Real dirt: techno fest

Real dirt: techno fest

Fuel injection coming to two-strokes?

It looks like the death knell for the carb on KTM and Husky racing smokers from 2018

By Dave Willet

KTM and sister brand Husqvarna may be the first major manufacturers to ditch the carb for its two-stroke motocross and enduro bikes and move to fuel injection for the 2018 models. KTM recently tested a fuel-injected 300 two-stroke in the Roof of Africa Rally and it’s believed the EFI system may come on 250, 300 and possibly 125 motocross and enduro bikes by next summer. And it’s likely Husky will follow suit as its bikes are closely related.

Adding fuel to the fire is that KTM and Husky both switched from long-term carb supplier Keihin for rivals Mikuni on their all-new 250 for 2017 and also the 125 and 150. It’s believed Keihin is now featuring totally on injection and would only continue to make carbs for KTM and Husky if it got a three-year commitment from the factory.

With the plan to go fuel injection imminently, the Austrian factory could give no assurances and hence bought carbs from rival supplier Keihin who would make batches of carbs to order.

On the 2017 models, the carburation has not been ideal. They all share the same carburettor yet the Husky seems to be a little more suited to the change, potentially down to the one-piece airbox giving a different airflow.

The 2017 KTM 125SX can load up into turns but next year might be fuel injected

All the bikes are set rich from stock. They can bogging when landing off jumps or you may detect a delay in power when exciting the turns.

The 125s seem to be more prone to it, too. The performance is fine once past quarter throttle and the main jet takes over the fuelling.

We’ve also had issues when rolling off the throttle into a turn. The motor just seems to load up with too much fuel which gives a delay when cracking the throttle back on and exiting the turn. It doesn’t happen on every turn but it's enough of an issue to make you adjust the carburettor jetting.

A properly set up fuel injection system would combat these issues as it constantly adjusts itself for changes in conditions.