I am going to rebuild my 250r i just bough before it siezes. It is bored one size over already. When i rebuild should run a higher compression? I dont want to run race gas but i have access to some 100 octane. Do you have to change jetting or anything with a higher compression and what compression do you recomend?
Ive also though about boreing. I dont want to affect reliability that much. What size does .20 over make it? How is the power increase. I want to keep up with my friend piped banshee.
What is a powervalve and how does this help you? Is it the same as a rad valve? WHen you get this does it help if you use a reed spacer?

Should i get an LRD pipe? When they say adjustable does that mean you can change were the powerband is by changing something on the pipe?
[b]HOW MUCH DOES ALL THIS COST?
I know i asked alot of questions but any help would be greatly apreciated.
Thanks

 

1)Higher compression create more heat, more heat requires larger jetting to compensate. Generally not a huge change, but must be accounted for.

2)Should you run higher compression, well that's a question you need to answer. Are you willing to keep a closer eye on the workings of your engine. It requires you to use good fresh fuel, mix at a good and consistent ratio, and ensure that your jetting is correct for most conditions. Higher compression alone isn't the end all of power gains, it helps, but it is simply just a portion of the equation to get more power.
3)A good race shop should be able to cut a head for you that will gain you more compression and more complete combustion with any octane requirement that you request. Set-up and run the highest octane that you can afford. Often the first question that I have to ask is, how much are you willing to pay for fuel and then start working from there.
4)I'm assuming you mean .020 not .2 (almost a quarter inch). Twenty-thousands of an inch will not make any discernable difference in power levels, it only adds a few cc's(<5cc). Now if you want to notice a gain, go with a 270 kit which is the max size bore, then you start to notice a difference.
5)Depending on where you ride and traction, keeping up with a piped Banshee requires a little more work than you are looking at right now.
6)Powervalves vary the exhaust height. Low exhaust port hgt's make wonderful low end power, but lack top-end power. Whereas the opposite is with high exh port hgt's. A powervalve varies the exh port hgt with in most cases a moveable guilateen(sp?), so you get low exh port hgt at low RPM, but as RPM increases the valve raises the guilateen and the exh port hgt is raised creating good top end power. Powervavles are truly one of the win-win items on a 2 stroke engine, you get tractor like low end power and road racer GP top-end too.
7)A RAD valve is an aftermarket reed cage assembly. Go to www.boyesen.com to read more about them.
8)Should you get a LRD, yes and no. Different pipes do different things, riding style and type often dictate this. The LRD adjustable pipe offers this, so yes maybe it's a "better" pipe. The adjustment is two sliding halves of the pipe that allows you to change the pipe's characteristics(tuned length) to suit better where/how you are riding.

9)It's how fast do you want to spend.

-Pipe, chrome, $250-300, nickel $180-200.
-Powervalve cylinder $1000 roughly(ported and cut head too)
-Machine work to rechamber and cut squish on head around $80 for a single cylinder head.
-RAD valve or equivalent $150-220

 

I totally forgot about porting. I understand how ports work. Isnt thre different type of porting ie. low ,mid and top? what would be the best for all aorund riding. I like to ride tracks but go to the dunes alot.
I have an 86r would i benifit from putting a 89 rod in? How much would this cost? and what else beside the rod would i need? Could you please tell me a little bit more about a 270 kit.
thanks for all the help

 

If you put anything other than an 86 rod in an 86 you will have to use a cylinder spacer unless you also add and later model piston. The 86 rod is 5mm shorter than all other years.
A longer rod can/will increase your compression without increasing your compression ratio.
You can have your cylinder ported for whatever riding style you want. You will need to talk to the engine builder that will be doing the porting to get what you want from it.

 

so if i rebuild would it be better to get a 87 and up rod and piston?. What is the difference between compression and the ratio?
Some responded to one of my post say 87 and up hvae 2 more hp.

PLEASe tell me more about big bore kits and engine mod i should do when i rebuild since i am getting a new piston adn ahve the engine apart.

 

The porting alterations can be taylored to suit any needs that you may have. Most of the big race shops have found packages that suit 95% of the people out there. They are decent packages that have had lots of riders input over time and most recieve little tweaks here and there to improve on them.

There are literally infinite possibilities in porting arrangements to get to your target. Low, mid, and top-end porting are simply an umbrella cover-all approach and way to describe a particular set-up. Same goes for the recreation port job or the "full-race port" It's to the degree and extent that the alterations are made.

A longer rod will not change the compression as long at the deck hgt(the positive or negative measurement from the edge of the piston crown to the top edge of the cylinder) stays the same, which it does when you use a '88 piston with a long rod. With a spacer and two gaskets on a uncut cylinder the compression will go down as the extra gasket has raised the deck hgt by .5mm This is why I reccomend using a CR250 head gasket with a spacer. Or cut the head to the desired set-up to account for the changed deck hgt.

I prefer long rod engines overall. For your application that you are looking at a '89 rod with a spacer plate would be a good more dune oriented engine, where as a '89 rod with a '88 piston would be more of a track oriented set-up. Again it also comes down to rider and preference. The long rod and spacer may have a weaker low end and throttle response but better mid and top-end. Whereas the long rod with 88 piston will have a good low end, a tad harder hit into the mid range and slightly less top-end potential than the spacer combo will.

Big bore kits as well as long rods help spread the power and tame the "hit" down some to make the engine easier to ride and maintain traction as well.

I'd reccomend going to www.macdizzy.com/sixtynine.htm and reading up some on the 270 kits.

A ported long rod 270 has much potential to make a fun and easy, but very stout, engine to ride.