pumping engine for displacement verification

[mc2032]

Have had the Sportster pumped many times, not a big deal.  On the bike, I have to pull a rocker box to disable the valves on one head.  Remove both spark plugs, replace one with an adapter from the pump kit/box if available (I made my own out of an old spark plug).  Let the inspector hook up the pump/hose to the adapter, put the bike in 3rd or 4th gear, drag the brake a bit and use the starter to bump the engine over.  in years past I spun the engine over using the rear wheel.  Their pumping results have been close to the engine displacement but I am quite a bit smaller than the class size limit.

[4-barrel Mike]

2005, one of ten or more similar pics.  As I remember, during one of the later pics, the gentleman said, "It can't be that hard, the NASCAR guys do it."

Mike

[MRK]

How in the world can a glass cylinder with a puck connected by a tube to the engine be remotely accurate? I can lose count naming the losses in such a rickety  arrangement. What happened to actually measuring bore and stroke?

At the BSMST event (AMA rules) measuring bore and stroke is the only way to demonstrate displacement. In some cases that can be done through the spark plug hole but for OVC engines with angled or off center plug holes, you must spend all day taking the head off to be measured. Forget about returning the bike to run again unless you brought your whole shop with you.

Don

I recently measured an engine and the competitor claimed it was a 347 cubic inches. Using the tool it measured out to 344.40 CI. That's a .23 cubic inch per cylinder difference. Pretty accurate in my book. The tool, if kept in good working order works really well. I've used it on both car and motorcycle engines with zero issues.

[Dynoroom]

I would like to add the following from the SCTA rule book in Section 1.H, 2nd paragraph, 2nd sentence...

Engine displacement measurement may be made with an SCTA approved
displacement device if the engine displacement is not within
3% of the upper or lower cubic inch break for the class.
All other engines will be measured by direct measurement
of bore and stroke or swept volume.

[Stan Back]

There the alternative to have an official measure your engine and seal it and note that in your Log Book right before you finish assembly.  Yes, this ain't always easy, but I believe it's still an option.