Railroad enthusiasts in Utah and Idaho will get a firsthand look at a working steam-powered locomotive this weekend.

Utahns will get the first peek at the two steam engines that made an emergency run into Salt Lake City earlier this week to avoid being stranded in Wyoming by the short-lived national railroad strike.Union Pacific's Challenger No. 3985, the largest working steam engine in the world, is scheduled to give train buffs an opportunity to see how well the old-time engines worked. It will pull a tender car and a string of passenger cars from Salt Lake City to McCammon, Idaho, on both Saturday and Sunday. The train will travel via Ogden, giving buffs in that area a chance to see the powerful locomotive as well.

The tour train is scheduled to leave Salt Lake City at 7 a.m. on both days, arrive in Ogden for a 30-minute layover at 8 a.m. with arrival in McCammon at noon. The return trip from McCammon will begin at 1:30 p.m., arrive in Ogden for a second 30-minute layover at 5 p.m., with arrival in Salt Lake City scheduled for 6:30 p.m.

No. 3985 will then team with Challenger No. 844, the last steam engine built for Union Pacific, on Wednesday at 8 a.m., for a run through Nevada for an appearance at "Railroad Fair '91" in Sacramento May 3-12. This year's fair is being billed as the greatest gathering of historic railroad equipment held in the United States in the past 50 years. The run to California will go via Wendover, Wells, Elko and Winnemucca, Nev. From Winnemucca, the engines will make a run through the northern Nevada desert to Portola, Calif., where it will then make a run through the rugged Feather River Canyon.

Utahns who miss Saturday and Sunday's opportunity will get a second chance for a peek on Friday, May 17, when the engines lay over in Salt Lake City for a full day on the return trip to Union Pacific headquarters in Omaha, Neb.

No. 3985 was built in 1943 and weighs more than 1 million pounds. Unlike its coal-fired predecessors, it runs on fuel oil and can pull double the load of most modern diesel locomotives.