XR400 Overhaul

In September 2019, I wrote about the Honda XR400R that I’d bought in June that year. It had spent most of July and August in the shop, awaiting some minor upgrades. Once I got the bike back from the shop, I realised that there were a couple of other issues that needed attention. Unfortunately, it transpired that the bike needed a major overhaul that would put it back out of commission for a few months!

Whilst riding the bike off-road, I’d noticed a bit of an issue with the clutch that I wanted to get checked. But the most significant issue was an oil leak, that appeared to be coming from the frame, beneath the fuel tank (the XR400 has an oil-in-frame design).

When I went to inspect the bike, before buying it, I had thoroughly inspected the engine and lower frame for any signs of oil leaks. There were none. What I neglected to do, during my inspection, was to actually check the level and condition of the oil in the bike. This was part of my check-list when inspecting potential bikes. I had checked the oil on several other bikes that I’d gone to see. I even walked away from one potential purchase as soon as I saw that no oil was visible on the dipstick. Somehow, for this particular bike, I didn’t check the oil and that omission came back to bite me. Big time!

It turned out that the oil level in the bike was low at the time that I bought it, which probably explains why it wasn’t leaking any oil. The low oil level was spotted whilst the bike was in the shop in July/August and they filled it up. Once I got the bike back, in September, it immediately began leaking oil over the frame whenever the bike was running. It did not continue to leak whilst parked. Having traced the oil up the frame, I was quite sure that it must be coming from a crack in the frame.

I took the bike to the shop for a diagnosis but they could not (initially) find a crack in the frame. But what they did find was more unpleasant! The clutch was worn out and would have to be replaced. The piston rings were worn and were allowing oil to pass into the cylinder head. This meant that I’d need to get a new piston and rings and have the cylinder re-bored. Further, the connecting rod showed signs of movement, so that would also need to be replaced, requiring the engine cases to be split. This news was particularly surprising to me, as one of the selling points for the bike was that it had recently had a new clutch fitted and also a new piston. Why the damage re-occurred so soon after the repairs is debatable, but it now needed to be re-done.

Whilst the engine and clutch were the two major issues, there were also additional concerns. The gear-change lever had been welded onto the gear shaft by the previous owner, after it had snapped off. As the engine was going to be stripped down anyway, it made sense to take the opportunity to fit a new gear shaft and gear-change lever. The clutch cable was a cheap after-market product that might have contributed to the clutch burnout. The clutch lever and brake lever were cheap Chinese items, so I decided to have a new cable fitted along with some better-quality levers. Similarly, the decompression lever was a ‘cheap and nasty’ replacement that wasn’t very sturdy. So that would be replaced with a stock Honda lever and cable. All I could do then was wait for the work to be completed.

Months later, in January 2020, I received a message asking me to visit the workshop as there were some things I needed to see. That sounded ominous, so I quickly made my way there. It was more bad news! The mechanic had completed the engine and clutch rebuild and had taken the bike out to test it, revealing a couple of problems in the process. The first problem was a crack in the frame resulting in an oil leak. The crack was very small, at the point of a weld in the frame, but it would require the oil to be removed and the crack to be welded. At this point, I was quite frustrated because that was the main reason I had taken the bike into the shop to begin this process and it should have been identified early. But there was more! After the engine was rebuilt, the mechanic tested it by leaning the bike to either side whilst the engine was running. When it was leaning in one direction, there was an abnormal knocking sound that was not present when the bike was upright, or leaning the other way. An inspection revealed a problem with the counterbalance. So, having already been stripped and reassembled, the engine would now have to be opened again so that the counterbalance could be removed for machining. Of course, this meant more money to remedy the problems.

After learning the extent of the problems with the bike, I had a couple of conversations with the previous owner. He assured me that he was unaware of the issues when he sold me the bike. As a gesture of good faith, and to provide me with at least some level of compensation, he gave me a brand new FMF exhaust muffler that he had bought for the bike but hadn’t fitted. With a value of €470, it went some way towards lessening the financial impact of the repairs. I also purchased a bash/skid-plate for the bike and delivered it to the shop, to be fitted once the engine went back in. Both items are now on the bike.

Finally, on 22nd January, I was able to collect the bike from the shop. By then, I had owned the bike for seven months but it had spent at least six of those months sitting in the shop. The repair cost was significant – as much as I had paid for the bike in the first place.

The work on the bike included:

  • New Barnett clutch kit
  • New clutch cable
  • New Racepro clutch lever (matching brake lever on order)
  • New Honda brackets for brake and clutch levers
  • New decompression lever and cable
  • New Vertex KT40 99-08 1.00 piston kit
  • New connecting rod and bearings
  • New gear shaft and gear change lever
  • Machining counterbalance
  • Frame welding to repair crack
  • New FMF exhaust
  • New Moose Racing skid plate


With all of the work completed, and so much money spent, I’m now hoping that the nightmare is finally over. It’s time to get the bike out on the trails to enjoy many months of trouble-free riding. Here are some photos from the first ride after the completion of the repairs – on some easy trails near Valongo.


  1. Nightmare! However if you want to sell it Clive would be interested!
    I haven’t started off roading yet apart from struggling on gravel roads in New Zealand on my CB500X so not ideal for a novice. I quite fancy an AJP PR3 having sat on one at the NEC last year. Nice height for me and very light. We will have to mark Valongo on the map!

  2. Hi Craig, You have been emailing my partner Amanda. I owned my xr400 for 20 Years before selling it to a friend last year. The only issue i had with mine was i ran it low on oil. I removed the engine and purchased a very good barrel and piston on a xr forum. I also split the cases to check everything else which was fine. I purchased genuine gaskets and cam chain and this done in 10 days. The bike still has its original clutch. I just did the basic servicing like changing the oil & oil filter chain & sprockets tyres ect. Check the oil when the engine is warm not cold. Look at the xr forums for this. The XR 400 is a brilliant bike and will last you years. Hope to meet up some time. Cheers Clive

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