Ported stock cylinder vs esr 310

[96motorhead]

I'm thinking about upgrading my 85 atc250r for this desert season because it's time to replace the piston and bore the cylinder.  Do you guys think I should have Duncan Racing port my stock cylinder, do the head mod and install a 39mm pwk carburetor or buy an esr 310 kit?  The esr setup is going to cost me about 300 dollars more than having my stock cylinder ported and setup.  I will be using this for drag racing up hills and just messing around.  Also reliability is my number one priority.

[croat1]

I would get the ESR 310 kit and then send it to a porter.  You still need a pipe correct?  I haven't heard of anyone sending a stock cylinder to Duncan in a very long time (I own a Duncan cylinder).  you could always sell the stock cylinder and head to help offset the cost of the 310 kit.

Joe

[96motorhead]

I have a paul turner high rev pipe on the bike.  Duncan does all the machine work for my bikes and they do excellent work and they sell the high rev so they should know what porting will suit it best.

[96motorhead]

How reliable are the esr 310 kits?  Like I said in my first post reliability is extremely important to me.

[Sand_Blaster]

My esr 310 has been super reliable. It's a older cylinder from him and zero mechanical issues. You really can't go wrong with both choices honestly. I know Duncan has said in the past they really enjoy working on the old 2strokes still.

[96motorhead]

Ya they do.  Whenever I go to their shop they always have trx250r's, banshee's and lt's there.  Also if I had the stock cylinder ported would it be worth it to have it setup for race gas?

[Sand_Blaster]

Depends if your chasing power I guess. Probably better just to have ported for premium fuel. My buddies stock cylinder that is ported was just tuned and dynoed only made 45hp. I think he has to run premium. Race fuel around here runs $8.75-$12.00 a gal so if cost is a issue then probably not worth the extra cash.

[96motorhead]

Yes I want the most power.  I already run 100 octane av gas but I can easily get vp110.  I'm not sure if 100 octane would be enough for the esr310 kit?  Basically my goal is to be able to beat piped banshees.  Right now they beat me by about 1 bike length.

[Sand_Blaster]

Well then step up to the 310 or bigger. Go race gas dome plan to upgrade your exhaust. I hear great things about the esr 5 pipe. I have a LRD and it holds me back a bit, but can still beat my brothers 450.

[The norm]

Hey there, I'm running a ESR 310 cylinder with a 4mil stroker crank. It would beat a piped banshee if I wasn't 280 lb. I had it set up for 110 race gas and ported for mid-top end power. I'm also running a trx-5 pipe. In my humble opinion I would have it custom ported by a skilled builder. I personally only let Pete at Hybrid Engineering touch my motors. Good luck, Loren

[96motorhead]

I'm definitely keeping the paul turner high rev pipe, that is the best bolt on pipe you can buy for an atc250r.  After doing more research it seems like the esr reliability is hit or miss which is a big deal to me.  I think I'm going to just setup a stock cylinder.  Also what gearing do you guys run?  I have stock gearing and I can't pull 5th or 6th up hill, I just scream in 4th but I feel I can get it into 5th gear if I change the gearing.