How To Tune DOWN A 2 Stroke.. ?
- Thread starter CROSS
- Start date
dirt bike dave
Sponsoring Member
- May 3, 2000
- 5,348
- 3
Make the jetting too rich.
Over-oil the air filter.
Put on a very restrictive spark arrestor/silencer.
Add some sort of throttle stop like Yamaha puts on the stock WR450 four stroke.
If the problem is the bike just has too much 'hit', a flywheel weight or some attention to jetting may smooth the power delivery and make it easier to ride, without costing any peak power.
Over-oil the air filter.
Put on a very restrictive spark arrestor/silencer.
Add some sort of throttle stop like Yamaha puts on the stock WR450 four stroke.
If the problem is the bike just has too much 'hit', a flywheel weight or some attention to jetting may smooth the power delivery and make it easier to ride, without costing any peak power.
AJ Waggoner
Crash Test Dummy
- Nov 5, 1999
- 4,368
- 34
flywheel weight.
timing
different styole of porting..
and o nlittle 2 strokes like a pw50 they have a restrictive gasket in the exhuast
it would certainly work on a larger bike,,lol
while i wouldn trun a rag i nth esilencer,, there could be possibilties..that would work..
and make the bike whisper quiet as a bonus..??
just random thoughts
timing
different styole of porting..
and o nlittle 2 strokes like a pw50 they have a restrictive gasket in the exhuast
it would certainly work on a larger bike,,lol
while i wouldn trun a rag i nth esilencer,, there could be possibilties..that would work..
and make the bike whisper quiet as a bonus..??
just random thoughts
I've really had good success with my 97 CR250R with mods to make it more rideable. It still has freakin awsome power if you wind it up, but I wanted smooth lowend delivery for woods riding.
If you want to detune a 2-stroke so you can "putt" around here is what I did.
Major improvements were- Flywheel weight, I went with the max oz weight. Steel clutch makes a big difference. Quiet silencer restricts back pressure and the addition of a DB Snorkel helped. 51 tooth rear sprocket was good. FMF Gnarly pipe moved the power hit lower and gave more bottom end boost. My jetting was good to begin with, so I was lucky. The jetting has alot to do with rideability of the bike.
If you do the mods and get the bike running clean, you can just putt thru the gears and enjoy it. You'll still have the power reserve on tap by just twisting the throttle if you want.
If you want to detune a 2-stroke so you can "putt" around here is what I did.
Major improvements were- Flywheel weight, I went with the max oz weight. Steel clutch makes a big difference. Quiet silencer restricts back pressure and the addition of a DB Snorkel helped. 51 tooth rear sprocket was good. FMF Gnarly pipe moved the power hit lower and gave more bottom end boost. My jetting was good to begin with, so I was lucky. The jetting has alot to do with rideability of the bike.
If you do the mods and get the bike running clean, you can just putt thru the gears and enjoy it. You'll still have the power reserve on tap by just twisting the throttle if you want.
With overly rich jetting you risk plenty of time for it to be tuned WAY down...all the time you spend swapping out fouled plugs. Better yet - be sure the jetting is RIGHT...often a bike jetting to rich down low will suddenly clear up when it come up off the rich pilot or needle setting and WHAM you now have power. Not good. Find out if the CR was set up with a multi taper needle - find out a good set up for a straight taper. Makes quite a difference on KTMS - dunno if it applys to a CR though. The flywheel weight comments are on the money though - makes much more controlable power. Another suggestion is a G2 throttle cam system - you can swap in more or less agressive cams as your skils improve - neat set up. Do go with a quiet silencer - not for power changes but just to keep it quiet. A side benefit MIGHT be a slight impact on power. Gearing it up (smaller rear sprocket or larger front) is a good suggestion as well.
Put a lid on the air box, with a smaller opening.
TRexRacing
Member
- Jul 23, 2002
- 440
- 0
Many times just jetting the bike well will tame the delivery enough to make ya happy.I'd try that then move on to the flywheel weight.I have one on my CRF and love it.
TRexRacing
Member
- Jul 23, 2002
- 440
- 0
Says the guy with little bikes.
digifox said:
Learn to keep your mouth shut or get a bigger brain.
inotocracy
Member
- Apr 22, 2008
- 208
- 1
Dem fightin werds.
A rich mixture will tend to hit harder. Its more a bog, then the plug cleans up and spooge away! Properly jetted it should pull even through the power range, and no spooge! Consequently, it makes it easier to ride. Especially in slick conditions.
2-Strokes 4-ever
~SPONSOR~
Retard the timing some.
Perhaps what you need to look into is moving the power around... pipes (top-end/low-end), rear sprocket (as mentioned), different reeds, lowering the port height (material off base of cyl) will give you more low-end BUT this allows you to short-shift and use the torque of the motor which makes the delivery less violent (works really well in hard-to-find-traction conditions).
Perhaps what you need to look into is moving the power around... pipes (top-end/low-end), rear sprocket (as mentioned), different reeds, lowering the port height (material off base of cyl) will give you more low-end BUT this allows you to short-shift and use the torque of the motor which makes the delivery less violent (works really well in hard-to-find-traction conditions).