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Discussion Starter #1
Hey guys this is my first post on here so plz bare with me. I have a trx250r 86 model. It already has a gold series pipe and fmf silencer. With a k&n air filter. Something's have been dont to carb and cylinder but I don't know the size of either or what's been done so if you can help me here it would mean a lot thanks. And should I put a 310 kit in it we have 3 of them since we have 2 trx250r's
 

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Michael: This is a sample of our cylinder worksheet. Whatever your top end project & whoever you take
your work to, you need to know these basic numbers about your engine.

Internet Work Sheet for www.smallenginemachineworks.com

1. Cranking compression
2. Deck height
3. Squish height: Check the link below& see how this is done.
4. Engine bore & stroke
5. Make, model & displacement
6. Wrist pin dia. & compression height.

http://forums.everything2stroke.com/threads/49513-How-It-s-Done-Projects-around-the-Shop/page37
Whether we are relining your cylinder or only assisting with your port work & rebuild questions, we need the information
so I can crank out some numbers. After you supply the numbers I can calculate for you a preliminary Squish Band
plot sheet from my www.bimotion.se software programs.

JT
 

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call Piranha Pete
Hybrid Engineering
Pete Schemnerger he is in Cama,Wa
1-(360)-281-2274

he is the man when it comes to the 250r.
 

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Discussion Starter #4
Thanks John Tice, will check that out. But is there anymore aftermarket parts I can put on it to make it run faster? and should I put in a 310cc kit
 

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You can get reeds, aftermarket heads etc. there is lots you can do. What type of riding do you plan to do?
 

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Discussion Starter #6
Not dunes I'm here in Mississippi. So trail and little dirt drag races with my friends for fun. Not serious. So like trails and some mx
 

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My recommendation...

1) Figure out what you've got (carb, bore, compression, jetting, etc)
2) Make sure you're getting everything you can out of what you already have. Must know if you've got the right jetting, no air leaks, good compression, right fuel/oil mix, etc.
3) Then start making mods with bolt-ons and machining work.
 

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My recommendation...

1) Figure out what you've got (carb, bore, compression, jetting, etc)
2) Make sure you're getting everything you can out of what you already have. Must know if you've got the right jetting, no air leaks, good compression, right fuel/oil mix, etc.
3) Then start making mods with bolt-ons and machining work.
I agree you gotta start with the basics. You can leave a ton of power on the table if your machine isnt dialed in right and running properly. Bolt ons will only get you a fraction of the power they are supposed to and youll waste a bunch of time and money in the process. Take it from me I went down the same path with my Zilla!! :Dope:
 

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Yes the Basics; the other guys are pretty much in line with me. A very simple trick, drop the gear ratio some. Smaller front sprocket, larger rear sprocket. This makes a huge difference although it drops your top end some.
I’m only a machinist; I raced karts for 10 years & rode cycles for another 10.
 

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Discussion Starter #12
Ok thanks guys me and my dad will look at it when he gets home. Any tips on finding this stuff out? Can someone give me an info link on jetting I've never really known what jetting is
 

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One of the first things you will want to do is a leak down test. You will never be able to jet it right if there is an air leak.
 

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:Dope:
I haven’t seen any comments on changing the gear ratio. Have any of you ever tried this? It only causes a drop on the top end. Come on guys, you should use a different gear set up for nearly every track that you ride.
:Dope:
 

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Discussion Starter #16
Someone said something about getting smaller sprocket in front and bigger and back. I want to get serious in mx racing. Any tips? My bike has a k&n air filter and we have some extra cylinders that have been ported. Should I put one on? We have a 310 kit also we can put on. We have a few extra carbs but not sure of sizes. We have a few reeds but there just plastic ones. So comment on anything I should do to run better and faster for mx
 

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Im not overly familiar with what guys run on 250R's so the different set ups can be left to the R guys. Personally im not a huge fan of K&N filters for offroad applications. I feel like whether or not a foam filter allows more air in, it definetly lets less crap through that can mess the motor up (just my opinion). Like John said, gearing is a big factor but that will probably be something you'll just need to spend time testing. Different tracks would call for different gearing so test, record lap times and just plain out see how it feels, then adjust. But no matter what setup you run, your tuning needs to be spot on. What ever set up you decide to go with whether its a 310 kit or stock jug, ported or unported, pipes, reeds, etc, you gotta have that motor dialed in jetting wise and make sure its air tight. Especially if you'll be running it hard in MX style races. Bad jetting or an air leak is a disaster waiting to happen. Its not the fun part because it involves a lot of trial and error and gets frustrating but in the long haul it can really separate a fast motor from a really fast motor!!
 

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Two-strokes are about mass, displacement, how much air & fuel you can flow through and burn all to make consistent power without blowing it up, and the right suspension & tire combo to put power to the ground and make it stick. Don't expect to get enough advice from the boards/forums to win races. You can have a $15,000 250R and still get beat if you don't know enough to harmonize all of it for the set of conditions there on the spot.

"For the track" is a broad term. Each track is going to bring some different characteristics with it -- short tight intricate track vs. wide open fast straight-away tracks, slick clay vs. hard pack, doubles/triples vs. flat-track, MX vs. endurance race, etc. So depending on what kind track you're taking on the combination of suspension, gearing and powerband WILL differ. Classes often have rules for equipment, too. Never forget about safety. And unless you're a banker, you've got a budget to work on.

First, in my sincere opinion, you need to understand the cards you've been dealt and make the best of them. Cover the basics. Get your stock machine running great & proper to get a good reliable starting point (i.e. known good compression, known bore, known piston wall clearance, known true crank, known tight main bearings, no air leaks, jetting known & dialed in, good seals, clean carb, brakes clean & tight, bolts torqued, cotter safety pins in place, bearings good, etc). If you start with an engine with issues, porting and bolt-on power ain't gonna' do anything but burn holes in your bank account. In fact, they'll just make a poorly tuned bike run even more erratic. Can't win a race unless you finish it. No sense putting an extended swing-arm long-travel Elka stage 9 suspension and Lonestar +5 axle on a bike than runs like crap on bald tires, either.

By getting the bike in proper-running form now, you will get to know it much better and will have a solid foundation from which to blossom. Then you can start with some bolt-ons and/or go to some experts for porting, shock valving, etc. Got to start somewhere -- not everywhere.
 
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