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WR 250 Big bore kit

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Does anybody know if theres a big bore kit offered for the 250f? And if so is there a link that I can find out more about it? Thanks fellas.

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Rick Petterson Racing is offering a 276 cc bolt on kit. It also uses a totally new designed cylinder which has no need for a head gasket. The website is www.rpmsbigbore.com, I believe. I have also talked with Eric Gorr's forward motion and Parts Unlimited will be offering a 290 kit that is bolt on and will be less expensive. It will be made by Athena and is due to be released any time. RPM's Kit around $1300.00 and Parts Unlimited kit around $800.00.

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Yeah for that kind of money should have just gone with the 450. I will tell my brother that he should have bought a 426 like me. hahahahha. I just thought it would be nice to see him riding next to me rather than trying to find him in a dust clowd. Thanks man.

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I sent my stuff to Eric Gorr last Saturday. I should get it back this week. :cry: I got the 262cc kit and had them check and clean the valve train. I'll let you know how things workout. Good Luck..

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Let us know how you like it.

A buddy had a 302 kit on his YZ and loved it until it grenaded. The motor completely self destructed.

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I sent my stuff to Eric Gorr last Saturday. I should get it back this week.

FPMX - It'll be CODE 3 back to you on Monday morning :cry:

I was amazed at how good the valves looked on it when I pulled it apart. Both the valve faces and seats looked outstanding. Except for a minor bit of carbon buildup (which is now gone) it looked like the engine had barely been run, and the valve clearances reflected that as well. The clearances have barely moved. Whatever you have been doing , keep it up.

You're going to love the 262 kit, it's a ton of fun.

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Hey Rich you must be a mind reader. I was going to call you this morning. I knew you would come thru. I must be the Amsiol and frequent oil changes. I was amazed when I took the cylinder off too, the thing looking brand new except the little bit of carbon. That thing was all original. Hey do you guys subscribe to this form of ring seating: web page

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Hey do you guys subscribe to this form of ring seating: web page

While he makes some useful points, he ignores just as many important considerations so I wouldn't use that method as a generic prescription for breaking in engines. I realize 8 or 80 or 800 people are going to disagree, but that's to be expected I guess. Based on the way your parts looked I'd say you have an outstanding grasp on what it takes to break it in properly already. :cry:

Your cylinder was plateau honed so there is no break in necessary. The nonsense about seating the rings in the grooves with some specific accell or decell sequence is just that NONSENSE.

What we do recommend is to start with a fresh oil filter, ride the bike for a few minutes (5-10) to get it nice and hot then dump the oil and clean the filter. Changing the oil in the first few minutes will help flush out any gunk that might have entered the engine during while you were working and the initial fine grit that comes from the rings hitting a fresh cylinder.

Other than than just ride it like you normally would, just try to avoid putting it under a HUGE load for the first hour or so. Basically no heading to Glamis to conquer the biggest sand hill for the first hour :cry:

I change the oil and filter after that first hour as well on the engines I do, but I'm overly conservative about always having clean oil in the engine, so take that for what it's worth. :cry:

Have fun with it. :cry:

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Thanks again Rich, I knew you'd come thru. I am so stoked to get the thing back together. I have a fire/Police Nationals at Glen Helen next month.. Can't wait!

Thanks again.. PS. Did you guys set the ring gap or do I? And I am running a 42 PJ and a 175 Main. It was running good at 2 1/2 turns on the fuel screw. I heard it might run rich with the new kit? :cry: It sounds like I should have enough adjustment in the fuel screw.. What do you think?

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PS. Did you guys set the ring gap or do I?

I only did the cylinder head, Eric handled the cylinder so I just checked with him. He gapped the rings assembled them on the new piston and installed the piston in a new 2mm over 04 cylinder with the big cutaways. Because the piston is already in the cylinder all you'll have to do is line it all up on the rod, slide in the pin and install one circlip in the piston. Just make sure you have a a good set of circlip pliers for that part. The Craftsman Pro series pliers are very good for this.

As for jetting it's worth starting out with what worked in the past. A fuel screw tweak and maybe a main jet drop should be all it needs.

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I am running the Thumper Racing 80mm 270 kit in my YZ with ZERO problems. I love the power. I live in Ohio - run a 175 main, needle clip 2nd groove from the top, stock pilot jet. I recently added the Dubach exhaust and my bike flat rips. 270 is the biggest you can go to without sleeving your cylinder.

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Thanks Rich, I will say that I am very impressed with everything you all have done. After talking to Eric last week and you this week I will be recommending you guys for any and all work needed. You can't beat the price and the personal touch you guys offer. Even such small things as installing the piston in the cylinder. For the average guy that's a pain in the butt! Thanks again....

:cry:

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Thanks again....

You're more than welcome.

Let us know how it works out for you and what changes you ended up making in terms of jetting. Good customer feedback is invaluable. :cry:

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Will do. I will get it on Wednesday and should have it running on Friday. Gotta catch bag guys for a few days. I am stoked.. :cry:

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Monkey see, monkey do.

I bought a 262 kit form Eric Gorr on Monday.

When I do a top end on a 2 stroke top end I assemble it dry. On a 4 stroke I lube the cam the followers but leave the piston and rings dry.

Is this the right way?

BTW your sending the piston in the cylinder is a great idea.

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My experience has been that assembling any top end without lubing the piston, rings, and bore could be a very BAD idea. Why would you not lube the piston and rings when assembling a 4-stroke? Assembly lube is very instrumental in preventing bore striping during start up with Nikasil bores.

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To be honest I would prefer to get it from an expert not another one of us shade tree mechanics.

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but leave the piston and rings dry.

Is this the right way?

I would never do it that way but I know some people do. Oil is NOT the enemy :cry:

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