The Japanese didn't have good tanks, true, but tanks are but one thing. The Japanese had lots of infantry to boot, and fanatic infantry at that.
To boot sums it up. It had excellent infantry but on foot, with the distances a war in Russia involves, not forgetting winter. To assume that its over quickly sounds like the same mistake Napoleon and Hitler both made. You have to allow for a winter. Germany at least had a reasionably sized air transport fleet, the Japanese had basically none, just a handful of aircraft. Ground transport was also almost insignificant.
Furthermore and even more crushing was the the Japanese airforce, which would quickly sweep the VVS out of the skies in the far east while the Luftwaffe easily dealt with their part in the west.
The IJAF was small and still in the spring of 1942 partialy equipped with the Ki27. The Russian airforce was just as well equipped, but larger and had done well against the Japanese Airforce before the war.
There's simply no way the Soviets could've dealt with this at all. They were hard pressed enough against the Germans alone, so a Japanese attack from the east would've proven disasterous for them.
I am sure that Russia woldn't have found it easy but a war in Russia was totally the wrong conflict for Japan. Its armies were too lightly equipped from rifles, SMG's, machine guns, AAguns, field guns and howitzers and once again, transport.
There's also no doubt that a combined landbased invasion of the USSR by the Germans and the Japanese would've resulted in a lot of technology shared, esp. within the area of tanks. So the Japanese would've very likely had a tank similar to the Panzer IV not far after.
There is every doubt that they would have shared technology. I am hard pushed to come up with more than one or two items of technology that they shared to the degree that it was deployed in the field. The ones that I can think of were out of date by the time they were deployed. If you could list any it would be appreciated. For instance, the MP40 and Panzerfaust alone would have made a huge difference to the Jananese Army in WW2 but none were deployed that I know of.
The IJA IJN would have a turkey shoot against the Soviet VVS and quickly establish airsuperiority, allowing for tank busting a/c to deal with the puny Soviet tanks until the Japanese cold devise a good one of their own. With the help of the Germans the Japanese might very well have had their own Panzer IV's ready not long after.
Simple question, what tank busting aircraft did the Japanese have and how long would it take to design, develop and build an effective Japanese tank capable of taking on a T34 or KV1?
That said the Japanese did have one thing that the Germans didn't and that was a good number of long ranged bombers that could have made life more difficult for Russia. They may have lacked payload but they did have the range to force Russia to spread out its fighter defences.