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  1. Eric Gorr

    Suspension Tuning, By Eric Gorr. Part 3

    The Shock Dyno A shock dyno is a computer controlled electro-hydraulic machine that simulates and measures the damping characteristics of dampers (rear shock or front fork). A shock dyno is comprised of an electric motor, a hydraulic ram, a mounting guide, and a load cell (pressure transducer)...
  2. Eric Gorr

    Suspension Tuning, By Eric Gorr. Part 2

    Internal and External Adjustments Suspension dampers can be adjusted two ways, internally and externally. External adjustments are limited to the riding circumstances and the adjustment range on the compression and rebound clickers. Internal adjustments are virtually unlimited because it...
  3. Eric Gorr

    Suspension Tuning, By Eric Gorr

    Suspension Revalving How Damping Works Suspension fluid (oil) flows through the ports of the piston and up against the shims. The shims pose a resistance to the oil flow, which provides a damping effect. The damping effect is directly related to the diameter and the thickness of the shim. The...
  4. Eric Gorr

    Porting: Tools Of The Trade, By Eric Gorr

    Tools of the Trade There are two main types of tools used in porting, measuring and grinding. Here is an overview of how these tools are used. Measuring The basic measuring tools include a dial caliper, an inside divider, and an assortment of angle gauges. The caliper is used to measure the...
  5. Eric Gorr

    Cylinder Porting: Basic Principles By Eric Gorr

    Terminology These are some common words and terms associated with porting. Ports Passageways cast and machined into the cylinder. Ducts The tube shape that comprises the ports. Windows The part of the port that interfaces the cylinder bore. Exhaust Port The large port where the burnt...
  6. Eric Gorr

    Cylinder Porting: Basic Principles By Eric Gorr

    The process of cylinder porting is a funny paradox. The people in the market to buy it are looking for information and the people in the market of selling it are hiding information on porting. So much myth and misinformation is associated with this complex machining and metal finishing process...
  7. Eric Gorr

    Carb Tuning - Page 6, By Eric Gorr

    < Previous Page ... 5 Fuel and Oil Mixture Ratios When we talk about the "fuel" in the air-fuel mixture for a two-stroke engine, we are really talking about a mixture of fuel and oil. If you richen the pre-mix ratio (20:1 as opposed to 30:1) there is more oil and less fuel in the same volume...
  8. Eric Gorr

    Carb Tuning - Page 5, By Eric Gorr

    < Previous Page ... 4 Jetting for Riding Techniques Certain types of riders require jetting to compliment their technique. For example beginner minibike riders will need slightly richer jetting on the pilot/slow jet and the needle clip position to mellow the powerband and make it easier to...
  9. Eric Gorr

    Carb Tuning - Page 4, By Eric Gorr

    < Previous Page ... 3 Jetting Shouldn't Be Scary! Jetting is the process of making adjustments to the air and fuel jet sizes in order to fine tune the carburation to suit the load demands on the engine and make the power delivery consistent and optimum. Too much anxiety is placed on jetting...
  10. Eric Gorr

    Carb Tuning - Page 3, By Eric Gorr

    < Previous Page 2 Mechanical Problems The process of jettingÑchanging air or fuel jets in order to fine-tune engines' performanceÑis very simple. Jetting becomes complicated because mechanical problems sometimes mimic improper jetting. This causes you to waste time and money trying to correct...
  11. Eric Gorr

    Carb Tuning - Page 2, By Eric Gorr

    < Previous Page Fuel Jets, Air Jets, and Throttle Positions Three circuits control the air: the air-screw, the throttle slide, and the air jet. Four circuits control the fuel: the pilot/slow jet, the spray-bar/needle jet, the jet needle, and the main jet. The different air and fuel circuits...
  12. Eric Gorr

    Carb Tuning - Page 1, By Eric Gorr

    The Differences in Two-Stroke and Four-Stroke Carbs The difference between a two-stroke and four-stroke engine is intake velocity. Two-stroke engines have lower velocity so the needle jet has a half-moon shaped hood protruding into the venturi to produce a low pressure area that aids in drawing...
  13. Eric Gorr

    Carburetor Tuning - Intro, By Eric Gorr

    Carburetor tuning has the greatest effect on engine performance. When a motorcycle manufacturer builds a bike, they usually install jets in the carb that are too rich. The manufacturers sell the same model worldwide, so they couldn't afford to install different jets in the carb to suit all the...
  14. Eric Gorr

    Article: VALVE TRAINS Part 2

    You can view the page at
  15. Eric Gorr

    Uh Oh, Piston hit head. Confused.

    The spark plug is off-set bon an angle on the 1992-96
  16. Eric Gorr

    2003 cr125 cylinder ???

    The 03 has a differnt base stud location and the 2003-07 are the same. I do a 144 kit on the 2005-07 so if you get a used top end it will fit on the 2003 and newer CRs. Pete is right in that you can only bore the cylinder to 139cc 57mm but if you buy a Hot Rod crank, you can stroke it 4mm to...
  17. Eric Gorr

    2001 yz 125 big bore question?

    The cases have to be grinded on the 144s but I also offer 134 and 139cc kits that don't require case mods. The cost is $450 for 134 and 139cc and $495 for 144s,
  18. Eric Gorr

    Stubborn swingarm bolt

    There is a picture in my CRF book of a KTM200 with a siezed swingarm bolt. It rusted to the frame. We (me and Rich Rohrich) put the bike in my 55 ton press and tried to press-out the bolt. What a mess! Rich was cranking on the press lever and the pressure backed up and the whole press lifted off...
  19. Eric Gorr

    2000 cylinder on a 1995 yz 125

    The piston window won't hinder the starting unless the piston is backwards. The rectangular window should face the intake side of the cylinder.
  20. Eric Gorr

    stroker yz250

    With the YZ you have to weld the bottom of the exhaust to prevent the piston from uncovering the bottom of the exhaust port at TDC. You also have to bore the crankcases to clear the rod and cut the head deeper. I wouldn't waste the money stroking this model, boring makes a much bigger difference...
  21. Eric Gorr

    2 Stroke exhaust tuning...

    The silencer simply bleeds-off pressure from the system, thats why silencer tuning is unpredictable. I have a spark arrestor on my big bore 125 and I think it has better transition from low to mid, plus I can sneak up on loud 250Fs on an mx track.
  22. Eric Gorr

    2005 yz125 stroker eg

    I built my 05YZ125 with several different configurations and ended up with a 167. The 155 was the best overall, quick out of the turns and still good on top. The 167 piston is so heavy and you can feel it rev slow, top end signs off quick too. I built my bike in to a WR with all the DOT and...
  23. Eric Gorr

    2005 yz125 stroker eg

    With the 2008 AMA rules I'm going to offer stroker cranks with 144 kits to get 153cc the new maximum limit. I stock 2 new 2005-08 Yamaha cranks stroked to 58.5mm
  24. Eric Gorr

    Eric Gorr

    150 guy, I offer a free book with every service job over $100. The choices range from my tech books to training, riding, vintage, and picture books. They're all published by Motorbooks Brian, thanks for the comments on my work, hope you like it. Its the latest "Team Gordon" specs, thats an...
  25. Eric Gorr

    Athena 05-07 YZ144 piston kit question

    Wiseco 846MO5800 Never seen an Athena yet, the Wiseco has a flat top and a 10 degree angle at the outer edge.