Info FZR250 valve seats

well, you put more effort into measuring it than i did i just eyeballed it. seems to have done the job. for now!

just popped kiwimatts 3ln1 head the other day, and its seats looked pristine, none of that recess ive noticed, well... maybe a smidge on one inlet only. quick lick with the cutter i made, sorted that out. nothing like my own head was. it would seem that theres a wide variation in the quality of these seats, i guess its time to pull my own 3ln1 apart as well? (havent even tried turning it over, was simply told its got the chugs)

but all valves themselves have developed, hmm, how to put it... a lip? i still reckon this is the main reason for "the dreaded chug". lack of back cut, the recess on the outer edge, and the valves no longer seating on the 45 but wedging into and hanging up on the 60, and/or carbon on the 30/32...


i might try this myself but try epoxy/polyester and a spray of silicone instead... personally im dubious about anything involving hotglue! too pliable. bad visions of dodgy YT videos with "free to rights" music...

really, shouldnt have to do a full plug, just lie it over, plasticine "dam" as required, and get a partial. let a screw set in there so you can yank it out. something that sets hard lets you get a good flat grind on it... really do have to be dead on centerline with that bit

imho, just cut it to 30 and accept that it will be cutting into the combustion chamber a bit. theres already some nasty shrouding in that area as it is that really needs a blending. i started that on my original head but for now, ive put that one aside for "sacrificial setups"... wish i hadd known the OEM spec BEFORE ordering a bunch of 3 angle cutters? my smallest is 1.2...

and if youre going for bigger valves its going to happen anyway. (stem diameters? guides?need input! more info!!!!!)


grrr, now you got me sidetracking... im trying to figure out 8 bit mathematics at the moment! i knew i shouldnt have logged in!

to RRF DECFSZ? or to SUBLW BTFSC?

 

no, use plasticine in the same way youre using the syringe plunger, but you can do it in the combustion chamber as well. make a little "dam", "bowl", call it what you will...

imho, hot glue is still too soft, especially if hacking with a scalpel. dont need a full plug, only a crescent, bit under half the seat imprinted. then its pretty easy to yank out.

hard epoxy/polyester resin lets you really get it spot on as you slice it down the centreline, and theres absolutely no chance it will deform. that being said, five minute epoxy isnt very hard, JBweld sticks like turds to a blanket, and polyester resin is probably the best option, used it before to get imprints of two smoker exhaust ports... i do have some "high strength" epoxy that may set hard but also tends to not stick to anything very well. meant to be for gluing golf clubs together? FORE!!!!! imho, its TOO hard for whats labelled "high impact", the stuff shatters... probably ideal for this job...


only takes a tiny offset from center to alter the apparent angle measured/produced. (this delves into sharpening machine tools... off topic!)

wish you had posted this last week or i would be doing it myself? not about to pop the intake valves out again, ive already ground them in... shame, as the seats were beautiful. meant to start thread on that one, but whatever. might post a pic or two anyway.

ah well, got another pair of 3ln1s, and a 2kr i can try it on... 2kr may be best as its NEVER had "the dreaded chug"...

every valve ive looked at has been "lipped", its what got me into backcutting them in the first place... definitely worthwhile, if not for performance, but to simply prevent this "hangup" i believe is happening. the 45 on the valves from eyeballing it is about 2.5, maybe 3mm... far wider than the seat itself.

yes, you want the contact as close to teh edge as possible for breathing ability, yet not so close that the edges overheat and burn out. then theres a fine line between sufficient seat area for cooling, whilst not overdoing it so they never truly seal as theyre too wide for the springs to do their job, or receding as its too narrow and the springs do their job too well... pretty easy on a 5L hemi with 40mm valves, another matter entirely on these pipsqueakers where theres absolutely no tooling available!!!!

amusing that the factory seems to have ignored their own OEM specs?

my personal approach is to use fzr400 valves (anyone got the stem length on them?), punch out the guides, and if i had my baby lathe setup for CNC (ANOTHER project? ) would spin up a new set... hmmm. maybe i can bore and lap some out to 4?

goodsons (neway) smallest arbor is 4mm. the aliexpress "3.5" is about 3.42 iirc... and their cutters were dubious. if ones going to widen the seats though, the neway cutter could be a good investment. cant justify modding one for a one-off, they arent cheap!

lol, you made me go and order two new blades last night, the 0.8mm and 1.00mm 3 angle inserts. one day i might actually set up the jig for the mill so this becomes a half hour job... biggest challenge is doing it with NO arbor at all... rigidity is the key, along with clocking up with a "tenths" indicator... (stupid "freedom units" measurements...)


youre game, hacking seats out and flipping new ones in ive run the idea through my brain, and thats about as far as i will go...


mmmm, beryllium bronze... dont breathe the dust! i have a 30mm bar of it here...

 

A couple of points arising...Plasticene is temp sensitive. Cool the head and the plasticene and it'll stay firm enough to cut and measure. Probably the wrong time of year to work with it in Oz.
For 1mm o/s valves I'd recut the OE seats. There should be enough material there.
If you really want to pull the seats and replace, the safest and least damaging way is to run a ring of weld - MIG or TIG - around the ID of the seat. When it cools, the seat will shrink and drop out.

 

Having just read all this, and doing some 2mm oversized valves on an XV1600 head (so far I have needed to throat the bejeezus out of the seats and then face them, then throat again to get the seat contact in the middle portion of the valve seating surface in the middle of the valve. Otherwise the sealing surface is back towards the stem on the valve).

The biggest problem I've found with the valves and seats on the 250's (aside from them being tiny and hard to find cutters for them) is valve recession. Most valves I look at on the 250's are cutting it very fine on the margin. Assumption is that they have all been recut in the past and this reduces the available margin on the valve, and recedes the valve further. My ZXR250 valves didn't have a lot of margin left to work with, nor did I have small enough cutters for them or the seats, so the best I could do was lap them in.

I think the most practical solution, if the seats are OK, is new valves with lots of margin. The new valves shouldn't need to be cut, but you will need to cut the seats to get the sealing surface in the right position and thickness.

Assuming you can get small enough seat cutters, I would recut all the seats to 60-45-30 with all new valves. Adjustable/removable blades are nice as they allow you to have the blades clear any shrouding on the head, otherwise you will be removing material from the combustion chamber.

Just my opinion.

 

same cutter. i had the urge to measure it today. yes, its 9mm. youve basically done everything i was thinking of a few months ago. looked at the ground rods, never ordered, etc etc. anyway, i got the whole range of (45) blades from 0.8 to 2 now? meh, $7-8 each, no big expense.

was just going to make the body/bush part over again, and that ties into not using an arbor at all... the cutter wont move over enough to get into the exhaust valves, and the arbor would have to be cut away past center as well to make room... leaving sweet eff all... whereas its pretty easy to make a solid shank with slot to take the forked insert holder.

had the urge to try the holder as it was today, try cutting a "seat" in a lump of steel pipe to see if it would chatter before wasting time... and yeah... why is it 9mm? WHY? i got 8 and 10 ground rod, but 9?... stupid effin...
"back to the shelf with you!" might dig out an old 9mm drill though, still wanna see if it will cut at least?

too many projects. im just gunna watch this thread and see if it works out or if you wind up with an anchor...

neway is 7.5mm through the cutter.

 

im assuming you got the second one from their list, the long skinny one. "multi angle cutter". possibly thats why mine look like they wont fit... theyre all multi angle, just... wider. "standard", judging by the listings. . some other vendor has that skinny blade listed as "brown", another one as "for small seats", etc etc. usual ali express i tossed up over getting that one but baulked due to the 0.8mm seat. seeing more than enough recession as it is. 0.8 seems to be cutting it a bit too fine.

meh, will cut a 9mm drill down in the next few days and see just how small a diameter i can get without hacking the holder...

 

yeah, with the skinny blade... because that cutting edge is all inside of the mounting screw hole. if only they had several choices on that seat width as well? if they had a 1 and 1.2, id buy them... maybe grab a few blanks and grind to single angle...

well, i had to have a go...
14MM bore.

16mm bore

18mm bore. only jst startng with the 60.


the "45" cutters, with a dimension for the seat width, are 30/45/60. this being the 2mm.
no dimension= single angle.
i think i ran the bore out to 19.6 for this one.


smallest seat at 45 with these blades, and this holder, is 23mm. so thats basically a 24mm valve.


and wow, it took a bit of doing to get that chatter down to the bare minimum and its still horrid. what one would expect with a wide blade like this on a chinese lathe.


just a lump of cast iron. old "sash-weight".

had better results with my home made cutters, really.

 

arbor? its a 9mm drill i hit against the grinder to get the cutter over as far as it goes, relying on the shank. did i measure it? no

no pilot hole, just bored through to respective diameters.

65RPM and gently blowing on the handle, with lots of oil... anything faster was just a howling mess.

main goal was to see what the min diameter these blades will do, without modifying anything. (i bet i need a 9mm drill tomorrow?)

real test will be to run it in the mill...

 

you pretty well much posted everything i deleted when re-writing and trimming long winded posts...
watching a few YT vids, like cutting butter.

this tailstock has been questionable at best (the base looks like they machined it with a chisel?) and a jacobs chuck is far from ideal for anything but drilling rough holes.

a properly toleranced arbor will probably work wonders in itself. im still not entirely sure about pilot holes, i still have my suspicion that the seats are cut with out the valveguide in place, or the whole lots done in one go... 3.5mm still seems pretty inadequate to me. even if the arbor does stay at 9mm until the last moment.

taking a wide cut like this is a challenge for ANY machine to pull off without chatter.

then again, they had real machine tools, not H&F garbage. for all i know, the headstock on this thing was probably run through the same chisel as the tailstock when made/assembled, lol. maybe even check that the bolts are tight might work wonders... never considered that before.


sigh. not in the mood for more tests right now, but im thinking i might just braze the main holder onto a decent arbor, 3/4 shank, and run it off the ER32 chuck. have to do something like that anyway if i want to use these blades. make holder/modify holder. amounts to the same thing in the end... i dont want to tamper with the forked blade holder/cutter part though.

lol, the 1mm cutter showed up. you think theyd stick both blades in one bag seeing as i ordered them at the same time?

still, that seat it did cut definitely LOOKs like the geometry is right. id be happy if that was a lawnmower and i was about to lap a valve to it...

will fiddle a bit more over the next week or two, might even try a pitbike head... got enough of them to sacrifice, all destined for the melting pot anyway...

 

these probably belong in my OWN thread, but seeing as YOU mentioned the magic word...



by chiselled, i mean chiselled...

well, ok, "loose/blunt cutter on last part on last shift of friday afternoon".


whilst this is what ive been up to on the odd hour or two for the last few evenings...

dovetail off my baby mill, gotta get it back together so i can do some CNC... been far too long sitting neglected... made a mess of it years back, with valve grinding paste (are we back on topic now? lol)

it was better than when new, but still... not up to my high criteria... lol. then the computer died, roof leaked, and yeah... sat rusting for probably a decade? does anyone else miss winXP and parallel ports? i do!

the table is done, and oh my it feels good now, all smooooooth with no jamming or sloppy bits. this is the last surface... the hardest!

and of course, the straightedge i made from an old sashweight. about five cycles of soaking whilst red-hot before it stopped warping overnight...

which is only half the length of the column, but with some careful placement and much practice, works pretty well... matter of judging where its touching to determine if the whole thing is straight/in line. overlap, check, overlap, check, overlap, check... scrape.

ok. back to the real subject....


my plan for the heads, cus i have the mill... jig, two ground bars and support by the camjournals as theyre guaranteed straight and true. then it simply has to flop over to a stop for matching the stem angles. clock it straight with table, clock in on the guide, then a matter of stepping over the appropriate distance. ideally once set up its repeatable and fairly easy to do. ha, ha. famous last words.

usual method for cutting seats... get the tool set up on the first one, set the depth stop, then run through them all, with another pass to get them all level with the lowest. remove as little material as possible...

unfortunately i might have to give the big mill a scrape before attempting this, but it should be a LOT easier than this fiddly little one is? nice big surfaces...