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Bige bore/ stroker?

13758 Views 21 Replies 8 Participants Last post by  outlawedrecon
OK I love my foreman to death. However I am riding with some larger quads and am looking for a significant jump in the power area. I just ordered an HMF , filter and jet kit but am sure it wont be enough. I have seen one stroker kit for the foreman in a mag but am curious to see what else there is out there. Any web links would be great
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Have you thought of just a " One over ", or a " Two Over "... A friend has a 450 Foreman and his was smoking bad. It needed new rings and piston because it overheated so bad. He went with a " Two Over " which is a bigger piston, rings, and jug... This took him from a 450 to almost 525.. Just a thought. Apparently, from what I have heard,you can go only to " Three Over ".

This would be a great mod for a bike with a good amount of miles and want a better seal in the motor. Apparently, they sell these in a kit and could probably do this yourself with some tools. He had the shop do his and he see's a big difference in power. Just a thought...
the power and torque would be awsome, but IMO it will not be dependable.
Why would it not be dependable?

I can definately do any of the work needed, Several years as a car mechanic.

This one over two over stuff is a little strange to me. Is this just a larger diameter cylander? It would take a much larger diameter to make 525cc's Any info on this would be apreciated though. one over would sound to me like a slight boreing of the cyl. Perhaps 1 mm?
From what I understand...They replace the sleeve inside and bigger piston and rings... I guess that this is why you can't go bigger that three over.. I can call tomorrow and get more specifics if you want me to. Apparently for people with bad cylenders (sp) this is the solution plus a little more power. I will check if your intrested. All this came from the local ATV shop in our area who did the work..
Its just that the air cooled engine can't handle the heat from the thin cylinder walls of the big bore kit. The big bore kit on a foreman will require the stock sleave to be pressed out and to have the jug itself bored out for the new sleave to be pressed in unlike an overbore of 0.25, 0.50, 0.75 or 1.00. And 1.00 being the biggest bore you can go on a stock sleave. Once the big bore kit has been install, you cannot go back to stock unless you buy a new complete cylinder, sleave and piston kit. There are a few company's that offer high compression piston kits for the foremans like JE or Wiseco and will only require you to only have the stock sleave bored out.
I dont really care about being able to go back to stock.

Rincon 650, if you could get me more info I would apreciate it. Thanks all
Will do and I think he is correct.. Now remember, I don't have this kit installed so that sounds right. I remember he showed me the old sleeve and the cylinder was out of the bike. I almost garantee that Dirty4man is correct. He said that if this goes bad again, he can go one more over than this one. I will call here in a minute and post back.....
Yup....Thats what it is.. They remove the cylinder and press out the sleeve. Bore out the jug and replace the sleeve with a larger diameter sleeve. This and a larger pistin and rings gives you more compresion and therefore more horsepower. Make sense??? Hope this helps and is a good alternative to good reliable horsepower at a reliable and reasonable price...
If your interested in this, I can ask the guys at the shop what is is " actually " called and get the price for each ( once, twice,and three times over ) and who makes these kits for you and your location so you can have the right termonology for your shop. Nothing worse that asking for a " Doo-Dad " and a " Whatchama-call-it ".......He He He...
i was pondering the idea of that as motor is fine but since it is paid off i tought about boring it and gaining a little power over the winter...i would like the info...i done neccessarily want a big bore kit, but for the right price you never know...
not meaning to interrupt but, does anybody know how much 200/1000 is on a bore?
Yes if you can get the actual terminology that would be great. It is something I would like to find out more about.
Thanks again
No problem...Unfortunately, they are closed because the shop rides on Sunday and cleans their bikes on Monday. I will call there first thing Tuesday morning and post as soon as I get off of the phone. Check back around 10am then.
if you want your foreman to scream, get all of this

Thumper racing 480bbk
clutch kit
port and polish
jet kit
k&n air filter

i have all of that installed on my foreman and it runs like a sport bike now
hey lifted450es, how fast does your 450 run?
Hey TheRookie...Just spoke to them and this is what they said.

HighLifter sells the kit and what happens is if you bore the stock sleeve out, it becomes too thin and causes problems. When you buy the kit, it comes with a thicker sleeve. They bore the cylinder out and replace the sleeve so you have plenty of thickness so not to overheat. This gives you more horsepower and the bike still runs cool. They said it is very safe and very durable. Just ask for a Highlifter Once Over kit...or Twice Over Kit depending on what you want. He said that the Three Times Over Kit is as safe as the Once Over Kit. It all depends on how much power you want, but remember 3 over is as much as you can go. Then you have to start over and buy a new jug back to stock so be wise...
Thank you verry much. I will contact highlifter and talk to them some about it.
I recomend getting the kit from Four Stroke Tech.I believe it is 298$ and you do NOT have to over bore the jug to have the new sleeve installed.The sleeve is by LA sleeve and the kit inlcude sleeve,piston,rings,wrist pin,circlips.these kits are very reliable if you have a good shop do the work.make sure the tolerances are correct and it will live a long and happy can also look on FST or LA Sleeve and you can find all the neat stuff they have.their sleeves are made to be a few thousandths of an inch larger than OEM and that is to be a press fit.most machine shops will place the new liner in a freezer and the jug in the sun to warm it.The new liner will be close to sliding in and they just use a little effort to press it in then they machine it to your piston,that's where the machine work comes in as it's an unfinished cylinder it needs to be bored and fitted to the piston.
Fourstroke tech only lists a stroker kit for the 450 on their page. thanks for the info, more to think about and research prior to takeing the plunge it appears.
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