[gmaa007]

Greetings from Baja Mexico!

I had been planning a 300 mile trip in the southern part of Baja for months, I prepped my bike for this trip as much as I could, I got a large desert tank, changed the fluids, cleaned the air filter, checked and re-rechecked everything as much as I could.

The week before the trip I decided to check my valve clearances, I took it to a local shop in La Paz since I had been so busy with work, the mechanic told me I needed new shims so he put them in and everything was ready to go!

The day of the trip is finally here, I leave home at 6am and started riding about 30 miles into the trip, bang! The engine dies and my rear tires locks on me. I instantly knew my trip was over. Long story short I got towed by an ATV all the way back. I opened the engine and sure enough big trouble.

One of the intake valves broke and damaged the piston and the head.

I am thinking that my problem is somewhat related to whatever the mechanic did to my valves the days prior, either way he does not want to take responsibility and I cannot prove it so I am stuck with a broke bike.

Where somebody sees this as a bad thing I would like to see it as an opportunity, an opportunity to learn more about my bike and to make a project out of it.

I am starting this thread to document the work on my bike and to get suggestions by the experts on what should I do.

By the way this is my first bike so I have no experience in working with bikes other than normal maintenance, I got my self a Honda Service manual that will help me in this project.

My goal is to have a much better bike than I started with designed specifically for trail riding in Baja.


Here are some pictures of the damage.

[JimDirt]

Welcome to the site !!

Sorry to hear about your bad luck , as far as the mechanic goes , what info i would have asked him is , what was the clearance of the valves before he shimmed them , if it was already 0 , then there would be a possibility of the stem breaking , it does happen ,, but there would be no proof that was the cause

The only way i could see it being a failure due to labor would be if a spring retainer was either worn and not replaced (they do wear) , or , if it were not installed correctly and it fell out , causing the valve to drop and hit the piston , causing the damage we see in the pictures you provided , which can not be proven easily either since when the stem breaks , its highly likely that the retainers would fall out anyway and the valve would fall and hit the piston causing the damage we see in the pictures

In your quest to rebuild the engine , please be aware that when a piston is impacted like yours was , the chance of a crank/rod bearing failure is imminent , so plan on a new crank/rod , piston , and a replacement or new head , basically the only salvageable parts in your engine would be the case and internal gears , and transmission components , and the cylinder , and cam assembly , the head , crank/rod , piston are toast

Good luck with your project and keep everyone posted of your progress (pics are welcomed), and feel free to ask any questions , or voice any concerns you may have , plenty of people to help , and having the manual will be a plus

Not trying to push anything here , but Ken (the owner here) , sells everything you would need to repair , rebuild or modify your bike/engine , and he offers fair prices and excellent service , so consider this your one stop shopping center (if you have other sources that you feel comfortable using , then that is fine as well , no pressure) , Good Luck !!

[mossman77]

Sorry for your misfortune. I'm sure Ken will recommend the same--you should get an '07 or '08 head to replace your '04 head, both of which have the newer valve seat material.

[gmaa007]

Thanks for the reply guys, Is there any way to check if the crank and rod are damaged?

[JimDirt]

without tearing the crank apart , and physically checking each bearing and journal for roundness , etc , unless its obviously got slop , its hit and miss , you could move it around by hand and think all is well , then when you fire it up and get a load on it , the rod will start knocking

The majority of experience is that when something hits the top of the piston , especially hard enough to leave major marks in the piston and head , its pretty much a given the crank is done , its honestly not worth taking a chance , if it does let go , its going to cost a lot more than it would just replacing it now , then to take the chance and have to replace much much more when things go boom , it sucks , but its the best thing to do when parts come in contact with other parts they are not supposed to .....

The marks on the piston are the equivalent to taking a hammer and beating the crap out of it , then you try slapping a new piston in it and throwing it back together and hoping your just going to ride off and nothing will happen ,,,, , the force that is put on the bearings and journals with a impact like that are more than they are built to withstand , and generally leads to a bad outcome .... , not counting the cost of paying someone to split the crank apart to check everything , then if it is bad , replacing the parts , in the end , its cheaper just to buy another crank and be done with it , and have the confidence knowing that its new and done right .... sorry