Honda Xl 125 Problems and Analysis

The Honda XL 125 has a good pedigree and reputation also there is many variants of these machines, the Americans love them for off roading as suggested on many U.S.A. forums. A favourite enhancement to the XL,s is to fit a molossi big bore barrel kit, The advantage in doing this mod is twofold, if you like performance you will get some! If you like buying big end bearings you will have to get some.

The big bore kit that brings the 220cc needs extra breathing through bigger valves but riders usually leave the head alone. The outcome of the big bore enhancement is more unreliability and the guilt of riding a bike illegally over the capacity limit. The Honda XL 125 came to me with all the problems that could be expected so I stripped it down and took off the big bore Malossi barrel and replaced it with a standard barrel. Renewed the bent valves and guides that had rattled about in the head. The out come was a reliable standard engine, Not so , as when I was getting oil from the other workshop to put in the engine that had been fitted with new piston and barrel, guides, and valves. I could hear the engine having its nuts revved off. “AAGH”! I cried, what are you doing? , just needed to hear the beat of the engine, it sounds great;”it won’t harm it just doing a few revs”. I put oil in it through the dipstick hole as I watched smoke coming from the hole as oil displaced it. The engine wasn’t restarted as he was eager to get it back home and get back to work.

A couple of weeks later I got a phone call saying “the engine doesn’t work and I spent £70 on getting it compression tested and I am not happy with your work. I replied, “I will pick it up and have a look at it”. On inspection I found the inlet valve was bent but only just enough to not cause a good gas seal. All was fixed free of charge. The bike was delivered back to his home. Several months passed and I received another call from a very disgruntled Honda Xl 125 rider threatening me with court and trading standards part 2 bollocks and so forth. He said I am bringing it over  and leaving it to you to fix I said ill have a look.

On dismantling the engine and seeing the piston and barrel scored beyond redemption I thought I am dealing with someone who shouldn’t own or ride a bike as it had definitely not been run in correctly. Phoning him back I said it had seized due to not being run in, he replied “I never went over 40mph” I thought in what gear were you in, first at 16,000,000 revs. The threats came thick and fast, I am going to have you hung, drawn and quartered and I am going to dance on your grave and then get trading standards on to you. At the end of the day he hadn’t adhered to the running in procedures and hadn’t even checked his oil of which the engine was devoid on final strip down.

My summing up is that the engine had been satisfactorily built to the correct specifications but the running in procedure had not been adhered to. Initially the engine had been revved with no oil in it causing damage to the rings, i.e. nipping up in there ring grooves. This was the major part of a loss of compression not the inlet valve. After I had fixed the bent valve I didn’t think to inspect the piston and barrel as they had only 200 miles under there belts. Inspection of spark plug showed a mixture on slightly the rich side and the tail pipe showed a little black dry residue. This showed the bike had been run prior to bending the inlet valves. Oil level and colour checked out ok. On it’s final strip down the plug showed white, barrel and piston as mentioned before was fixed and the tail pipe was 3mm thick of fluffy black soot. This beasty had burnt a whole sump of oil leaving it dry. As one of the top manual toolmakers and mechanical engineers in the UK and a doctorate in mechanical engineering also with 34 years of experience to boot. Don’t try to pull the wool over my eye’s I will see through your untruths. If perfection cannot be attained we will not take on the task.