Nicky Hayden had complimentary things to say about the handling and electronic progress of his new Open class Honda after day one of 2014 MotoGP testing at Sepang.

But the bottom line seems to be that the RCV1000R needs more engine performance.

On a day when the rival Open Yamaha of Aleix Espargaro featured in the top four and finished ahead of the Factory class Tech 3 Yamahas, Hayden was the best of the Open Honda riders in 17th place.

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Hayden's best lap was 1.9s slower than Espargaro and three seconds behind Factory Honda pace setter Marc Marquez.

Speaking outside the Drive M7 Aspar pits on Tuesday evening, Hayden said: "It was nice to be back on the bike after so long and of course we have a lot of work to do. I'm not completely thrilled because we're quite far off the front guys.

"The [control ECU] electronics were definitely better than in Valencia, they smoothed out a couple of the flat spots. I liked that, but we still have to work a lot for the acceleration and engine because that's where we're losing the most now.

"The handling is very good, but we're losing on the long straights and acceleration out of the slow corners. I think it's a power issue. We can help with electronics, but now we're basically full power everywhere."

Comparing the riding characteristics with his former factory Ducati, Hayden added:

"Quite a lot different actually. For sure the chassis soaks up the bumps a lot better than the Ducati did. And it's a lot less physical. But I'm sure once we get the engine running better this bike is going to get more physical. Now on the straights you have time to breathe and relax."

Switching from factory electronics to the new Dorna control ECU system is also a major change.

"Some parameters are quite a lot different. You only have one wheelie control for example, on the Ducati you could do a different setting on every straight and every corner. But the bike is all new so it's hard to understand what is engine character and what is electronics."

However the American star reiterated that he feels the main limitation is the engine.

"For sure we need more power. I mean the first exit or two [on track] we had a little margin in places but... I was just going wide open. We went immediately, pretty much full power everywhere. Not so much on the edge [of the tyre], but when you pick the bike up.

"But this track is very big. Maybe if we were at somewhere like Jerez, the problem wouldn't be so big or I wouldn't be complaining too much about it."

With all four Open Hondas in the final third of the timesheet, many were suggesting that HRC has been too conservative with engine output. Others also pointed to the use of steel, rather than pneumatic, valves.

The main differences between Hayden's Honda and the title-winning Factory class machine are the steel valve springs and a conventional rather than seamless shift gearbox.

The changes have been made to keep the price of the motorcycle, which is sold rather than leased (Forward's pneumatic Yamaha engines are leased), as affordable as possible. Asked if Honda may be able to raise the engine performance once they have more testing mileage to evaluate, Hayden replied:

"This is a new project. I don't want to speak for Honda, but I'm sure they are not just going to sit still. Of course, they are about developing and improving. I'm sure once they get more data and things.

"As I said already they have improved some stuff with the electronics. They know this software is going to be their future. The reason why they are investing so much in it is to get prepared. We have a good connection with Honda and they are listening to our comments.

"I'm sure we're going to find some power somewhere... I know Honda were taking trap [top] speeds today."

Hayden was a factory Repsol Honda rider from his 2003 MotoGP debut until switching to Ducati in 2009, winning the world title in 2006.

Asked if the new Honda reminds him of the previous factory RCVs, Hayden gave a wry smile: "I would say it reminds me at the moment, unfortunately, more of the 800 than the 990!"

For Tuesday's second day, Hayden will continue getting to know his new machine.

"Tomorrow we're going to try springs, wheelbase. Normal stuff. This bike has a few less options. The pivot is what it is. But we're definitely going to try and improve corner entry grip. It's snaking quite a lot."

Hayden's team-mate Hiroshi Aoyama was just 0.009s slower, with the other Open Honda riders - Gresini's Scott Redding and Cardion's Karel Abraham - 21st and 26th respectively.

In return for using the full control ECU system, Open class riders enjoy perks such as four litres more race fuel and twelve rather than five engine changes during the season, relative to the Factory class. There is also no freeze on engine development.