Most of the tuned engines use an OEM crankshaft, which is not optimal balanced for a tuned engine. When a lighter or heavier piston and connecting rod are used, the balance is not correct anymore, which results in more vibrations.
We can perform modifications on certain OEM crankshafts for better performance. We then change the balance percentage and inertia of the crankshaft, using tungsten and / or aluminium material. This results in a better feeling and handling of the bike and leads to reduced vibrations.
It starts with your (used) OEM crankshaft, which we will need to receive to start the modification. When we've received it, we'll first determine the total reciprocating weight. With our advanced computer simulation, we'll calculate the best balance for each application. Material like tungsten will often be used to modify the balance (factor). After performing the modification, we'll assemble and align the crankshaft with high precision. When it's all finished, you'll receive the modified crankshaft back and you'll definitely notice the difference!
We often classify if a crankshaft modification has a high or low inertia. But what does that mean exactly? Here's an explanation.
High inertia
A crankshaft with a higher inertia has more resistance for changing in rotational speed. The crankshaft will accelerate slower.
Benefits
It depends on the riders feeling, torque and power of the engine and track conditions. It's very useful when engines are tuned and have even more torque and power. On tracks with less traction, you will get less spinning of the rear wheel and get more traction, thus better acceleration. When the engine is very hard to handle with a narrow power band and is constant lifting the front wheel, then a crankshaft with a higher inertia will give the engine a smooth power delivery to the rear wheel. The bike will be much more in control.
Low inertia
A crankshaft with a lower inertia has less resistance for changing in rotational speed. The crankshaft will accelerate faster.
Benefits
Again, it depends on the riders feeling and the torque and power of the engine. It's useful when the engine has a lot of top power but less bottom power. Also useful when the inertia of the crankshaft is already too high and results in a poor throttle response and acceleration. A lower inertia of the crankshaft can improve the throttle response and acceleration of the bike. The handling of the bike feels more aggressive.
Example crankshaft modification drawing
Scroll down to see the complete list of crankshaft modifications we perform. You can request such a modification by sending an email to your VHM dealer.
The cranskhaft modifications can't be found in our website assortment, only in the list below.
You can also download the list as a PDF:
We can also perform customized crankshaft modifications on your OEM crankshaft. If you have a specific idea or an OEM crankshaft which is not mentioned in the list, you can always ask us for a custom modification.
In the past we've already made customized modifications for the following motocross engines: Honda CR125R, CRF250R, Kawasaki KX250F, KTM 350SX-F, Suzuki RM125, RM-Z250, TM MX250, MX300, Yamaha YZ250 and YZ450F.
Furthermore, we've also performed several crankshaft modifications for various kart engines like Maxter MXO 125, Vortex DDJ 125, DDS 125, TM OK125 S-Junior, 60cc mini, KZ10C and Iame 60cc Waterswift.
Over the years we've gained a lot of experience with various engines, so don't hesitate to contact us about the possibilities.
MC50 | 2021 - 2023 | AK20123-002 | High inertia |
MC65 | 2021 - 2024 | AK20136-002 | Middle inertia, modified balance |
MC85 | 2021 - 2024 | AK20224-001 | Middle inertia |
MC125 | 2021 - 2023 | AK20202-002 | Middle inertia |
MC125 | 2024 | AK20277-004 | Middle inertia |
MC250F | 2021 - 2023 | AK20203-002 | High inertia, modified balance |
MC250F | 2021 - 2023 | AK20203-006 | Low inertia, modified balance |
MC250F | 2024 | AK20279-001 | Low inertia, modified balance |
MC450F | 2021 - 2023 | AK20211-003 | Middle inertia, modified balance |
MC450F | 2024 | AK20272-002 | Middle inertia, modified balance |
XX125 | 2021 | AK20063-002 | High inertia, modified balance |
XX125 | 2021 | AK20063-006 | High inertia, modified balance, using +3mm longer Prox conrod 03.2221 |
XX125 | 2022 - 2024 | AK20269-001 | Low inertia |
XX125 | 2022 - 2024 | AK20269-002 | Middle inertia, using 3mm longer conrod CRK2001 |
CR250R | 2005 - 2007 | AK20038-001 | Middle inertia, modified balance |
CRF250R | 2019 - 2021 | AK20246-001 | High inertia |
CRF450R | 2017 - 2024 | AK20221-001 | High inertia, modified balance |
TC50 | 2017 - 2023 | AK20123-002 | High inertia |
TC65 | 2017 - 2023 | AK20136-002 | Middle inertia, modified balance |
TC85 | 2018 - 2024 | AK20224-001 | Middle inertia |
TC125 | 2016 - 2022 | AK20202-002 | Middle inertia |
TC125 | 2023 - 2024 | AK20277-004 | Middle inertia |
FC250 | 2016 - 2022 | AK20203-002 | High inertia, modified balance |
FC250 | 2016 - 2022 | AK20203-006 | Low inertia, modified balance |
FC250 | 2023 - 2024 | AK20279-001 | Low inertia, modified balance |
FC450 | 2019 - 2022 | AK20211-003 | Middle inertia, modified balance |
FC450 | 2023 - 2024 | AK20272-002 | Middle inertia, modified balance |
KX65 | 2000 - 2024 | AK2066-004 | Middle inertia, modified balance |
KX85 | 2006 - 2013 | AK20041-007 | High inertia, modified balance |
KX85 | 2014 - 2024 | AK20178-001 | High inertia, modified balance |
KX85 | 2014 - 2024 | AK20178-002 | Middle inertia, modified balance |
KX125 | 2003 - 2010 | AK20033-001 | High inertia, modified balance |
50SX | 2009 - 2023 | AK20123-002 | High inertia |
65SX | 2009 - 2023 | AK20136-002 | Middle inertia, modified balance |
85SX | 2018 - 2024 | AK20224-001 | Middle inertia |
125SX | 2016 - 2022 | AK20202-002 | Middle inertia |
125SX | 2023 - 2024 | AK20277-004 | Middle inertia |
150SX | 2016 - 2022 | AK20202-003 | Middle inertia |
250SX-F | 2016 - 2022 | AK20203-002 | High inertia, modified balance |
250SX-F | 2016 - 2022 | AK20203-006 | Low inertia, modified balance |
250SX-F | 2023 - 2024 | AK20279-001 | Low inertia, modified balance |
450SX-F | 2016 - 2022 | AK20211-001 | Middle inertia, modified balance |
450SX-F | 2023 - 2024 | AK20272-002 | Middle inertia, modified balance |
RM85 | 2003 - 2012 | AK20039-001 | High inertia, modified balance |
YZ85 | 2019 - 2024 | AK20232-001 | Middle inertia |
YZ125 | 2005 - 2021 | AK20063-002 | High inertia, modified balance |
YZ125 | 2005 - 2021 | AK20063-006 | High inertia, modified balance, using +3mm longer Prox conrod 03.2221 |
YZ125 | 2022 - 2024 | AK20269-001 | Low inertia |
YZ125 | 2022 - 2024 | AK20269-002 | Middle inertia, using 3mm longer conrod CRK2001 |
YZ250F | 2019 - 2022 | AK20233-001 | Low inertia |
YZ250F | 2019 - 2022 | AK20233-002 | Middle inertia |
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De Vlonder 208
5427 DH Boekel
Netherlands
+31 492 32 45 95
info@vhm.nl
Mon-Fri, 8am - 5pm