Blueprint: Calculate deck height, squish clearance, trapped volume, port timing and compression ratio and list on your permanent Spec-Sheet.CR250R BIG BORE 330cc BUILD
Notes: This is a complete engine build, it requires you to send us your entire engine for modification with kick starter and shifter. Notes: Prices listed are to install stroker kit parts in good condition engine. Should your engine need rebuild parts there will be additional charges. We will call for approval before we install any parts that will have additional charges. Call us for current pricing. Notes: The CR is a great all over power improvement.
It adds tons of bottom and mid but also revs out on top. MX, Woods, hill shooter, dunes, and desert, it does it all well. We can even change the porting a touch for Kart applications. We love this kit and you will too. Your email address will not be published. Save my name, email, and website in this browser for the next time I comment. Power Valves: Machined to match big bore ports. Head: Re-chamber to work with the Big Bore piston and stroker crank.
Crankcase: Modified to clear stroker crank. Submit a Comment Cancel reply Your email address will not be published. Search for:.Bore and plate to a forged piston with head and power valves modifications includes top end gasket with bearing. For years this size motor was the biggest you could to without custom pistons. Easy to build and inexpensive to rebuild. The pistons are final bore sizes and with Nikasil plating they can be rebuilt should you have to do so.
Power come on in the bottom and mid ranges for the trail and riders wanting the bottom end. Or we can do port work to make it have more mid and high end if your desire. Just tell us what kind of riding your doing.
So from desert to trails this is a easy inexpensive choice. Cylinders are Nikasiled or if you have a Sleeve we can bore and hone to size. What can we say about these old dogs but there fun to ride! This kit come with a 74mm custom forged piston that is bored and plated to your cylinder.
If you want the most power out of an old horse this it the way to go! This YZ kit is a newer because 72mm pistons are available from Wiseco and Wossner as a stock part. Your cylinder is bored and Nikailed plated to a 72mm piston. Head and Power Valves modification along with top end Gaskets and Bearing are included. As always let us know what kind for riding your doing so we can port time it for you. Our biggest YZ kit!
The is a 73mm custom made forged piston with some added adjustments. If your looking to out run the 's this is the one you want. We are currently racing this in CA in some enduro desert 6, 8 and 24hr races. Our motor gives the all around power that goes with the territory. Your cylinder is bored and Nikasiled to a 73mm piston. If you can't run with the big dogs you have to stay on the porch.Patent pending. It says "Incredible bottom end and top end power. Nothing close. Comes on the pipe without hesitation.
Power band feels 3 times wider" This will be something to watch. Is it the piston, or the big bore? I like to build big bore bikes, as my buddies know lol. The power feels so much better the stock. Would like to see test vs stock bore. ESR has been around forever from the micro sprint days in the 90s. We were taking CRs and bore and stroking them on methanol. Clutch gone, power valves gone, huge pipes and replaceable domes and a host of other shit. Was getting close to 90 HP out of a cc honda engine.
They still race them back east. It's all in the squish Monk wrote:. Not saying it can't happen, but that's a pretty big claim. YZ ESR is awesome, similar to a but not as broad of a power band! Might be worthwhile to upgrade.
ESR Engine. Interesting: Concave Piston I wonder what the head shape is - Flat, or curved to mirror the piston profile, or any number of other designs? Or, better still, just vacuum without a diaphragm. Simple, though, of course, far more complicated than just a plain port. My neighbor, across the street, has a wall full of melted pistons from his old Methanol sure makes power Tony - I've been in contact with Eddie the last couple of yrs.
The production date has been pushed back a few times in that span, but it shows mid Nov.
YZ285 Big Bore 1999-Current YZ250 YZ250X
I've been unable to get in contact with him since this thread got started probably due to the holidays. With his kits, Do you know if a pipe can be run or do you need the ESR pipe I see on your list of mods? Can the standard 38mm carb be run or does it need to be tapered for a bigger bore size to a 39mm? I would think the mods above would help to get optimum performance out of his kits. H4L wrote:. Stay with a 38mm Carb, changing this will complicate things.
I tired a lot of sizes, but in the end main and 42 pilot. Godzilla, mine is the current technology, which is outstanding. Obviously the top of the piston is concave Don't have a clue what it does, lol Neither with the hollow side. Any good 2 stroke tech around? Pit Pass Moto.Notes: This kit requires you to send us your cylinder, head, and power valves for modification.
The YZ is the most popular big bore kit we sell for any because it works so good. It provides a smooth predictable power delivery with just the right amount of hit to keep things fun. You will love this kit. Going bigger than a 71 mm bore on the stock YZ casting requires welding work to cylinder to keep it from popping o-rings. The transfer ports also start to drop into that area where it becomes more of a bottom end chugger and not nearly as snappy.
Our Custom 71 mm Wiseco piston is made to be as light as possible without sacrificing durability. If you already have an Athena YZ kit it can be livened up to close to a YZ style power with some porting and head adjustments. YZ Kit is awesome This is a must do when your old needs to be replated. Spend a few extra bucks.
The speed is deceiving. First race out I hit Everything was a blur…. YZ Yamaha really should make this bike.
It is the best 2 stroke around. I am on my 3rd year and have had no problems, the cylinder plating still looks great. The best thing it adds is the torque, when your off the pipe with theyou get a little power when you turn the throttle, you turn more but no more power, that is where the shines, kepp turning and power keeps coming, you can grunt it up hills from almost a standstill in 2nd, or do switchbacks in 3rd all day long.
It will get you lazy and short shift the jumps on the track, but that is ok for us vet guys. Your friend will be bummed I have been running the kit on my 05 for almost two years this last fall I put a wide ratio tranny in my Yamaha.
I have a friend that just got a 09 f. He just shakes his head,and says that thing is really fast. So last week he ordered a new bomb header and new computer programmer. He says it is only to make it start better. I highly recommend the staff at Max RPM they have been awesome to deal with.
Love it Thanks RPM! Your email address will not be published. Save my name, email, and website in this browser for the next time I comment.
Honda CR280 Big Bore/Stroker
Power Valves: Precision machined for optimum performance. Head: Re-chamber to work with the Big Bore piston. You choose the octane. Crankshaft: No crank mods required. Crankcase: No crankcase mods required. DirtSaw on December 1, at am. Everything was a blur… Reply.
Dirt Bike Reviews - RPM's Big-Bore Honda CR280 Kit - Dirtbike Experts at Dirt Rider Magazine
Vet Racer on January 30, at am. Submit a Comment Cancel reply Your email address will not be published. Search for:.Most of the slump can be blamed on the four-stroke's phenomenal motor, but we'd be remiss if we overlooked the less-than-stellar powerplant wedged between the aluminum spars of the ''04 frame. RPM's needs the complete engine for these mods.
First, the company splits the cases and phones the customer with a list of worn parts that might need replacing. The cylinder is then bored out 2mm, ported, decked and plated with nikasil. This is the same plating that many of the factory teams have Peterson put on their works cylinders. The crank is pressed apart, and the crankpin holes are machined 2mm farther from the center of the crank.
These larger holes are then sleeved down with hardened steel collars so the stock rod kit can be used. RPM's balances the crank by drilling holes opposite the crankpin and pressing in tungsten. The crank gains a few ounces, but the reduction in vibration is amazing. Finally, the engine is reassembled, and the head is chambered to run the octane you specify on your order form. This was standard equipment on ''01 CRRs and is much lighter than the ''04 piece.
The lighter crank gives more of a snappier feel than the electric smooth feeling of the newer CR. The minute we took off on it we could tell this CR has a very powerful mid to top-end. However, it still had the CRR's smooth-feeling bottom-end, which is not a bad thing, as it makes the bike easy to ride.
As you roll the throttle on more, you feel the pull of the When shifting from third to fourth gear, the bike could be left in each gear longer than the stockwhich was very lethargic compared with this motor.
On top, the bike actually revved higher also. On long, fast, choppy straights where the wheel comes off the ground and overrev is noticeable, the CR is clean and revs much longer than any other CR we've ridden to date.
That is important in outdoor racing. You want a motor that is broad but also can be revved. The CR delivers. This bike would also be great for the vet racer who does not want the heavy feel of the CRFR but still wants its tractability and smoothness.Portal Forums Photo Gallery. Hi, I just bought a Cr with a top and bottom end recently rebuilt.
It runs great and has lots of power but was trying boost my low end and get just a little more power.
I have a spare blown engine and spoke to a well known engine rebuilder who said he would trade my old engine and do the big bore for free in exchange for the blown one. Parts and all. My roomate who has been riding for years said dont do it unless I want a headache down the road, and I disagree. Should I do this at all? I am not gonna do anything with the blown engine anyway. Any thoughts?
Thanks in advance, Chris. Last edited by ctroger24; at PM. Reason: add on. If you want it to be reliable I wouldn't do it.
I just sold the last CR that I made a big bore, which was a 2 weeks ago and wasn't sad to see it go. Ya, if it dosn't need it don't do it. There are plenty of modds out there that will give you more low end power without messin with the bore.
Before I would do that, I would do one of two things: 1 Add a flywheel weight for better bottom end 2 Change to a Gnarly Pipe FMF for increased power and better bottom end. A kit seems like overkill. What about a ? Maybe even a I think you would have better luck with those than a kit.
Good luck. I have been thinking about the same thing for my CR I talked to Eric Gorr, he said you would not loose any reliability as long as you don't go to big. Go to Eric's website, give him a call, hes a nice guy. I think im gana go to on my bike. Eric Gorr is acutally who I have been speaking to. He was talking about doing a That is the biggest he will do. He said I will not have to do anything but bolt the head on and go.
I have no questions or doubts about him and have confidence in what he can do. I just wanted to see what everyone thought. He just said it will make a world of difference in my low end, which is why I was considering it. Right now I have the FMF fatty pipe and shorty silencer. It does have aftermarket reeds I believe but am not positive. The reed plate appears to be gold. I think I am gonna do the filter and check if I have reeds and if not do that to.
I know I have the option to go the big bore route if I need to. Ill just see what those mods do first, I think I have decided theres just no point in ripping into a freshly rebuilt engine. Thanks for all the replys.Remember Me? What's New? Page 1 of 2 1 2 Last Jump to page: Results 1 to 15 of Misleading R Big Bore Info. The following is a revelation to me and may be to some of you as well or it may be common knowledge but either way, I thought I'd share.
I sent the cylinder off to ESR for boring and a new piston. When I got it back, I noticed the piston size as being Since there's no replacement for displacement, I was curious about how many cc's I gained by going to the next size overbore so I rung up my trusty displacement calculator, entered the figures and came up with cc's.
I must have made a mistake! I ran the figures again, same answer. I ran the figures using the previous 72mm bore and came up with cc's. This just doesn't make sense. Maybe they sold me a mislabled cc cylinder by mistake and not the I ordered.
I called ESR and come to find out the stock bore of their kit is 72mm's and that you don't get to cc's until you reach the 5th and final bore of 74mm's.
I know a motor is not always the exact displacement as what it's labled as a R is acutally cc's but that's false advertising on ESR's part if you ask me, however, if I keep my R another 20 years I might reach cc's eventually. Current Ride Purchased new in Oct. Join Date Jun Location arizona -- Thats true,but Ive changed the bore from the first to the last,and no real power gains,so,I bore as needed now!!
I always thought I had the kit. I just did the last bore on mine, my piston is La Sleeve tells me thats as big as they go, which is where I got my piston from. So from what your telling I have a We'll thats sweet. Ive heard this info from someone else too.
That suck that you were totally mislead. Sounds like you just have the sleeve like me. Join Date Sep Location florida -- Esr I know you could always buy a bigger esr. But you would need a fat stack of cash. Well you learn somthing new every day here 3 wheelworld. Join Date May Location illinois -- Originally Posted by jason