I have added a spacer to mellow out the hit of the engine. The spacer increases crank case volume, and since air is elastic, (it stretches and compresses), more crank case volume means the reeds will actually open up a bit slower. If you want to mellow out the power hit, use the spacer. If you want it to hit harder, don't use the spacer. Peak power should also be a tinge higher with no spacer. I am making a lower end trail monster, (whooped out sand trails, not really tight stuff.), out of a high revving stock 2019 YZ250, and all the mods are reversible if ever needed. To shift the power to the lower RPM's, I am using a FMF Gnarley pipe, lowering the cylinder by removing the stock .5mm thick cylinder gasket, (seal it with a gasket sealer that resists gasoline, no silicone), which will lower the exhaust port timing to better match the FMF pipe, and add compression, (may need more than 93 octane fuel, but I doubt it because the 2019 has pretty low compression and a lot of squish clearance.), using v-force 3 reeds with no spacer. I am not done with the changes, but I do port 2-stroke engines for a living, and I know I am on the right track. Doug in Michigan
Oh yea, re-jet the carb after the mods are done. I like to drop the needle first (may use a little spacer to only drop it half way, or it may run lean.), and then change the main jet if needed.
@@Jake-rp9cv I had 04 motor and chassis with alu frame so decided to put it together. Engine fits pretty good you need to modify the top mount a little.
@@konradenduro1996 if use this boyesen plate, pilotjet must up big size or maintain? i can't setting this reedvalve plate after install.. it's very hard to find fine tune.. plug also lean after install this.. mainjet set up more big size but still lean..
I have added a spacer to mellow out the hit of the engine. The spacer increases crank case volume, and since air is elastic, (it stretches and compresses), more crank case volume means the reeds will actually open up a bit slower. If you want to mellow out the power hit, use the spacer. If you want it to hit harder, don't use the spacer. Peak power should also be a tinge higher with no spacer. I am making a lower end trail monster, (whooped out sand trails, not really tight stuff.), out of a high revving stock 2019 YZ250, and all the mods are reversible if ever needed. To shift the power to the lower RPM's, I am using a FMF Gnarley pipe, lowering the cylinder by removing the stock .5mm thick cylinder gasket, (seal it with a gasket sealer that resists gasoline, no silicone), which will lower the exhaust port timing to better match the FMF pipe, and add compression, (may need more than 93 octane fuel, but I doubt it because the 2019 has pretty low compression and a lot of squish clearance.), using v-force 3 reeds with no spacer. I am not done with the changes, but I do port 2-stroke engines for a living, and I know I am on the right track. Doug in Michigan
Oh yea, re-jet the carb after the mods are done. I like to drop the needle first (may use a little spacer to only drop it half way, or it may run lean.), and then change the main jet if needed.
Is that the stock motor? Looks like a 1996-2004 yz 125 motor.
This is 2004 motor.
@@konradenduro1996 thats very cool! Can I ask you why you did the swap and how easy was it?
@@Jake-rp9cv I had 04 motor and chassis with alu frame so decided to put it together. Engine fits pretty good you need to modify the top mount a little.
does it have huge difference after installing the spacer.. is it advisable to use spacer on technical terrain
Did you have to re-jet after adding the spacer and reeds?
Yes
@@konradenduro1996 thanks for the quick reply! Looks like I know what I'll be doing this weekend
@@konradenduro1996 if use this boyesen plate, pilotjet must up big size or maintain? i can't setting this reedvalve plate after install.. it's very hard to find fine tune.. plug also lean after install this.. mainjet set up more big size but still lean..
@@2strokelovers441You need to install richer pilot jet and leaner main jet. What bike do you have?
@@konradenduro1996 ohh i see.. i use yamaha 125z.. by the way i'm from malaysia..
What spacer function for?
For better low end
So could you tell a difference or ?@@konradenduro1996