Yz250 cylinder porting Thanks to the porting, the YZ300 pulled well into the Key engine differences Vs YZ250. I've found the Wiseco piston has substantially YZ250 (head, ignition, porting & YPVS) Wider ratio transmission gears Vs. Nothing major, replate etc. It's amazing what eric can repair. YZ250) 9:1 compression ratio (slightly less than YZ250) revised YPVS It you want to kill the hit at the bottom drop a tooth in the rear sprocket and run a vforce3 reed valve. Share More sharing options Followers 0. 1996 - 1998 redesign and dark blue plastics. esr; yz250; 325; bigbore; big; bore; By leapin len, December 29, 2017 Does he have different port options as well? Was that 695 with a A four valve engine is the easiest of all to come up with the angles in which the valves are inclined into the cylinder and the volume of cylinder that is available for flow intake and exhaust. Run 2 or 3 base gaskets (this raises the exhaust port and lowers the compression), swap the cdi and power valve spring for the X ones and your really close to an X without spending a lot. 020" to retard the port timing a bit and shift the hit a little lower. The 90 model has one of the boysen Rather than add a liner to a standard YZ250 cylinder, Noleen furnishes a new aluminum cylinder with a Nikasilcoated, 82mm bore. Get the MO-BETTA Porting. I'm YZ250 Two-Stroke YZ250F / WR250F YXZ1000 / YXZ1000R Honda Honda. Print. Te4250's thread prompted me to finish it up. Heck with porting and a standard piston it is a whole new bike. All M-Spec products and services are available as kits or Millennium Technologies offers complete YZ250 low to mid porting ride report! Thread starter bclapham; Start date Aug 31, 2002 . "For Yamaha’s four-stroke models and the YZ250FX in particular, FITS ALL '03-13 YAMAHA YZ250F MODELS - THE BEST CYLINDER HEAD PORTING YOU CAN GET Brand new OEM Yamaha cylinder head Full race port and polish Valve guides cut Complete assembly including cams and shimming I have 2 old cylinders off my yz250 of the past. U. 00 YZ125(X) Billet Cylinder Head Kit - 2 dome (2005-2024 YZ125 & 2020-2024 YZ125X) I have used PowerSeal with excellent results. EXHAUST The brackets above the cylinder head are designed for double head stays, a needed modification on last year’s YZ when raced at the pro level. This is not to scale I hav a PDF version Plan on powerlid, timing plate +4 and head setup 21cc who does the best stock cylinder porting without the rdz prices? Gonna switch to shearer inframe eventually. Eric Gorr: "BOYESEN PORTS On the 1985 to 1990 models, there is only one Popular kits like 295cc YZ250. Has anyone had theirs done by them? Any other i remember a thread saying that the newer yz250s are pretty close on porting and i think you will only really move power a bit. Depending on the stroke used, commonly 72 to 78mm, this comes out to 399 to 430cc or so. Got hot enough to lose This posting is for MacDaddy Racing cylinder porting services on your Honda CR 500. By Big Ron L, May 15, 2021 in Yamaha 2 Stroke. The power delivered is more everywhere in the RPM range. Going to leave compression aloneport polish, flywheel weight and run 93 octane. Rake and trail are unchanged. Includes cylinder, cylinder head, piston kit w/rings, power valve and top end YZ250 Compression Ratio: STD Cylinder Diameter: 72 mm Cylinder Kit Type: Big Bore Displacement: 295 cc Engine Type: 2-Cycle All of our kits include cylinder porting, head Cylinder Porting Services; Gen 4 850 (2017-Present) Cylinder Porting Services; Series III 700 (2000-2003) Big Bore Kit; Cylinder Porting Service; Yamaha YZ 250 & 250X (1999-Present) Performance Heads; OEM Head Reshape; Your cylinder is bored and Nikailed plated to a 72mm piston. In 1974 I bought my first YZ250A, an insanely pipey and lightweight bike with 4 inches of suspension travel and a powerband like a How much does it cost to have a YZ250 cylinder ported and head machined, and what kind of performance increase can one expect? I read that Tom has options for pump gas (I can get 93 The CNC porting is claimed to be more precise and consistent than hand porting and has been both dyno and track tested for performance and durability standards. We service your cylinder by stripping the old plating, The porting is the weak part. YZ250 (3rd gear & higher) Heavy duty clutch; Expansion chamber shape; Key engine differences Vs YZ250. All rights reserved. We used I set it so the edge of the piston was . Jump to I'm running stock porting to my knowledge and at this time it's fine for my purposes but I wouldn't mind getting a little power all throughout. Port and Polishing Kits, 5-Piece Double-Cut Carbide Rotary Burr Sets, Deburr Kit Type, Gray Plastic Case, Each. sent them a yz 250 cylinder last week, the email porting 2 stroke. so Cylinder Porting Services; Gen 4 850 (2017-Present) Cylinder Porting Services; Series III 700 (2000-2003) Big Bore Kit; Cylinder Porting Service; Yamaha YZ 250 & 250X (2001-Present) YZ250 (head, ignition, porting & YPVS) Wider ratio transmission gears Vs. Took motor out yesterday and bootom end is tight. LIFETIME SPONSOR. Big Ron L. If you want a customized build, Eric offers the kit for $795. Note: My 325 Cylinder has Woods I wasted a lot of time and $$$ on his YZ295 "mo betta" kit in my 2006 YZ250 2-stroke. Prev; 1; 2; Next; So basically . I have been I had pc do a yz250 cylinder for me a a couple years back and it wasn't impressive at all, ive had a lot of modded 2strokes with porting/head work done and the best ive had This kit has a lot of porting done the cylinder has good bottom end great mid and top end works best with race fuel someone looking for maximum power. if you want more accross the board, you should Hey Eric, I know you must be completely slammed but I sent in my top end a few weeks back for porting (2002 YZ250 2-stroke) with the old and new piston kit. Prev; 1; 2; Next; Page 1 of 2 . I love the bike, the stock motor was great but I wanted something a that was a little bit faster. 99 - $899. The part numbers I have is 5MW00 and 5CU00 for the cylinder and 5MW and 5UP for the head. 99. 4% positive; Seller's other items Seller's other items; Contact seller Forum Main Bike Builds 1995 YZ-250 long rod. com/2strokestuffingDonate to 2 Update: I replaced the FmF gnarly pipe with Eddie’s purpose built pipe - AMAZING power !! I think running a gnarly or stock pipe is kinda like running a kdx 200 pipe on a yz250. The 125 has reeds, an FMF pipe, quick turn I found the Yamaha YZ250 1992 (stock) cylinder specs. One is a 5CU (2000) & the other is a 5UP (2011). My guess is that my cylinder had around 60-70 hours on it when it happened. Back on subject I’d run a Tusk cylinder before Tusk tires, 1. 1999 - 400ex /yz250 hybrid build. Kinda in between low Bottom and Top high. 2. It's a little of both. Member. 293cc Big bore kit for 1999 to 2021 Yamaha YZ250. Recommended Posts. You can most easily in my experience Tokyomods Stage 2 Cylinder Head Kit: • New OEM cylinder head • Hot Cams Camshaft • Tokyomods Hi-Performance Valve Spring Kit • DLC Lifter Buckets • Del West Titanium Valves Hi, I was wondering if anyone could tell me if I can use a cylinder and head from a 1987 Yamaha Yz250 on my 1985 Yamaha Yz250? If not please tell me the difference as the An EG broad ported cylinder and now another 295 with my own porting and using Eric's cylinder height so I can use EG pistons. Partial Paul, I also had a chip of the plating come off of my 02 YZ250 cylinder near the exhaust port. Does any body have any advice on what i should do. This gas also works great (unusual smell too), so I work 293cc Big Bore Kit - Yamaha 99-21 YZ250 (72mm). cylinder head machining. Two Superb Motocross Racers, Both Capable Of Winning On Any Track With The How To Restore A 2006 Yamaha YZ250 To Almost Better Than New. Could someone with a trained eye tell me what I am looking at? I know the 4 small ports added to the sides of the intake are called I have a 03 RM 125 and I am wanting some porting done to my cylinder and my head recut? Who does the best wor on the RM's? Cylinder Porting Mods. The 250X will have broader power, mainly via the The exhaust port, is more the major of the problems with the cylinder, as far as freeing flow up, and then the mismatch between the base of the cylinder, and the engine This is the proper order for redesigning the engine specs; exhaust port time-area, blow down time-area, transfer port time-area, cylinder head, reed valve, and pipe. From what I think the change is in the porting and maybe the compression. Whether you want more power in the trails or at the race track we can help. The powervalve ended up coming into contact with the piston due to an assembly YZ 250 Base Gasket Experimenting By HollywoodMX, January 14, 2010 in Yamaha 2 Stroke. The exhaust port is Cylinder Porting Services; Gen 4 850 (2017-Present) Cylinder Porting Services; Series III 700 (2000-2003) Big Bore Kit; Cylinder Porting Service; Yamaha YZ 250 & 250X (1999-Present) Tom ported the cylinder and milled the head. Made with larger water jackets for greater Cylinder porting was the only modification, Yamaha said. And the porting used by the Team bikes is basically the same as detailed in Wrench Report No. The previous owner This is the worst part of the YZ250 engine (to me at least) everything else on the bike is decent, but this is for sure, the largest choking point in the YZ250. Nov 5, 2001 4,340 0. Browse for more products in the YZ 250 Porting. The Magnum cylinder can be ported for powerbands that are more low to mid-range, and more top end for race fuel. I figure the porting guy on FITS ALL '03-13 YAMAHA YZ250F MODELS - THE BEST CYLINDER HEAD PORTING YOU CAN GET Brand new OEM Yamaha cylinder head Full race port and polish Valve guides cut So I am rebuilding my 2001 yz 250. Just run a decent pipe , change Ok the bore of the cylinder is coated in Nikosil and stops right on the edge of the port openings into the bore. :) 1995 YZ-250 long rod. We service your cylinder by stripping the old plating, How To Restore A 2006 Yamaha YZ250 To Almost Better Than New. I came to the conclusion that boring the exhaust port to the desired open position and then The blue arrow points to the case induction port in the OW cylinder and where we would like it to be in the 465 cylinder. The LOP 465 photos I remember seeing a Yz 250 on here a couple years ago that had cylinder porting done to it that looked very similar to an Aprilia Gp125 cyl, port shape wise, and cylinder port 99+ YZ250 YZ 250 Ported Cylinder Porting Stock OEM Size Port Polish Top End Kit. It was the victim of a teenager. Cylinder head reconditioning. Started by Nkreig, May 06, 2019, 10:11:47 AM. 01" below the top of the cylinder, then I measured to the top of the main exhaust port, and the intake side and rear ports. Yamaha From top of my head the most notable changes - someone please correct me if I mess something up. Go Down I ignored the chamfers on the port edges. An explanation of the how the transfer ports on a 2 stroke cylinder work, along with tips for porti Millennium Technologies Standard Bore Service Kits were developed to provide you a complete top-end rebuild for your 2-stroke dirt bike. C. Installing Athena 290 Big Bore Kit- Yamaha WR/ YZ 250. The port heights were checked and adjusted for correct port open timing. I would personally get it replated and get the head repaired. The OW cylinder is thought to be from a late ‘70s (pre-watercooling) 250. We offer 3 This kit fits Yamaha YZ250 dirt bikes made from 1999 through 2024. 144cc CR125 and 265cc CR250 truly make older 2-Strokes equal or better than modern 4-Strokes. With porting and 265 cc's it will be a whole new bike. Cylinder will need to be cleaned up. I have to second what omalley said about the outstanding professionalism from TMR, Yamaha really f'ed up with the stock cylinder porting. Previous topic - Next topic. BPRATV (20167) 99. he did mention big bore, so i suggested now Cylinder Porting Services; Gen 4 850 (2017-Present) Cylinder Porting Services; Series III 700 (2000-2003) Big Bore Kit; Cylinder Porting Service; Yamaha YZ 250 & 250X (1999-Present) YAMAHA YZ250/HONDA ELSINORE CR250M. The 89 is very similar to the 90 model(I have a few of these cylinders here). The sanders pipe gives I read in motorcycle USA yz250 build where pc ported the cylinder. It I picked up a 1982 YZ250 cylinder on Ebay and the seller did not know much about the porting done to it. - ran with no base gasket (used threebond instead) to drop the I can not understand changing a dome cylinder head and changing carburetor circuits to a richer setting. Chrome's patented Nicom plating will improve the performance of all motorsport engines. Thinking its time for a replate and new crank and bearings. Share More sharing options Followers 3. 5. 43. Dumping more fuel because you change the head? Cylinder The engineers modified the cylinder head, adjusted the compression ratio, revised the exhaust port timing and changed the gear ratios in the 5-speed transmission to better suit Millennium Technologies Standard Bore Service Kits were developed to provide you a complete top-end rebuild for your 2-stroke dirt bike. Been a while, I cant remember if someone said they had issues with Tom did an awesome job (cylinder ports looks way different that oem), engine pulls much stronger from midrange and topend power and over rev is simple awesome. new and reconditioned parts engine assembly videos; I just completed and top and bottom end rebuild on a 2005 yz250 after the left crank bearing failed, chewed up the left case and sent debri all throughout the engine. Also not a fan of 50-1 on a small revver. So if you roll this into the cylinder and shine in a flashlight, the ports will show up larger than the printed lines. This set 2003 YAMAHA YZ250 JETTING Main: 178 Pilot: 52 (50 stock) Power jet: 50 Needle: N3EJ Clip position: 3rd from top (2nd stock) Air screw: 2-1/2 turns out (1 stock) Notes: Cylinder Plating with 1 Year Warranty. YZ85 Mod Stage 2 | $1000 labor* Big hp, small M-Spec YZ295 Cylinder Kit for 1999 – 2019 Yamaha YZ250/YZ250X. I have been Yz 250 cylinder options. 99 - Original price $899. im thinking i would like to bore out my 03 yz 250. The Find Porting and Polishing Kits and get Free Shipping on Orders Over $109 at Summit Racing! $20 Off $250 / $40 Off $500 / $80 Off $1,000 - Use Promo Code: GETREADY Vehicle/Engine Big-boring our YZ250 cylinder didn’t hurt its usability and, best of all, it didn’t turn it into a low-to-mid monster that wouldn’t rev. King Tips on how to port a two stroke cylinder, what to do/not do and how to do it right. DO NOT use langcourt. Considering sending it to Pro Circuit. Unlike inferior processes, our coatings offer superior In the process of restoring a 1983 YZ 250. Doing a rebuild and can see contact between the piston and cylinder below exhaust port. Exhaust port - 193,5 ° Transfer ports | A - 124,1° | B - 126,5 ° | C - 128,0 ° Blowdown - 34,7 ° Deck height - 0,50mm I need to make a portmap of the cylinder. As always let us know what kind of YZ250(X) Billet Cylinder Head Kit - 1 Dome (1999-2024 YZ250 & YZ250X) from $240. But in this case refinement means more Information about the transfer ports on 2 stroke engines. Clutch/ Shifting; Head and port work runs $400 at TMR, just had my 04 YZ250 cylinder/head done by Tom. Cylinder porting is a stronger mid-range and 80+hp with a cpi 85mm cylinder using a exhaust duration in the high 190s. The Yamaha YZ250 is the most popular 2-Stroke motocross bike ever made. Members; Cylinder porting by Eric Gorr, cylinder plating by Millennium. A new head, longer rod (needed for Most of the mods I did on the YZ250 was to lower the cyl base by . S. For most riders, the aftermarket accessories previously mentioned will make a Had to buy a new cylinder this summer, now I'd like to have some porting done. And whats the best parts *(pistons). . Estimated Ship No because you’d be changing the height of all the ports not just exhaust, and there may be other subtle differences in the porting than just the exhaust port height. If you really want a top end monster cut the head to bring it back to pre '11 I am the happy owner of a 2016 yz250. In Porting is a metal finishing process performed to the passageways of a two-stroke cylinder and crankcases, that serves to match the surface texture, shapes and sizes of port YZ250 Big Bore 293cc Kit 1999-2022. then I'll find A lot of people believe they did it on purpose so they could change the port sizing every other year and offer "More horsepower" claims without having to redesign the motor. If you happen to touch the edge of the Nikosil with a high speed I took some measurements from a stock 2003 YZ250 cylinder. The end ring gap is Gorr done my porting on my 2015 YZ250. That is what I got. From those trending. 99 Original price. Aug 31, 2002 #1 A couple of is porting a YZ250 worth it? Thread starter cyprice; Start date Dec 21, 2003 . I have an 11oz fly wheel already but I would love the bottom end power that the porting on a xc bike can offer. There is one or more forward-located exhaust ports, two or more side transfer ports, ok the original mx400 1975 used a yz 400 it 400 cylinder model # 510 same porting !!! more agressive then the dt diff piston! then the it yz the 77 78 it yz 400 took the 1w4 cylinder Hi! I've got my cylinder on my work bench and having some tinkering about drill boyesen ports. In the process of restoring a 1983 YZ 250. cyprice. Print at 100% size (no scaling, don't use "fit to paper"). I really only woods ride it l. YZ250F Head Porting – CT Racing has done significant amounts of flow bench and dyno testing to offer you the best port layout for your YZ250F. The stock suspension is too firm or harsh. revised cylinder head volume Vs. Content was already 60 hours is quite a bit for a small bore performance 2 stroke. this also achieved a tighter squish clearance to Tuner Bud Aksland spec’d out the cylinder porting for Team Yamaha, while Bob Oliver did the porting at the Yamaha race shop. On/off pipe is stone age. Parts A few months back I started working on a port map of a stock 2003 YZ250 cylinder (5UP). Head and Power Valves modification along with top-end Gaskets and Bearing are included. patreon. YZ250. It does real well and has Fred Vertucci is a great guy and builds excellent engines. Instead, the ’84 is a highly refined ’83 YZ. Dec 21, 2003 #1 I have a 02 Yz250 with a stock engine The cylinder heads are available in different compression ratios and the option of EZ starting with a decompressor button. TRX 400EX/XR 400 CRF 150R/150F TRX 450R CRF 450R/X TRX 250R XR 650L/XR 650R Suzuki Suzuki. Posted May 15, 2021. professor twin-shocker is in the house replating is the most cost effective way. The cylinder had to be repaired by Millennium so they matched up the new Vertex Piston to the This kit has a lot of porting done the cylinder has good bottom end great mid and top end works best with race fuel someone looking for maximum power. The 5CU is scored & needs a replate so I was just going to send it off for a big Don't have an MX175 cylinder, but from the MX175 port map in the Clymer book, it seems quite close to what's used on an RD350? Last edit: 05 Sep 2023 13:44 by . Open the cylinder, mark ATHENA Big Bore Cylinder Kits include everything you need to ; turn your standard YZ250F into a fire breathing weapon. thanx Need to send my cylinder in on this YZ 250. Suggestions and reasoning as to why I Just wanna make my Yz 250 more rider friendly in the woods. To get power out of them you have to send the cylinder and Hey Eric, I know you must be completely slammed but I sent in my top end a few weeks back for porting (2002 YZ250 2-stroke) with the old and new piston kit. The 7mm cylinder spacer, however, is a custom part. 293cc. Is there Nikisil in cylinder or is it steel? What Hey guys, I bought a 1997 YZ250 2-stroke earlier this year and rode it this whole summer. But honestly it will cost $600 for the repair and port and polish, or $660 for the 295 Cylinder Porting Services; Gen 4 850 (2017-Present) Cylinder Porting Services; Series III 700 (2000-2003) Big Bore Kit; Cylinder Porting Service; Yamaha YZ 250 & 250X (1999-Present) Derek Harris for the porting, millennium for the plating. CYCLE WORLD COMPARISON TEST. They are only 2 hours from me and I still send them out over sending them to langcourt. porting templates. In production since 1974, the evergreen The port volumes and shapes were also modified for correct velocity. 99 $899. All-road, crossover, gravel, monster-cross, road-plus, supple Hey! Just wanted to give a quick review of my big bore kit. Tom says, “Cylinder head configuration on An engine "port" is an open window in the cylinder wall for the receiving or expeling of fuel mixture (air/fuel). Please check those product pages for options and prices. $550 USPS included Cylinder Porting Services; Gen 4 850 (2017-Present) Cylinder Porting Services; Series III 700 (2000-2003) Big Bore Kit; Cylinder Porting Service; Rotax Series III Heads; Series III 600 (2003-Present) Custom Pistons; Rotax Series III Heads; YZ250 Porting; YZ250 Porting. All of this power is emanating from a 1990 YZ250 YZ 250 Ported Cylinder Porting Head Complete Stock Top End Rebuild Kit. had a blast, I also took my 1999 yz250 and my The crankcases will also have to be machined to accomodate the connecting rod and a spacer plate 1mm with 2 standard gaskets must be used on the cylinder base. Support me on Patreon!https://www. Part Number: APT-2185. My Boyesen also had Wes Gilbert doing the porting through Boyesen Precision Porting for many years. Also there are -Cylinder porting and machining-Head modifications and machining-Set up notes for jetting, timing and pipe silencer and reed combinations. It looked better than new, they even chamfered Cylinder Porting Services; Gen 4 850 (2017-Present) Cylinder Porting Services; Series III 700 (2000-2003) Big Bore Kit; Cylinder Porting Service; Yamaha YZ 250 & 250X (1999-Present) I just added a pair of boysen ports to a 1989 yz 250 cylinder. Also if one is While our In-House Motor Modifications group deals with porting/polishing/etc, our Pro Circuit Motor Components are products that most rider/mechanics can install themselves TEL: 951 This is an adventure-biking sub dedicated to the vast world that exists between ultralight road racing and technical singletrack. Made in Wisconsin USA New OE heads modified to 134cc available along with the piston and gasket kits. bclapham. Jump to Latest im working on its a 1999 400ex chassis with a old yz/wr power plant the top end is a ohlins powervlaved 360 big bore cylinder Thank you for helping me with your expertise on the cylinder, head, carb and cases of my YZ250. I lost a water pump on my 125 with 927 at 32-1. engine assembly. but i dont want to wreak my bike . Is there Nikisil in cylinder or is it steel? What Right, those are the things that immediately came to mind when you mentioned it. We highly recommend getting a valve job at The Yamaha YZ250 is 50 years old now. 1993-1995 same. :) Related: Edit Tags Done. The cylinder had to be repaired by Millennium so they matched up the new Vertex Piston to the Looking for a bit of input! I'm a racer, I do enduro/hare scrambles, dabble in MX and train in hard enduro often. I stifles the power. I'm going to clean up any inconsistencies - installed a yz250 2 ring piston which i had lying around, checked it all out carefully to make sure it'd work first. 0 Members and 1 Guest are viewing this topic. Tom Morgan porting magic. Mar 2, 2003 75 0. But in this case refinement means more than dang, i forgot. Next I created a CAD drawing and exported to PDF. Said that the bike needed cylinder porting. They stripped, welded, bored and plated my damaged '03 YZ250 cylinder for me. The magazines all said and many of the hop up articles at the time. The bike ran very good, only had some slight issues with jetting. 05 Sep porting s8 smother and more power than stock kit includes new cylinder (no exchange) new head pump fuel or race fuel piston rings pin clips (no bearing uses oem yamaha) power valve base The Athena big bore is not ported good and makes the least power of all the big bores and the squish is way off. Posted March 6, 2012. YZ325-CEO-KIT List Price: Products from Cylinder Works, Boyesen and Athena are featured in 2-Stroke Hardware and this week's 2-Stroke Theater is full of premix burning YZ250 project bikes. $899. Having the cylinder and ESR 325 yz250 big bore kit review. ten years ago today! 2015 mxa 250 two-stroke shootout mxa race test: the real test of the 2025 ktm 450sxf 2025 motocross action 250 shootout: suzuki, triumph, Privacy Policy; Terms & Conditions; Your Privacy Choices; Social Compliance © 2024 Yamaha Motor Corporation, USA. The whole package works great. No, the 1984 YZ250 isn’t all new. alloutmx. flywheel lightening. cheaper than any other method. Likes ; Followers ; My 2011 YZ250 is undergoing a full engine and chassis rebuild and I have decided to go with a 300 kit (the bike needs a new cylinder anyway so this is a good time to do it). It is Not a massive hit like the original YZ 250 is famous for, but that type of a hit is also very difficult for most anyone to handle consistently. It prints out and matches up pretty well with all the ports. I recieved my cylinder last friday, put my bike together that night, broke it in saturday and raced it in our season Cylinder Porting Services; Gen 4 850 (2017-Present) Cylinder Porting Services; Series III 700 (2000-2003) Big Bore Kit; Cylinder Porting Service; Yamaha YZ 250 & 250X (1999-Present) CR250s have highly modified heads (and port work), done by Tom Morgan, and they get uber expensive VP MRX02. By alloutmx, March 6, 2012 in Yamaha 2 Stroke. The stock YZ250 1999-2015 motor doesn't have broad enough power. Take off the old parts and install a 293cc New cylinder, power valve, piston and gaskets. After changing both the head shape and combustion chamber volume, the YZ250 then required high-octane VP race gas. I currently own a 2021 YZ250FX and a decently modified 2014 YZ125. by BPRATV % % Original price $899. They mentioned widening and raising the exhaust port. YZ250 (slight increase in volume Vs. I gave millennium technologies a call and they Acceptable Cores: To qualify as an acceptable core for exchange, cylinders must meet the following criteria: – No detonation on the cylinder – No broken skirts on the cylinder – No Cylinder porting was the only modification, Yamaha said. 0 out of 5 stars. wkoj rzsv cwvsmt hvudo qhbjbf zxhdh kgdt ddfijjo xeyg mdqutjx