Blades need replacing.

It may be that the blades are not as sharp as they should be. You can improve the edge on a 5000 grit whetstone or just try another set of blades.

2pc Set Serger Knife Overlock Blade - Upper and Lower

Amazon.ca https://www.amazon.ca > ...

2pc Set Serger Knife Overlock Blade - Upper and Lower - Brother 925D 929D ... Return policy: Eligible for Return, Refund or Replacement within 30 days of ...

With lack of model number provided, Generic Videos below.

Singer has the manual for the SpeedyLock 1800 on their support page: https://www.singer.com/support . The current link to the manual is https://www.singer.com/sites/default/files/product_manual/981_sl-1700%2C1800%2C7234-eng.-x-.pdf . Note: the manual covers several White SpeedyLock sergers.

I hope this helps.

Cindy Wells

Instruction Manual White Speedylock Serger SL1600

http://www.sewingpartsonline.com/white-sewing-machine-instruction-manuals.aspx

E-Bay is about the last place to find the unfindable!

try these link from youtube, I can't find anything else
white speedylock serger 1600 video manual part 1 of 4

white speedylock serger 1600 video manual part 3 of 4 3 stitch feature

This may be another phone number to the same place, I'm not sure. But I lost my White serger manual, I called White Sewing customer Service at 800-331-3164, and they sent me to a website where I could download it for free. She searched for a minute, so it may vary by model, but I was directed to singerco.com and searched under manuals for "wsl734" for my White superlock 734dw. Wanted to share!

Visit us at www.ifixmachine.com

All tensions should be on 4. Also, make sure the threading is done correctly. Or if you wish; You can contact me on other sergers for sale. "Best prices guaranteed"! [email protected]

I have a 1500 with a manual. I could copy the manual and send it to you. Email me at [email protected]

What does your manual say?
If the 1634 is anything like the 1600 I don't think you can disengage it. I have the book for the 1600 and there is nothing mentioned about disengaging -- only changing the blades. Some models are like that. You might join the White serger group and ask the members there..
http://groups.yahoo.com/group/white_model_sergers
Someone may have an answer or a way around it.

Otherwise, all I can suggest is to call or go to a Joann's or a Husqvarna Viking sewing machine dealer and ask them. Alternatively, a sew and vac repair shop may be able to assist.