Hi All, I recently spent some time with @Murdo going over some fine-tuning options for my ZX2R engine. Part of the lessons was a look at cleaning up inlet and outlet ports on the head. I had brought up a ZXR250 head that was 'sacrificial' due to some issues. After looking at the head, Murdo suggested it was actually fixable (?) so I started looking around for what he said he needed. I read through some of Blair's posts and found the following company (amongst others). Of all the companies I contacted, they (Moldstar) were the only ones to get back to me and provide pricing etc. Murdo suggested buying some rod and turning it down to make the seats, so that's what we'll probably do. Happy to buy some rod for multiple projects and share the cost if anyone is interested. Not sure about duty and import taxes etc, but at least there is an option for anyone wanting to refurbish a head with damaged valve seats. The valve seats on the ZXR250 head are 18mm and 21mm. The contact and company details are below if anyone is interested in buying any rod of them or having custom seats made. Scott Moberg <scottm@moldstar.com> wrote: We make and sell the rod. You would need MS90 .750” dia x probably 3”-4” long. We can make the seats also, but we are currently at a 7-8 week lead time. 20mm (approx range .786”-.788”) X 100MM $29.27 US Dollars 26mm (approx range 1.029” – 1.034”) X 100MM $29.27 US Dollars I was not able to calculate shipping based on the address (Tamworth, NSW) provided. Scott Moberg Performance Alloys & Services, Inc. Performance Mold Products, Inc. N116 W18515 Morse Dr. Germantown, WI 53022 Ph: 262-255-6662 ext. 104 Email: scottm@moldstar.com Fax: 262-255-3655 www.moldstar.com
Count me in for some rod for seats if you get some, I'd also be interested in getting some thinner rod for valve guides which I believe is a different # material IIRC Moldstar is the stuff IMO and has fantastic thermal conductivity characteristics compared to iron!
I will ask about a smaller rod for valve guides. In the meantime, another of my enquiries has had a response. There's a crowd called Kibblewhite Precision Machining in the USA that is used by drag racers. They don't have any seats (or rod) that meet our requirements, but they did give me some details that might come in handy down the road. Their website is https://www.kpmi.us/home.html We don’t make any seats that small. If you want to make a bronze seat, you can order C630 bronze from onlinemetals.com. I don’t know how it will hold up with steel valves in that application. Iron based seats are typically made by casting a blend of alloys together or are sintered in dies if the materials won’t blend correctly in the casting process. There isn’t a bar per say of that type of material. Seats can be made from Ductile Iron, but you need the correct grade, and it has to be heat treated to give the correct hardness. You might try the Tucker Valve Seat Company in Texas. I don’t see anything as small as your specs in their catalog, but they might be able to help you. It’s my understanding that they make short runs of custom seats in a reasonable time frame.
Sounds like it's the same material for the valve guides. This is the email I just got from them... Yes valve seats and valve guides, anything where there is high heat and you are trying to remove the heat. When machining, you have to make sure to use carbide cutters and flood with coolant or oil. You do not want to allow the material to work harden or it is very difficult to work with. It will work harden with expose to time and temperature in the application and that is where the gains come in. Let me know how much rod you want for valve guides and I will order everything in one go. @Murdo do you want to have a go at the valve guides too?
Just need to get the right interference fit and find someone who can cut them. Early model Ducati's used what looked like Al-Bronze seats and they were hard as. For guides, check the wear properties on the Moldstar or material you choose. I used to hardchrome the stems for Duc's with bronze guides. I would say the life of the guide was 3 times what it would have been otherwise. There is a shop in Brisbane that as one of those new fangled CNC seat machines so they could do any size. Let me know if you want details. You will need to start measuring where the OEM valve seat is in the head so that the new ones are cut to the same spec.
Before you go too far check your shop in Brisbane can cut seats that small. Remember Mike Green's turbo FZR250 and the problems getting seats cut ? Then you need to sort an interference fit dimension for the seats - and presumably a source of liquid nitrogen to shrink them before fitting. And make up pilots to hold and align the seat rings as they go in.....It's all good fun. Removal of seats without damaging the head is best done by putting a ring of weld around the ID of the seat - MIG or TIG. As it cools the seat shrinks and will fall out.
I'll have to check my research, IIRC it was moldstar 90 for seats and moldstar 22 for guides, to be verified, I did do a lot of reading on these materials a few years ago Guides mentioned in this http://www.moldstar.com/misc/Racing Moldstar MS22.pdf Seats pictured in this http://www.moldstar.com/misc/Racing Moldstar MS90.pdf This page confirms http://www.moldstar.com/MotorsportApplications.htm
I found a local place with a seat cutter, cannot recall the name right now, European brand that goes onto a Serdi base, the smallest cutter 'almost ' goes into the throat of an FZR250 exhaust and it uses a single carbide cutter blade, I've sorted carbide guides, just need to get back down to see them again. They don't use the smallest cutter and were prepared to turn it down on the lathe to go into the exhaust throat. I'd be interested in seeing if we can sort a common seat cutter(s) between the 250's My goal is to fit CBR250RR [larger] valves into the FZR250 head, all doable EDIT - the valve seat cutter was a Mira, very capable tool
@ruckusman MoldStar replied with details for valve guides (Rods available). I'm happy to buy a new ZXR250 Valve Guide from Kawasaki so we have the exact dimensions to make them. I'll let you guys figure out what's needed and we'll go from there. http://www.moldstar.com/newproducts.html MoldStar®90 Rounds Nominal Approx. Range 1/4 inch diam - .285 to .289 3/8 inch diam - .386 to .391 1/2 inch diam - .530 to .531 5/8 inch diam - .668 to .680 3/4 inch diam - .786 to .788 I would believe you are running something in the .375” - .500” OD range.
@Frankster - I can visit the engine reconditioning shop local to me and get the measurements of the Mira valve seat cutter if you like [you don't have to use them obviously]; The Mira will do 16mm seats with 4mm stems, so that's the ZXR250 covered hopefully. https://www.miratool.ch/MIRA-VGX-21-and-VGX-21-Starter-Package.php If you can take a measurement of the ZXR250 exhaust valve throat, I'll get the measurement of the tool holder diameter. At least that gives you a target to aim for when it comes to the seat cutting machines.
