Elvin Hayes of the NBA champion Bullets flies high again this week, starting on eight-day (merchandisersponsored tour tomorrow of AAFES shopping centers (PXs to you, military did-timer) in Germany - Munich, Stuttgart, Mannheim, Heidelberg, Furth, Kaiserslautern, Ramstein, Vogelweh, Wiesbaden, Berlin and Frankfurt - with visits to the troops at several stops . . . Bill Walton of the dethroned NBA champion Portland Trail Blazers made an unannounced visit last week to the Cascade Mountains and raised fresh question marks about his future, on which hang the Blazers' comeback hopes:

Walton had checked in by private plane to Winthrop, Wash, to see Dr. William Kelley, a dentist known better for nutritional work with cancer patients (but the American Cancer Society has been sharply critical of Kelley's practice). Chatting with smoke jumpers (parachuting forest-fire fighters) at the airport, Walton said he felt fine but "for this darned foot." Treatments all the way to a stretch at Healing Waters mineral springs resort in Eden, Ariz., last month evidently have not succeeded in healing as fast as expected the left foot the big guy broke in the playoffs against Seattle April 22 after hurting the right one in regular season; he was limping noticeably.

No indication of cancer or any such - but Walton told the airport group that Kelley told him he had been nutritionally deficient for five years. (So much for Walton's longtime natural foods regimen?) Anyway, smoke jumpers who'd seen him play on TV remarked, "He didn't look healthy . . . He didn't look good. No one around here has skinny arms like that."

Walton carrying a bulky book on nutrition after his consultation, was heard to say to his woman companion: "You have to cook this food, you know" . . .

Jimmy Connors has indicated he might pass up next week's North Conway, N.H., of which he is a two-time winner: he cited exhaustion - and who could doubt him? - after winning the Washington Star International in all that heat and humidity. But hundreds of New Hampshire fans head by Gov. and Mrs. Meldrin Thomson have signed a petition to be forwarded to him later this week at his East St. Louis home urging him to come on and play . . .

Chris Knapp, the balky 10-6 Cal Angel right-hander, has ended his baseball "retirement" after 12 days. No longer through with the game forever at 24, because the club wouldn't almost double his sophomore salary of $40,000 at midseason, Knapp telegraphed the required petitions for reinstatement to the Angels and the American League office yesterday. And apparently the team is taking him back; told him to report Monday. Knapp gave no direct explanation for his change to heart; the K.C. Royals' hot streak in the AL West pennant race could explain the Angels' quick acquiescence . . .

Mark Fidrych is another comebacker. The Bird of the Tigers has put his pitching arm to the test for the first time since April 17 - and turned in a fancy three-inning scoreless stint for Detroit's Lakeland Class A team against the Fort Myers Royals. A crowd of 3,000 in Fort Myers gave him a standing ovation and Fidrych said that felt as good as did his arm, so long racked with tendinitis, after his 24 pitches to 11 batters. He exulted, I had my control, I've got my rhythm back and I feel great" . . . And righty Wayne Garland of the Indians, presumed lost for the season after major shoulder sugery May 5, plans to begin serious throwing in about two weeks. The former Oriole 20-game winner said he is considering trying game action before season's end, then winter ball . . .

Kathy Miller, the Scottsdale, Ariz., teen-ager whose comeback from horrible auto accident injuries to running 10,000 meters won her the International Award for Valour in Sport, visited the White House yesterday. First Lady Rosalynn Carter was presented a hologram of the golden laurel trophy . . .

Three youth crews from the Potomac Boat Club, after winning in the National Trials on the Occoquan Reservoir, are up for the World Junior Rowing Championships in Belgrade Thursday through Sunday. Local strokers involved: Fort Hunt High's Chris Peterson and Rich Califf, T.C. Williams' George Nalls and Kevin Michalowski, Silver Spring's Paul Hannah and Washington's Matt and Burgess Smith.

Comes now a tobacco-chewing horse, 6-year-old pacer Lee's Best, whose owner-trainer-driver Virgil White discovered his charger would rather have that than carrots or sugar for good work there around Louisville. When passersby stop to gawk, White says, "I tell 'em to stand back, because chewing isn't so bad, but when he starts spitting - you have to watch it" . . . Earl Campbell, whose pro debut for Houston the oither night saw him gain 37 yards in 10 carries as the Oilers rookies free agents lost to Kansas City's 9-0, has signed a commercial contract that's up to snuff. The Heisman man now calls himself, ugh, the first Skoal brother.

But we all make mistakes. That other superhitter, Rod Carew, was all set to endorse, gasp, Bob Short last week in the bid by the Senators' last owner to become a senator - challenging Rep. Donald Fraser in Minnesota's Democratic primary Sept. 12. The Twin star and Viking linebacker Wally Hilgenberg were to announce formation of an Athletes for Short committee at a news conference; Hilgenberg showed up. But 15 minutes before the appointed time, Carew's attorney called, according to Short's campaign manager, and said he had make a public endorsement. News conference canceled; sorry, Bob . . .