You will be surprised how many RPM's this motor gains between 50 degrees and 58ish degrees.

So this is my first venture into 2wd and stock class racing, all my previous experience has been 4wd. Stared with 4x4 SC, then 1/8 buggy and 1/10 4x4 buggy.
I wanted to try some 2wd racing so last night I bought a used B5 rm and the D4 17.5 maxzilla. I've read thru this thread at least twice haha, it seems not too many are running this in rear motor. I'm looking at getting a 69 & 72 spurs and 31-34t pinions. and start at ~40-50* can timing.
Am I on the right track? Any help is greatly appreciated!

Here's a vid of our track.

https://www.youtube.com/watch?v=drfrtm9RWfM

For that track I would start at 28/72 with 55 degrees timing. See how your temps are after 3 min of running. The tallest gear I would use on a track that size is 29/72. Anything higher and your gonna sacrifice bottom end and probably get hot. Same thing goes for a 69 spur. You dont need to gear for that kind of top end because you wont use it. Instead your motor will get hot because you are taking away the bottom end power.

This sheet was from this past weekend on a track just a little bigger then the one in your video. I was geared 27/72 with 59 degrees timing running my MM Serpent Spyder.

Glad i asked before ordering then haha. I saw you recommend 34/69 to someone else with a rear motor but that must have been for a larger track i suppose. Thanks again!

I have to totally disagree with Elex, not to say he is wrong but my experience has been very different. The highest you would gear a D4 is 29/72? I have NEVER seen someone run one that low, literally ever. You are going to want to have up to either 34 or 35 Jmc.

I said 29/72 is the highest I would gear that motor for that particular size track especially at 55 or higher degrees of timing. Obviously if you are on a larger track you can gear higher. Why would you gear for so much top end on a small track? I would much rather have my power down low so I could get up to speed faster on a tight track.

I gear my rear motor buggy a little different. The main reason is there is less drag in a rear motor buggy transmission due to 1 less gear and 2 less bearings. I usually run a 69 (Serpent 70) spur in rear motor buggy and 72 in MM.

So should i go with the 69 or 72 for RM? What pinion range should i get? Now I'm thinking 27-30?

For a rear motor 30-32/69 with 55 degrees timing. See how the temps are at 30 and if you want to go up 1 or 2 teeth then do so.

I can personally back this information up. This is where I ran my D4, and it was a ROCKET. 32/69 was perfect for my local track, and this motor loves a ton of timing. I backed off to 50 degrees for the mid motor car, but for the rear motor I was up to 55-58.

In my mm RB6 I ran 34/69 with 50* timing. After the 10 minute main (finished 2nd by the way) my motor temped around 120ish. Didn't even break a sweat. For 8 minutes though I followed my buddy's b5m with Protek's new slingshot motor. My car was clearly faster but he was driving perfectly to close off any lines. When he finally made a mistake, I was gone.... After the race, his motor was well over 200 degrees and definitely faded at the end. Going to bump up the timing on the D4 and go after the leader! (Who also runs the D4.)

Very happy with the motor and glad I upgraded from the Killshot.

So assuming that you have the gearing low enough how much can timing could you run? The can only shows 60°, is all that it can you run or can you run more than that?

I would'nt go much past 60. There comes a point where you are no longer gaining speed but just increasing amp draw making the motor inefficient.

That being said I have 1 motor that had to be turned up a touch past 60 to match the amp draw of one that was at 57. This is why I cant stress enough to people that you cant rely on the markings. You need either a inline meter or a motor tester. They are much more accurate for setting up motors.

Is an amp clamp sufficient or do you really need to set it by an inline ...and if using an amp clamp should you still leave drove train connected just take off tires or should I remove pinion to get a more accurate reading with the clamp style checker?

Im not sure about using a Amp Clamp. If you use an inline you can just remove the wheels or you can remove the pinion. Some people prefer not to freerev but it's ok for a quick reading.