Should a tech marine with a servo arm or servo harness be able to req a jump pack? I ask because I was thinking of making a mission where having one was pretty manditory.

I don't allows a Servo-Arm to be mounted with a Jump Pack (or the Ammo Backpack or the Back Banner), but I don't think you'll find anything official that prohibits it.

Doesn't it triple your weight or something horrific, or am I thinking of DH?

I personally wouldn't allow a Tech to use one.

If you were to have a mission effectively require one, I would probably allow a Techmarine to use it but severely restrict its movement for the Tech; Instead of doubling speed, it would only move AT speed, and instead of being able to fly at speed 12, you fly at speed 6, or whatever the real numbers are.

That way a tech marine can still grant himself some much-needed mobility, but won't get the same benefit as other, lighter classes. You might consider doing the same for a Devastator if he wants to take an Ammo Backpack as well (or, if he's just taking the weapon, give him the jetpack's full benefits).

If they need to get up onto something a Jumppack will be the only possibility.
If it's just about getting down from somewhere you could give him a pimped up astartes grav chute instead or wait with this special mission till gains the talent to be his own grave chute. Maglev grace I think it's called.
But in the last caste be careful, he can't use that often.

Given that neither the harness, nor the arm are permanent, he can easily requisition a jump pack. Whether he'll be able to field both is another question.

By RAW it's certainly possible. By common sense + watching the concept arts the following items should be restricted to one only per marine:

• Servo Arm
• Servo Harness
• Jump Pack
• Back Banner
• Ammo Backpack

Actually I believe it might be an interesting roleplaying opportunity - having to convince the techmarine to leave his 'badge of office' behind on a mission.

I agree, a Jump Pack w a Servo-Arm does not work! Leave it behind is a good idea for a specific mission.

My Techmarine have the following equipment now:

- Heavy Bolter

- Ammo Backpack (agree w GM that it is a customized backpack)

- Servo-Arm

- Bolt Pistol

- Chain Sword & Knife

Any comments if this is reasonable?

Also I have a question regarding jumping/leaping tests with my Techmarine. My Techmarine have Bionic Legs (exceptional, +20), Strength Bonus of 10 and Tougness Bonus of 10, in total 20 in carrying/lifting capacity (under Move section). How would you rule his jumping and leaping capacity?