Big Bore

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#1
I'm thinking about getting a big bore kit for my 02 cr250 and was wondering if you can buy the complete cylinder from Eric gore already bored and done up. What sizes, options do I have to choose from ect.? I dont race competitively do displacement dosen't really matter but I am looking for reliability. Also what kinds of mods am I looking at to make it run at its full potential with the larger displacement? Any info/ experiences would be apreciated.

Thanks Eric
 

Sawblade

Timmy Timmy Timmy!
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#2
Eric,
Check out Eric Gorr's web site at:

http://www.eric-gorr.com/

There is DRN member with a 02 CR 250 that had Eric do a big bore kit on his bike, I believe its a 265. With Dirtweek happening this week replys may be slow, so be patient.
 
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#3
Yes you can usually buy the big bore kits complete from Eric. Call him for current stock.
 
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#4
Thanks I think I will get in touch with him this winter when his new shop is open and things have slowed down a bit. I suspect with him not being open for a month he will have a ton of work to catch up on.

Eric
 
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#5
No reason to wait at this point because Eric is back up and running.
Turn around time is about 2 weeks on porting & plating. Big bore kits and parts that are in stock ship in 24-48 hours.
 

Faded

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#6
Originally posted by CRfury
I will get in touch with him this winter
NOT to mention that winter time keeps Eric running...how many people do you know ride in the snow? FWIW it took almost six weeks for me to get my CR265 motor back when I sent it to him back in January. I am NOT complaining at all, I knew about the wait and was very patient. I'm just trying to give you an idea of what turnaround time can be during the winter months.

After owning one I would definitely do it again, Eric does a great job. I had two small hang-ups when I got the motor back, but I the guy was buried and he's human just like the rest of us. The only down side is the jetting. Blame Mikuni, blame Honda, just do what ever you have to do and then sit down and spend some time playing with the jetting and getting it dialed. I have a little over 25 hrs on mine and everything is holding up well.
 
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#7
I will wait until winter anyway because I wouldn't be able to go without my bike for more than a week until there is snow on the ground. Then its time to fire up the snowmobile.
 
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#8
By the way Faded what parts did you have to send him for the 265? Does the jetting get worse than it already is with the bigger engine? If so what would be the best alternative carb to clean up the jetting.
 

Faded

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#9
Originally posted by CRfury
By the way Faded what parts did you have to send him for the 265?
Normally just the cylinder w/power valve assembly and the head are required. I took the lazy man's route and sent Eric my whole engine and had him replace the con rod, true the crank and swap in all new bearings and seals. Then he went to work boring/porting/plating the cylinder and reshaping the head. When I got it back it was ready to go.

Does the jetting get worse than it already is with the bigger engine? If so what would be the best alternative carb to clean up the jetting.
Well, there will have to be changes. Stock jetting is way off on a stock bike! I've found that the motor needed leaner jets in all but one area. At 1/8-1/4 throttle, which is affected by needle straight section diameter, there is/was a big lean spot. So far my best guess is:

30 Pilot
1.5 turn out on the A/S
Stock slide
6BEY30-72 Needle, 2nd clip
S-8 Nozzle
350 Main

4700ft, 32:1 mix

My needle is still too lean, I want to try the 30-70. I think I could also go down to a 340 main but I'm still playing with it. I should have had this thing figured out by now, but it was/is my first whole hearted attempt at jetting and this season has not been very forgiving. Between injuries, work and personal schedules, excuses excuses... I have just 25 hrs on my bike. :debil:

About the alternate carb...you could always call Service Honda and ask them about getting a Kehein PWK. Do a search, a few people have made the switch. I will probably stick to the Mikuni.
 

Faded

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#10
I reread your first post...
I'll try to answer the questions you asked first

Originally posted by CRfury
What sizes, options do I have to choose from ect.?
If you are considering doing only the big bore then you'd be looking at the 2.10mm oversized piston (68.50mm) which would make you a 265cc. You can add stroke to get 280ccs. Smarttoys here has one but has said that in hindsight he wishes he would have only done the 265cc setup (at least that's what he said last time I talked w/him).

I am looking for reliability.
So far no complaints here. My jetting was so far off I thought I lost a crank seal but it turned out okay. Like I said I'm at/a little over 25hrs. I'll be doing a top end soon, but I've had the reeds/pipe off many times and inspected the piston. All is well and it still blows good compression numbers.

Also what kinds of mods am I looking at to make it run at its full potential with the larger displacement?
I'm running everything else stock w/out problems. As stated above the big hang up is jetting. I'm sure if you need more a Boysen Rad Valve would help. The stock pipe is as good as any but if you talk with Eric Gorr he can give you a better recommendation. I'm not sure if it will be worth the $$ though. Your best bet is run good race gas, get the jetting dial in and then experiment with advancing the ignition a couple of degrees.
 
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#11
Thanks a lot for all the info faded. I dont really want to have it stroked so I will stick with the 265. You guys have been very helpful thanks.

Eric
 

Faded

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#12
Once you get the jetting figured out you won't regret it! :aj: Let us know what you think when you get it back.