Judging by the colour of their clothes I had a good idea what the road ahead was like. And they were in a vehicle. The tohelandback duo, two young English guys I'd briefly met in Yaounde, who are driving around Africa in a sponsor-emblazoned Land Rover, met us for lunch and kindly donated their dust masks before wishing us well for the road out of Bertoua.

They were welcome gifts. Once we passed a rare sign post showing Bangui, Central African Republic's capital to be 841km away, the town's tarmac soon ended. It wasn't long before we disappeared into a cloud of red dust, then another, and another, and so on.

We were still on one of Central Africa's main logging truck corridors, but now it was narrower, unpaved and there was no escape as large wheels rumbled over corrugated laterite and transported the loose surface of the road into the air, from where it would settle on whatever object it first came into contact with – often us.

I was glad I hadn't bothered cleaning the bike, other than the chain, although inside that plastic guard it stays remarkably free of dust. This, I should note, is a worthwhile piece of kit for anyone considering a long tour on poor roads.

Cameroon takes on a different appearance in its far eastern quarter. Apart from the fact that vegetation at the roadside is a closer shade of red than green, the people living alongside it are predominantly Muslim. This doesn't mean the end of bars and beer, for we're still in Africa's beer drinking capital, but there is a different atmosphere and appearance to those small dust-covered truck-stop towns. Mud brick mosques and market stalls selling unidentifiable slabs of char-grilled meat remind me more of rural Nigeria than the Christian-dominated beer-guzzling nation of Cameroon. I soon discovered people out here speak a Hausa dialect and there is a large fulani population, the latter easily recognisable from their lighter complexion. There are also a lot of refugees from CAR living along this road to the border, having fled the conflict and upheaval in their country over recent years – a comforting scene for someone about to ride a bicycle there.

There was however one minor problem about me leaving Cameroon and entering CAR. My visa for Cameroon had expired two weeks previously. In most parts of the world this should and would mean a fine, calculated on a daily basis for the length of overstaying the visa. It probably would have done in Cameroon, had I not taken a tip-ex correction pen to the date of entry on my Cameroon stamp (written in biro). A foolish thing to do you'd think? Absolutely. Tampering with your passport is a crime and I have no desire of visiting an African prison.

The tip-ex job was a result of having previously failed to get a visa extension at the immigration office in Yaounde. Here I had been told to pay for an entire new visa. It was partly something about the rudeness of the woman who told me this and partly my mood at the time that had me decide there was no way I was paying another $100 to stay in Cameroon for a few more weeks.

A few years ago I'd changed the dates on a Libyan visa and exited the country without a problem. Here in the less official and alcohol-induced state that so many things seem to get done in Cameroon I decided the risk of being accused of forgery was preferable to the cost I would encounter for a new visa  in Yaounde.

So when Hiromu and I rolled up to the immigration office in the border town of Kentzou I was relieved to find the official in charge was from the anglophone part of Cameroon. He was also sober and more interested in hearing about our journey than checking the dates we had entered Cameroon. A few minutes later another official in another office was giving us the exit stamps without having even looked at the entry stamp and my DIY tip-ex job. Another big relief. I hoped entering CAR would be as easy as leaving Cameroon, but something had me thinking otherwise.