Problem with new BDS 871 blower rotor issue
 

Need what you think about that rotor issue, the casse is in perfect condition inside, it is like the rotor tuch them a litle together until making this.
I dont speak english very well but i have talk by phone with Tim at BDS and they wont honor the warranty and want to charge me 2500$ to repair because he tell me this was cause by backfire but this engine never backfiring. The blower was only 60h since it is new. The wear is identical on each blower lobe an in my opinion this is a too tight rotor timing problem and not a backfiring problem because of the wear is strait an identical on each lobe.
The only problem i having last summer is i ran out of fuel on boost due to a fuel pump problem other than that i never had any problem so another time i dont think this was the cause of that rotor wear.

Thanks for any help.

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how much are you over driving the blower?i have seen that on larger blowers with a lot of overdrive.also,are you running carb or fuel injection?

I am runing carb dual 850 quick fuel marine, the blower is 5% underdrive at 10lbs boost

looks like improper clearance to me..

do you have the same swipe marks on the backside of the lobes? Meaning, you have the swipe marks on the rotor tips but where's the corresponding swipe marks in the valley of the lobe? That will tell you a lot IMHO.

That is what i think because the wear is there on each lobe of the rotors and the inside of the case still like new without any sing of wear or scuffing. I am just disapointed that the shop who made this blower wont admit the real cause of the problem and wont respect is warranty on a brand new product.

with that being said,their has to be contact and if it is not rubbing the case i believe it must be contacting the inside of the rotor lobe.if you see that i think rotor timing might be the issue.maybe they forgot to lock tite the rotor bolts.

Wich bolt you are talking? The one that bolt the gear to rotors? Or the bolt pin we can see in the pics?

Slowly turning over the blower can you hear any sounds of rotor contact? Re-timing the blowers is quite easy if that's what has to be done. You can either shim one of the gears or machine the backside of the other, your call.

I've rebuilt my own and also a few B&M 420's which are almost the same (not a helical rotor). My gears are machined, the B&M's was timed with shims. I think guys are afraid to work with them because companies like Blower Shop etc. charge a lot of money to do it. The bearings and seals can all be ordered at your local Napa. The only thing I don't get involved in is stripping them but then again, that's only because I haven't had the chance to do it yet.
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yes i mean the bolts for the gears.