beeing the best of the little un's, have a habit of tightening their valve clearances very quickly when continually thrashed.

If you're not on top of it, the valves are not permitted to close properly and a bit of a rev and WALLOP!

Aparently

[FROSTY:Me]

Yea my foot slipped off the gearchange as I was accelerating from castrol in the pissing rain.
Yea funny innit but mella yella is definitely a bloke -dunno why but he has a bloke personality.

[FROSTY:Me]

ZXR400s, although beeing the best of the little un's, have a habit of tightening their valve clearances very quickly when continually thrashed.

If you're not on top of it, the valves are not permitted to close properly and a bit of a rev and WALLOP!

Aparently

Thanks WT
I needed reminding I f#$#d up --
actually it was more like a bloody gigantic overrrev
still I was gonna pull the head off anyways

[Hoon]

I wouldn't worry about the rebore yet, just go for new rings, valve grind and 3 valves to get the engine sorted properly then go for the big bore once everything is sweet - will only cost you an extra head gasket and set of rings, otherwise you could end up with a big bored lemon.

We did a top end refresh on my ZXR (valve grind, clearances, and polish up) and now I get 190-210psi on all cylinders. I found a lot of valves were tight and pitted with heaps of carbon on the seats - over 1/2 of them weren't closing properly. You might want to check your valve guides too as mine were worn but not yet ready for the bin.

Also did you get your carbs sorted? Mine have been stripped/cleaned/checked and are all sweet so if you still want to borrow a set for comparison I'm sure we can work something out.......

Ohh and make sure nothing is missing from the airbox. I thought I'd do a little optimizing and left off a little snout but it made my bike run like a sack of shit.

[Milky]

Any idea on the cost of this job? would be interesting to find out for my purposes...

also, on compression testing, it is reasonably easy when the spark plugs are near the surface of the motor... With these ones being stuck so damn far inside, what can you use to check compression by yourself? Would a big long tube do the job? I guess not, unless it is solid pipe. My only experience with compression testing is using the dial gauges that go directly into the plug holes themselves...

[Milky]

We did a top end refresh on my ZXR (valve grind, clearances, and polish up) and now I get 190-210psi on all cylinders. I found a lot of valves were tight and pitted with heaps of carbon on the seats

Did you do the grind yourself or get a shop to do the dirty work for you? I *might* have a go at it someday after uni has finished if the whole job is cheap enough...

[Kwaka-Kid]

Milky mate whip em on round here! Got all the valve grinding tools and im sure dad will give you a hand. Been considering doing mine too... but the head is so sealed etc it seems a waste to break it :S hmm.. maybe if i run into a nother engine

[Hoon]

Did you do the grind yourself or get a shop to do the dirty work for you? I *might* have a go at it someday after uni has finished if the whole job is cheap enough...

Nope did it myself under the close eye of my mechanic. Its a long and tedious job and would prob cost you close to $2K if you got a shop to do it because 95% of it is labour. Only cost me $70 for a new head gasket but I was able to reuse all my parts. Took me close to 2 weeks (of evening work) to get it done so not really something that can be accomplished in a Sat aftn.

[FROSTY:Me]

Hoon--I hear what you're saying.Its become bloody clear though that a lot of my "carburation" problems were actually valve gear related.
You could as easily have been describing my engine When talking about yours. with the rust etc.
Im doing the job "properly'-Ie strip. down to crank so the motor will be fresh.
If I still have problems then i'll be looking further afeild.
One problem is a funny foam filter that is affecting how she runs.

[Milky]

Milky mate whip em on round here! Got all the valve grinding tools and im sure dad will give you a hand. Been considering doing mine too... but the head is so sealed etc it seems a waste to break it :S hmm.. maybe if i run into a nother engine

Ditto here... got the tools, and a dad, and considering doing mine in the distant future, so maybe you would want to whip round here

Nope did it myself under the close eye of my mechanic. Its a long and tedious job and would prob cost you close to $2K if you got a shop to do it because 95% of it is labour. Only cost me $70 for a new head gasket but I was able to reuse all my parts. Took me close to 2 weeks (of evening work) to get it done so not really something that can be accomplished in a Sat aftn.

I have done the valves on the R65 and on a CB250RS, so i would like to think there was nothing stopping me on this bike... I was never considering going to a shop to do it - money grabbing, pocket lining, 200% markup, couldnt care less about the customer b*&%^$~#s

[Kwaka-Kid]

haha nice one milky!
Sweet dude! And nah i seen what a sack of spuds that 250 was compared to mine with my old mans valve grinding and engine rebuild /port skim the lot... and guess whos turned out betteR? :P HAHA! Didnt yours end up using all the left over slow bits mine didnt need? hhahaha! all good bro, yeh itd be interesting to see other ppls ways, how many angles do you guys aim for on a valve grind? i think stock is 2, race is usually 3 but i heard a rumour of 5's! s'all about getting the most flush wearing surface to seal up right?

[FROSTY:Me]

haha nice one milky!
Sweet dude! And nah i seen what a sack of spuds that 250 was compared to mine with my old mans valve grinding and engine rebuild /port skim the lot... and guess whos turned out betteR? :P HAHA! Didnt yours end up using all the left over slow bits mine didnt need? hhahaha! all good bro, yeh itd be interesting to see other ppls ways, how many angles do you guys aim for on a valve grind? i think stock is 2, race is usually 3 but i heard a rumour of 5's! s'all about getting the most flush wearing surface to seal up right?

Its all in the lapping I think.A 3 angle cut is fine But when its done the lapping in to get a perfect seal in my opinion is more important.
Concept I've been playing with here guys.A valve head is a highly polished surface made none the less of steel. No matter how good a grind we do on a race bike it spends an awful lot of time sitting not running. Im Aucklands damp enviroment could it be we are getting rust on our valve heads?

[FROSTY:Me]

I just had the parts arrive for mella yella.
Head gasket $50
Base gasket$40
Valves $30 each -x4
pistons $120 each X4
Rings $60 per set x4
now I guess its time to poke a boring bar down the holes and wear out the fingers with the lapping paste.