Tech Questions & Answers - Shop Talk

Got a question? Try to stump Mark at zimmemr@aol.com

Chain Me Up-Chain Me Down
Q. I've got a new 650 ABS V Strom and it's everything I expected it to be-great. The chain I swore I'd never have is also everything I expected it to be-a pain.

My question is tension. The spec is 0.8 to 1.2" on the side stand. After 4K miles, it was about 1.5" so I decided to adjust it. The problem is, what is "free play" or "slack"? The way I have it set now, if I very lightly push on the chain, I get about 3/4" of free play (total up and down). If I use just moderate finger pressure, it's about 7/8" or just comfortably at the tight end of the allowable range. If I use firm finger pressure, I can maybe squeak a full inch out of it. What's the "right" answer?

I agree with statements in your book that I'd rather be too loose than even a tad too tight. However, I wouldn't mind being at 7/8" as that would take care of future wear for a while. I can see, however, where the chain can get pulled really tight as the swing arm-based and front-sprocket-based movements of the rear axle move thru their respective arcs-too tight and catastrophic failure results. Thoughts?

I did install a Scott Oiler. The chain is always clean, slightly covered with a film of oil, and I wipe the spots off the rear wheel every couple hundred miles. Hopefully, that'll take care of the lubing, cleaning, and extend the life of the chain as promised.
Dave Melcher
Via e-mail

A. Chain slack or 'free play' might be defined as droop, sag or bow. Essentially, it's the distance the chain is allowed to hang down without any pressure being placed on it other than gravity. To measure the slack you simply lift up the chain until it reaches its limit, without placing any tension on it (see the drawing below). The distance it travels is the slack.

Typically, slack is checked and adjusted when the chain is at its tightest point; because no sprockets are truly concentric, you'll need to rotate the chain until the tightest point is found before measuring it, and in most cases, the chain slack is measured with the rider's weight on the bike. However, if your manual says to measure play with the bike on the stand then that's how to do it.

Lastly, here are two rules of thumb on slack. First, the amount of slack a chain requires under most circumstances is equal to about 5% of its total length, which on most bikes works out to about 3/4 to 1 inch (at the tightest point). Secondly, it's only necessary to adjust a motorcycle drive chain when the slack reaches double the recommended amount. In your case I'd only bother adjusting the chain when slack reached 2.5 or so inches. Judging by what you've told me that's probably going to mean an adjustment every 8,000 miles or so, which is about what belts require.

Braking News
Q. I have an '06 Harley Classic Springer Softail. I am considering putting chrome five-spoke mags on it and would like to put a braking system on the front that doesn't have a disc hiding the mag. The only brake I have found is the PickardUSA 360 brake-it is about the size of the hub. My question: is the PickardUSA brake a good one to your knowledge and can you recommend any other similar brakes by other manufacturers? The engineering sounds interesting, but their web site tells little about its efficiency, durability, and consumer satisfaction, or how it works.
Craig Phillips
Spokane, Washington

A. I have no experience with the Pickard so I took a quick look at their web site, which in all honesty is long on platitudes and a bit short when it comes to technical details. From what I can see the 360 seems to be built along the lines of a multi-disc/clutch-pack style aircraft brake, and I agree the concept is interesting. My problem with this sort of brake is that it generates a lot of heat when used vigorously, which isn't a problem in an aircraft application - they only use the brakes when landing and lightly during taxiing - but might be when a fully loaded bike is descending a long hill. It's certainly not a high-performance brake, and reading through the manufacturer's sales pitch, they more or less admit that.

My guess is that the 360 probably works well enough under normal riding conditions, and it's certainly attractive and appears to be well-made, but without actually testing one, a guess is all I can offer. To the best of my knowledge, Pickard is the only one manufacturing this type of brake.

It's All About The Mix
I've noticed that almost all of the manufacturers have gone to EFI, except Honda. Since you have your finger on the pulse of everything with a motor and two wheels (which includes my car from time to time), I figure you would have the inside scoop. Do they just have too many carbs in stock and want to use them up?
Ron Rickers
Elk River, MN

I think your criticism is a little overstated there Rickers, although I certainly wish Honda had at least endowed the VTX I'm riding with a nozzle or two instead of that vintage lawnmower mixer it's wearing. My thinking, which admittedly can be pretty fuzzy at times, is that Honda plans to phase out the remaining carburetor-equipped models in the near future or at least give them a substantial redesign. Because of that, they're understandably reluctant to retrofit them with expensive EFI systems.

Tech Questions Answers - Motorcycle Cruiser Magazine