There is a potential major issue in the Harley-Davidson Twin-Cam engines. This is a statement of fact, not a bunch of wild guesses. I’m not here to bash Mother Harley, but you should be educated to its causes, and possible solutions.
Okay, what issue are we looking at? It’s a very serious one that is enough to alarm you. However, you can fix these defects and end up with a nice bike. Our objective today is to educate, and we are also going to outline some ways to fight back. Yes, even the new Harley’s have serious, potential problems. Even the expensive CVO (Custom Vehicle Operations) bikes have issues not to be taken lightly.
Here we go…..
The problem is the design of the cam chain system. It uses plastic “shoes” riding on the cam chains that can (and do) wear out. Harley has made some changes in later model bikes, but even with the new hydraulic tensioning system, it is not a true fix. What is the problem? The shoes rub against the two chains and the plastic shoes wear out. When they wear in extreme cases, there will be metal to metal contact and this grinding creates metal shavings that can result in a catastrophic engine failure. If not caught soon enough, this can be so bad that the entire engine can be destroyed; cams, pistons, crankshaft and even engine cases broken. It is a wickedly serious possible engine problem. Be aware… it can fail as soon 15,000 miles (in extreme cases). Even the newer hydraulic system can fail at 50,000 miles or less. The cam chain tensioners have a section in every service manual that covers the Twin Cam engines and is very enlightening.
The scary thing is every Twin-Cam engine has the potential to have the cam chain follower issue, even the new models. Check things out before this happens to you. If it has a cam chains, it has the potential problem.
It is our intent to make you aware that pre ’06 Dyna’s and the 1999 to 2006 Twin-Cam Harley-Davidson engines have possible, serious issues and they can mess up. How? In the most severe cases, as the spring loaded cam chain follower fails it shreds plastic material that fouls the rotary gear oil pump cutting off oil flow to the engine that can cause sudden catastrophic engine failure and destruction. Also, metal to metal contact in these shoes produces metal filings to disperse into the oil prior to being filtered by the oil filter. If this happens be prepared (worst case) to buy a completely new motor as rebuilding the engine may not be feasible. This is not a likely situation, but a realistic possibility.
Are the 2007 and newer, updated Twin-Cam engines immune? No. Do not be fooled. Hydraulic cam chain followers are now used to get rid of the stiff spring that put too much pressure on the followers rubbing on the cam chain, but this is “no cure” as it only “delays” the problem. Instead of the engine failing at 15,000 to 30,000 miles, it now fails at 50,000 to 75,000 miles. There is only one true cure… getting rid of the chain system entirely and switch to gear driven cams. Harley-Davidson should, in my opinion, make this a standard fix and not an after the fact option. If you can’t afford to install the gear drive system, then you need to disassemble and inspect the inner and outer shoes every 15,000 miles or risk engine failure. The shoe material can also clog the oil pump destroying the engine. There are plenty of motorcycle magazines explaining how to fix this problem and they can fail beyond the factory warranty period. The problem has not been fixed; only delayed to fail above 50,000 miles and when the engine fails it may not covered under warranty. Check the fine print in your extended warranty as this cam chain related failure may not be protected. Dealers will tell you it is a failed maintenance issue unless you take the steps we suggest.
You won’t even get a straight, honest answer from Harley dealers regarding this engine defect. As I did research for this article, I called a local dealership, and the service writer would not answer my questions, and frankly gave me quite a song and dance, refusing to forward my questions and concerns to the mechanic or management. Disturbed and curious, I read a number of different service manuals, and while the drawing of what is good and bad with the cam tensioner shoes is published, there is no inspection interval listed. This leads me to believe Mother Harley knows a problem exists and Harley-Davidson dealers are actively not giving straight answers to customers. How can they not have published inspection intervals? The only mention of this possible failure is in the troubleshooting guide under “Valve train noise.” You will not hear any rubbing sounds or receive any indications the cam follower has failed even if you have quiet stock exhaust pipes on the bike. This is an issue that nobody wants to talk about, but is a real threat to your pocket book.
OK, now that we have ruffled everybody’s feathers, how can we combat this? S&S has truly been visionary in solving this issue. They had the foresight to develop a gear drive system to combat this very issue. It is my opinion, that all Twin Cam engines should have this conversion done, so you can rest easy on your higher mileage TC engines. The gear drive replacement is an excellent and the only true bulletproof solution.
As an alternative to gear drive, our only choice would be periodic tensioner shoe inspection. While not outlined in any Harley Service manual I’ve seen, looking at them and replacing as needed should be done every 15,000 miles. There are nice pictures of what to look for, but no recommended inspection interval. If you decide not to go gear drive, this is emphatically recommended. This periodic inspection can make any future warranty claim valid. On earlier engines, an update to the later style hydraulic tensioners will relive pressures and delay required service, but periodic inspection is still recommended. Check things out before this happens to you.
One way to help understand what may be happening inside your engine is to cut apart your oil filter at each oil change. Look through the pleats for any metallic or plastic debris. If you see junk, it’s time for your engine to come apart. You may be able to save your engine’s life by doing this.
Another thing to consider is better oils. Today’s better performing premium oils can delay the destruction. While a bit more expensive than conventional oils, oil is still cheaper than engine rebuilds. Here, synthetics, such as the Bel-Ray Synthetic (part number 900-405), the Revtech MTP Synthetic (part number 740-786) or the Lucas Synthetic (part number 900-687) may be your best choice.
As we have a decent oil filtration system in our TC engines, a way to help the filter is to apply a magnet such as PN 740-742 to the outside of the filter. This will help trap any metallic grunge that may be floating in our oil. Remember though, most of the bad stuff is plastic, and the magnet will not capture that.
I have tried not to bash Harley regarding this, and I’m sure they don’t care about my opinions. It has been my objective here to educate, not to assassinate the dealer network. Being forewarned is to be forearmed. As we pointed out earlier, if you have a higher mileage TC, you might want to inspect the tensioners before they bite you.