M750 runs better with new belts?

[MongoReturns]

So I had a strange flash of inspiration today and changed the belts, finally.  Current mileage 21,700; last changed at 12k, 4/1/2005 according to my notes.  Ahem.  Wow, I should really clean my k&N! Anyway.

Old belts looked fine, all tickmarks lined up nicely.  Sure, 7mm gap on the horiz, 12mm on the vert (?!?!), all rollers spinning freely.

New belts on, gaps set to 5mm horiz & 6mm vert, spun the wheel a few times, fired her up.  First off, the starter motor REALLY cranked - I though I forgot to put a plug back in, and it'd been sitting for 2 weeks.  I only had about half a cup of old gas in there, so had some starting issues.  But my starting circuit's been buggered for awhile.  On & hot, filled up (4.15 gallons), seems to pull stronger, and with less sputtering.  Put 30 miles on, running like a champ.

So, this makes no sense to me - why would it run better with new belts?  The old ones are pretty stiff compared to the new ones (see, 6 years old) and MAYBE the timing was off a bit due to the gaps.  But I don't know.  Thoughts?

[Howie]

More accurate valve timing, think of it as synching two one cylinder engines.

[lawmaster891]

More accurate valve timing, think of it as synching two one cylinder engines.

agreed

[MongoReturns]

So same results if I'd just adjusted the old ones?  In theory anyway, I really needed to get the old belts out.  Would the better flexibility of the new belts factor in?  I just can't figure it when the tick marks were all lined up on the old ones.

[Howie]

So same results if I'd just adjusted the old ones?  In theory anyway, I really needed to get the old belts out.  Would the better flexibility of the new belts factor in?  I just can't figure it when the tick marks were all lined up on the old ones.

Until one broke.

[DarkStaR]

My guess would be that even if the timing marks all lined up with the old belts, and the tension was set, it was all still running a fraction or some degrees off due to the stretched belts.

Just think that there are X amount of belt teeth between the 2 cogs = about Y of distance. If the belt stretches, there are still X amount of belt teeth between the 2 cogs, but the Y distance has changed.

P.S.  I'm drunk so...

[MongoReturns]

Until one broke.

Yeah, I haven't been riding the 750 too much (rather too far) due to the fear of that happening.

DarkStar, I can see the stretched-belts idea.

[MongoReturns]

P.S.  I'm drunk so...

Yeah my posts aren't very reliable after 10pm...

Come to think of it, the vert cyl tick mark was off a little, relative to the crank & horiz.  New belts, it was better.  I'm also thinking the belts may be the reason the 1098's been running rough.  I ain't doing those though.

[H-2 CHARLIE]

  I  would  like to know if the belts look like new , how can you tell if they are in spec from streching  ?                         I  guess you have to look at the slack adjuster for play ?

[Howie]

  I  would  like to know if the belts look like new , how can you tell if they are in spec from streching  ?                         I  guess you have to look at the slack adjuster for play ?

Problem is you can't since the strength comes from the Aramid cords. 

[MongoReturns]

  I  would  like to know if the belts look like new , how can you tell if they are in spec from streching  ?                         I  guess you have to look at the slack adjuster for play ?

They do look like new, no chips or damage to the teeth, all writing is still on them.  Other than being a little stiff, if you washed them off you'd probably think they were new.  I bet they'd lift Chris Kelley's van right up!

But like Howie says, the strength doesn't come from the outside.  Everything flexible will eventually break.  On the other hand, for the people that replace their Monster belts every 2 years, have fun with that.  I qualify with Monster because I've seen 1098 belts end up as shredded wheat.