KX Riders

Maintenance & Technical => KX500 Steel Frame Conversion (SFC) => Topic started by: Extranasty on October 07, 2011, 05:42:41 AM

Title: changing and welding chromoly tube on RM 250 Frame?
Post by: Extranasty on October 07, 2011, 05:42:41 AM

     I have a 2005 RM 250 roller I am doing will probably need to change one of the front tubes slightly,how hard is it to grind out cut and then lengthen a tube so I can get the motor as low as possible in front on chromoly and how hard is it 2 find the right tubing to do it right. Thanks.

Title: Re: changing and welding chromoly tube on RM 250 Frame?
Post by: jonny500 on October 07, 2011, 05:51:12 AM

the obvious answer is to find an rm donor frame, perhaps one that is damaged and take some tube from it. you could then use the remainder to experiment with different weld wire and settings before doing the finished frame. just some ideas anyway :-D

Title: Re: changing and welding chromoly tube on RM 250 Frame?
Post by: Extranasty on October 07, 2011, 05:53:56 AM

tHANKS.  :mrgreen:

Title: Re: changing and welding chromoly tube on RM 250 Frame?
Post by: Extranasty on October 07, 2011, 09:12:26 AM

If I can put a 1/4 inch dent in the down tube I can get the motor as low as I want.Can this be done professionally with out messing up the strutural integrity of the frame?

Title: Re: changing and welding chromoly tube on RM 250 Frame?
Post by: KevinTwoStk on November 08, 2011, 07:26:52 PM

You probably don't need a complete donor frame to get that extra tubing from, especially if all you need is a short piece.

If you don't have a local source for chromoly, Aircraft Spruce (www.aircraftspruce.com) is a great source for 4130 tubing, and they can ship you what you need.

I'm not sure what wall thickness is the most common for dirt bike frames. I'm used to off-road trucks where .120-wall tubing is practically standard-issue. I'd guess a lot of motorcycle frames are built using .065-wall or .083.

Mild steel TIG rod or MIG wire should work fine. Most high-end off-road trucks are built using chromoly tubing and mild steel filler rod. These same trucks typically do not get heat treated after welding.

For the "dent" you need put in your frame, you might be able to get away with heating up the area and knocking the dent in with a hammer. If that doesn't seem right, you can have a "cove" cut into the frame and then plate the area back in with either flat plate or a piece of round tubing cut in half down the middle...if that makes sense.

Can you post some pics of the area in question?

Title: Re: changing and welding chromoly tube on RM 250 Frame?
Post by: kxpegger on November 16, 2011, 01:28:56 AM

You might be able to use a Dremel to cut a half section of your tubing out. Take the same piece you just removed and flip it around and weld it back into the remaining portion of the frame tubibg for a concave section. You should then also find a way to gusset or strengthen the area where you have made the modification in case this weakens the tubing. Now you just have to figure what type of welding rod to use with your TIG.

Title: Re: changing and welding chromoly tube on RM 250 Frame?
Post by: 81cr450 on November 16, 2011, 01:46:34 AM

One thing I read about on doing conversions is use a jack to spread the frame, the people who were doing it were working with aluminum frames& just stuffing a bottle jack in there & making room where they needed. Should work easier with chromoly. Also be careful how low you drop the motor as it might cause kicker interference. Are you using the k5 motor? If so I really wanna see pics on this build