Join Date: Apr 2016
Location: Sonora, CA
Year/Make/Model: 1997 Vulcan Classic
I've been studying the factory service manual almost every night since getting the Fat Bastard, and have the following to offer based on what I see and my experiences:
1. The hydraulic lash adjuster (HLA) is designed to take up play in the valvetrain. Properly functioning, the top end of the motor should be nearly silent at all speeds. If you hear ticking - it's not functioning properly. I disagree with the "It's ticking, and that's normal" comment and here's why:
2. A collapsed lifter typically has about double the lash one would find acceptable on a solid lifter motor - sometimes triple. Solid lifter cams have a "ramp" built into the lobe profile to gradually take up the lash in the valvetrain, while hyd lifter cams do not. A collapsed lHLA will allow the valvetrain to "hammer" itself to failure - eventually. I had a friend with a consistent tick in his motor; he opted not to address it, as he felt it to be normal. The engine did eventually fail, but it took about 15K miles from the onset of the tick.
3. I don't know if this would work in the Vulcan motor, but first generation hydraulic lifters (GM was one of the pioneers in the use of hyd lifters in the late 40's/early 50's) were prone to collapse due to deposits forming in the assembly. The solution was to use a detergent, marketed as Lifter Medic, if I recall. Other mechanics swore by automatic transmission fluid. You'd drain out some oil, add in the medic (or ATF) then let the motor idle for about a half hour (no load) in the driveway. Typically the lifter noise disappears after about ten minutes. I've resurrected several engines over the years by using this technique - saves stripping down the engine. Please note I have no idea what sort of impact this would have on clutch plates - but since the materials used are similar to those in automatic transmissions, I doubt it would be significant.
4. The problem I see with additive cleaning is it would not address what I believe to be the root cause - clogged HLA filters. The design conditions for engine oil (design conditions = highest heat in this case) occur at the exhaust valve stem. Above a certain temp, oil breaks down, or "cokes". The HLA filters are fairly close to the exhaust valve stems - while not likely, it's possible coked oil is either forming in the HLA or contaminating the HLA filter. In reading threads about HLA's, the oil coming out of bled HLA's is often black - a sign of coking.
5. Without starting an oil thread, it's been my experience synthetics have two advantages in this case. First, their viscosity curve is flatter - meaning the oil is thinner cold which reduces cold start clatter. Second (and this is the important one) they have a higher breakdown, or coking, temperature. I started using synth on turbocharged applications back in the mid 80's and was always impressed with how clean a motor was after teardown.
6. I'm fortunate to have all the service records on the Fat Bastard, as the first owner kept meticulous records, and the second kept all receipts. It's had synth the entire time, and with 29,000 miles on the clock it starts and runs without sign of any valvetrain noise. 1500's and 1600's are essentially the same internally, BTW.
If it were my bike, I'd attempt the additive route first, following the manufacturer's instructions. If that didn't work - then yes. I'd pull the motor and manually clean the HLA's while replacing the filters.
Hope this helps.