by Gman255
Most mild performance camshafts that are design for small cc, signal cylinder, 2 valve engine, are within 225-235 degrees of duration. Regardless of the brand of machine or Camshaft supplier. These cams will have no loss in off idle performance. Increase engines performance in the mid to upper rpm ranges.
A 10 degree increase in duration is equivalent to about 1500 rpm increase in the targeted rpm rang.
Peak power numbers are somewhere about 7000 rpm for a stock 100 engine. Adding a mild performance cam in the 230 degree range will be about 8500 rpm depending on other engine modifications.
Here is a list of cam specs that I've posted in another threads
The web 68/69 seems to be the most popular. Most performance camshafts produce close to about the same specs.
However, some performance camshaft manufactures don't disclose their specification. Powroll, Trial bikes, Engines Only, and BBR.
Here are some aftermarket camshaft specifications for a comparison. All specification taken from the manufactures web sites.
Lift..............intake/exhaust........duration
Stock XR...........240 ....................225 @.04 stated in Megacycle catalog
Trail Bikes...........?
Hot cam ..........268/.232...............236/216@.05
Web 68/69........275/.285...............236/230@.05
Powroll ............280/.275....................?
Megacycle........275/.273...............232/232@.04
Engines Only.........?
BBR.....................?
Web 68.............285/.285..............222/233@.05
Megacycle .........300/.281.............256/256@.04 Head mods grind cam tower for lobe clearance
Web 58c/58b......330/.330.............242/235@.05 head mods grind cam tower for lode clearance, sink valve pockets
Megacycle..........325/.325.............274/274@.04 same mods as above
http://www.hotcamsinc.com/index.cfm?...&productid=470
http://www.powroll.com/P_HONDA_XR100_79-00.htm
http://www.bbrmotorsports.com/Products/Products.aspx
http://www.webcamshafts.com/
http://www.megacyclecams.com/
http://www.hondatrailbikes.com/catal...roducts_id=495
Takegawa cams
Stage 1:
235* In. duration @.040
234* Ex. duration
.256" In. lift
.256" Ex. lift
This cam is Close to the Web 68/69 and the Megacycle 129-00!
By these numbers it looks to be a good all around cam: increase performance in the mid to upper RPM ranges
Stage 2:
248* In. duration @.040
249* Ex. duration
.354" In. lift
.354" Ex. lift
Lobe separation angle play in big roll in performance
Safe to assume take all cams for the stock head have tight lobe separation agile cuz of the valve orientation.
Brief Glossary of term taken from the http://www.webcamshafts.com/
VARYING LOBE SEPARATION ANGLE
Tighten........................................... ........................... Widen
Moves Torque to Lower RPM............................ Raise Torque to Higher RPM
Increases Maximum Torque ..............................Reduces Maximum Torque
Narrow Powerband .........................................Broadens Power Band
Builds Higher Cylinder Pressure .........................Reduce Maximum Cylinder Pressure
Increase Chance of Engine Knock .....................Decrease Chance of Engine Knock
Increase Cranking Compression ........................Decrease Cranking Compression
Increase Effective Compression ........................Decrease Effective Compression
Idle Vacuum is Reduced...................................Idle Vacuum is Increased
Idle Quality Suffers........................................ Idle Quality Improves
Open Valve-Overlap Increases .........................Open Valve-Overlap Decreases
Closed Valve-Overlap Increases .......................Closed Valve-Overlap Decreases
Natural EGR Effect Increases............................Natural EGR Effect is Reduced
Decreases Piston-to-Valve Clearance................Increases Piston-to-Valve Clearance
LOBE SEPARATION ANGLE
Above 114 Deg. = Extremely Wide
114-112 Deg. = Wide
112-110 Deg. = Moderately Wide
110-108 Deg. = Moderate
108-106 Deg. = Moderately Tight
106-104 Deg. = Tight
Below 104 Deg. = Extremely Tight
ADVANCING / RETARDING CAM TIMING
ADVANCING......................................... ................ RETARDING
Begins Intake Event Sooner......................... Delays Intake Event Closes Intake
Open Intake Valve Sooner..................... ......Keeps Intake Valve Open Later
Builds More Low-End Torque........................ Builds More High-End Power
Decrease Piston-Intake Valve.......................Clearance Increase Piston-Intake Valve
Increase Piston-Exhaust Valve Clearance... .....Decrease Piston-Exhaust Valve Clearance
Few additional inexpensive low rpm performance alternatives.
A attentive is Advancing your Takegawa cam. Engines Only has slotted upper timing sprockets available to tailor your power curve.
BTW what stage kit do you have?
Advancing the ignition timing a few degrees. Will also help with low rpm response.
I see the horizontal engine crowd has some 2-4 degree offset Woodruff keys available for an inexpensive option. Or slotting the stock pick up. Assuming your ruining the stock ignition step up...
Dialing in the jetting, for mid rang. pilot and needles. Carb size also affects low rpm performance.
Increase exhaust back pressure.
TAKEGAWA 136 SCUT DYNO CHART
