Idler bracket question

[Bru]

On my recently-acquired 6512.5, got the new belt installed, and all belt retainers properly postitioned. However, on 2 out of 2 starts, the belt immediately jumps off at the flat-belt idler pulley. Looking at the assembly, the flat-side-of-the-belt idler and the V-side idler are not at all in the same plane. I.e., the belt is at an angle to the face of the idlers as is passes from one to the other. I an wondering if somehow that idler bracket assembly is bent--does anyone have a known good one where it can be looked at and see if the idlers are /are not in the same plane? Parts diagrams show this part as 1679857, and as being used in all the 6500 series, the GTH series, the 1814, 1816, and 1817H series, and the 6516H series. If it turns out that these are suposed to be co0-planar, I'll post in the classifieds to locate one. Thanks, all.

[BLT]

Try engaging mower at a moderate, say half throttle, engine speed and do it smartly. Slow engine speed engagement with some long belt wraps like yours will cause the belt to get real jumpy and sometimes jump off. The operators book does show the idler (F, page 23, in the OM) coming off the engine pulley to be at a bit of angle. I am assuming the the model below is yours, http://bsintek.basco.com/BriggsDocumentDisplay/default.aspx?filename=heCyEN8csI2rE3CGh5kbp796Dq

[Bru]

Bob: Thanks for the reply. My original msg was not particularly clear--apologies. The idlers to which I refer are in the clutch and brake group on the 6500 tractor itself, not the mower deck. In the parts diagrams for the clutch and brake groups of all the models I referred to in my original inquiry, the idler pulley bracket is tagged as part # 12, a bent "T" shaped item which holds the two idler pulleys and rotates when the clutch / brake is operated. (This does not apppear to be the same as on the 6200 tractor.) It's the drive belt which is jumping off the "flat-side" idler pulley and jamming between the edge of that pulley and the Z-shaped belt retainer. I haven't figured out how to attach / link to the appropriate parts diagrams, but for example, the diagrams at Jack's Small Engines show it in the diagrams for the 1691468 tractor, clutch and brake group, tagged as part # 12. Simpler form of original question: If you lay a straight-edge across either of these idlers, should the straight-edge also run flat across the other idler pulley in this assembly? Sorry about the lack of precision in the original question.

[MysTiK]

Having installed deck several times, I recently wondered what was all wrong; and then discovered I had reversed the routing of the rubber from deck center pulley to the V and from deck center pulley to the Flat. I thought I knew this. 8) But I never saw it clearly before.