In this week's blog post, we are going to discuss the downfalls of waiting to rebuild your engine, some obvious reasons and some not so obvious reasons. We are also going to talk about how a simple swapping of old valves for new ones can save you over $2,000 in repair bills and why you should always rebuild your engine and other critical components during the off-season.
Many of today's modern 4-stroke off road race bikes with engines straight from the manufacturer are pushing the 14,000RPM mark when the throttle is held wide open and you are reaching the upper echelons of your transmission's individual gears. For the sake of conversation, we're going to assume you understand this means the engine rotates 14,000 times per minute when bouncing off the rev limiter. We all know you love bouncing off the rev limiter while sailing over the finish line triple at your local race track, and we're not here to tell you to stop. But we do want you to consider the strain you are putting on your engine and hope you will consider spending a few bucks every now and then to make sure your engine will continue running strong.
One of our designers (who wishes to remain unnamed for fear of embarrassment) here at Moto3Designs thought he was keeping his engine in tip-top shape...changing the engine and trans oil every 5 hours of riding, checking the valve clearance every 10 hours, plopping a new piston and rings in every 40 hours...Daniel thought he was doing great. Ooops did we just say his name?? Hmmmmm oh well;-)
Little did Daniel realize that he should swap out those valves in his CRF every now and then too. In November of last year, while riding at his local practice track, Daniel's back wheel locked up on his CRF250. When he came to a stop, he was resting on the take-off of one of the track's doubles, so his situation could have actually ended up a lot worse than just a damaged engine.
The bike would no longer turn over, even in neutral, and the kickstarter would not budge. Daniel knew he was in trouble and right away started tearing the top end of his engine apart.
Once he had the cylinder head off, Daniel thought he saw the extent of the damage, a valve head had snapped off of its stem...he would need a new valve train, cylinder, cylinder head, and piston kit...the parts would set him back around $1000. Still a lot of money, but manageable when the end result would be an entirely new top-end. Daniel would also do the rebuild himself, saving several hundred dollars over having a race shop do the work for him. Just to be on the safe side, Daniel took his engine in to a local engine repair shop to have everything else looked over.
The engine shop called a couple days later to tell Daniel that his rod was bent and that he would need a new crank and bottom end bearings. At this point Daniel was starting to consider whether saving the engine and doing a complete rebuild, or just buying a new bike would be the better option.
After careful consideration, and luckily for us and this story, Daniel decided to stick with the bike he had and rebuild his CRF's engine from the ground up. Opting to stick entirely with OEM parts, Daniel was out around $1700 when the damage to his wallet was all said and done. This still pails in comparison to the thousands of dollars the local repair shop would've charged him. Daniel is also a hands on guy and figured a refresher course on rebuilding an engine's bottom end wouldn't be the worst thing in the world.
Also on Daniel's side was the local engine shop. For just $60 they seated all 4 new valves and made sure everything in the top-end of the engine fit just right. This was the deal of the century in Daniel's eyes.
Daniel split his CRF's cases and after some finagling, he was able to get his new crank and bearing installed and put the bottom end back together. Next was the top-end, which went together as smooth as hot butter on toast thanks to the help of the local engine shop.
Were there warning signs before Daniel's CRF dropped a valve? We think the backfire at idle that Daniel mentioned he remembered his last couple rides in November was a dead give away. It is not normal for an engine to just decide to do extensive damage to itself without some sort of clue.
Pay attention to your engine and if something starts acting weird, take things apart. Investigate. Have your local race shop investigate. The few bucks you may spend on diagnostics or on a top end rebuild and valve replacement, will be money well spent to make sure you do not need a new motor before your next ride or race!
Do yourself a favor and get off that couch this February. Go through your race bike in its entirety and replace anything that looks worn out. This way, you'll be ready to go when the snow melts and the ground thaws and the outdoor racing season kicks into gear in late March and early April.