Any change in Russia pre-WW 1 that benefits their economy would have serious repercussions in the rest of Europe. Germany would not have appreciated a powerful country to it's east, Austrio-Hungary likewise, and Britain wouldn't want a powerful Russia moving south into the British controlled areas of India.
Under Nicholas II, things were beginning to move towards some openness, and it was troubling enough to Germany that it had been more or less decided they'd have only a couple years after 1914 to take on Russia before it was on equal or superior footing, so 1914 was as good a time as any.
Now, if you take Russia as it was in 1917, and somehow prevent the second revolution from happening, you'd have a fledgeling democracy facing huge economic problems and a very unhappy populace. Keeping the Communists out would likely prevent the Civil War that followed WW 1.
If they had remained in the war, the Germans wouldn't have been able to shift the forces they used to break the deadlock on the western front, and the allies would have had to wait for the Americans to show up so they could break it instead. Losses of life would have been tremendous, and possibly Russia could have demanded the Germans surrender in the East. This, of course, would potentially have made the rest of the allies upset at Russia leaving the fight earlier than desired.
What you might wind up with is an extremist seizing power later on, either in the 20s or the 30s, under the fascism brand that was so popular throughout Europe in those times. People like a strong leader, and Russia was certainly capable of generating those. Maybe a guy named Stalin, who'd been in the Tsar's secret police and might have been instrumental in crushing the communists, gets elected under dubious circumstances and uses gile and trickery to seize power, and make himself ultimate ruler of Russia. he then faces off against his traditional enemies, the British and the French for their punitive economic measures enacted at the end of WW 1, when Russia was denied a huge portion of the spoils divvied up at Versailles...
So you wind up with Russia starting to annex little surrounding countries, like the Baltic states, and eventually, Finland is threatened with invasion. A hastily convened conference at St Petersburg seems to solve the situation, with the British PM returning home declaring he had achieved "peace in their time". Within a year, WW2 breaks out when Russia invade Poland.
Germany is utterly unprepared for this, and despite a hastily set up defence, is quickly over run, as it Austria and part of Holland and Belgium. Italy strikes into Hungary and Austria, keen to seize territory denied it after Versailles. France and Britain once again ally to defeat a common foe, and the long dark World War 2 begins to cast its' pall across Western Europe...Japan shifts the balance in 1941 when they attack Russia in the East, awakening a terrible angry bear. Several years of diplomacy by Britain has paid off, however, and Japan signs a treaty with Britain and France to defeat Russia.
Without any overt acts against the US by either side keeps the US handily out of the War, seen as a continuation of the previous one. American munition companies make a decent profit selling to both sides however, and the resulting boom in the US Economy helps end the Great Depression to much acclaim for the president, Alfred Landon.
The European war drags on and the Eastern Front quickly goes badly for Japan. They do well at sea, destroying Vladivostok, but their land forces are no match for the Russian tanks and troops. Commonwealth countries help shore up the British assets in Asia, and Australian and Canadian troops are diverted from the UK to the Mongolian frontier to assist the Japanese. Sympathy in the US for the Japanese rises after one of the American destroyers is attacked by Russian aircraft while in port in Korea, and Japanese naval aviators force back the attack.
Limited US assistance begins to be seen in the Far East, and warnings are given by Stalin for the US to mind it's own business. An attack on Anchorage by Russian naval units on August 17, 1943 drags the US into the war, albeit reluctantly.
Russian forces are sent to assist the hopeless Italians in North Africa, so we have the scenario of desert camo T-34s fighting Shermans at Kasserine pass!
Yaks tangling with Zeroes over China!
Spitfires in Japanese markings, Zeroes flying for the FAA!
No nukes, possibly longer range bombers as the targets in Russia would be really far from RAF bases. France never falls, and French tanks and planes would be seen in action longer into the war. Lend lease and outright buyts would happen more for France, so the Douglas and Curtiss plane buys would go through, and the French Air forces would be flying P-39s and Douglas Bostons in those awesome 1939 type schemes.
I've no idea how it would end tho.