Best kit for 250R fun riding

[ak_stick]

Hey guys,


So I'm sitting here, looking at all these kits and I think I'm gonna go ahead and order all my R stuff so it'll be waiting for me when I return home. I've got the tires done, and the Steering Stabilizer decided on, just not ordered. But I think I'm gonna go with a motor upgrade too.

All I do is fun riding on our MX track, and lots of riding, from beach blasting, to trails that will make MX'ers cry for momy. Most the guys I ride with own 450's and I haven't realy had a chance to run my 250 against them, since I left right after I got it (damn the man!). So I have quite a bit of sport quad experince (12+ years), but this is the first quad I realy owned, paid for, and ride.

I'm a helicopter mechanic, so I have access to most tools, and there realy isn't anything on the quad I cant do work wise, if I've got a manual and tools. I'm already running a 300 somthing or other big bore that came on this thing, is that enough to eat 450's up?

So I'm looking at a Big bore kit,

I'm look at the PSI, DR, and ESR kits. Have you used one? anyone heard anything about the PSI kits? I've run snowmachines they've modded and they were damn near unequaled in the field, but not ever heard much of them in the ATV side. what about DR?


Thanks,
your pal in the sand
Stick

[BLACKeR]

if you have the $$ i think the best over all topend is a 310 PV. the Power Valve will make it easier to ride, and the 310's put out some real good power. get a good port on it and youll have no trouble eating 450's. ESR has a good name, but there porting is sub par. duncan will probly give you a really good port. and you could get a nikasil plated sleeve from them which is going to last longer than a steel sleeve.the duncan top ends are pricey though. and youll have to machine your cases if you run their 310. but i have heard thats not a big deal at all. ive heard of people doing it themself. i would also recomend some suspention upgrades. they will make a huge difference. the R's when set up will handle better than the 450's take advantage of that and slap on some aftermarket shocks, extended a-arms and an extended axle...

[Eddiesanders250]

I would look at curtis sparks 265 PV. From what ive heard they can keep up with some 310's. If you like to ride on a track that would be one of the best setups. If you are looking at something a little bigger i would go with ESR. ive heard nothing but good things from their engines. Although ive heard their porting isnt top notch, its like a light switch.

[wilkin250r]

I haven't heard a whole lot about the PSI kits except for the gigantic 425. There is one guy on this site that had (or still does have) one.

However, I've heard from several sources that their customer service absolutely sucks. They're impossible to get a hold of, replacement parts are a nightmare, ect ect.



How committed are you to this project? Are you willing to spend several days reading and doing research before you jump in? Mechanical ability and tools are one thing, but you need to really understand two-strokes if you want to build your own motor effectively. The devil is in the details. Sometimes, just a few thousands of an inch can mean 10HP, and it's not the kind of detail you'll find in the manual.

[beerock]

the best size mtoor is the 310 or 330 if you go with a 330 you really dont need a powervalve. there is plenty of torque.

if you go with a 330 though i would get the cases machned to accpet the 330 cylinder there are two versions, the non machined cases which has a thinner sleeve and I dont htink its the best way to go. if you dont want to go with a 330 with machined cases. go with either a 310 or 310 P/V

[TheFontMaster]

The PSI kits are crazy. Chef has a 425 PSI 250r. It's in the Quad of the Month if you want to check it out. With all the stuff that I have read just over time I would go with a LRD265 P/V top end. I think it's the Jeramiha Jones 265 kit, it's suposed to have killer power, more than 310's.

[wilkin250r]

I've heard of some 265s making pretty good power, but they generally have to get pretty high in the RPMs to make more than the 310s.

High RPMs tend to decrease the life of your engine. A 55HP 310cc would probably last you a lot longer than a 55HP 265cc.

The more I learn about these engines, it just seems like they prefer to chug more than scream. The 310 and 330cc kits seem to have the best combination of performance and reliability.

When you get larger, like the 350-370 range, they vibrate and cause a few problems.

The smaller bores, like the 265cc, they have to scream to make high HP number, which decreases their reliability.

The 310 and 330 seem to be the magic combinations.

[slamdak8782]

I just got the psi 330 kit. I 'll let you know in a few weeks.

[beerock]

Originally posted by wilkin250r

The 310 and 330 seem to be the magic combinations.

yep, im starting to think the 330 may make mroe power then the bigger bores because they have the torque but can still rev enough to pull in the bigger bore motors.

the lrd 265 PV is a great motor but any 310 with a decent port job will walk all over it. and yes they wear faster because of the high rpms to keep up with big bores..

[wilkin250r]

You look at the new 4-strokes, they have a huge bore and a fairly short stroke, to achieve high revs, especially the first year YFZ450.

Now, granted, their pistons are quite a bit lighter for any given bore size, because they don't need a long piston skirt, but is still seems like an over-square engine is a little better for high revs and high HP.

Most people will say the 250r, in stock form, was probably the slowest 250cc quad in it's day. Both the Suzuki LT250R and Tecate-4 were slightly faster. The 250r is under-square at 68mm x 72mm, the LT was a little more toward square at 67mm x 70mm, and I believe the Tecate-4 was even MORE so, but I can't really find the specs on that.

The banshee is over-square at 64mm x 54mm per cylinder, and it's a screamer.




To achieve high HP and reliability, the 250r just seems to do better when you square it up.

[slamdak8782]

not to be a jerk wilkin but im pretty sure the 250r was bore 66/ stroke 72 but like you said it is still under square

[slamdak8782]

I think i would rather have an over square engine as well becuase they usually have a nice smooth power delivery that finishes stong and not the other way around

[wilkin250r]

Originally posted by slamdak8782
not to be a jerk wilkin but im pretty sure the 250r was bore 66/ stroke 72 but like you said it is still under square

Yeah, I should have said the 265 is 68mm x 72mm, because people are saying the 265 kits are so great.

The problem with over-square engines is the short stroke and cylinder wall height. It's not a problem on the 4-strokes, but the 2-strokes need that cylinder height for ports, and port-time area. A shorter stroke would reduce the adjustability of the port timing.

I wonder how a 265 would do if you destroked it, like to 69mm x 70mm. I bet you could get a lot more revs out of it.